阅读说明：本技术 聚合物涂覆的纸和纸板 (Polymer coated paper and paperboard ) 是由 V.里布 K.内瓦莱宁 于 2019-10-01 设计创作，主要内容包括：本发明涉及纸或纸板,所述纸或纸板包括通过PET(聚对苯二甲酸乙二醇酯)树脂的挤出涂覆形成的至少一个涂层,其特征在于PET树脂包含至少50重量％的根据ISO 1628测定的特性粘度小于0.7dl/g、优选小于0.65dl/g的PET共聚物。(The invention relates to paper or paperboard comprising at least one coating formed by extrusion coating of a PET (polyethylene terephthalate) resin, characterized in that the PET resin comprises at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628.)

1. Paper or paperboard comprising at least one coating layer formed by extrusion coating of a PET (polyethylene terephthalate) resin,

characterized in that the PET resin comprises at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO 1628.

2. The paper or paperboard according to claim 1, wherein the intrinsic viscosity of the PET copolymer, determined according to ISO1628, is in the range of 0.55 to 0.63dl/g, preferably in the range of 0.57 to 0.61 dl/g.

3. The paper or paperboard of any of the preceding claims, wherein the PET copolymer is a PET copolymer comprising repeat units from terephthalic acid, isophthalic acid, monoethylene glycol, and diethylene glycol.

4. The paper or paperboard of claim 3, where the molar ratio of terephthalic acid to isophthalic acid in the PET copolymer is in the range of 99:1 to 50: 50.

5. The paper or paperboard of claim 3, where the molar ratio of monoethylene glycol to diethylene glycol in the PET copolymer is in the range of 99:1 to 50: 50.

6. The paper or paperboard according to any of the preceding claims, wherein the PET resin comprises at least 70 wt.%, preferably at least 90 wt.% of the PET copolymer.

7. The paper or paperboard of any of the preceding claims, where the remainder of the PET resin comprises PET having an intrinsic viscosity of 0.7dl/g or higher as determined according to ISO 1628.

8. The paper or paperboard of any of the preceding claims, where the PET resin is added at less than 50g/m²Preferably less than 40g/m²More preferably less than 35g/m²Is applied to the substrate.

9. The paper or paperboard according to any of the preceding claims, where the PET resin comprises at least one additional component selected from polymers other than PET, pigments, dyes and fillers.

10. The paper or paperboard of any of the preceding claims, further comprising at least one additional polymeric coating layer disposed on top of the extrusion coated PET resin, wherein the additional polymeric coating layer has a different composition than the extrusion coated PET resin.

11. The paper or paperboard according to claim 10, wherein the at least one further coating layer comprises polyethylene terephthalate (PET), Polyethylene (PE), polypropylene (PP) and/or polylactic acid (PLA).

12. The paper or paperboard according to claim 10 or 11, wherein the at least one further coating layer is formed by extrusion coating or by extrusion film lamination.

13. The paper or paperboard according to any one of claims 10-12, comprising at least two further polymer coatings, which are arranged on top of the extrusion coated PET resin,

wherein at least one of the additional polymer coating layers has a different composition than the extrusion coated PET resin, and

wherein the outermost further polymer coating comprises at least 50 wt.% of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628.

14. Bakeable tray comprising a paper or paperboard according to any of the preceding claims.

Use of a PET resin comprising at least 50% by weight of a PET copolymer having an Intrinsic Viscosity (IV) determined according to ISO1628 of less than 0.7dl/g, preferably less than 0.65dl/g, for coating a paper or paperboard substrate.

16. Use according to claim 11, wherein the PET resin is as further defined as set forth in any one of claims 2-9.

17. A method of making a PET resin coated paper or paperboard substrate, the method comprising:

a) a paper or paperboard substrate is provided,

b) applying at least one layer of molten PET resin to the surface of the substrate by extrusion coating,

c) allowing the PET resin to cool and solidify, an

d) The PET resin-coated substrate was recovered,

characterized in that the PET resin comprises at least 50% by weight of a PET copolymer having an Intrinsic Viscosity (IV) of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO 1628.

18. The method of claim 17, wherein the PET resin is further defined as set forth in any one of claims 2-9.

19. The method of claim 17 or 18, the method further comprising:

applying at least one further polymeric coating layer disposed on top of the extrusion coated PET resin, wherein the further polymeric coating layer has a different composition than the extrusion coated PET resin.

20. The method of claim 19, wherein the at least one additional coating layer comprises polyethylene terephthalate (PET), Polyethylene (PE), polypropylene (PP), and/or polylactic acid (PLA).

21. The method of claim 19 or 20, wherein the at least one additional coating layer is formed by extrusion coating or by extrusion film lamination.

22. The method of any one of claims 19-21, wherein at least two additional polymer coating layers are applied on top of the extrusion coated PET resin,

wherein at least one of the additional polymer coating layers has a different composition than the extrusion coated PET resin, and

wherein the outermost further polymer coating comprises at least 50 wt.% of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628.

Technical Field

The present disclosure relates to polymer coated paper and paperboard. More particularly, the present disclosure relates to paper or paperboard including at least one coating layer formed by extrusion coating of PET (polyethylene terephthalate) resin.

Background

Paper and paperboard are often coated with plastic for combining the mechanical properties of the paperboard with the barrier and sealing properties of plastic films. Even providing paperboard with relatively small amounts of suitable plastic materials can provide the properties required to make the paperboard suitable for many demanding applications.

Extrusion coating is a method of applying molten plastic material to a substrate (e.g., paper or paperboard) to form a very thin, smooth and uniform layer. The coating may be formed from the extruded plastic itself, or molten plastic may be used as the adhesive to laminate a solid plastic film to the substrate. Common plastic resins used in extrusion coating include Polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET).

Extrusion coating and lamination can be used to achieve, for example, moisture resistance, barrier properties to water vapor, oxygen, fragrance, etc., dirt or grease resistance, heat sealability, and/or to impart a desired finish (finish) or texture to the substrate surface.

The paper or paperboard itself is generally suitable for packaging of dry products. However, the use of untreated board in direct contact with moist or greasy products is limited, since moisture can affect the mechanical properties of the packaging and absorbed grease can lead to contamination of the paper. These effects can impair the protective function and the appearance of the package.

Extrusion coating or lamination greatly expands the range of applications for paper and paperboard. The thin plastic layer imparts resistance to grease and moisture, and in some cases also heat resistance. Plastic coatings may also be used for heat sealing. Depending on the application, the paper or paperboard may be extrusion coated on one or both sides.

One application where the properties of extrusion coated or laminated paperboard are particularly useful is in ovenable packages, i.e. packages that can be used to cook or heat a packaged food product in an oven. In bakeable packaging, the packaging material must be able to withstand moisture and grease at elevated temperatures without absorption into the paperboard.

PET has been found to have excellent properties for bakeable packaging, including high grease resistance, heat sealability, and heat resistance at elevated temperatures. PET also improves the stiffness and tear strength of the coated paperboard.

For environmental and economic reasons, it is generally desirable to keep the plastic coating as thin as possible, as long as the barrier and protective properties are kept at acceptable levels. Generally, only very thin layers are required to provide adequate barrier and protective properties, as long as the coating is uniform and free of defects. However, in many cases, further reduction in the thickness (or grammage) of the plastic coating is limited by impairment of adhesion and film formation stability during extrusion, and the formation of pinholes. For example, conventional PET resins cannot be extrusion coated onto paper or paperboard to less than 40g/m²Without losing adhesion and film forming stability, leading to defects in the coated product.

In extrusion coating and lamination of paper and paperboard with plastics, it is very important to obtain satisfactory adhesion of the plastic to the substrate. The adhesion of the plastic depends mainly on the surface properties of the substrate and the heat content of the plastic melt when applied to the paperboard. Insufficient adhesion between plastic coatings and paper or paperboard is a common and persistent problem.

Pinholes are tiny holes that can be formed in the plastic film during the coating process. The main causes of pinholes include irregularities in the substrate surface (e.g., high surface roughness or loose fibers), uneven coating distribution, or too low a coating grammage.

Adhesion can be improved by surface treatment of the substrate (e.g. with corona discharge or ozone), but there is still a need for improved solutions for reducing the grammage of plastic coatings, especially in extrusion coating of PET, while maintaining good adhesion and film forming stability during extrusion.

Drawings

Fig. 1 is a graph illustrating adhesion to a paperboard substrate as a function of coating grammage of PET resin according to the present invention.

Fig. 2 contains two graphs illustrating the runnability of the coating of PET resin according to the invention.

Figure 3 is a graph illustrating adhesion for different PET grades as a function of grammage in extrusion coating (single layer).

Figure 4 is a graph illustrating the grammage for different PET grades as a function of line speed in extrusion coating (single layer).

Figure 5 is a graph illustrating runnability (standard deviation of grammage) for different PET grades as a function of line speed in extrusion coating (single layer).

Examples

Example 1 Co-extrusion coating of paperboard with PET copolymer and Standard PET resin

Will have a density of about 350g/m²A grammage paperboard substrate (Trayforma 350Natura, Stora Enso Oy) was co-extrusion coated in an extrusion coating test line with standard PET grade a and PET copolymer resin B. PET copolymer resin B was extruded from extruder B onto a cardboard substrate and the stopper (plug) was BBAAA-DD. Coextrusion was carried out in extruders A and B at screw speeds of 140 and 100rpm, respectively.

PET copolymer B is a PET copolymer comprising repeating units derived from terephthalic acid, isophthalic acid, monoethylene glycol and diethylene glycol and having an Intrinsic Viscosity (IV) of 0.59dl/g, determined according to ISO 1628. The Intrinsic Viscosity (IV) of standard PET grade A, determined according to ISO1628, is 0,82-0,85dl/g, the glass transition temperature (T)_g) Is 75-80 deg.C, and has a melting temperature (T)_m) 245 ℃ and 250 ℃.

The coextruded substrates (a + B) were analyzed for adhesion, runnability, and MAP sealability and compared to corresponding substrates prepared using only standard PET grade (a).

Adhesion property

The adhesion test was performed by visual evaluation based on the X-cut method and the evaluation criteria in table 1. The coating was manually peeled off the fibrous substrate.

Table 1 adhesion test.

Value of	Evaluation criteria
		0	No adhesion of coating
1	Fibres stripped without any tearing
		2	Stripped out, with some torn fibres
3	The mixture is stripped out of the mould,<50% of the area is covered by the torn fibers
		4	The mixture is stripped out of the mould,>50% of the area is covered by the torn fibers
5	Peeled off and the area was completely covered with torn fibres (100%)

Adhesion testing showed that the coextruded substrate retained an adhesion value of 5 up to a coating grammage of 20g/m²(see FIG. 1). The corresponding substrates prepared with standard PET grade A alone maintained an adhesion value of 5 up to a coating grammage of 30g/m²。

Operation property

Runnability was evaluated based on the standard deviation of the grammage of the coating in the cross direction and the machine direction. A deviation level below 3 is acceptable.

Runnability testing showed that the coextruded substrate remained runnability until the coating grammage was 15g/m²(see FIG. 2). The corresponding substrates prepared with standard PET grade A alone remained runnability until the coating grammage was 20g/m²。

MAP-test

The oxygen permeability of PET coated substrates was evaluated using the so-called Modified Atmosphere Packaging (MAP). The coated substrate was used in a tray package and tightly sealed closed with a lid. MAP sealability was evaluated based on oxygen levels in the package after 7, 14 and 28 days. Oxygen levels below 1% after 14 days were considered acceptable. The results are shown in Table 2.

Table 2 MAP-test.

The results in Table 2 show that a slightly thinner coating (30 g/m) is used²Compared with 40g/m²) The MAP sealability of the coextruded substrates was also significantly higher than that of the substrates prepared with standard PET grade A alone. The oxygen value after 14 days for the standard PET grade was 0.93%. Although this value is below 1%, it is still not considered acceptable due to measurement uncertainty. Even with thinner coatings, the value of 0.37% for the coextruded substrate is clearly within an acceptable range.

Example 2 comparison of different PET copolymers

Five different poly (ethylene terephthalate) s were tested in a single extrusion coating on an extrusion coating test line of the stamp University of Technology (TUT). The PET grades tested are shown in table 3.

PET grades differ in chemical structure and intrinsic viscosity. The web material used was Stora Enso Trayforma 190.

Figure 3 shows the adhesion for five PET grades as a function of grammage in extrusion coating (single layer, extruder a, plug AAAAA-DD, air gap 130mm, corona treatment 3.4 kW). Figure 4 shows the grammage for five PET grades as a function of line speed in extrusion coating (single layer). Figure 5 shows the runnability (standard deviation of grammage) for five PET grades as a function of line speed in extrusion coating (single layer).

The extrusion coating parameters were similar for the five PET grades tested (see fig. 3). The screw speed of extruder A was 140rpm, so the throughput, depending on the PET grade, was 103-115 kg/h. The target melting temperature was about 300 ℃ 310 ℃ (compare 1, 2 and 4) or 280 ℃ (present invention and compare 3).

It is clear that the best bulk properties are achieved with low viscosity copolymers (invention) made from terephthalic acid, isophthalic acid, monoethylene glycol and diethylene glycol.

Table 3 properties of five different poly (ethylene terephthalate) grades were tested in extrusion coating.

Detailed Description

It is an object of the present disclosure to reduce the minimum grammage of PET resin required to achieve sufficient adhesion and film-forming stability in extrusion coating.

It is another object of the present disclosure to provide a PET resin coated paper or paperboard that allows for a reduced grammage of the PET resin, e.g., less than 40g/m²While maintaining good adhesion of the PET resin to the paper or paperboard.

It is another object of the present disclosure to provide a PET resin coated paper or paperboard having improved adhesion of PET resin to paper at low grammage of PET resin.

It is another object of the present disclosure to provide a method of making PET resin coated paper or paperboard that allows for a reduced grammage of the PET resin, e.g., less than 40g/m²While maintaining good film forming stability during extrusion.

It is another object of the present disclosure to provide a method of making PET resin coated paper or paperboard that allows for improved film forming stability during extrusion with low grammage of PET resin.

The above objects, as well as other objects that will be recognized by those skilled in the art in light of the present disclosure, are achieved by various aspects of the present disclosure.

According to a first aspect shown herein, there is provided a paper or paperboard comprising at least one coating formed by extrusion coating of a PET (polyethylene terephthalate) resin, characterised in that the PET resin comprises at least 50 wt% of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO 1628.

Paper generally refers to a material made in the form of a sheet from wood pulp or other fibrous material containing cellulose fibers, for writing, drawing or printing thereon, or as a packaging material.

Paperboard generally refers to strong, thick paper or cardboard (cardboard) containing cellulosic fibers for boxes and other types of packaging. The paperboard can be bleached or unbleached, coated or uncoated, and can be produced in a variety of thicknesses, depending on the requirements of the end use.

As used herein, the term coating refers to an operation in which the surface of a substrate is covered with a composition to impart a desired property, finish, or texture to the substrate. The coating may be a single layer or a multi-layer coating, wherein the PET coating resin may be used in one or more layers. The coating may be applied to one or both sides of the paper or paperboard.

Today, PET extrusion coatings for ovenable packs are produced using PET grades similar to those used in the manufacture of PET bottles. Typical PET grades used have an intrinsic viscosity of about 0.8 to 0.9dl/g, determined according to ISO 1628. These conventional PET resins cannot be extrusion coated onto paper or paperboard to less than 40g/m²Without losing adhesion and film forming stability, resulting in defects in the coated product.

The present inventors have now found that the use of a particular type of PET resin having a low intrinsic viscosity can reduce the minimum grammage of the PET resin required to achieve sufficient adhesion and film formation stability in extrusion coating of paper and paperboard. In many converting operations (e.g., printing and heat sealing), adequate adhesion is important.

In addition, it has been found that the particular type of PET resin used in the present invention has further advantages over standard extrusion coating grade PET, including better runnability, allowing higher line speeds in the extrusion coating process, and reduced oxygen permeability.

The PET resin used in the present invention comprises at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO 1628. In some embodiments, the intrinsic viscosity of the PET copolymer, as determined according to ISO1628, is in the range of 0.55 to 0.63dl/g, preferably in the range of 0.57 to 0.61 dl/g. In a preferred embodiment, the intrinsic viscosity of the PET copolymer is 0.59 dl/g.

In some embodiments, the PET copolymer is a PET copolymer comprising repeat units from terephthalic acid, isophthalic acid, monoethylene glycol, and diethylene glycol. It has been found that the combination of low intrinsic viscosity and PET structure comprising repeat units from terephthalic acid, isophthalic acid, monoethylene glycol and diethylene glycol provides additional improvements in adhesion and runnability. This allows further reduction of the necessary PET resin grammage in extrusion coating. Surprisingly, the copolymer composition does not limit the heat resistance of the coating compared to conventional high intrinsic viscosity PET polymers.

In some embodiments, the molar ratio of terephthalic acid to isophthalic acid in the PET copolymer is in the range of 99:1 to 50: 50.

In some embodiments, the molar ratio of monoethylene glycol to diethylene glycol in the PET copolymer is in the range of 99:1 to 50: 50.

In some embodiments, the PET copolymer consists of repeat units from terephthalic acid, isophthalic acid, monoethylene glycol, and diethylene glycol.

In a preferred embodiment, the PET resin comprises at least 50 wt% of a PET copolymer, wherein the PET copolymer comprises repeat units from terephthalic acid, isophthalic acid, monoethylene glycol, and diethylene glycol, wherein the molar ratio of terephthalic acid to isophthalic acid in the PET copolymer is in the range of 99:1 to 50:50 and the molar ratio of monoethylene glycol to diethylene glycol in the PET copolymer is in the range of 99:1 to 50:50, and wherein the intrinsic viscosity of the PET copolymer, determined according to ISO1628, is in the range of 0.57 to 0.61 dl/g.

The PET resin of the present invention comprises at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7 dl/g. In some embodiments, the PET resin comprises at least 70 wt%, preferably at least 90 wt% of the PET copolymer. The PET resin of the present invention may also consist of or consist essentially of a PET copolymer. Embodiments in which the PET resin consists of or consists essentially of PET copolymer are of particular interest because such single material coatings provide significant recycling advantages.

The remainder of the PET resin may be comprised of other polymeric or non-polymeric coating ingredients. In other words, the PET resin may be a blend of a PET copolymer and another polymer. In some embodiments, the remainder of the PET resin comprises PET having an intrinsic viscosity of 0.7dl/g or higher as determined according to ISO 1628. In some embodiments, the remainder of the PET resin comprises PET having an intrinsic viscosity of 0.7 to 0.9dl/g as determined according to ISO 1628.

The formulation of the coating resin can vary widely depending on the intended use of the coating and the coated paper or paperboard. The coating composition may include a wide range of ingredients in various amounts to improve the final properties of the product or the processing of the coating. In some embodiments, the PET resin comprises at least one additional component selected from the group consisting of: polymers other than PET, pigments (e.g. TiO)₂Or carbon black), dyes, and fillers (e.g., CaCO)₃Talc).

The PET resin used in the present invention allows the production of coated paper or paperboard having a low grammage (e.g., less than 50 g/m)²Grammage) of PET resin and adhesion of the PET resin to paper. Thus, in some embodiments, the PET resin is applied at less than 50g/m²Is applied to the substrate.

The PET resin used in the present invention allows the production of extrusion coated paper or paperboard having a reduced grammage of the PET resin, e.g. less than 40g/m²While maintaining good film forming stability and adhesion of the PET resin to the paper or paperboard. Thus, in some embodiments, the PET resin is applied at less than 40g/m²More preferably less than 35g/m²Is applied to the substrate.

The paper or paperboard of the invention may be coated with only PET resin comprising at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628. Alternatively, the paper or paperboard of the present invention may include a PET resin coating as one of two or more polymer coatings. Since the PET resin coating of the present invention provides good film-forming stability and adhesion of the PET resin to paper or paperboard, it can be preferably used as a first (or innermost) coating layer directly applied on the surface of paper or paperboard. Extrusion coated PET resin coatings can be used to promote adhesion of subsequently applied or coextruded polymer coatings. The extrusion coated PET resin coating can be used as an adhesive for polymer films in extrusion film lamination processes.

In some embodiments, the paper or paperboard extrusion coated with PET resin further comprises at least one additional polymeric coating layer disposed on top of the extrusion coated PET resin, wherein the additional polymeric coating layer has a different composition than the extrusion coated PET resin.

In some embodiments, the at least one additional coating layer is formed by extrusion coating or by lamination of extruded films.

In some embodiments, the at least one additional coating layer comprises polyethylene terephthalate (PET), Polyethylene (PE), polypropylene (PP), and/or polylactic acid (PLA). In a preferred embodiment, the at least one further coating comprises polyethylene terephthalate (PET).

PET resins comprising at least 50 wt% of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g have good heat sealing properties and can also be used as the outermost coating (or top layer) applied on top of the intermediate polymer coating.

In some embodiments, the paper or paperboard extrusion coated with PET resin further comprises at least two additional polymeric coating layers disposed on top of the extrusion coated PET resin,

wherein at least one of the additional polymer coating layers has a different composition than the extrusion coated PET resin, and

wherein the outermost further polymer coating comprises at least 50 wt.% of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628.

In some embodiments, the total combined grammage of the PET resin and the additional PET coating on the paper or paperboard is less than 50g/m²Preferably less than 40g/m²More preferably less than 35g/m²。

The paper or paperboard of the present invention is particularly useful in the manufacture of bakeable trays. According to a second aspect illustrated herein, there is provided a bakeable tray comprising paper or paperboard according to the first aspect described herein.

According to a third aspect shown herein, there is provided the use of a PET resin comprising at least 50 wt% of a PET copolymer having an Intrinsic Viscosity (IV) of less than 0.7dl/g, preferably less than 0.65dl/g, as determined according to ISO1628, for coating a paper or paperboard substrate.

The present inventors have found that the use of a particular type of PET resin having a low intrinsic viscosity can reduce the minimum grammage of the PET resin required to achieve sufficient adhesion and film formation stability in extrusion coating of paper and paperboard.

The PET resin of the third aspect may be further defined as described above with reference to the first aspect.

In a preferred embodiment, the PET resin comprises at least 50 wt% of a PET copolymer, wherein the PET copolymer comprises repeat units from terephthalic acid, isophthalic acid, monoethylene glycol, and diethylene glycol, wherein the molar ratio of terephthalic acid to isophthalic acid in the PET copolymer is in the range of 99:1 to 50:50 and the molar ratio of monoethylene glycol to diethylene glycol in the PET copolymer is in the range of 99:1 to 50:50, and wherein the intrinsic viscosity of the PET copolymer, determined according to ISO1628, is in the range of 0.57 to 0.61 dl/g.

According to a fourth aspect shown herein, there is provided a method of making a PET resin coated paper or paperboard substrate, the method comprising:

a) a paper or paperboard substrate is provided,

b) applying at least one layer of molten PET resin to the surface of the substrate by extrusion coating,

c) allowing the PET resin to cool and solidify, an

d) The PET resin-coated substrate was recovered,

characterized in that the PET resin comprises at least 50% by weight of a PET copolymer having an Intrinsic Viscosity (IV) of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO 1628.

The PET resin of the fourth aspect may be further defined as described above with reference to the first aspect.

In a preferred embodiment, the PET resin comprises at least 50 wt% of a PET copolymer, wherein the PET copolymer comprises repeat units from terephthalic acid, isophthalic acid, monoethylene glycol, and diethylene glycol, wherein the molar ratio of terephthalic acid to isophthalic acid in the PET copolymer is in the range of 99:1 to 50:50 and the molar ratio of monoethylene glycol to diethylene glycol in the PET copolymer is in the range of 99:1 to 50:50, and wherein the intrinsic viscosity of the PET copolymer, determined according to ISO1628, is in the range of 0.57 to 0.61 dl/g.

The paper or paperboard of the invention may be coated with only PET resin comprising at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628. Alternatively, the paper or paperboard of the present invention may include a PET resin coating as one of two or more polymer coatings. Since the PET resin coating of the present invention provides good film-forming stability and adhesion of the PET resin to paper or paperboard, it can be preferably used as a first (or innermost) coating layer directly applied on the surface of paper or paperboard. Extrusion coated PET resin coatings can be used to promote adhesion of subsequently applied or coextruded polymer coatings. The extrusion coated PET resin coating can be used as an adhesive for polymer films in extrusion film lamination processes.

In some embodiments, the method further comprises applying at least one additional polymeric coating layer disposed on top of the extrusion coated PET resin, wherein the additional polymeric coating layer has a different composition than the first extrusion coated PET resin.

In some embodiments, the at least one additional coating layer comprises polyethylene terephthalate (PET), Polyethylene (PE), polypropylene (PP), and/or polylactic acid (PLA). In a preferred embodiment, the at least one additional coating layer comprises polyethylene terephthalate (PET) having a different composition than the first extrusion coated PET resin.

In some embodiments, the at least one additional coating layer is formed by extrusion coating or by lamination of extruded films. In a preferred embodiment, the at least one additional coating layer is formed by coextrusion coating with the first PET resin.

In some embodiments, at least two additional polymer coating layers are applied on top of the extrusion coated PET resin,

wherein at least one of the additional polymer coating layers has a different composition than the extrusion coated PET resin, and

wherein the outermost further polymer coating comprises at least 50 wt.% of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, determined according to ISO 1628.

In a preferred embodiment, the paper or paperboard comprises at least one coating layer formed by extrusion coating of a PET (polyethylene terephthalate) resin, wherein the PET resin consists of: at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO1628, and of PET having an intrinsic viscosity of 0.7dl/g or higher, measured according to ISO 1628.

In a preferred embodiment, the paper or paperboard comprises: a first coating layer formed by extrusion coating of a PET (polyethylene terephthalate) resin, wherein the PET resin consists of: at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, as determined according to ISO1628, and of PET having an intrinsic viscosity of 0.7dl/g or higher, as determined according to ISO 1628; and

a second coating consisting of PET having an intrinsic viscosity of 0.7dl/g or higher, determined according to ISO 1628.

In a preferred embodiment, the paper or paperboard comprises:

a first coating layer formed by extrusion coating of a PET (polyethylene terephthalate) resin, wherein the PET resin consists of: at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, as determined according to ISO1628, and of PET having an intrinsic viscosity of 0.7dl/g or higher, as determined according to ISO 1628;

a second coating consisting of PET having an intrinsic viscosity of 0.7dl/g or higher, determined according to ISO 1628; and

a third coating layer formed by extrusion coating of a PET resin, wherein the PET resin consists of: at least 50% by weight of a PET copolymer having an intrinsic viscosity of less than 0.7dl/g, preferably less than 0.65dl/g, measured according to ISO1628, and of PET having an intrinsic viscosity of 0.7dl/g or higher, measured according to ISO 1628.

In a preferred embodiment, the PET copolymer comprises repeat units from terephthalic acid, isophthalic acid, monoethylene glycol and diethylene glycol, wherein the molar ratio of terephthalic acid to isophthalic acid in the PET copolymer is in the range of 99:1 to 50:50 and the molar ratio of monoethylene glycol to diethylene glycol in the PET copolymer is in the range of 99:1 to 50:50, and wherein the intrinsic viscosity of the PET copolymer, determined according to ISO1628, is in the range of 0.57 to 0.61 dl/g.

In some embodiments, the total combined grammage of the PET resin and additional PET coating applied to the substrate is less than 50g/m²Preferably less than 40g/m²More preferably less than 35g/m²。

The inventors have shown that a slightly thinner coating (30 g/m) is used²Compared with 40g/m²) The MAP sealability of substrates co-extruded coated with the PET copolymer of the invention and standard PET grades is also significantly higher than the sealability of substrates extrusion coated only with standard PET grades.

While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.