阅读说明：本技术 聚氨酯涂布的可热收缩膜 (Polyurethane coated heat shrinkable film ) 是由 C·杜瓦勒 J·C·卡萨鲁贝斯 M·扎内蒂 M·G·德奥利韦拉 J·C·戈梅斯 于 2019-02-27 设计创作，主要内容包括：一种可热收缩膜,其包括基于乙烯的聚合物多层或单层膜和在基于乙烯的聚合物膜的外表面上的涂层。所述基于乙烯的聚合物膜具有由第一层、第二层以及在第一层与第二层之间的至少一个内层形成的单层或多层结构。所述涂层包含聚氨酯,所述聚氨酯是以下物质的聚合反应产物；多元醇；和芳香族异氰酸酯官能预聚物。此外,提供了一种使聚合物包裹的初级包装单元化的方法。所述方法包括用所述可热收缩膜包裹所述初级包装中的一个或多个,其中所述涂层安置在所述一个或多个初级包装近端,以及施加热能以减小所述可热收缩膜的尺寸,以将所述初级包装限制在所述可热收缩膜内。所述涂层用于减轻所述可热收缩膜与所述聚合物包裹的初级包装之间的粘连。(A heat shrinkable film comprising an ethylene-based polymeric multilayer or monolayer film and a coating on an outer surface of the ethylene-based polymeric film. The ethylene-based polymer film has a single-layer or multi-layer structure formed of a first layer, a second layer, and at least one inner layer between the first layer and the second layer. The coating comprises a polyurethane that is a polymerization reaction product of; a polyol; and an aromatic isocyanate functional prepolymer. Further, a method of unitizing a polymer-wrapped primary package is provided. The method includes wrapping one or more of the primary packages with the heat shrinkable film, wherein the coating is disposed proximal to the one or more primary packages, and applying heat energy to reduce the size of the heat shrinkable film to confine the primary packages within the heat shrinkable film. The coating is used to reduce blocking between the heat shrinkable film and the polymer-wrapped primary package.)

1. A heat shrinkable film comprising:

(a) a multilayer film, the multilayer film comprising:

(i) a first layer comprising from 30 to 100 weight percent of a first ethylene-based polymer having: 0.905 to 0.930g/cm³(ii) a density of (d); a melt index (I) of 0.1 to 2.0 grams/10 minutes when measured at 190 ℃ and under a 2.16kg load according to ASTM D1238₂) (ii) a And a peak melting point of less than 126 ℃ as measured using Differential Scanning Calorimetry (DSC);

(ii) a second layer comprising from 50 to 100 weight percent of a second ethylene-based polymer having: 0.905 to 0.970g/cm³And a peak melting point in the range of 100 ℃ to 135 ℃ measured using DSC; and

(iii) at least one inner layer between the first layer and the second layer, the inner layer comprising from 10 to 50 weight percent of a third ethylene-based polymer having from 0.930 to 0.970g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃; and

(b) a coating on an outer surface of the first or second layer of the film, the coating comprising a polyurethane that is a polymerization reaction product of: (a) a polyol; (b) an aromatic isocyanate functional prepolymer.

2. The heat shrinkable film of claim 1, wherein

(i) The first layer and the second layer each comprise 50 to 70 weight percent of an ethylene-based polymer having a melt index (I) of 0.1 to 0.4 grams/10 minutes measured according to ASTM D1238₂) And a peak melting point of less than 120 ℃; and is

(ii) The at least one inner layer between the first layer and the second layer comprises from 20 to 40 weight percent of an ethylene-based polymer having from 0.930 to 0.970g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

3. A heat shrinkable film of any of the preceding claims, wherein

(i) The first layer and the second layer each comprise 30 to 50 weight percent of an ethylene-based polymer having a melt index (I) of 0.4 to 1.0 grams per 10 minutes measured according to ASTM D1238₂) And a peak melting point of less than 125 ℃; and is

(ii) The at least one inner layer between the first layer and the second layer comprises from 60 to 80 weight percent of an ethylene-based polymer having from 0.910 to 0.930g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

4. A heat shrinkable film of any of the preceding claims, wherein

(i) The first layer and the second layer each comprise 60 to 80 weight percent of an ethylene-based polymer having a melt index (I) of 0.3 to 1.2 grams/10 minutes measured according to ASTM D1238₂) And a peak melting point of 115 ℃ to 135 ℃; and is

(ii) The at least one inner layer between the first layer and the second layer comprises from 60 to 85 weight percent of an ethylene-based polymer having from 0.910 to 0.930g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

5. The heat shrinkable film of any of the preceding claims, wherein the multilayer film comprises 40 to 60 wt.% of a low density polyethylene having a density of 0.905 to 0.930g/cc and a melt index (I) of 0.1 to 2.0 grams/10 minutes₂)；

6. The heat shrinkable film of any of the preceding claims, wherein the coating is applied according to a defined pattern of coated and uncoated areas on the outer surface of the first or second layer of the multilayer film.

7. A heat shrinkable film comprising:

(a) a monolayer film comprising from 30 to 60 weight percent of a fourth ethylene-based polymer, wherein the fourth ethylene-based polymer has from 0.905 to 0.930g/cm³A melt index (I) of 0.1 to 0.9 g/10min when measured according to ASTM D1238 at 190 ℃ and a load of 2.16kg₂) (ii) a And a peak melting point of less than 126 ℃ as measured using Differential Scanning Calorimetry (DSC);

(b) a coating on an outer surface of a monolayer film comprising a polyurethane that is a polymerization reaction product of: (a) a hydroxyl terminated polyol; and (b) an aromatic isocyanate functional prepolymer.

8. The heat shrinkable film of claim 7, wherein the monolayer film comprises:

from 40 to 60 weight percent of an ethylene-based polymer having from 0.910 to 0.930g/cm³And a melt index (I) of 0.2 to 0.3 g/10min measured according to ASTM D1238₂)；

20 to 40 weight percent of an ethylene-based polymer having 0.910 to 0.930g/cm³And a melt index (I) of 0.9 to 1.1 g/10min₂) (ii) a And

10 to 30 wt% of an ethylene-based polymer, the ethylene-based polymerThe compound has a density of 0.940 to 0.960g/cm³And a melt index (I) of 0.85 to 1.05 g/10min₂)。

9. The heat shrinkable film of any of the preceding claims, wherein the polyol is a hydroxyl terminated polyether polyol.

10. The heat shrinkable film of claim 9, wherein the hydroxyl terminated polyol comprises a hydroxyl terminated polyether polyol, a hydroxyl terminated polyester polyol, or a combination thereof.

11. The heat shrinkable film of any of the preceding claims, wherein the aromatic isocyanate functional prepolymer comprises toluene diisocyanate, methyl diphenyl diisocyanate, or a combination thereof.

12. The heat shrinkable film of any of the preceding claims, wherein the heat shrinkable film is a blown film.

13. The heat shrinkable film of any of the preceding claims, wherein the coating is applied according to a defined pattern of coated and uncoated areas on the outer surface.

14. A packaging assembly, comprising:

a plurality of packages, wherein each package comprises a plurality of articles bundled together by a primary packaging film comprised of a polymeric material, wherein the primary packaging film is wrapped around the plurality of articles to form a primary package; and

a secondary packaging film for bundling the plurality of packages, wherein the secondary packaging film comprises the heat shrinkable film according to any of the preceding claims.

15. A method of unitizing a polymer-wrapped primary package, the method comprising:

wrapping one or more of the primary packages with a heat shrinkable film according to any of the preceding claims; and

applying heat energy to reduce the size of the heat shrinkable film to confine the primary package within the heat shrinkable film;

wherein a coating comprising polyurethane is disposed proximal to the one or more primary packages.

Technical Field

Embodiments described herein relate generally to heat shrinkable films and, more particularly, to heat shrinkable films having a polyurethane coating. Such heat shrinkable films can be used as secondary packaging to group multiple products together in a unitized process.

Background

Shrink films are commonly used in the packaging of products, such as consumer products. For example, the bundles of plastic bottles may be secured by shrink-wrap that secures the plastic bottles together. The shrink film may comprise a polymeric film that is placed around the object and shrunk relative to its original dimensions to at least partially surround the object and secure the one or more articles contained therein and create the primary package. For example, plastic beverage containers may be bundled and secured in a shrink film. Advantages of shrink films over other conventional packaging (e.g., paperboard packaging) may include reduced environmental impact, cost savings, transparency, and the ability to be used as shipping packaging and consumer display packaging.

Logistics and supply chains that bring individually packaged products to the market often require unitization of the individually packaged products. Unitization is the grouping of several individually packaged products together to simplify handling, shipping and storage and to provide protection for the individually packaged products during handling, shipping and storage. Unitization is typically achieved by applying a secondary shrink film or secondary package over the primary package. However, when currently available shrink films are used as over shrink films to provide secondary packages and to bundle individual primary packages, adhesion of the secondary packages to the primary packages after shrinkage of the secondary packages is often caused. Such adhesion is undesirable and results in structural and visual damage to the primary package, resulting in an unsaleable or defective product.

Therefore, there is a need for a coated film for secondary packaging that unitizes primary packages and easily removes the underlying primary packages without damage.

Disclosure of Invention

Embodiments of the present disclosure meet those needs by providing a heat shrinkable film comprising a coating on an outer surface of the heat shrinkable film. When heat shrinkable films are used to singulate individual saleable products into larger packages, the coating can reduce the adhesion of the heat shrinkable film to the underlying shrink film used to package the individual products for handling and protection during logistics and supply chains for storage on shelves.

In accordance with at least one embodiment of the present disclosure, a heat shrinkable film is provided. The heat shrinkable film includes (a) a multilayer film and (b) a coating on an outer surface of the first or second layer of the film. The multilayer film includes (i) a first layer formed from 30 to 100 weight percent of a first ethylene-based polymer having from 0.905 to 0.930g/cm³A density of 0.1 to 2.16kg load when measured according to ASTM D1238 at 190 ℃Melt index (I) of 2.0 g/10min₂) (ii) a And a peak melting point of less than 126 ℃ as measured using Differential Scanning Calorimetry (DSC); (ii) a second layer formed from 50 to 100 wt.% of a second ethylene-based polymer having 0.905 to 0.970g/cm³And a peak melting point in the range of 100 ℃ to 135 ℃ measured using DSC; and (iii) at least one inner layer between the first layer and the second layer comprising 10 to 50 wt.% of a third ethylene-based polymer having 0.930 to 0.970g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃ measured using DSC. The coating comprises a polyurethane formed from: (a) a polyol; and (b) an aromatic isocyanate functional prepolymer.

According to other embodiments of the present disclosure, a heat shrinkable film is provided. The heat shrinkable film includes (a) a monolayer film and (b) a coating on an outer surface of the monolayer film. The monolayer film comprises 30 to 60 weight percent of a fourth ethylene-based polymer, wherein the fourth ethylene-based polymer has from 0.905 to 0.930g/cm³A melt index (I) of 0.1 to 0.9 g/10min when measured according to ASTM D1238 at 190 ℃ and a load of 2.16kg₂) And a peak melting point below 126 ℃ as measured using DSC. The coating comprises a polyurethane formed from: (a) a polyol; and (b) an aromatic isocyanate functional prepolymer.

According to another embodiment, a packaging assembly is provided. The packaging assembly includes a plurality of packages, wherein each package contains a plurality of articles bundled together by a primary packaging film composed of a polymeric material, wherein the primary packaging film is wrapped around the plurality of articles to form a primary package. The package assembly further comprises a secondary packaging film for bundling a plurality of packages, wherein the secondary packaging film comprises a heat shrinkable film according to embodiments of the present disclosure.

According to yet another embodiment of the present disclosure, a method of unitizing a polymer-wrapped primary package is provided. The method includes wrapping one or more primary packages with a polyurethane coated heat shrinkable film according to an embodiment of the present disclosure, and applying heat energy to reduce the size of the polyurethane coated heat shrinkable film to confine the primary packages within the polyurethane coated heat shrinkable film. During wrapping, a polyurethane coating is disposed proximal to one or more primary packages.

These and other examples are described in more detail in the detailed description. It is to be understood that both the foregoing summary and the following detailed description present embodiments of the technology, and are intended to provide an overview or framework for understanding the nature and character of the technology as it is claimed. The accompanying drawings are included to provide a further understanding of the technology, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operations of the technology. Moreover, the drawings and description are meant to be illustrative only and are not intended to limit the scope of the claims in any way.

Drawings

The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

fig. 1A is a schematic depicting a polyurethane coated single layer heat shrinkable film unitizing a plurality of primary packages according to one or more embodiments of the present disclosure.

Fig. 1B is a schematic depicting a polyurethane coated multilayer heat shrinkable film unitizing a plurality of primary packages according to one or more embodiments of the present disclosure.

Fig. 2 is a graph depicting comparative heat seal forces between multilayer films with a seal residence time of 0.3 seconds.

Fig. 3 is a graph depicting comparative heat seal forces between multilayer films with a seal residence time of 0.5 seconds.

Detailed Description

Definition of

The term "polymer" refers to a polymeric compound prepared by polymerizing monomers of the same or different types. Thus, the generic term polymer encompasses the term "homopolymer", which is commonly used to refer to polymers prepared from only one type of monomer, as well as the term "copolymer", which refers to polymers prepared from two or more different monomers.

"polyethylene" or "ethylene-based polymer" shall mean a polymer comprising greater than 50 mole percent of units derived from ethylene monomer. This includes ethylene-based homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include, but are not limited to: low Density Polyethylene (LDPE); linear Low Density Polyethylene (LLDPE); ultra Low Density Polyethylene (ULDPE); very Low Density Polyethylene (VLDPE); a single-site catalyzed linear low density polyethylene comprising both a linear low density resin and a substantially linear low density resin (m-LLDPE); medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

The term "LDPE" may also be referred to as "high pressure ethylene polymer" or "highly branched polyethylene" and is defined to mean that the polymer is partially or fully homopolymerized or copolymerized in autoclave or tubular reactors at pressures above 14,500psi (100MPa) using free radical initiators (e.g., peroxides) (see, for example, U.S. patent No. 4,599,392, which is incorporated herein by reference). The density of LDPE resins is typically in the range of 0.916 to 0.940 g/cm.

The term "LLDPE" includes resins prepared using Ziegler-Natta (Ziegler-Natta) catalyst systems as well as resins prepared using single site catalysts, including but not limited to dual metallocene catalysts (sometimes referred to as "m-LLDPE"), phosphinimines, and constrained geometry catalysts, and resins prepared using post-metallocene, molecular catalysts, including but not limited to bis (biphenylphenoxy) catalysts, also referred to as polyvalent aryloxyether catalysts. LLDPE includes linear, substantially linear or heterogeneous ethylene-based copolymers or homopolymers. LLDPE contains less long chain branching than LDPE and includes: a substantially linear ethylene polymer, further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 5,582,923, and U.S. Pat. No. 5,733,155; homogeneously branched ethylene polymers, such as those described in U.S. Pat. No. 3,645,992; heterogeneously branched ethylene polymers, such as those prepared according to the methods disclosed in U.S. Pat. No. 4,076,698; and blends thereof (e.g., blends as disclosed in U.S. patent No. 3,914,342 or U.S. patent No. 5,854,045). The LLDPE resin can be prepared by gas phase, solution phase or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art. The LLDPE resin can be prepared by gas phase, solution phase or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

The term "HDPE" refers to polyethylene having a density of about 0.940g/cm or greater, which is typically prepared with ziegler-natta catalysts, chromium catalysts, or even metallocene catalysts.

"polypropylene" or "propylene-based polymer" refers to a polymer comprising greater than 50 wt.% of units derived from propylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polypropylene known in the art include homopolymer polypropylene (hPP), random copolymer polypropylene (rcPP), impact copolymer polypropylene (hPP + at least one elastomeric impact modifier) (ICPP) or high impact polypropylene (HIPP), high melt strength polypropylene (HMS-PP), isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), and combinations thereof.

"multilayer structure" means any structure having more than one layer. For example, a multilayer structure (e.g., a film) can have two, three, four, five, or more layers. A multi-layer structure may be described as having layers named with letters. For example, a three-layer structure having a core layer B and two outer layers a and C may be represented as a/B/C. Also, a structure having two core layers B and C and two outer layers a and D is represented as a/B/C/D.

The terms "heat shrinkable film", "shrink film" or "collation shrink film" refer to any polymeric film material that can be shrunk to fit and secure one or more articles. This may include "primary packaging" and "secondary packaging". Without being bound by theory, shrinkage may occur in the shrink film due to relaxation of plastic orientation stresses during shrinkage. The shrink film may include a polymer such as, but not limited to, an ethylene-based polymer or a propylene-based polymer as mentioned above. The shrink film may be a multilayer structure or a single layer structure.

The term "primary package" refers to a polymeric film that is placed around an object and shrunk relative to its original dimensions to at least partially surround the object and secure the object therein and make up the primary package. The primary package is typically a vendable item placed on a store shelf or delivered to a consumer, such as a wrapped 6 unit pack beverage bottle.

The term "secondary package" refers to a polymeric film that is placed around a plurality of primary packages to provide a consolidated grouping of primary packages for ease of handling, shipping and storage, and to provide protection to the primary packages during handling, shipping and storage.

Unless otherwise indicated, the disclosure of any range in the specification and claims should be understood to encompass the range itself as well as any and all endpoints contained therein.

Referring to fig. 1A and 1B, an embodiment of the presently disclosed heat shrinkable film 10 includes a polymeric film 20 and a coating 30 on an outer surface of the polymeric film 20. Specific embodiments of the present application will now be described. The present disclosure may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth in the disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

Referring to fig. 1A, in one or more embodiments, the heat shrinkable film 10 includes a single layer polymer film 21 as its polymer layer 20. The monolayer film 21 comprises an ethylene-based polymer.

Referring to fig. 1B, in one or more embodiments, the heat shrinkable film 10 includes a multilayer film 22 as its polymeric film 20. The multilayer film 22 may include a first layer 24, a second layer 26, and at least one interior layer 28 between the first layer 24 and the second layer 26. As shown in the multilayer structure, the multilayer film 22 may be formed as a three-layer structure having a core layer B and two outer layers a and C, which are arranged as a/B/C. Also, the multilayer film 22 may be formed into a structure having two core layers B and C and two outer layers a and D, which are arranged as a/B/C/D. It will be appreciated that the multilayer structure of the embodiment of the multilayer film 22 provides a myriad of possibilities, such as a/B/A, A/B/C/a and a/B/C/B/D, with each possibility being covered by the present disclosure.

Referring again to the embodiment of fig. 1B, the first layer 24 of the multilayer film 22 comprises 30 to 100 weight percent (wt.%) of a first ethylene-based polymer having a density of 0.905 to 0.930 grams per cubic centimeter (g/cm)³) Melt index (I) measured according to ASTM D1238₂) From 0.1 to 2.0 grams/10 minutes (g/10min), and a peak melting point of less than 126 ℃ as measured by Differential Scanning Calorimetry (DSC). All individual values and subranges from 30 to 100 wt.% are included herein and disclosed herein; for example, the amount of the first ethylene-based polymer having the depicted characteristics can range from a lower limit of 30, 40, or 50 wt.% to an upper limit of 70, 80, 90, or 100 wt.%. For example, the amount of the first ethylene-based polymer may be 30 to 80 wt.%, or, in the alternative, 40 to 90 wt.%, or, in the alternative, 35 to 55 wt.%, or, in the alternative, 62 to 87 wt.%.

As shown, the first ethylene-based polymer may have a molecular weight of from 0.905 to 0.930g/cm³The density of (c). From 0.905 to 0.930g/cm³All individual values and subranges included herein and disclosed herein; for example, the first ethylene-based polymer may have a density of between 0.928, 0.925, 0.920, or 0.915g/cm³With an upper limit of 0.910, 0.915, 0.920 or 0.925g/cm³Between the lower limit of (c).

As shown, the first ethylene-based polymer may have a melt index (I) of 0.1 to 2.0 grams per 10 minutes measured according to ASTM D1238₂). All individual values and subranges from 0.1 to 2.0 grams/10 minutes are included herein and disclosed herein; for example, the first ethylene-based polymer may have a melt index between an upper limit of 2.0, 1.7, 1.4, 1.1, or 0.9 grams/10 minutes and an upper limit of 0.1, 0.2, 0.3, 0.4, 0.6, or 0.8 gramsBetween the lower limit of 10 minutes.

In some embodiments, the first ethylene-based polymer may have a peak melting point of 126 ℃ or less. In various other embodiments, the first ethylene-based polymer may have a peak melting point of 125 ℃ or less, 120 ℃ or less, 118 ℃ or less, or 115 ℃ or less. Additionally, in various embodiments, the first ethylene-based polymer may have a peak melting point greater than 95 ℃, greater than 100 ℃, or greater than 105 ℃.

Examples of the first ethylene-based polymer may include those available from Dow Chemical Company, Midland, MI, of Midland, michigan, including, for example, Dow^TMLDPE 132I、DOWLEX^TMNG2045B and ELITE^TM5111G。

Referring again to the multilayer film 22 embodiment of fig. 1B, the second layer 26 comprises 50 to 100 wt.% of a second ethylene-based polymer having a density of 0.905 to 0.970g/cm³And a peak melting point in the range of 100 ℃ to 135 ℃. All individual values and subranges from 50 to 100 wt.% are included herein and disclosed herein; for example, the amount of the second ethylene-based polymer having the depicted characteristics can range from a lower limit of 50, 60, or 70 wt.% to an upper limit of 80, 90, or 100 wt.%. For example, the second ethylene-based polymer may be 50 to 80 wt.%, or in the alternative, 60 to 90 wt.%, or in the alternative, 65 to 85 wt.%, or in the alternative, 62 to 87 wt.%.

As shown, the second ethylene-based polymer can have from 0.905 to 0.970g/cm³The density of (c). From 0.905 to 0.970g/cm³All individual values and subranges included herein and disclosed herein; for example, the first ethylene-based polymer may have a density of between 0.968, 0.960, 0.955 or 0.950g/cm³With an upper limit of 0.910, 0.915, 0.920 or 0.925g/cm³Between the lower limit of (c).

The second ethylene-based polymer may have a peak melting point in the range of 100 ℃ to 135 ℃. In some embodiments, the second ethylene-based polymer may have a different peak melting point than the first ethylene-based polymer. In various other embodiments, the second ethylene-based polymer may have an upper peak melting point of 135 ℃, 130 ℃, 125 ℃, or 120 ℃ and a lower peak melting point of 100 ℃, 105 ℃, 110 ℃, or 115 ℃.

Examples of the second ethylene-based polymer may include those available from Dow chemical company of Midland, Mich, including, for example, DOW^TMLDPE 132I、DOWLEX^TMNG 2045B、UNIVAL^TMDMDA 6200 NT7 and ELITE^TM5111G。

In one or more embodiments in which the film is a multilayer film, the at least one inner layer 28 comprises 10 to 50 wt.% of a third ethylene-based polymer having a density of 0.930 to 0.970g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃. All individual values and subranges from 10 to 50 wt.% are included herein and disclosed herein; for example, the amount of the third ethylene-based polymer having the depicted characteristics can range from a lower limit of 10, 20, or 30 wt.% to an upper limit of 30, 40, or 50 wt.%. For example, the amount of the third ethylene-based polymer may be 10 to 40 wt.%, or in the alternative, 20 to 50 wt.%, or in the alternative, 15 to 45 wt.%, or in the alternative, 22 to 47 wt.%.

The third ethylene-based polymer may have a density of 0.930 to 0.970g/cm³. From 0.905 to 0.930g/cm³All individual values and subranges included herein and disclosed herein; for example, the third ethylene-based polymer may have a density of between 0.968, 0.960, 0.955 or 0.950g/cm³With an upper limit of 0.930, 0.935, 0.940 or 0.950g/cm³Between the lower limit of (c).

In some embodiments, the third ethylene-based polymer may have a peak melting point in the range of 120 ℃ to 135 ℃. In various other embodiments, the second ethylene-based polymer may have an upper peak melting point of 135 ℃, 132 ℃, 130 ℃, or 128 ℃ and a lower peak melting point of 120 ℃, 122 ℃, 125 ℃, or 128 ℃.

Examples of the third ethylene-based polymer may include those available from the Dow chemical company of Midland, Mich, includingE.g. DOWLEX^TMNG 2038B and UNIVAL^TMDMDA 6200 NT7。

Specific examples of multilayer film components and configurations are provided after a brief description of the extent and width of the multilayer film of the heat shrinkable film. In one or more embodiments, the multilayer film comprises: a first layer 24 comprising 30 to 100 wt.% of a first ethylene-based polymer, a second layer 26 comprising 50 to 100 wt.% of a second ethylene-based polymer, and at least one inner layer 28 between the first layer 24 and the second layer 26, the inner layer comprising 10 to 50 wt.% of a third ethylene-based polymer. The first ethylene-based polymer may have a density of 0.905 to 0.930g/cm³Melt index (I)₂) From 0.1 to 2.0 g/10min and a peak melting point below 126 ℃. The second ethylene-based polymer may have from 0.905 to 0.970g/cm³And a peak melting point in the range of 100 ℃ to 135 ℃. Finally, the third ethylene-based polymer may have a density of from 0.930 to 0.970g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

In some embodiments, the multilayer film comprises: a first layer 24 comprising 50 to 70 wt.% of a first ethylene-based polymer, a second layer 26 comprising 50 to 70 wt.% of a second ethylene-based polymer, and at least one inner layer 28 between the first layer 24 and the second layer 26 comprising 20 to 40 wt.% of a third ethylene-based polymer. The first ethylene-based polymer and the second ethylene-based polymer may each have a melt index (I) of 0.1 to 0.4 grams/10 minutes₂) And a peak melting point of less than 120 ℃. The third ethylene-based polymer may have a density of from 0.930 to 0.970g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

In some embodiments, the multilayer film 22 comprises: a first layer 24 comprising 30 to 50 wt.% of a first ethylene-based polymer, a second layer 26 comprising 30 to 50 wt.% of a second ethylene-based polymer, and at least one inner layer 28 between the first layer 24 and the second layer 26, the inner layer comprising 60 to 80 wt.% of a third ethylene-based polymer. The first ethylene-based polymer and the second ethylene-based polymerThe di-ethylene-based polymers may each have a melt index (I) of 0.4 to 1.0 g/10min₂) And a peak melting point below 125 ℃. The third ethylene-based polymer may have from 0.910 to 0.930g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

In some embodiments, the multilayer film comprises: a first layer 24 comprising 60 to 80 wt.% of a first ethylene-based polymer, a second layer 26 comprising 60 to 80 wt.% of a second ethylene-based polymer, and at least one inner layer 28 between the first layer 24 and the second layer 26 comprising 60 to 85 wt.% of a third ethylene-based polymer. The first ethylene-based polymer and the second ethylene-based polymer may each have a melt index (I) of 0.3 to 1.2 grams/10 minutes₂) And a peak melting point in the range of 115 ℃ to 135 ℃. The third ethylene-based polymer may have from 0.910 to 0.930g/cm³And a peak melting point in the range of 120 ℃ to 135 ℃.

It should be understood that one or more of the first, second, and third ethylene-based polymers disposed in the first, second, and inner layers 24, 26, and 28, respectively, may comprise the same basic ethylene-based polymer. For example, first layer 24 and second layer 26 may each comprise one or more of the same polymers.

As described above, in certain embodiments, the ethylene-based polymer layer 20 is a single layer film 21 as shown in fig. 1B. In such embodiments, the monolayer film 21 comprises 30 to 60 wt.% of a fourth ethylene-based polymer having a density of 0.905 to 0.930g/cm³Melt index (I) measured according to ASTM D1238₂) From 0.1 to 0.9 g/10min and a peak melting point below 126 ℃. All individual values and subranges from 30 to 60 wt.% are included herein and disclosed herein; for example, the amount of the fourth ethylene-based polymer having the depicted characteristics may range from a lower limit of 30, 40, or 50 wt.% to an upper limit of 40, 50, or 60 wt.%. For example, the amount of the first ethylene-based polymer may be 30 to 50 wt.%, or in the alternative, 40 to 60 wt.%, or in35 to 55 wt.% in the alternative, or 42 to 57 wt.% in the alternative.

As shown, the fourth ethylene-based polymer may have a molecular weight of from 0.905 to 0.930g/cm³The density of (c). From 0.905 to 0.930g/cm³All individual values and subranges included herein and disclosed herein; for example, the fourth ethylene-based polymer may have a density of between 0.928, 0.925, 0.920, or 0.915g/cm³With an upper limit of 0.910, 0.915, 0.920 or 0.925g/cm³Between the lower limit of (c).

As shown, the fourth ethylene-based polymer may have a density melt index (I) of 0.1 to 0.9 grams/10 minutes measured according to ASTM D1238₂). All individual values and subranges from 0.1 to 2.0 grams/10 minutes are included herein and disclosed herein; for example, the fourth ethylene-based polymer may have a melt index between an upper limit of 0.9, 0.8, 0.7, or 0.6 grams/10 minutes and a lower limit of 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6 grams/10 minutes

In some embodiments, the fourth ethylene-based polymer may have a peak melting point of 126 ℃ or less. In various other embodiments, the first ethylene-based polymer may have a peak melting point of 125 ℃ or less, 120 ℃ or less, 115 ℃ or less, or 110 ℃ or less. Additionally, in various embodiments, the fourth ethylene-based polymer may have a peak melting point greater than 95 ℃, greater than 100 ℃, or greater than 105 ℃.

It will be appreciated that one or more of the fourth ethylene-based polymer may be the same as one or more of the first ethylene-based polymer, the second ethylene-based polymer, and the third ethylene-based polymer forming the multilayer film 22. For example, the first layer 24 and the monolayer film 21 of the multilayer film 22 may each comprise one or more of the same polymers.

Referring again to fig. 1B, in multilayer embodiments in which first layer 24 comprises less than 100 wt.% of a first ethylene-based polymer, first layer 24 of multilayer film 22 may further comprise one or more additional ethylene-based polymers, e.g., one or more Low Density Polyethylenes (LDPE) having a melt index of 0.1 to 5 grams/10 minutes, a polyethyleneOne or more additional densities of 0.930g/cm³Or less and a melt index of 0.1 to 5 g/10min, or one or more Linear Low Density Polyethylenes (LLDPE) having a density of 0.940g/cm³Or higher and a melt index of 0.1 to 5 g/10 min. LDPE can be added to increase melt strength, which is beneficial for the extrusion process. LLDPE may be added to increase the flexibility of the resulting film. HDPE may be added to increase the strength of the resulting film and to obtain barrier properties. In one or more embodiments, the first layer 24 may include up to 40 wt.% HDPE to increase the strength characteristics of the multilayer film 22. Additional ethylene-based polymers that may comprise the remainder of the first layer 24 of the multilayer film 22 include those known under the name AFFINITY^TM、DOWLEX^TM、UNIVAL^TM、AGILITY^TM、TUFLIN^TM、ATTANE^TM、INNATE^TMAnd ELITE^TMThose commercially available from the Dow chemical company, including, for example, UNIVAL^TMDMDA 6200 NT7。

Further, in multilayer embodiments in which the second layer 26 of the multilayer film 22 comprises less than 100 wt.% of a second ethylene-based polymer, the second layer 26 further comprises one or more additional ethylene-based polymers, e.g., one or more Low Density Polyethylenes (LDPE) having a melt index of 0.1 to 5 grams/10 minutes, one or more additional densities of 0.930g/cm³Or less and a melt index of 0.1 to 5 g/10min, or one or more Linear Low Density Polyethylenes (LLDPE) having a density of 0.940g/cm³Or higher and a melt index of 0.1 to 5 g/10 min. Additional ethylene-based polymers that may comprise the remainder of the second layer 26 of the multilayer film 22 include those known under the name AFFINITY^TM、DOWLEX^TM、UNIVAL^TM、AGILITY^TM、TUFLIN^TM、ATTANE^TM、INNATE^TMAnd ELITE^TMThose commercially available from the dow chemical company of midland, michigan.

Further, in embodiments where the inner layer 28 comprises less than 100 wt.% of a third ethylene-based polymer multilayer, the inner layer 28 of the multilayer film 22 may further comprise one or moreAdditional ethylene-based polymers, e.g., one or more Low Density Polyethylenes (LDPE) having a melt index of 0.1 to 5 g/10min, and one or more additional densities of 0.930g/cm³Or less and a melt index of 0.1 to 5 g/10min, or one or more Linear Low Density Polyethylenes (LLDPE) having a density of 0.940g/cm³Or higher and a melt index of 0.1 to 5 g/10 min. In one or more embodiments, the inner layer 28 may include up to 70 wt.% LDPE to increase the melt strength characteristics of the multilayer film 22 during extrusion. In one or more embodiments, the inner layer 28 may include up to 300 wt.% LLDPE to increase the flexibility of the multilayer film 22. Additional ethylene-based polymers that may comprise the remainder of the inner layer 28 of the multilayer film 22 include those known under the name AFFINITY^TM、DOWLEX^TM、UNIVAL^TM、AGILITY^TM、TUFLIN^TM、ATTANE^TM、INNATE^TMAnd ELITE^TMThose commercially available from the Dow chemical company, e.g. including DOW^TMLDPE 132I and DOWLEX^TMNG 2045B。

Having a density of 0.905 to 0.930g/cm³Density of 0.1 to 0.9 g/10min, melt index (I)₂) And a peak melting point of less than 126 ℃ and forming 30 to 60 wt.% monolayer film 21 include those commercially available from DOW chemical company, midland, michigan, including, for example, DOW^TMLDPE 132I。

For embodiments in which the single layer film 21 comprises less than 100 wt.% of the fourth ethylene-based polymer, the single layer film 21 may further comprise one or more additional ethylene-based polymers, for example, one or more Low Density Polyethylenes (LDPE) having a melt index of 0.1 to 5 grams/10 minutes, one or more additional densities of 0.930g/cm³Or less and a melt index of 0.1 to 5 g/10min, or one or more Linear Low Density Polyethylenes (LLDPE) having a density of 0.940g/cm³Or higher and a melt index of 0.1 to 5 g/10 min. Additional ethylene-based polymers that may comprise the remainder of the monolayer film 21 include those known under the name AFFINITY^TM、DOWLEX^TM、AGILITY^TM、TUFLIN^TM、ATTANE^TM、INNATE^TMAnd ELITE^TMThose commercially available from the Dow chemical company, including, for example, DOWLEX^TM2045B and DOWLEX^TM2050B。

In some embodiments, one or more of the multilayer film 22 or the monolayer film 21 may include one or more additives. Depending on the requirements of a particular application, additives may include, but are not limited to, antistatic agents, colorants, dyes, lubricants, fillers (e.g., Ti 0)₂Or CaC0₃) An opacifying agent, a nucleating agent, a processing aid, a pigment, a primary antioxidant, a secondary antioxidant, a UV stabilizer, an antiblock agent, a slip agent, a tackifier, a flame retardant, an antimicrobial agent, an odor reducing agent, an antifungal agent, an oxygen scavenger, a moisture scavenger, and combinations thereof.

Conventional shrink films are formulated to adhere to themselves or other polymeric films when subjected to heat. This phenomenon is desirable when sealing the package. However, as previously discussed, in the unitization process, a plurality of previously shrink-wrapped vendible items may also be wrapped with shrink film into a single unit for each transport and storage. Blocking or adhesion between the films would be problematic as the vendible items may be damaged, resulting in loss or disposal of the product. To avoid this detrimental effect, shrink films for unitization can be formulated and manufactured to avoid blocking or adhesion.

The present invention provides a polyurethane based coating 30 on the outer surface of the heat shrinkable film 10. In the case of the multilayer film 22 forming the ethylene-based polymer layer 20, the outer surface is the outer surface of the first layer 24. The term "polyurethane-based coating" is used to indicate that when cured, the coating 30 primarily comprises polyurethane, but in some embodiments, the coating 30 may also include unreacted reactants (e.g., polyols, isocyanates, etc.) as well as other additives.

In some embodiments, the polyurethane of the coating 30 is the polymerization reaction product of a hydroxyl terminated polyol and an isocyanate functional prepolymer. In some embodiments, the isocyanate functional prepolymerComprises an aromatic isocyanate. Without wishing to be bound by theory, it is believed that the aromatic isocyanate provides the desired anti-adhesion properties to the resulting polyurethane. Examples of aromatic isocyanates that may be used in some embodiments of the present disclosure include any or all isomers of Toluene Diisocyanate (TDI) and/or any or all isomers of methylene diphenyl diisocyanate (MDI). The hydroxyl terminated polyol can comprise at least one of a hydroxyl terminated polyether, a hydroxyl terminated polyester, or a combination thereof. In one or more embodiments, the hydroxyl terminated polyol comprises VORANOL from Dow chemical company of Midland, Mich^TM220-110N polyether polyol (propylene glycol initiated, homopolymer diol with a molecular weight of 1000), VORANOL from Dow chemical company of Midland, Mich.)^TM220-260 polyether polyol (homopolymer diol of nominal molecular weight 425) and trimethylolpropane.

Furthermore, the polyurethane of the coating 30 is solvent-based. In one or more embodiments, the polyurethane may be dissolved in ethyl acetate and hexane for application to the ethylene-based polymer layer 20.

The polyurethane of the coating 30 may be formed by mixing two separate components together in a specified mixing ratio and then curing upon reaction between the two components. In some embodiments, two reactant components may be prepared to provide 1: 1 (ratio of hydroxyl-terminated polyol to isocyanate functional prepolymer) to facilitate measurement and mixing. In some embodiments, such a mixing ratio may be in the range of 1: 0.2 to 1: 2, or a salt thereof. At such mixing ratios, in some embodiments, the isocyanate index is between about 1: 3 to about 3: 1, in the above range. The isocyanate index is defined as the ratio of the equivalents of isocyanate used to the theoretical equivalents multiplied by 100. The theoretical equivalent is equal to 1 equivalent of isocyanate (A-side) per 1 equivalent of B-side compound. The amount of free isocyanate in component a may be from 1% to 15%. In some embodiments, the polyurethane may be a one-part isocyanate-terminated prepolymer that reacts with ambient moisture or humidity to complete its cure.

In some embodiments, coating 30 is formed from a polyol having a molecular weight between 100 and 4700 daltons using branching imparting multifunctional agents such as triisopropanolamine and trimethylolpropane. The materials so selected, when reacted together and combined with certain non-reactive additives, may advantageously provide the coated film with desired heat resistance, blocking resistance, or other characteristics.

In one or more embodiments, the non-reactive additive in the coating 30 comprises a release wrap. The release packaging may include one or more oils, one or more waxes, or both. In various embodiments, the one or more oils comprise refined corn oil. Further, in various embodiments, the one or more waxes include Synaceti 125, commercially available from wiener smith corporation of cleveland, ohio (Werner g.smith, inc.cleveland, OH).

The coating 30 can be applied to the outer surface of the polymeric film 20 using a variety of techniques, typically by techniques including, but not limited to, gravure coating and flexographic coating, for example. Other thin coating techniques may also be used. Those skilled in the art can readily adapt their process to apply a polyurethane coating onto the polymer film 20 to obtain the coated heat shrinkable film 10 of the present disclosure using equipment for applying solvent-based coatings and adhesives. To obtain sufficient dynamic viscosity, the target solids at the time of application will depend on the particular coating, but in some embodiments may be in the range of 15% to 80%.

In some embodiments, the amount of coating 30 applied to the polymer film 20 may be at least 0.1 grams per square meter. As used herein, the coating amount is determined by measuring the difference between the weight of the ethylene-based polymer layer 20 before coating and after the coating 30 is applied and dried. In some embodiments, the amount of coating 30 applied to the ethylene-based polymer layer 20 is up to 5 grams per square meter. It should be appreciated that the coating 30 does not have a maximum coating thickness, and is limited only by economic factors that avoid unnecessarily thick and expensive coatings beyond those needed to provide the desired coating characteristics and performance. In some embodiments, the amount of coating 30 applied to the film is 0.1 to 0.8 grams per square meter (g/m)²). From 0.1 to 5g/m²All individual values and subranges thereof are included herein and disclosed herein; for example, the coating amount may be from a lower limit of 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6g/m²To an upper limit of 0.7, 0.8, 0.9, 1, 3 or 5g/m². For example, in some embodiments, the amount of coating 30 can be 0.3 to 0.8g/m²。

In one or more embodiments, the coating 30 is applied according to a defined pattern of coated and uncoated areas on the outer surface of the polymer film 20. When the coated heat shrinkable film 10 is typically provided in roll form, the uncoated regions are positioned in alignment with the sealed regions when the coated heat shrinkable film 10 is used as a wrap around an object. The absence of the coating 30 in the uncoated areas allows the coated heat shrinkable film 10 to seal or adhere to itself when the object is wrapped with the coating 30, retaining the benefit of eliminating adhesion when aligned with the coated areas. For the multilayer film 22 shown in fig. 1B, the coating 30 is applied according to a defined pattern of coated and uncoated areas on the outer surface of the first layer 24 or the second layer 26 of the multilayer film 22 shown in fig. 1B. Similarly, for a single layer film 21 as shown in fig. 1A, the coating 30 is applied according to a defined pattern of coated and uncoated areas on the outer surface of the single layer film 21.

Embodiments of the present disclosure also provide articles formed from any of the heat shrinkable films 10 described herein. Examples of such articles may include secondary packaging for grouping several products together to facilitate handling, transporting, and storing the unitized groups of products.

Referring to fig. 1A and 1B, the application of a heat shrinkable film 10 as an over shrink film to unitize a plurality of primary packages 60 is illustrated. Each primary package 60 is shown containing a plurality of individual articles 62, with primary packaging film 64 bundling the individual articles 62 into a marketable primary package 60. The primary packaging film 64 may be a polymeric film. The heat shrinkable film 10 is then used as a secondary packaging film to bundle a plurality of primary packages 60 into larger packages for ease of handling, shipping and storage, and to provide protection to the primary packages 60 throughout the logistics chain. The polyurethane coating 30 serves as an intermediate functional layer between the primary packaging film 64 of the primary package 60 and the ethylene-based polymer layer 20 of the heat shrinkable film 10 to substantially reduce or completely prevent adhesion therebetween. The anti-adhesion helps maintain the integrity of the primary packaging film 64.

A method of unitizing a polymer-wrapped primary package 60 includes wrapping one or more of the primary packages 60 with the heat shrinkable film 10 of the present disclosure and applying heat energy to reduce the size of the heat shrinkable film 10, thereby restraining the primary package 60 within the heat shrinkable film 10. The coating 30 comprising polyurethane is disposed proximate the one or more primary packages 60 during wrapping such that the polymeric film 64 of the individual products 62 that are bundled with the primary packages is exposed to the coating 30 and isolated from the underlying ethylene-based polymer layer 20.

It should be appreciated that primary package 60 may contain various types of individual products 62 therein. While fig. 1A and 1B show plastic bottles as individual products 62, additional non-limiting examples include food products such as pet food or rice, glass bottles, household items, or other products that are unitized into a consolidated bundle during supply chain operations.

In various embodiments, the heat shrinkable film 10 may be heated to at least about 120 ℃, at least about 140 ℃, at least about 150 ℃, at least about 180 ℃, or even greater than 250 ℃ to induce one or more shrinkages of the heat shrinkable film 10 around the primary package 60. In an embodiment, the heat shrinkable film 10 may be heated to a temperature in the range of about 140 ℃ to about 190 ℃ or about 150 ℃ to about 180 ℃ to induce shrinkage of the heat shrinkable film 10 about one or more of the primary packages 60. The heating hold time may be from about 1 second to about 1 minute, from about 2 seconds to about 30 seconds, or from about 3 seconds to about 20 seconds.

The thickness of the heat shrinkable film 10 used to unitize the plurality of primary packages 60 of wrapped individual products 62 into a single grouping as a secondary package may be selected based on a number of factors including, for example, the size of the primary packages 60, the volume of the primary packages 60, the weight of the primary packages 60 and the individual products 62, the contents of the primary packages 60, the desired characteristics of the secondary package, and other factors. In some such embodiments, the heat shrinkable film 10 has a thickness of 20 to 500 micrometers. All individual values and subranges from 20 to 500 microns are included herein and disclosed herein; for example, the heat shrinkable film 10 can have a thickness from a lower limit of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180 or 190 microns to an upper limit of 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 220, 250, 280, 300, 330, 350, 370, 400, 430, 450, 470 or 500 microns. It should be noted that a thickness of 25.4 micrometers is equal to 1 mil, providing a disclosed range of about 1 mil to 20 mils for the thickness of the heat shrinkable film.

Test method

Unless otherwise indicated herein, the following analytical methods are used for the descriptive aspects of the present invention:

melt index

Melt index I₂And I₁₀Measured at 190 ℃ and under 2.16kg and 10kg loads, respectively, according to ASTM D-1238. Their values are reported in g/10 min. "melt flow rate" is used for polypropylene-based resins and is determined according to ASTM D1238(230 ℃, 2.16 kg).

Density of

Samples for density measurement were prepared according to ASTM D4703. Measurements were made within one hour of sample pressing according to ASTM D792, method B.

Peak melting point

The peak melting point was determined by Differential Scanning Calorimetry (DSC) in which the film was conditioned at 230 ℃ for 3 minutes and then cooled at a rate of 10 ℃ per minute to a temperature of-40 ℃. After holding the film at-40 ℃ for 3 minutes, the film was heated to 200 ℃ at a rate of 10 ℃ per minute.

Dart falling device

The film dart test measures the energy that causes a plastic film to fail under specified impact conditions produced by a free falling dart. The test results are energy expressed as the weight of the projectile falling from a specified height (which would cause 50% of the test specimen to fail).

Dart impact strength (Dart) was measured according to ASTM D1709, method A using a 26 inch + -0.4 inch (66cm + -1 cm) drop height and a polished hemispherical aluminum head with a diameter of 38.10 + -0.13 mm.

Secant modulus

MD (machine direction) and CD (cross direction) 2% secant moduli were determined according to ASTM D882 with a crosshead speed of 20 inches/minute. The sample width was 1 inch and the initial clamp spacing was 4 inches. The reported 2% secant modulus value is the average of five measurements.

Tear test

Type B-constant radius Elmendorf tear test was performed in Machine Direction (MD) and Cross Direction (CD) according to ASTM D1922.

Puncture resistance

Puncture resistance was measured on ZWICK Z010 model using TestXpertII software. The sample size was 6 "x 6" and at least 5 measurements were made to determine the average puncture value. A 1000 newton load cell is used with a round product rack. The samples were 4 inch diameter circular samples. The puncture resistance procedure followed ASTM D5748-95 standard with modifications to the probes described herein. The piercing probe was a spherical polished stainless steel probe with a diameter of 1/2 inches. No gauge length; the probe should be as close to the sample as possible, but not touching the sample. The probe is set by lifting it until it contacts the sample. The probe is then gradually lowered until it does not contact the sample. The crosshead is then set to zero. The distance is about 0.10 inches, considering the maximum travel distance. The crosshead speed used was 250 mm/min. The thickness is measured in the middle of the sample. The thickness of the film, the distance traveled by the crosshead, and the peak load can be used to determine the puncture by the software. The piercing probe is cleaned after each specimen. Puncture energy is the area under the curve (in joules) of the load/elongation curve.

Young's modulus

The MD (machine direction) and CD (cross direction) young's moduli (i.e., elastic moduli) were obtained in the same apparatus as the secant modulus determined according to ASTM D882. The sample width was 1 inch and the initial fixture spacing was 4 inches and the crosshead speed was 20 inches/minute. The reported young's modulus values are the average of five measurements. Young's modulus is the slope of the linear portion of the stress-strain plot.

Free shrinkage rate

The unlimited linear heat shrinkage of the plastic film and the sheet was measured according to the Dow interior method based on ASTM D2732-70. 5 samples with a diameter of 50mm were prepared and conditioned for 40h at 23. + -. 2 ℃ and 50. + -. 5% relative humidity prior to testing. The tests were carried out in HANATEK Mod 2010. When the test temperature of 150 ℃ was reached and stabilized, a few drops of silicone oil were added to the copper plate. When the oil diffused and stabilized at a given temperature, the sample was placed flat on the hot plate for 20 seconds with the utmost care. The samples were then removed from the carrier tray and placed in a cooling zone, concentrated, so that the percent shrinkage could be read.

The percentage of free shrinkage is given by: % of [ (L)₀-L_f)/L₀]× 100, wherein L₀Initial length of the edge, L_fLength after shrinkage. The free shrinkage values are calculated in the MD (machine direction) and CD (cross direction) directions and are the average of five measurements.

Heat seal test

Heat seal measurements were performed on the films on a commercial tensile tester according to ASTM F-88 (technique A). The heat seal test is a method of evaluating the strength (seal strength) of a seal in a flexible barrier material. It is accomplished by measuring the force required to separate a test strip of material containing the seal and identifying the mode of sample failure. Seal strength is related to opening force and package integrity. Prior to cutting, the film was conditioned at 23 ℃ (+2 ℃) and 50% (+ 5%) r.h. (relative humidity) for a minimum of 40 hours according to ASTM D-618 (procedure a). A sheet of about 11 inches in length and about 8.5 inches in width was then cut from the three-layer coextruded laminated film in the machine direction. The sheets were heat sealed in the machine direction on a Brugger HSG-C sealer under the following conditions over a range of temperatures: sealing pressure or retention force: 0.138N/mm²(20psi) and residence times of 0.3 and 0.5 seconds.

Some embodiments of the invention will now be described in detail in the following examples.

Examples of the invention

Preparation of monolayer films of polyurethane coatings

A heat shrinkable monolayer film of an ethylene-based polymer was produced by blown film extrusion as comparative film 1. Comparative film 1 was prepared according to standard formulations currently used for commercial ethylene-based polymer heat shrinkable films. The formulations are provided in table 1 below, and the properties of the individual resins are provided in table 2. Comparative Film 1 was produced on a Collin Blown Film (Collin blow Film) line with a Blow Up Ratio (BUR) of 3.0, a die diameter of 80mm, a die gap of 1.8mm and corona treatment with 40 dynes. In addition, comparative film 1 was prepared under the following processing conditions: the melting temperature was 219 ℃, the mold temperature was 235 ℃, the RPM was 59RPM, the throughput was 22.43 kg/h, the pressure was 258bar, and a 377 mm plate (layflat).

Table 1-comparative film 1 formulation

TABLE 2 selected resin Properties

Resin composition	Density (g/cm)3)	Melt index (g/10min)	Peak melting Point (. degree. C.)
				DOWTMLDPE 132I	0.921	0.25	110
DOWLEXTM2045.11B	0.921	1.0	122
				DOWLEXTM2050B	0.950	0.95	130

Comparative film 1 was coated with 0.8g/m using a Labo Combi 400 laminator operating at 100 feet/min²From the Dow chemical company of Midland, Mich^TMHGT 202/2021。OPULUX^TMHGT 202/2021 is a solvent-based polyurethane according to the present disclosure. Coating OPULUX to be produced^TMThe heat shrinkable film of HGT was named inventive film 2. The layer structure and formulation are provided in table 3.

TABLE 3 inventive film 2 formulation

Performance testing of monolayer films

Comparative testing of comparative film 1 and inventive film 2 was done to assess the adhesion of the shrink film to the primary package. Specifically, each of comparative film 1 and inventive film 2 was used to bundle six different types of primary packages. A description of each type of primary package is provided in table 4. The primary packages were bundled together with each of comparative film 1 and inventive film 2, respectively, and passed through a Smipack BP shrink tunnel operating at a speed of 2 meters per minute and a temperature of 180 ℃. At 2 m/min and 180 c through the typical temperature range used in the shrink tunnel of a packaging line.

TABLE 4 Primary packaging for the study

The adhesion between the inner wrap of the unitized bundle of six package types and the over-shrink film of comparative film 1 and inventive film 2 was tested. The test was completed by removing the over-shrunk film from the bundled package and checking for melting or stickiness to the primary package and damage to the original package due to removal of the comparative film 1 and the inventive film 2. Adhesion results are provided in tables 5 and 6.

Table 5-adhesion results for comparative film 1

As shown in table 5, all primary packages except package 5 were damaged by the use of comparative film 1. Specifically, comparative film 1 exhibited adhesion to PE formulated primary packaging. That is, packages 1, 2, and 3 were damaged by the over shrink film adhered to comparative film 1 and thus would not be displayed on a shelf in a retail environment. With regard to package 4, comparative film 1 was not specifically adhered to the outer surface of PET food bag comprising PET, but did adhere to the edge of the exposed PE core layer. As expected, the comparative film 1 did not stick to the inner package, since the package 5 consisted of PP/PE/PP. Finally, comparative film 1 exhibits some adhesion to package 6, requiring a force to separate and spoiling the appearance of the primary package. Evidence of adhesion after shrinkage is left on the surface of the removed comparative film 1 and the surface of the package 6.

Table 6-adhesion results for inventive film 2

After passing through the shrink tunnel, the inventive film 2 does not stick to any primary packaging. Each of the six primary packages is tightly wrapped and bundled by the inventive film 2 and the integrity of the primary package is maintained without any damage when the inventive film 2 is removed.

Measurement on applying OPULUX^TMHGT polyurethane coating to generate inventive film 2 compares the retention of mechanical and shrinkage properties of film 1. The mechanical and shrinkage characteristics need to be maintained to achieve adequate shrinkageAnd package robustness, thereby limiting the unitization of individual packages throughout the distribution chain. The mechanical and shrink characteristics of comparative film 1 and inventive film 2 are provided in table 7. Various properties were evaluated, including dart resistance according to ASTM D1709; elmendorf tear evaluation was performed in the Cross Direction (CD) and Machine Direction (MD) according to ASTM D1922; puncture resistance evaluation according to ASTM D5748; secant modulus according to ASTM D882 of 2%; tensile properties according to ASTM D882; and shrinkage in the Cross Direction (CD) and Machine Direction (MD) at 150 ℃ according to ASTM D2732.

TABLE 7 mechanical and free shrink characteristics of the exemplary films

	Comparative film 1	Inventive film 2
			Dart (method A) (g)	184±15	265±15
Elmendorf MD (g)	336±21	354±27
			Elmendorf CD (g)	1113±29	807±33
Puncture energy (J)	4.60±0.32	3.68±0.095
			Puncture resistance (J/cm)3)	6.84±0.531	6.16±0.175
Secant modulus 2% MD (MPa)	270±5	257±15
			Secant modulus 2% CD (MPa)	282±12	288±15
Young's modulus MD (MPa)	418	452
			Young's modulus CD (MPa)	475	441
Free shrinkage at 150 ℃ MD (%)	57.5	40
			Free shrinkage at 150 ℃ CD (%)	20	12

The inventive film 2 substantially maintains the mechanical and shrink characteristics of the uncoated film of the comparative film 1 and provides a film suitable for secondary packaging and unitization. Although the shrinkage measured in the Machine Direction (MD) at 150 ℃ was reduced by 30%, insufficient shrinkage was not actually observed.

Preparation of multilayer film of polyurethane coating

Three ethylene-based polymer heat-shrinkable multilayer films were produced by blown film extrusion. The formulation of each of the prepared multilayer films is provided in table 8 below, and the properties of the individual resins are provided in table 9. A first multilayer film, designated comparative film 3, having first and second layers composed of the same polymer formulation and an inner layer composed of a second polymer formulation was prepared. A second multilayer film, designated comparative film 4, having first and second layers composed of the same polymer formulation and an inner layer composed of a second polymer formulation was also prepared. Finally, a third multilayer film, designated comparative film 5, was also prepared having first and second layers composed of the same polymer formulation and an inner layer composed of a second polymer formulation. Comparative film 3, comparative film 4 and comparative film 5 were each produced on a kolin blown film line with a Blow Up Ratio (BUR) of 3.0, a die diameter of 80mm, a die gap of 1.8mm, and corona discharge with 40 dynes.

TABLE 8 multilayer film formulation

TABLE 9 selected resin Properties

Resin composition	Density (g/cm)3)	Melt index (g/10min)	Peak melting Point (. degree. C.)
				DOWTMLDPE 132I	0.921	0.25	110
DOWLEXTM2045B	0.921	1.0	119
				DOWLEXTM2038B	0.935	1.0	126
ELITETM5111G	0.925	0.85	123
				UNIVALTMDMDA 6200NT7	0.953	0.38	131

Each of comparative film 3, comparative film 4 and comparative film 5 was used at 0.1g/m²、0.3g/m²And 0.5g/m²OPULUX^TMHGT2020/2021 was coated to produce a series of inventive films described in Table 10. OPULUX^TMIs a two-component reactive polyurethane, wherein OPULUX^TM2020-OH end-capping and OPULUX^TM2021 is-NCO-terminated. Formation of OPULUX Using bifunctional Poliol 1000 and 2000^TMAnd reacted with Toluene Diisocyanate (TDI) or methyl diphenyl diisocyanate (MDI). In addition, OPULUX^TMIs solvent based and is dissolved in ethyl acetate and hexane for the application.

TABLE 10 OPULUX^TMHGT 2020/2021 coated multilayer film

Each of comparative film 3, comparative film 4 and comparative film 5 also used 0.1g/m²、0.3g/m²And 0.5g/m²Available from Lanxess Chemical Company, Cologne, Germany, and

bottom 51 UD coating, resulting in a series of comparative polyurethane coated example films described in table 11.Bottom 51 UD is a polyurethane dispersion in water containing a long chain difunctional poliol PM 2000 reacted with isophorone diisocyanate (IPDI) and dimethylpropionic acid (DMPA). The reaction was terminated with Trimethylamine (TEA) and Propylenediamine (PDA) was added to consume any isocyanate (NCO) residues. Therefore, the temperature of the molten metal is controlled,bottom 51 UD includes and OPULUX^TMAliphatic isocyanates which are contradictory to the aromatic isocyanates of HGT 2020/2021.

Watch (A)Multilayer film coated by Bottom 51 UD

Performance testing of multilayer films

For comparison of the bottom packaging with multilayer films according to the invention (inventive films 6 to 14) having a coating of OPULUXTMHGT2020/2021 with respect to the uncoated multilayer film (comparative film 4) with the adhesive with multilayer film according to the invention (comparative film 4)Comparison of Bottom films of Bottom 51 UD coatings (films 15-23 of the invention) adhesion properties of Bottom packages were completed for heat seal studies. Specifically, each of the multilayer example films under study (example films 3-23) was subjected to a heat seal test with an uncoated standard polyethylene collation shrink film (comparative film 4) to simulate contact of such an outer film wrapped around the inner unitized package and through a shrink tunnel. The heat seal test was completed according to ASTM F88, with a dwell force of 20 pounds per square inch (psi) in the first test, a dwell time of 0.3 seconds(s), and 0.5 seconds in the second test. The test was also completed at a sealing temperature of 150 ℃ and a sealing temperature of 180 ℃ for each film combination and residence time. The resulting heat seal force (gram force/square inch-grf/in) required to separate the test example film from the ordinary uncoated polyethylene shrink film of comparative film 4²) Provided in tables 12 to 17. Specifically, tables 12, 13, and 14 provide the heat seal force required to separate the molten films with a dwell time of 0.3 seconds and tables 15, 16, and 17 provide the heat seal force required to separate the molten films with a dwell time of 0.5 seconds.

Table 12-heat sealing force-uncoated multilayer film-residence time: 0.3 second

TABLE 13 Heat sealing force-OPULUX^TMCoated multilayer film

Residence time: 0.3 second

Watch (A)

Coated multilayer film-residence time: 0.3 second

Table 15-heat sealing force-uncoated multilayer film-residence time: 0.5 second

TABLE 16 Heat sealing force-OPULUX^TMCoated multilayer film-residence time: 0.5 second

Watch (A)

Coated multilayer film-residence time: 0.5 second

And (a) adhesion between two uncoated multilayer films and (b) an uncoated multilayer film and

application of OPULUX according to embodiments of the present disclosure, in comparison to adhesion between Bottom 51 UD coated multilayer films^TM2020/2021 coating to a multilayer film significantly reduces the heat seal force. Referring to FIG. 2, application of OPULUX can be visually seen for a 0.3 second dwell time seal^TM2020/2021, the reduction in sealing force. Similarly, referring to FIG. 3, for a seal with a dwell time of 0.3 seconds, it can be seen visually that OPULUX is applied^TM2020/2021, the reduction in sealing force. In addition, it is also sharply seen in both FIG. 2 and FIG. 3 that the density varies from 0.1g/m with the coating density²Increased to 0.5g/m²The decrease in sealing force increases. Despite the inclusion of aliphatic isocyanates

The Bottom 51 UD shows a reduction in heat sealing force, but includes an OPULUX of an aromatic isocyanate functional prepolymer^TM2020/2021 excellent performanceAs will be apparent.

Obviously, modifications and variations are possible without departing from the scope of the present disclosure, which is defined in the appended claims. Rather, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

It will be apparent from the claims and drawings that the use of the singular also includes the possibility of the plural. For example, reference to a coating also implicitly includes reference to at least one coating.