LOW DENSITY POLYETHYLENE WITH ENHANCED ADHESION-TO-ALUMINUM FOIL BY BLENDING-IN ACID COPOLYMER RESINS

Abstract

The polymer blend includes at least 90% by weight low density polyethylene (LDPE) polymer and from 1% to 10% by weight acid copolymer based on the total weight of the polymer blend. In the polymer blend, the LDPE polymer has a melt index (I? 2#191) from 2 g/10 min to 8 g/10 min as determined in accordance with ASTM D1238, and a molecular weight distribution from 5 to 10.5. In the polymer blend, the acid copolymer is a polymerized reaction product of: at least 60% by weight ethylene, based on the total weight of the monomers present in the ethylene acid copolymer; from 1% to 20% by weight monocarboxylic acid monomer, based on the total weight of the monomers present in the ethylene acid copolymer; and from 0 to 20% by weight alkyl acrylate monomer, based on the total weight of the monomers present in the ethylene acid copolymer.

Claims

1. A polymer blend comprising: at least 90% by weight low density polyethylene (LDPE) polymer based on the total weight of the polymer blend, the LDPE polymer having a melt index (I.sub.2) from 2 g/10 min to 16 g/10 min as determined in accordance with ASTM D1238 (190° C., 2.16 kg), and a molecular weight distribution (MWD) from 5 to 10.5 as determined by a conventional gel permeation chromatography method; and from 1% to 10% by weight acid copolymer based on the total weight of the polymer blend, wherein the acid copolymer is a polymerized reaction product of: at least 60% by weight ethylene, based on the total weight of the monomers present in the ethylene acid copolymer; from 1% to 20% by weight monocarboxylic acid monomer, based on the total weight of the monomers present in the ethylene acid copolymer; and from 0 to 20% by weight alkyl acrylate monomer, based on the total weight of the monomers present in the ethylene acid copolymer.

2. The polymer blend of claim 1, wherein the LDPE polymer has a density of 0.910 g/cm.sup.3 to 0.935 g/cm.sup.3 and an MWD of 8.5 to 10.5.

3. The polymer blend of claim 1, wherein the melt index of the LDPE polymer is from 2 g/10 min to 5.8 g/10 min as determined in accordance with ASTM D1238 (190° C., 2.16 kg).

4. The polymer blend of claim 1, wherein the melt index of the LDPE polymer is from 2 g/10 min to 4.5 g/10 min as determined in accordance with ASTM D1238 (190° C., 2.16 kg).

5. The polymer blend of claim 1, further comprising a linear low density polyethylene (LLDPE) polymer having a melt index (I.sub.2) from 0.5 g/10 min to 30 g/10 min as determined in accordance with ASTM D1238 (190° C., 2.16 kg), and a density of 0.910 g/cm.sup.3 to 0.935 g/cm.sup.3.

6. The polymer blend of claim 1 any preceding claim, further comprising an ethylene copolymer having a melt index (I.sub.2) from 0.5 g/10 min to 30 g/10 min as determined in accordance with ASTM D1238 (190° C., 2.16 kg), wherein the ethylene copolymer comprises the reaction product of: at least 50% by weight ethylene, based on the total weight of the monomers present in the ethylene acid copolymer; and from 0.1% to 40% by weight comonomer, based on the total weight of the monomers present in the ethylene copolymer, the comonomer being chosen from vinyl acetate, acrylate, or carboxylic acid comonomer.

7. The polymer blend of claim 1, wherein the polymer blend comprises from 2% to 6% by weight acid copolymer, based on the total weight of the polymer blend.

8. The polymer blend of claim 1, wherein the polymer blend comprises from 2% to 6% by weight acid copolymer, based on the total weight of the polymer blend.

9. The polymer blend of claim 1, wherein the acid copolymer has a melt index (b) from 2 g/10 min to 30 g/10 min as determined in accordance with ASTM D1238 (190° C., 2.16 kg).

10. The polymer blend of claim 1, wherein the alkyl acrylate monomer comprises methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, or combinations thereof; and the monocarboxylic acid monomer comprises acrylic acid, methacrylic acid, or combinations thereof.

11. The polymer blend of claim 1, wherein the ethylene acid copolymer comprises at least 65% by weight ethylene monomer, based on the total weight of the monomers in the ethylene acid copolymer; from 1% to 15% by weight monocarboxylic acid monomer, based on the total weight of the monomers in the ethylene acid copolymer; and from 0 to 15% by wt. alkyl acrylate based on the total weight of the monomers in the ethylene acid copolymer.

12. The polymer blend of claim 1, wherein the ethylene acid copolymer comprises at least 75% by weight ethylene monomer, based on the total weight of the monomers in the ethylene acid copolymer; from 2% to 6% by weight monocarboxylic acid monomer, based on the total weight of the monomers in the ethylene acid copolymer; and from 1% to 15% by wt. alkyl acrylate based on the total weight of the monomers in the ethylene acid copolymer.

13. A coated metal substrate comprising: a metal substrate; and a coating comprising the polymer blend of claim 1 adhered to the metal substrate.

14. The coated metal substrate of claim 13, wherein the metal substrate comprises aluminum.

15. The coated metal substrate of claim 13, wherein the coating has peel strength of at least 0.6 N/in as measured by ASTM F904.

16. The coated metal substrate of claim 13, wherein the coating has peel strength of at least 1 N/in as measured by ASTM F904.

17. The coated metal substrate of claim 13, wherein the coating has peel strength of at least 2 N/in as measured by ASTM F904.

18. An extruded article comprising the polymer blend of claim 1.

Description

EXAMPLES

[0067] Twenty-five example compositions were prepared, and polymer characteristics of each were measured. Each of the example compositions was a blend of a LDPE homopolymer and an acid copolymer. The properties of the LDPE homopolymers are listed in Table 1.

TABLE-US-00001 TABLE 1 Polymer Properties of the LDPE homopolymer Melt Index MWD Density Product (dg/min) (Mw/Mn) (g/cm.sup.3) AGILITY EC 7030 2.5 8.97 0.918 AGILITY EC 7000 3.9 8.82 0.919 LDPE 5005 5.7 9.29 0.922 LDPE PG 7008 7.5 8.83 0.918 LDPE 6211 2.3 11.00 0.918 LDPE 722 8.0 10.81 0.918 LDPE 4010 10 11.89 0.917 LDPE 4016 16 9.54 0.919

[0068] Example 1 was a polymer blend prepared from 95% by weight AGILITY™ EC 7030 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, 6% by weight iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min. Example 2 was a polymer blend prepared from 95% by weight AGILITY™ EC 7030 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, 10% by weight iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0069] Example 3 was a polymer blend prepared from 95% by weight AGILITY™ EC 7030 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0070] Example 4 was a polymer blend prepared from 95% by weight AGILITY™ EC 7000 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0071] Example 5 was a polymer blend prepared from 95% by weight AGILITY™ EC 7000 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0072] Example 6 was a polymer blend prepared from 95% by weight LDPE 5005 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0073] Example 7 was a polymer blend prepared from 95% by weight LDPE PG 7008 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0074] Example 8 was a polymer blend prepared from 95% by weight LDPE 4016 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0075] Example 9 was a polymer blend prepared from 95% by weight LDPE 6211 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0076] Example 10 was a polymer blend prepared from 95% by weight LDPE 722 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0077] Example 11 was a polymer blend prepared from 95% by weight LDPE 4010 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 2% by weight methacrylic acid, and 6% of iso-butyl acrylate, and 92% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0078] Example 12 was a polymer blend prepared from 95% by weight LDPE 6211 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0079] Example 13 was a polymer blend prepared from 95% by weight LDPE 5005 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0080] Example 14 was a polymer blend prepared from 95% by weight LDPE 722 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0081] Example 15 was a polymer blend prepared from 95% by weight LDPE PG 7008 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0082] Example 16 was a polymer blend prepared from 95% by weight LDPE 4010 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0083] Example 17 was a polymer blend prepared from 95% by weight LDPE 4016 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 9% by weight methacrylic acid, and 91% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0084] Example 18 was a polymer blend prepared from 95% by weight LDPE 6211 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, and 10% of iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0085] Example 19 was a polymer blend prepared from 95% by weight LDPE 5005 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, and 10% of iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0086] Example 20 was a polymer blend prepared from 95% by weight LDPE 722 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, and 10% of iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0087] Example 21 was a polymer blend prepared from 95% by weight LDPE PG 7008 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, and 10% of iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0088] Example 22 was a polymer blend prepared from 95% by weight LDPE 4010 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, and 10% of iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0089] Example 23 was a polymer blend prepared from 95% by weight LDPE 4016 manufactured by Dow, Inc. as the LDPE component and 5% by weight acid copolymer. The acid copolymer included 10% by weight methacrylic acid, and 10% of iso-butyl acrylate, and 80% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 10 dg/min.

[0090] Example 24 was a polymer blend prepared from 97% by weight AGILITY™ EC 7030 manufactured by Dow, Inc. as the LDPE component and 3% by weight acid copolymer. The acid copolymer included 4% by weight methacrylic acid, and 15% of iso-butyl acrylate, and 81% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 27 dg/min (g/10 mins).

[0091] Example 25 was a polymer blend prepared from 97% by weight AGILITY™ EC 7000 manufactured by Dow, Inc. as the LDPE component and 3% by weight acid copolymer. The acid copolymer included 4% by weight methacrylic acid, and 15% of iso-butyl acrylate, and 81% by weight ethylene based on the total weight of the monomers of the acid copolymer and had a melt index of 27 dg/min (g/10 mins).

[0092] Characteristics of each of the polymer blends and comparative polymers are summarized in Table 2.

TABLE-US-00002 TABLE 2 Polymer Blend Peel Strength Average peel strength Peel strength Peel Strength mean (N/in) improved improved Run Absolute* (N/in)** (%)*** LDPE Homopolymers Agility EC 7030 1.56 — — Agility EC 7000 0.62 — — LDPE 5005 0.20 — — LDPE 722 0.11 — — LDPE PG 7008 0.12 — — LDPE 4010 0.06 LDPE 4016 0.07 Examples Example 1 2.10 0.6 35 Example 2 2.49 0.9 60 Example 3 2.56 1.0 65 Example 4 1.72 1.1 175 Example 5 2.96 2.3 375 Example 6 1.02 0.8 418 Example 7 0.80 0.7 591 Example 8 0.75 0.7 1012 Example 9 Not processable**** Example 10 0.55 0.4 401 Example 11 0.16 0.1 163 Example 12 Not processable**** Example 13 0.25 0.05 27 Example 14 0.20 0.1 87 Example 15 0.47 0.4 302 Example 16 0.14 0.07 119 Example 17 0.41 0.3 510 Example 18 Not processable**** Example 19 0.32 0.12 24 Example 20 0.17 0.06 53 Example 21 0.32 0.21 178 Example 22 0.12 0.06 100 Example 23 0.29 0.22 334 Example 24 2.35 NA**** NA Example 25 2.96 2.3 375 *Peel bond strength is reported in average peel strength from 1 inch of extension to 4 inches of extension or until the sample fails if less than 4 inches; and the bonded substrate was an aluminum foil laminate. **The Peel strength improved is the calculated by the difference between the peel strength of the pure LDPE and the peel strength of the LDPE and acid copolymer. ***The Peel strength improved (%) was calculated by the following formula: [00005]$\frac{\begin{array}{c}\left(\mathrm{adhesion}\mathrm{strength}\mathrm{of}\mathrm{LDPE}+\mathrm{ACR}\right)-\\ \left(\mathrm{adhesion}\mathrm{strength}\mathrm{of}\mathrm{pure}\mathrm{LDPE}\right)\end{array}}{\mathrm{peel}\mathrm{strength}\mathrm{of}\mathrm{pure}\mathrm{LDPE}}*100$****The blend cannot be run in an extrusion coating line with line speed of greater than 440 ft/min (134 meters per minute).

[0093] The addition of 5% by weight of an acid copolymer to a LDPE polymer resulted in a polymer blend having a greater peel strength than the LDPE polymer.