Adhesive composition based on ethylene copolymers, useful for extrusion-coating and extrusion-lamination on a variety of supports

Abstract

The invention concerns an adhesive composition consisting of at least one ethylene polymer or copolymer, said composition comprising at least one unsaturated carboxylic acid ester comonomer, and at least one functional comonomer, useful in an extrusion-coating process for application on a support or in an extrusion-lamination process for bonding together several supports of different type or not, in a wide temperature range. The invention is characterized in that said composition has an unsaturated carboxylic acid ester content higher than 5 wt % and in that the functional comonomer consists of at least one reactive function in the form of an acid group, anhydride or epoxy, whereof the proportion is less than 1 wt % of the composition. Said composition has advantageous uses, in particular for bonding together substrates selected among aluminum, paper or cardboard, cellophane, films based of polyethylene, polypropylene, polyamide, polyester, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyacrylonitrile (PAN) resins, oriented or not, metal-coated or not, physically or chemically treated or not and films coated with a thin inorganic barrier layer, such as polyester (PET, SiOx or AlOx).

Claims

1. A multilayer structure comprising: a) an adhesive composition consisting of: at least one ethylene polymer or copolymer; at least one alkyl methacrylate, the alkyl group having from 1 to 24 carbon atoms; and at least one functional comonomer, wherein said alkyl methacrylate(s) are present at from 6 to 25 weight percent of the composition and wherein said functional comonomer comprises at least one reactive function in the form of maleic anhydride, wherein in said adhesive composition the content of maleic anhydride is between 0.15% and 0.6% by weight of the composition, wherein the adhesive composition is extruded at temperatures ranging from 290 to 320° C. to form the multilayer structure, and b) a support, wherein said support is chosen from aluminum; paper or board; cellophane; films based on polyethylene, polypropylene, polyamide, polyester, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC) or polyacrylonitrile (PAN) resins, wherein said films are oriented or unoriented, metallized or unmetallized, treated or untreated by physical or chemical means; and films coated with a thin inorganic barrier layer, wherein said multi-layer structure is formed by an extrusion-coating process or an extrusion lamination process.

2. A multilayer structure comprising: a) an adhesive composition consisting of: at least one ethylene polymer or copolymer; at least one alkyl methacrylate, the alkyl group having from 1 to 24 carbon atoms; and at least one functional comonomer, wherein said alkyl methacrylate(s) are present at from 6 to 25 weight percent of the composition and wherein said functional comonomer comprises at least one reactive function in the form of acid, anhydride or epoxide group, the level of which is less than 1% by weight of the composition, wherein the adhesive composition is extruded at temperatures ranging from 300° C. to 320° C. to form the multilayer structure, and b) a support, wherein said support is a polyethylene terephthalate; wherein said multi-layer structure is formed by an extrusion-coating process or an extrusion lamination process.

3. The multilayer structure as claimed in claim 2, wherein the adhesive composition consists of the at least one ethylene polymer or copolymer, at least one alkyl methacrylate, and the at least one functional comonomer.

4. A multilayer structure comprising: a) an adhesive composition comprising at least one ethylene polymer or copolymer, at least one unsaturated carboxylic acid ester type comonomer, and at least one functional comonomer, wherein said unsaturated carboxylic acid ester type comonomer is at least one alkyl methacrylate, the alkyl group having from 1 to 24 carbon atoms, and wherein said alkyl methacrylate(s) are present at from 10 to 25 weight percent of the composition and wherein said functional comonomer is maleic anhydride, the level of which is between 0.05% and 0.9% by weight of the composition, wherein the adhesive composition is formed by high-pressure radical polymerization of all the comonomers in a single step, wherein the adhesive composition is extruded at temperatures ranging from 290° C. to 300° C. to form the multilayer structure, and b) a support, wherein said support is aluminum film; wherein said multi-layer structure is formed by an extrusion-coating process or an extrusion lamination process.

5. The multilayer structure as claimed in claim 4, wherein the adhesive composition consists of the at least one ethylene polymer or copolymer, at least one alkyl methacrylate, and the at least one functional comonomer.

6. A multilayer structure comprising: a) an adhesive composition comprising at least one ethylene polymer or copolymer, at least one unsaturated carboxylic acid ester type comonomer, and at least one functional comonomer, wherein said unsaturated carboxylic acid ester type comonomer is at least one alkyl methacrylate, the alkyl group having from 1 to 24 carbon atoms, and wherein said alkyl methacrylate(s) are present at from 10 to 25 weight percent of the composition and wherein said functional comonomer comprises at least one reactive function in the form of an acid, anhydride or epoxide group, the level of which is less than 1% by weight of the composition, wherein the adhesive composition is extruded at temperatures ranging from 310° C. to 320° C. to form the multilayer structure, and b) a support, wherein said support is chosen from aluminum film, wherein said multi-layer structure is formed by an extrusion-coating process or an extrusion lamination process.

7. The multilayer structure as claimed in claim 6, wherein in said adhesive composition the functional comonomer is chosen from unsaturated carboxylic acid anhydrides.

8. The multilayer structure as claimed in claim 6, wherein the adhesive composition is formed by melt-blending at least two ethylene copolymers obtained by high-pressure radical polymerization, of which one at least comprises the functional comonomer.

9. The multilayer structure as claimed in claim 6, wherein the adhesive composition consists of the at least one ethylene polymer or copolymer, at least one alkyl methacrylate, and the at least one functional comonomer.

10. The multilayer structure as claimed in claim 6, wherein in said adhesive composition said functional monomer is maleic anhydride.

11. A multilayer structure according to claim 6, wherein the adhesive composition is formed by high-pressure radical polymerization of all the comonomers in a single step.

12. A multilayer structure according to claim 6, wherein the functional comonomer comprises at least one reactive function in the form of an acid, anhydride or epoxide group, the level of which is between 0.05% and 0.9% by weight of the composition.

13. The multilayer structure as claimed in claim 6, wherein in said adhesive composition said functional monomer is maleic anhydride.

Description

EXEMPLARY EMBODIMENTS

(1) General Conditions:

(2) Adhesives of different compositions (the characteristics of which are specified in Table 1) were coextruded with one layer of radical low-density polyethylene (rLDPE) and layered on various supports using a COLLIN extrusion-coating line. The operating conditions were chosen so as to impose a draw ratio (ratio of the drawing speed to the speed of the molten polymer exiting the die) of 5.8.

(3) It will be noted that in the composite structures obtained that are described in the following examples, the polyethylene layer may be completely formed by extrusion or partially by lamination on a polyethylene film.

(4) Strips having a width of 15 mm were cut out from the center of the width and along the extrusion direction. The polymer coating was manually separated from the support over a distance of a few centimeters, then the two sections thus released (respectively aluminum and polymer coating) were then each placed in one of the two jaws of an MTS SYNERGIE 200 tensile testing machine. The peel strength was then assessed with a peeling rate of 200 mm/min. Five testpieces were tested per adhesive reference. The tests were carried out in the 15 minutes following the implementation (peel at to) and also after conditioning for one month at 23° C. and 50% relative humidity.

(5) TABLE-US-00001 TABLE 1 Adhesive wt % wt % wt % wt % MFI (2.16 kg reference Acrylate MAH MAA GMA @ 190° C.) LDPE — — — — 4.1 Resin 1  6.2(BuA) 3.1 — — 5.5 Resin 2 18.2(MeA/BuA) 0.29 — — 9.9 Resin 3 13.6(MeA) 0.32 — — 8.3 Resin 4 17.7(BuA) 2.9 — — 5.8 Resin 5 18.2(MeA) 0.29 — — 7.7 Resin 6 21.3(MeA) 0.3 — — 8.5 Resin 7 15.8(MeA/BuA) — 0.45 — 8.9 Resin 8 24.1(MeA) — — 0.8 6.9

(6) The low-density polyethylene (LDPE) was LACQTENE® LD 304 from Total Petrochemicals.

(7) Resin 1 was the ethylene/butyl acrylate/maleic anhydride (MAH) terpolymer sold under the trademark LOTADER® 3210 by Arkema.

(8) Resin 4 was the ethylene/butyl acrylate/maleic anhydride (MAH) terpolymer sold under the trademark LOTADER® 3410 by Arkema.

(9) Resins 2, 3, 5 to 8 were compositions according to the invention.

(10) Resin 2 was obtained by blending an ethylene/butyl acrylate copolymer containing 18.6 wt % of acrylate with an ethylene/methyl acrylate (17.7 wt %)/maleic anhydride (1 wt %) terpolymer, in a weight ratio of around 70/30, in a FAIREX 45/26 D type single-screw extruder, having a rotation speed of 50 rpm, at a temperature of 150° C.

(11) Resins 3, 5 and 6 were ethylene/methyl acrylate/maleic anhydride terpolymers obtained by high-pressure radical polymerization.

(12) Resin 7 was obtained by blending, in an extruder as for resin 2, an ethylene/methyl acrylate copolymer containing 20 wt % of acrylate with an ethylene/butyl acrylate (6 wt %)/methacrylic acid (1.5 wt %) terpolymer, in a weight ratio of around 70/30.

(13) Resin 8 was obtained by blending, in an extruder as for the preceding resin, an ethylene/methyl acrylate copolymer containing 24 wt % of acrylate with an ethylene/methyl acrylate (25 wt %)/glycidyl methacrylate (8 wt %) terpolymer, (sold under the trademark LOTADER® AX 8900 by Arkema), in a weight ratio of around 90/10.

(14) The abbreviations MeA, BuA, MAH, MAA and GMA denote methyl acrylate, butyl acrylate, maleic anhydride, methacrylic acid and glycidyl methacrylate respectively.

(15) MFI is the melt flow index measured at a temperature of 190° C. under a load of 2.16 kg (according to standard ASTM D 1238).

Example 1

(16) The support used was an aluminum film having a thickness of 37 μm. The structure produced was: aluminum (37 μm)/adhesive (10 μm)/rLDPE (100 μm). Two extrusions temperatures (290-300° C. and 310-320° C. respectively) were assessed for each of the adhesives tested (including those being used as comparative adhesives).

(17) The results obtained are given in Table 2 below (the values measured are followed by the standard deviation):

(18) TABLE-US-00002 TABLE 2 Peel strength at Peel strength at Adhesive reference t.sub.0 (N/15 mm) 1 month (N/15 mm) Material temperature: 290-300° C. Resin 1 (comparative) 2.9 ± 0.1 2.5 ± 0.1 Resin 2 3.9 ± 0.3 4.2 ± 0.2 Resin 3 3.7 ± 0.1 3.7 ± 0.1 Resin 4 (comparative) 3.8 ± 0.1 3.5 ± 0.1 LDPE (comparative)   1 ± 0.05 0.18 ± 0.05 80% resin 1 in LDPE 2.2 ± 0.1 2.1 ± 0.1 (comparative) 20% resin 1 in LDPE 1.6 ± 0.1 0.8 ± 0.1 (comparative) Material temperature: 310-320° C. Resin 1 (comparative) 3.3 ± 0.1 3.1 ± 0.0 Resin 2 5.7 ± 0.1 5.9 ± 0.0 Resin 3 5.4 ± 0.1 5.0 ± 0.0 Resin 7 5.0 ± 0.1 5.2 ± 0.0 Resin 4 (comparative) 5.0 ± 0.1 4.4 ± 0.1 LDPE (comparative) 1.3 ± 0.1 0.8 ± 0.1 80% resin 1 in LDPE 2.9 ± 0.1 2.8 ± 0.1 (comparative) 20% resin 1 in LDPE 1.9 ± 0.1 1.8 ± 0.1 (comparative)

(19) In particular, the improved adhesion characteristics of the compositions according to the invention (resins 2, 3 and 7) were observed, especially after aging, relative to the normal adhesives used in extrusion (resins 1 and 4, comparative tests).

(20) In addition, the blend of resin 1 with LDPE, according to the teaching of Examples 9 to 13 of Patent EP 222 789, cited as prior art, gave even lower adhesion values than with resin 1 used alone.

Example 2

(21) For this example, two oriented polyethylene terephthalate (OPET) supports of reference MYLAR 813 (14 μm thick) and MYLAR 800 (12 μm) from DuPont Teijin were used.

(22) In the case of MYLAR 813, the adhesive was deposited onto the side of the film that had not been treated by physical or chemical means (by a “primer”), and in both cases a corona treatment was applied in-line to the PET film just before the deposition of the adhesive.

(23) The structure produced was: PET film/adhesive (10 μm)/rLDPE (30 μm). The results obtained are given in Table 3 below:

(24) TABLE-US-00003 TABLE 3 Average Peel Peel Nature of material strength strength Adhesive the temperature at t.sub.0 at 1 month reference support (° C.) (N/15 mm) (N/15 mm) Resin 1 MYLAR 813 310 0.6 ± 0   2.5 ± 0.5 (comparative) thickness Resin 4 14 μm 310 2.8 ± 0   4.7 ± 0.2 (comparative) Resin 5 310 4.8 ± 0.5   6 ± 0.2 Resin 6 310 5.2 ± 0.2 6.1 ± 0.3 Resin 6 MYLAR 800 290 2.4 ± 0.1 4.6 ± 0.1 Resin 6 thickness 300 2.5 ± 0.1 4.8 ± 0.3 Resin 6 12 μm 310 3.9 ± 0.3 5.2 ± 0.2 Resin 7 310 3.2 ± 0.1 5.0 ± 0.2 Resin 8 310 5.1 ± 0.1 5.8 ± 0.2 Resin 6 320 4.8 ± 0.2 4.7 ± 0.1

(25) The highly improved adhesion characteristics of the compositions according to the invention (resins 5, 6, 7 and 8) were observed relative to the comparative resins 1 and 4.

Example 3

(26) In this example, the adhesives were deposited onto an oriented nylon-6 film having a thickness of 25 μm. The structure of the samples was the following: OPA film/adhesive (10 μm)/rLDPE (85 μm). The results obtained are given in Table 4 below:

(27) TABLE-US-00004 TABLE 4 Adhesive Peel strength at Peel strength at reference t.sub.0 (N/15 mm) 1 month (N/15 mm) Material temperature: 310-320° C. Resin 1 1.7 ± 0.2 4.7 ± 0.1 Resin 2 3.7 ± 0.1 5.5 ± 0.1 Resin 4 4.1 ± 0.1 7.4 ± 0.2 Resin 6 5.8 ± 0.2 7.5 ± 0.1

(28) Resin 6 according to the invention also had improved adhesion characteristics on this type of substrate made from oriented polyamide.

(29) In all the tests, a large reduction in the odors emitted during the processing of the resins according to the invention, and in the final products, was also observed relative to conventional resins.

(30) In addition, the resins of the invention in granule form have a remarkable insensitivity to moisture.