General purpose thermoplastic adhesive for multilayer films

Abstract

Embodiments of the present disclosure relate to a thermoplastic adhesive composition comprising: at least one maleic anhydride grafted ethylene-based polymer; at least one ethylene / alpha-olefin / non-conjugated diene interpolymer having a molecular weight distribution (MWD) > 2.5, where MWD = Mw / Mn, where Mw is the weight average molecular weight and Mn is the number average molecular weight, both of which are measured by gel permeation chromatography; a very low density polyethylene (VLDPE) having a density in the range of 0.885 to 0.915 g / cm 3 ; and optionally at least one ethylene alkyl (meth)acrylate copolymer, where the alkyl group comprises one to four carbon atoms.

Description

[0001] This application is a divisional application of Chinese patent application No. 201980048721.0 (filed on June 26, 2019, entitled "General thermoplastic adhesive for multilayer films").

[0002] Cross-reference to related applications

[0003] This application claims priority to European Patent Application No. 18305862.7, filed on 2 July 2018, the entire disclosure of which is incorporated herein by reference. Technical Field

[0004] Embodiments of this disclosure generally relate to thermoplastic adhesive compositions, and more specifically to thermoplastic adhesive compositions used as adhesive layers in multilayer films. Background Technology

[0005] Packaging films are increasingly being manufactured using co-extrusion systems and processes. In turn, these systems are constantly evolving. Therefore, it is advantageous to develop materials for multilayer films that can be manufactured using a variety of co-extrusion systems, including blown film, cast film, injection molding, sheet / bottle, etc. A few years ago, extruders were typically capable of co-extruding three to five layers, while today, machines often need to co-extrude nine or more layers, for example, by feeding these layers into the same number of extruders.

[0006] Multilayer films used in food packaging, such as shrink films, sealable films, cap films, and packaging films, can be produced using various co-extrusion and biaxially oriented methods, such as tenter frame processes, triple-bubble processes, or double-bubble processes. The Triple Bubble® process, developed by Kuhne Anlagenbau GmbH, can produce co-extruded biaxially oriented high-performance multilayer films in a single operation without the need to separately prepare a biaxially oriented mechanical support layer and laminate it onto a second multilayer film to obtain the final structure. This greatly simplifies the manufacturing process for such films. However, because triple-bubble films typically contain many different layers, maintaining a reasonable adhesive strength of at least 2 N / 15 mm after biaxial orientation between all the different layers (e.g., between polyethylene and polyamide layers, or between polypropylene and polyamide layers, or between polyester and polypropylene layers, or between polyester and polyethylene layers) is a challenge.

[0007] Therefore, conventional triple-bubble films utilize a variety of different co-extrudeable adhesive compositions (also known as adhesive layers), each of which is specifically tailored for the particular polymer layers that need to be bonded together. Consequently, there is a ongoing need for universal adhesive layer formulations that can provide suitable adhesion across the various polymer layers in a multilayer film. Summary of the Invention

[0008] Embodiments of this disclosure address the discussed need by providing an adhesive composition (adhesive layer) that provides adhesion to both polar and nonpolar substrates after biaxial orientation in co-extrusion and bidirectional orientation processes (e.g., tenter frame process, double bubble process, or triple bubble process). This eliminates or at least reduces the need for so many different adhesive layer formulations in triple bubble films.

[0009] According to one embodiment, a thermoplastic adhesive composition is provided. The thermoplastic adhesive composition comprises: at least one maleic anhydride-grafted vinyl polymer; at least one ethylene / α-olefin / non-conjugated diene interpolymer with a molecular weight distribution (MWD) ≥ 2.5, wherein MWD = Mw / Mn, where Mw is the weight-average molecular weight and Mn is the number-average molecular weight, both measured by gel permeation chromatography; and a density of 0.885 to 0.915 g / cm³. 3 Very low density polyethylene (VLDPE) within the range.

[0010] In another embodiment, the thermoplastic adhesive composition comprises at least one ethylene alkyl (meth)acrylate copolymer, wherein the alkyl group comprises one to four carbon atoms. Attached Figure Description

[0011] The following detailed description of specific embodiments of the present disclosure is best understood when read in conjunction with the accompanying drawings.

[0012] Figure 1 This is a bar graph describing the adhesive strength performance of the adhesive layer formulation of the present invention and a comparative adhesive formulation, wherein each formulation bonds a polyamide and a polyethylene layer in 13 layers of triple bubble film.

[0013] Figure 2 This is a bar graph illustrating the adhesive strength performance of the adhesive layer formulation of the present invention and a comparative adhesive formulation, wherein each formulation bonds a polyester and polypropylene copolymer layer in 13 layers of triple bubble film. Detailed Implementation

[0014] definition

[0015] The term "polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers. Therefore, the general term polymer encompasses the term "homopolymer," which is typically used to refer to a polymer prepared from only one type of monomer; and "copolymer," which refers to a polymer prepared from two or more different monomers. As used herein, the term "interpolymer" refers to a polymer prepared by polymerizing at least two different types of monomers. Therefore, the general term interpolymer includes copolymers and polymers prepared from two or more different types of monomers, such as terpolymers.

[0016] "Polyethylene" or "vinyl polymer" should mean a polymer comprising more than 50% by molar amount units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include: low-density polyethylene (LDPE); linear low-density polyethylene (LLDPE); ultra-low-density polyethylene (ULDPE); very low-density polyethylene (VLDPE); single-point catalytic linear low-density polyethylene, which includes both linear low-density resin and substantially linear low-density resin (m-LLDPE); medium-density polyethylene (MDPE); and high-density polyethylene (HDPE).

[0017] As used herein, "polypropylene" or "propylene-based polymer" refers to a polymer contained in polymeric form, meaning a polymer comprising more than 50% by molar amount of units derived from propylene monomers. This includes propylene homopolymers, random copolymer polypropylene, impact copolymer polypropylene, propylene / α-olefin copolymers, and propylene / α-olefin copolymers.

[0018] The term "LDPE" can also be referred to as "high-pressure ethylene polymer" or "highly branched polyethylene," and is defined as meaning that the polymer is partially or fully homopolymerized or copolymerized in an autoclave or tubular reactor at pressures above 14,500 psi (100 MPa) using a free radical initiator (such as a peroxide) (see, for example, U.S. Patent No. 4,599,392, which is incorporated herein by reference). The density of LDPE resin is typically in the range of 0.916 g / cc to 0.935 g / cc.

[0019] The term "LLDPE" includes resins prepared using Ziegler-Natta catalyst systems, as well as resins prepared using mono-site catalysts (including, but not limited to, bis(biphenylphenoxy) catalysts (sometimes referred to as "m-LLDPE"), phosphine imides, 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 aryloxy ether catalysts)). LLDPE includes linear, substantially linear, or heterogeneous ethylene copolymers or homopolymers. LLDPE contains fewer long-chain branches than LDPE and comprises: substantially linear ethylene polymers, further defined in U.S. Patent Nos. 5,272,236, 5,278,272, 5,582,923, and 5,733,155; homogeneously branched linear ethylene polymer compositions, such as those in U.S. Patent No. 3,645,992; heterogeneously branched ethylene polymers, such as those prepared according to the method disclosed in U.S. Patent No. 4,076,698; and blends thereof (such as those disclosed in U.S. Patent Nos. 3,914,342 or 5,854,045). LLDPE resins 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.

[0020] As used herein, vinyl polymer resins typically in the range of 0.928 to 0.940 g / cc are sometimes referred to as medium-density polyethylene (“MDPE”) or linear medium-density polyethylene (LMDPE). Polyethylene with a density greater than 0.940 g / cc is high-density polyethylene (“HDPE”), which is typically prepared using Ziegler-Natta catalysts, chromium catalysts, or even single-center catalysts such as metallocene catalysts.

[0021] Very low density polyethylene (“VLDPE”) can be produced by many different methods, resulting in polymers with different properties. However, they typically have densities less than 0.916 g / cc, for example, 0.880 to 0.915 g / cc, or 0.900 to 0.915 g / cc.

[0022] "(Meth)acrylic acid" includes methacrylic acid and / or acrylic acid, and "(meth)acrylate" includes methacrylate and / or acrylate. Alkyl (meth)acrylate refers to alkyl acrylate and / or alkyl methacrylate.

[0023] "Multilayer structure" or "multilayer membrane" means any structure having more than one layer. For example, a multilayer structure (e.g., a membrane) can have two, three, four, five, or more layers. In some embodiments, a multilayer membrane may include 13 or even more layers.

[0024] Furthermore, when amounts, concentrations, or other values ​​or parameters are given as a list of ranges, preferred ranges, or higher and lower preferred values, it should be understood that all ranges formed by any pair of any upper or preferred range values ​​and any lower or preferred range values ​​are specifically disclosed, whether or not the ranges are disclosed individually. When numerical ranges are stated herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. When defining ranges, it is not intended to limit the scope of the invention to the specific values ​​stated. When indicating the presence of a component in a range starting from 0, the component is an optional component (i.e., it may or may not be present). When present, the optional component may be at least 0.1% by weight of the composition or copolymer.

[0025] When materials, methods, or machinery are described herein using the terms “known to those skilled in the art,” “conventional,” or other synonyms or phrases, such terms indicate that materials, methods, and machinery that are conventional at the time of filing this application are covered by this embodiment.

[0026] thermoplastic adhesive composition

[0027] Embodiments of this disclosure relate to thermoplastic co-extrudeable adhesive compositions comprising: at least one maleic anhydride-grafted vinyl polymer; at least one ethylene / α-olefin / non-conjugated diene interpolymer with a molecular weight distribution (MWD) ≥ 2.50, wherein MWD = Mw / Mn; and very low density polyethylene (VLDPE) with a density of 0.885 to 0.915 g / cc.

[0028] Maleic anhydride-grafted vinyl polymers

[0029] Maleic anhydride-grafted vinyl polymers are vinyl polymers grafted with maleic anhydride graft monomers. Suitable vinyl polymers for use as maleic anhydride-grafted vinyl polymers include, but are not limited to, polyethylene homopolymers and copolymers with α-olefins, copolymers of ethylene and vinyl acetate, and copolymers of ethylene with one or more alkyl (meth)acrylates. In a specific embodiment, the maleic anhydride-grafted vinyl polymer may include one or more of maleic anhydride-grafted linear low-density polyethylene (LLDPE), maleic anhydride-grafted polyethylene elastomers, or combinations thereof.

[0030] When the vinyl polymer is a polyethylene homopolymer or a copolymer of ethylene and one or more α-olefins, the vinyl polymer can be linear or substantially linear. Suitable α-olefin comonomers (which can be aliphatic or aromatic) can include C3-C4. 20 α-olefins, C3-C 16 α-olefins or C3-C 10 α-olefin. In one or more embodiments, the α-olefin may be a C3-C olefin selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. 10 Aliphatic α-olefins. In one embodiment, the α-olefin is propylene.

[0031] As used herein, the term "substantially linear" refers to a polymer backbone replaced by long-chain branches ranging from 0.01 to 3 long-chain branches per 1000 carbons. The long-chain branches have the same comonomer distribution as the polymer backbone and may have the same length as the polymer backbone. The length of the long-chain branches is greater than the carbon length of the short-chain branches, which are formed by α-olefin comonomers incorporated into the polymer backbone. In contrast, as used herein, the term "linear" refers to a polymer backbone lacking measurable or verifiable long-chain branches, i.e., the polymer backbone being replaced by less than 0.01 long-chain branches per 1000 carbons. The degree of long-chain branching can be assessed using carbon-13 nuclear magnetic resonance (NMR). 13 It can be determined by C-NMR spectroscopy and quantified using the Randall method (Rev. Macromol.Chem. Phys., C29 (2 &3), 1989, p.285-297).

[0032] In one or more embodiments, the maleic anhydride-grafted vinyl polymer may have a melt index (I2) of 1 to 500 g / 10 min, or 1 to 20 g / 10 min, or 1 to 10 g / 10 min, or 1 to 5 g / 10 min, or 2 to 4 g / 10 min, as measured according to ASTM method D1238 at 190ºC and 2.16 kg.

[0033] In a further embodiment, the density of the maleic anhydride-grafted vinyl polymer, measured according to ASTM Method No. D792-91, is less than 0.900 g / cc, or from 0.860 to about 0.900 g / cc. Other density ranges may be from about 0.870 to about 0.890 g / cc, or from 0.875 to about 0.885 g / cc. (1 cc = 1 cm³) 3 )

[0034] In one or more embodiments, the maleic anhydride-grafted vinyl polymer comprises up to 10 wt.%, up to 5 wt.%, or 1 to 4 wt.% of maleic anhydride-grafted monomers, based on the total weight of the maleic anhydride-grafted vinyl polymer. The weight percentage of the vinyl polymer is complementary to the amount of the maleic anhydride-grafted monomers, such that the sum of the weight percentages of the vinyl polymer and the maleic anhydride-grafted monomers is 100 wt.%. Therefore, the maleic anhydride-grafted vinyl polymer comprises up to 90 wt.%, up to 95 wt.%, or 96 to 99 wt.% of vinyl polymers, based on the total weight of the maleic anhydride-grafted vinyl polymer.

[0035] Various commercial implementation methods are considered suitable. For example, suitable maleic anhydride-grafted vinyl polymers are commercially available from DuPont's functional polymers under the trademark Fusabond®.

[0036] Various amounts of maleic anhydride-grafted vinyl polymers are expected to be suitable for use in thermoplastic adhesive compositions. For example, a thermoplastic adhesive composition may include 10 to 40 wt.%, 15 to 35 wt.%, 15 to 25 wt.%, or 25 to 35 wt.% of maleic anhydride-grafted vinyl polymers.

[0037] Ethylene / α-olefin / non-conjugated diene interpolymer

[0038] The ethylene / α-olefin / non-conjugated diene interpolymer may include one or more interpolymers, wherein each ethylene / α-olefin / non-conjugated diene interpolymer comprises ethylene, α-olefin, and non-conjugated diene in polymeric form. In a particular embodiment, the ethylene / α-olefin / non-conjugated diene interpolymer is a terpolymer.

[0039] Suitable examples of α-olefins (which can be aliphatic or aromatic) may include C3-C 20 α-olefins, C3-C 16 α-olefins, or C3-C 10 α-olefin. In one or more embodiments, the α-olefin may be a C3-C olefin selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. 10 Aliphatic α-olefins. In one embodiment, the α-olefin is propylene.

[0040] Suitable examples of nonconjugated dienes include C4-C 40Non-conjugated dienes. Exemplary non-conjugated dienes include straight-chain acyclic dienes, such as 1,4-hexadiene and 1,5-heptadiene; branched acyclic dienes, such as 5-methyl-1,4-hexadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, 3,7-... Mixed isomers of dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene, 5,7-dimethyl-1,7-octadiene, 1,9-decadiene, and dihydromyrcene; monocyclic alicyclic dienes, such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, and 1,5-cyclododecene; polycyclic alicyclic fused and bridged cyclic dienes, such as tetrahydroindene and methyltetrahydroindene; alkenyl, alkylene, cycloalkenyl, and cycloalkylene norbornenes, such as 5-methylene-2-norbornene (MNB), 5-ethylene-2-norbornene (ENB), 5-vinyl-2-norbornene, 5-propylene-2-norbornene, 5-isopropylene-2-norbornene, 5-(4-cyclopentene)-2-norbornene, and 5-cyclohexylidene-2-norbornene. In a particular embodiment, the nonconjugated diene is selected from the group consisting of: ENB, dicyclopentadiene, 1,4-hexadiene, 7-methyl-1,6-octadiene, preferably ENB, dicyclopentadiene and 1,4-hexadiene, more preferably ENB and dicyclopentadiene, and even more preferably ENB.

[0041] In a further embodiment, the ethylene / α-olefin / non-conjugated diene interpolymer is an ethylene-propylene-diene terpolymer (EPDM), particularly a terpolymer product of ethylene, propylene, and ENB.

[0042] Various amounts of each monomer in the ethylene / α-olefin / non-conjugated diene interpolymer were considered; however, the interpolymer comprises the majority amount of polymerized ethylene. In one or more embodiments, the ethylene / α-olefin / non-conjugated diene interpolymer comprises 50 to 80 wt.% ethylene, 55 to 75 wt.% ethylene, or 60 to 70 wt.% ethylene, based on the total weight of the ethylene / α-olefin / non-conjugated diene interpolymer. Similarly, the ethylene / α-olefin / non-conjugated diene interpolymer comprises 15 to 45 wt.% propylene, 20 to 40 wt.% propylene, or 25 to 35 wt.% propylene, based on the total weight of the ethylene / α-olefin / non-conjugated diene interpolymer. In addition, based on the total weight of the ethylene / α-olefin / non-conjugated diene interpolymer, the ethylene / α-olefin / non-conjugated diene interpolymer includes 0.1 to 10 wt.% of non-conjugated diene, 0.1 to 5 wt.% of non-conjugated diene, or 0.1 to 1 wt.% of non-conjugated diene.

[0043] In one or more embodiments, the ethylene / α-olefin / non-conjugated diene interpolymer has a crystallinity of 7 to 20%, as measured by differential scanning calorimetry. In further embodiments, the crystallinity is 8 to 18, 10 to 15, or 12 to 15.

[0044] In addition, ethylene / α-olefin / non-conjugated diene interpolymers are characterized by Mooney viscosity (ML). 1+4 The values ​​are 5 to 50, or 10 to 40, or 15 to 30, where the Mooney viscosity (ML) is... 1+4 (This is measured according to ASTM D1646.)

[0045] The weight-average molecular weight (Mw) of the ethylene / α-olefin / non-conjugated diene interpolymer, as measured by conventional gel permeation chromatography (GPC), can be at least 90,000 g / mol, at least 100,000 g / mol, at least 110,000 g / mol, at least 120,000 g / mol, at least 200,000 g / mol, at least 220,000 g / mol, or at least 240,000 g / mol, or at least 260,000 g / mol, or at least 280,000 g / mol. In addition, the weight-average molecular weight (Mw) of the ethylene / α-olefin / non-conjugated diene interpolymer can be less than or equal to 500,000 g / mol, or less than or equal to 450,000 g / mol, or less than or equal to 400,000 g / mol, or less than or equal to 250,000 g / mol, or less than or equal to 200,000 g / mol, or less than or equal to 150,000 g / mol.

[0046] Furthermore, the number-average molecular weight (Mn) of the ethylene / α-olefin / non-conjugated diene interpolymer can be greater than or equal to 20,000 g / mol, or greater than or equal to 25,000 g / mol, or greater than or equal to 30,000 g / mol. In one or more embodiments, the number-average molecular weight (Mn) of the ethylene / α-olefin / non-conjugated diene interpolymer can be less than or equal to 60,000 g / mol, or less than or equal to 55,000 g / mol, or less than or equal to 50,000 g / mol, or less than or equal to 40,000 g / mol.

[0047] As described above, the ethylene / α-olefin / non-conjugated diene interpolymer may have a molecular weight distribution (MWD) of at least 2.5, where MWD = Mw / Mn. Furthermore, the MWD of the ethylene / α-olefin / non-conjugated diene interpolymer may be less than or equal to 10.00, further less than or equal to 9.50, further less than or equal to 9.00, or further less than or equal to 5. In one embodiment, or in combination with any one or more embodiments described herein, the MWD of the ethylene / α-olefin / non-conjugated diene interpolymer may be greater than or equal to 3.00, or greater than or equal to 3.25, or greater than or equal to 3.50.

[0048] Various commercial implementations are considered suitable. For example, a suitable ethylene / α-olefin / non-conjugated diene interpolymer may include NORDEL™ IP 3720P manufactured by Dow Chemical Company of Midland, Michigan.

[0049] Various amounts of ethylene / α-olefin / non-conjugated diene interpolymers suitable for use in thermoplastic adhesive compositions have been considered. For example, a thermoplastic adhesive composition may include 10 to 40 wt.%, 15 to 35 wt.%, or 20 to 30 wt.% of ethylene / α-olefin / non-conjugated diene interpolymers.

[0050] VLDPE

[0051] Furthermore, the VLDPE in the thermoplastic adhesive composition may include a polyethylene homopolymer or a copolymer of ethylene with one or more α-olefins. Suitable α-olefin comonomers (which may be aliphatic or aromatic) may include C3-C4. 20 α-olefins, C3-C 16 α-olefins or C3-C 10 α-olefin. In one or more embodiments, the α-olefin may be a C3-C olefin selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. 10 Aliphatic α-olefins. In one embodiment, the α-olefin is 1-butene.

[0052] In one or more embodiments, the VLDPE has a density of 0.885 to 0.915 g / cc, or 0.890 to 0.910 g / cc, or 0.895 to 0.905 g / cc. Furthermore, the low-density vinyl polymer may have a melt index (I2) of 0.5 to 20 g / 10 min, or 1.0 to 10 g / 10 min, or 2 to 8 g / 10 min, or 3 to 6 g / 10 min.

[0053] Various commercial implementations are considered suitable. For example, a suitable VLDPE polymer may include FLEXOMER™ DFDB-9042 NT, manufactured by Dow Chemical Company, Midland, Michigan.

[0054] Various amounts of VLDPE suitable for use in thermoplastic adhesive compositions have been considered. For example, a thermoplastic adhesive composition may include 15 to 60 wt.%, 15 to 50 wt.%, 20 to 50 wt.%, 20 to 30 wt.%, or 40 to 50 wt.% of a low-density vinyl polymer.

[0055] Ethylenealkyl (meth)acrylate copolymer

[0056] Further embodiments of the thermoplastic adhesive composition may include at least one ethylene alkyl (meth)acrylate copolymer, wherein the alkyl group comprises one to four carbon atoms. In one embodiment, the at least one ethylene alkyl (meth)acrylate copolymer is an ethylene methacrylate copolymer.

[0057] For ethylene alkyl (meth)acrylate copolymers, various amounts of ethylene and (meth)acrylate copolymers are considered. In one or more embodiments, the ethylene alkyl (meth)acrylate copolymer comprises 55 to 90 wt.% ethylene, or 60 to 80 wt.% ethylene, or 70 to 80 wt.% ethylene, based on the total weight of the ethylene alkyl (meth)acrylate copolymer. Similarly, the ethylene alkyl (meth)acrylate copolymer comprises 10 to 45 wt.% alkyl (meth)acrylate, or 15 to 35 wt.% alkyl (meth)acrylate, or 20 to 30 wt.% alkyl (meth)acrylate, based on the total weight of the ethylene alkyl (meth)acrylate copolymer.

[0058] In one or more embodiments, the density of the ethylene alkyl (meth)acrylate copolymer may be 0.920 to 0.960 g / cc, 0.930 to 0.955 g / cc, 0.935 to 0.950 g / cc, or 0.940 to 0.950 g / cc. Furthermore, the ethylene alkyl (meth)acrylate copolymer may have a melt index (I2) of 0.5 to 50 g / 10 min, 1 to 10 g / 10 min, 1 to 5 g / 10 min, or 1 to 3 g / 10 min.

[0059] Furthermore, according to ASTM D3418, using differential scanning calorimetry (DSC), ethylene alkyl (meth)acrylate copolymers can have a melting point of at least 80°C. In a further embodiment, the ethylene alkyl (meth)acrylate copolymer can have a melting point of at least 85°C or at least 90°C. Additionally, the ethylene alkyl (meth)acrylate copolymer can have a melting point less than 105°C, less than 100°C, or less than 95°C. Without being bound by theory, from a processing point of view, the melting point of the ethylene alkyl (meth)acrylate copolymer can be advantageous because it makes the thermoplastic adhesive composition easier to granulate.

[0060] Suitable copolymers of ethylene and alkyl (meth)acrylates can be synthesized in an autoclave by methods described, for example, in U.S. Patent Nos. 2,200,429; 2,953,551; and 3,350,372. In other cases, copolymers of ethylene and alkyl (meth)acrylates are “tubular reactor produced,” meaning that the copolymers are produced under high pressure and high temperature in a multi-zone or “tubular” reactor, where the different reactivity rates of the ethylene and alkyl acrylate comonomers are mitigated, either wholly or partially, by introducing monomers along the reaction flow path within the tubular reactor. As a result, the primary structure of the copolymer reflects a higher degree of randomness in the distribution of comonomers within the polymer chain. Therefore, ethylene copolymers produced in tubular reactors can be physically distinguished from those produced in autoclaves. Regarding bulk properties, ethylene alkyl (meth)acrylate copolymers produced in tubular reactors are generally stiffer and more elastic than those produced in autoclaves. Ethylene copolymers produced in tubular reactors and methods for preparing said copolymers are described, for example, in U.S. Patent Nos. 3,350,372; 3,756,996; and 5,532,066. The ethylene alkyl (meth) acrylate copolymers produced by a suitable tubular reactor are commercially available from DuPont's acrylic copolymers under the trademark Elvaloy® AC.

[0061] Various amounts of ethylene alkyl (meth)acrylate copolymers suitable for use in thermoplastic adhesive compositions have been considered. For example, a thermoplastic adhesive composition may comprise up to 40 wt.%, 10 to 40 wt.%, 20 to about 40 wt.%, or 25 to 35 wt.%, based on the total weight of the ethylene alkyl (meth)acrylate copolymer.

[0062] Multilayer film

[0063] The aforementioned thermoplastic adhesive compositions are particularly suitable as adhesive layers in multilayer structures (e.g., multilayer films), especially as adhesive layers in co-extruded and subsequently biaxially oriented multilayer films. Suitable adhesive layers comprise, or are substantially composed of, a thermoplastic adhesive composition, or consist of a thermoplastic adhesive composition. The thickness of each adhesive layer in the multilayer structure can be independently less than 1 μm, between 1 and 100 μm, between 5 and 50 μm, or between 5 and 30 μm.

[0064] Multilayer films can be formed and oriented (e.g., biaxial orientation) by any suitable process. Information on these processes can be found in reference texts such as the Kirk Osmo Encyclopedia, the Encyclopedia of Modern Plastics, or the Wiley Encyclopedia of Packaging Technology, 2nd edition, edited by AL. Brody and K.S. Marsh, published by Wiley-Interscience (Hoboken, 1997). Multilayer films can be formed, for example, by dip coating, film casting, sheet casting, solution casting, compression molding, injection molding, lamination, melt extrusion, blown film (including circular blown film), extrusion coating, tandem extrusion coating, or any other suitable process. Preferably, sheets are formed by melt extrusion, melt co-extrusion, melt extrusion coating, or tandem melt extrusion coating processes. Suitable orientation processes include tenter frame technology and longitudinal orientation (MDO) technology.

[0065] In a particular embodiment, the co-extruded multilayer film structure is manufactured by a co-extrusion process having gas-oriented orientation, such as the "two-bubble process" or preferably the "three-bubble" process described in International Patent Application Publications WO2007 / 099214 and WO2016 / 100277. In short, the three-bubble (3B) process for manufacturing a co-extruded multilayer film structure includes the following steps: co-extruding a tubular multilayer film structure; cooling the co-extruded tubular multilayer film structure in a first bubble, and uniaxially or biaxially oriented co-extruded a tubular multilayer film structure in a second bubble while heating it; and heat-fixing the biaxially oriented co-extruded tubular multilayer film structure in a third bubble while heating it.

[0066] The multilayer film described in this article can be used for packaging, especially for food packaging. Multilayer films can be used as shrink-wrap films, sealable films, cap films, wrapping films, etc. Furthermore, multilayer films can be further processed to form shrink bags, pouches, balloons, artificial turf, etc.

[0067] The multilayer embodiments of the present invention relate to a multilayer structure comprising at least one layer containing a co-extrudeable thermoplastic adhesive composition. These layers of the multilayer film may independently have a thickness of less than 1 μm, 1 to 100 μm, 1 to 5 μm, 5 to 50 μm, or 5 to 30 μm. In one embodiment, the multilayer film comprises: a first layer comprising a polyamide; a second layer comprising a vinyl polymer; and an adhesive layer comprising the aforementioned thermoplastic adhesive composition disposed between the first and second layers. Additionally, the adhesive layer comprising the aforementioned thermoplastic adhesive composition may be disposed between a polyester layer and a polyolefin layer, either as a separate multilayer film or within the same multilayer film.

[0068] Polyolefins may include vinyl polymers or propylene polymers. Suitable polyesters and their copolymers include, but are not limited to: polycarbonates; aliphatic polyesters, such as polyhydroxyalkanoates, including, for example, polylactic acid or poly(3-hydroxybutyrate); and semi-aromatic polyesters, such as polyethylene terephthalate (PET), and their copolymers, such as PETG, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Polyethylene terephthalate (PET) is an example material for polyester layers.

[0069] Surprisingly, without being limited by theory, the adhesive layer of the present invention is found to be universal, meaning that it can be used at different locations on a triple-bubble film, rather than using different adhesive layer compositions at each location. Specifically, the adhesive layer of the present invention can bond different substrates, such as polyamides, to vinyl polymers with the desired adhesive strength, while also bonding other different substrates, such as polyesters, to polyolefins with the desired adhesive strength. Thus, in some embodiments, the adhesive layer of the present invention eliminates the need for multiple adhesive layers, or at least reduces the number of adhesive layer formulations required to bond the individual layers of a multilayer film. In certain embodiments, the adhesive layer of the present invention is advantageous for maintaining adhesion after the multilayer film has been biaxially oriented in a process such as a double-bubble or triple-bubble process.

[0070] In one embodiment, the adhesive layer has an adhesive strength of at least 2.5 N / 15 mm at a temperature of 60°C. In another embodiment, the adhesive layer has an adhesive strength of at least 3.0 N / 15 mm at a temperature of 60°C. This adhesive performance is highly desirable to prevent shrink film delamination.

[0071] Starting from the basic multilayer membrane framework described above, the following discussion provides details of the layers commonly used in multilayer membranes. These layers are also described in detail in PCT international patent application publication number WO2016 / 100277 by Hausmann et al.

[0072] outer layer

[0073] The outer surface layer or outer layer of a food shell or food film provides the outer layer of the packaging and is the layer furthest from the contents of the packaging.

[0074] The outer layer can comprise polyester, polyamide (PA), polystyrene (PS), polycarbonate (PC), poly(methyl methacrylate) (PMMA), cyclic olefin copolymer (COC), polypropylene (PP), polyethylene (PE) (including high-density polyethylene (HDPE)), or combinations thereof, enabling welding or sealing of the film at high temperatures without the film adhering to the sealing end. As a result, a higher number of cycles can be achieved on the sealing machine. Furthermore, outer layers produced from these materials are less susceptible to physical damage and possess excellent optical properties such as gloss and transparency. Therefore, the outer layer provides mechanical support and protection for the other layers of the film. In addition, the outer layer film is particularly suitable for engraving or printing.

[0075] As described above, thermoplastic adhesive compositions are specifically used as adhesive layers to bond polyester layers to polyolefin layers. Therefore, the outer layer may comprise one or more polyesters or be substantially composed of one or more polyesters. Polyesters possess excellent optical properties, such as gloss and transparency, and due to their high-temperature resistance, higher processing speeds (cycle counts) can be achieved.

[0076] The polyester can be oriented under typical conditions of a co-extrusion process with orientation, for example, at temperatures in the range of 80 to 100°C. Preferably, the polyester layer is oriented in one or more directions. More preferably, the polyester layer is oriented in the longitudinal (MD), transverse (TD), or both longitudinal and transverse directions. Even more preferably, the polyester layer is biaxially oriented in both the longitudinal and transverse directions.

[0077] Combinations of two or more layers having the structure described above can be used to provide the mechanical and / or protective functions of the outer layer.

[0078] Polyolefin layer

[0079] Thermoplastic adhesive compositions are particularly used as adhesive layers to bond polyester layers to polyolefin layers. Therefore, multilayer films preferably include layers comprising one or more polyolefins or are substantially composed of one or more polyolefins. The polyolefin layer, sometimes referred to as the “bulk layer” or “building layer,” can be used to provide properties such as shrinkage, puncture resistance, and stiffness in multilayer films.

[0080] Suitable materials for the polyolefin layer include, for example, ionomers of copolymers of propylene-based polymers, vinyl polymers, ethylene, and (meth)acrylic acid, optionally further comprising copolymerized alkyl (meth)acrylates. Preferred materials for the polyolefin layer include, but are not limited to, copolymers of ethylene and vinyl acetate, alkyl (meth)acrylates, carboxylic acids and ionomers of ethylene-acrylic acid copolymers, and copolymers of polypropylene with other olefins such as ethylene. Ionomers and copolymers of propylene and ethylene are more preferred materials for the polyolefin layer. Random or block copolymers of polypropylene, and random or block terpolymers of propylene with ethylene and another olefin such as butene are still more preferred. A preferred material is commercially available from Lyondell Basell in Rotterdam, Netherlands, under the trade name Adsyl. For example, Adsyl 5C30F resin is a suitable terpolymer of propylene, ethylene, and butene.

[0081] Some preferred polyolefin layers are bulk shrinkable layers. Suitable polyolefins for bulk shrinkable layers are described in U.S. Patent No. 8,202,590 and Research Database Publication No. 448065, which were disclosed anonymously and in the journal *Research Open Journal* (Kenneth Mason Publications, Ltd., Hants, UK; August 2001). Ionomers of vinyl acid copolymers are preferred materials for bulk shrinkable layers.

[0082] Gas barrier

[0083] Multilayer membranes may optionally include a gas barrier layer. As used herein, the term "gas barrier layer" refers to a membrane layer that allows less than 1000 cc of gas, such as oxygen, to permeate the membrane per 24 hours at 1 atmosphere and 23°C at a relative humidity of 50%.

[0084] The barrier layer can provide multilayer films with concentrations below 500, below 100, below 50, below 30, or below 15 cc / m 2 Oxygen permeability per day. When considering thickness, the oxygen permeability level of the membrane is preferably less than 40 or less than 30 cc.mil / m. 2 Other polymers may be present as other components in the barrier layer, as long as they do not increase the permeability of the barrier layer to the limits defined above.

[0085] Suitable barrier layers may be selected from layers including ethylene-vinyl alcohol copolymers, cyclic olefin copolymers, polyvinyl acetate, or mixtures of one or more of these polymers with polyethylene, polyvinyl alcohol, or polyamide.

[0086] As previously mentioned, thermoplastic adhesive compositions are specifically used as adhesive layers to bond polyamide layers to polyolefin layers, such as layers comprising vinyl polymers. Various polyamides are suitable, such as amorphous polyamides like MXD6 and Nylon 6I / 6T (hexamethylene isophthalamide-hexamethylene terephthalamide copolymer).

[0087] sealant layer

[0088] Multilayer films may also include an inner surface layer or a sealant layer. This is the innermost layer of the packaging that is closest to the contents. It also provides a method for sealing or enclosing packaging around a product, such as by heat-sealing two portions of the sealant layer together or sealing it to the surface of another part of the packaging, such as sealing a capping film to a thermoformed packaging assembly. The composition of the sealant layer is chosen to affect the sealing ability of the inner surface layer, for example, to achieve high seal adhesion strength at the lowest possible sealing temperature.

[0089] The sealant layer may comprise one or more polymers capable of being melt-bonded to another layer by conventional heat-sealing methods. The sealant layer may comprise one or more polyolefin polymers, such as polyethylene homopolymers or copolymers, ethylene alkyl (meth)acrylate copolymers, or ethylene alkyl (meth)acrylate copolymers or their ionomers, or mixtures thereof. Preferably, the one or more olefin homopolymers and / or copolymers are selected from vinyl polymers, and / or copolymers, ethylene copolymers, such as ethylene (meth)acrylate copolymers and their corresponding ionomers, and / or mixtures thereof.

[0090] In addition, the sealant may comprise a copolymer of ethylene with one or more α-olefins. Suitable α-olefin comonomers may include 1-butene, 1-hexane, or 1-octene. Various commercially viable implementations are considered suitable, such as AFFINITY™ and ELITE™ polymers, both manufactured by Dow Chemical Company, Midland, Michigan.

[0091] Other adhesive layers

[0092] Optionally, in some embodiments, the co-extruded multilayer structure may include one or more additional layers to serve as adhesive layers between the functional layers, thereby improving interlayer adhesion and preventing layer delamination. For example, such a co-extruded adhesive layer may be located between the outer layer (PET) composition and the gas barrier layer composition, or between the ionomer-containing layer and the polyolefin layer. For example, the adhesive compositions described in U.S. Patent Nos. 6,545,091; 5,217,812; 5,053,457; 6,166,142; 6,210,765; and U.S. Patent Publication No. 2007 / 0172614 are suitable.

[0093] Exemplary adhesive compositions are described in detail in PCT International Patent Application Publication No. WO2016 / 100277, which is cited above. Optional other adhesive compositions, including olefin polymers and modified polymers, are commercially available from DuPont as peelable sealant resins under the trademarks Appeel®, co-extrudeable adhesive resins under the trademark Bynel®, ethylene acrylate copolymers under the trademark Elvaloy® AC, and ethylene vinyl acetate copolymer resins under the trademark Elvax®.

[0094] additive

[0095] Additional layers of the thermoplastic adhesive composition and multilayer film structure may further include one or more modifiers or other additives, including but not limited to plasticizers, impact modifiers, stabilizers (including viscosity stabilizers and hydrolytic stabilizers), lubricants, antioxidants, UV stabilizers, antifogging agents, antistatic agents, dyes, pigments or other colorants, fillers, flame retardants, reinforcing agents, foaming agents and bubbling agents, and processing aids known in the field of polymer compounding, such as antiblocking agents and release agents.

[0096] The amount of one or more of these additives present in each layer may be up to 20% by weight, preferably 0.01 to 7% by weight, and more preferably 0.01 to 5% by weight, based on a weight percentage of the total weight of the composition of the layers. Finally, these additives may be incorporated into the composition of each layer by methods known in the art. See, for example, Kirk-Otmer Encyclopedia of Chemical Technology, 5th Edition, John Wiley and Sons (New York, 2004).

[0097] Exemplary multilayer film

[0098] Representative examples of multilayer films include, but are not limited to, those listed in Table 1 below. In these descriptions, the symbol “ / ” represents the boundary between consecutive layers. Additionally, the outer to inner layers of multilayer films intended for use in packaging are listed in left-to-right order. Furthermore, “PET” stands for polyethylene terephthalate, and “PA” stands for polyamide, for example, as described in PCT International Patent Application Publication No. WO2016 / 100277 cited above. Depending on the composition of the layers adjacent to the adhesive layer, two or more adhesive layers in a single film may have the same composition or different compositions. Thus, when an adhesive layer comprises the thermoplastic adhesive composition described herein, the adhesive layer is referred to as “Tie,” while when an adhesive layer comprises any other adhesive composition (such as those adhesive compositions described above applicable to optional other adhesive layers), the adhesive layer is referred to as “T.” When the consecutive layers are ionomer layers, each layer has a different composition. Apart from this exception, and another exception for PET layers, two or more consecutive layers may have the same composition, and these consecutive layers will form a monolayer in the multilayer film. Finally, depending on the intended packaging use or other application, each multilayer film will have specific advantages.

[0099] Table 1

[0100]

[0101]

[0102] In preferred multilayer films, at least one layer is uniaxially or biaxially oriented. More preferably, at least one layer is oriented in the longitudinal direction, the transverse direction, or both. In even more preferred films, the oriented layer is a polyester layer or, in particular, a PET layer. Still more preferably, the polyester layer or PET layer is biaxially oriented. Also preferably, the polyester layer or PET layer is the outer layer.

[0103] Some preferred multilayer films include a structure having three consecutive layers of PET / adhesive / PA, PET / adhesive / PO, or PA / adhesive / PO, and some preferred multilayer films consist of three consecutive layers of PET / adhesive / PA, PET / adhesive / PO, or PA / adhesive / PO, wherein "adhesive" is as defined above. In these preferred films, the polyolefin layer "PO" can be a bulk layer or a sealant layer.

[0104] Test methods

[0105] Melt index (I2)

[0106] Melt flow index (I2) values ​​were measured according to ASTM D1238 at 190°C and 2.16 kg.

[0107] density

[0108] Density measurements were performed according to ASTM D792 Method B.

[0109] Gel permeation chromatography (conventional GPC)

[0110] The GPC-IR high-temperature chromatography system from PolymerChar (Valencia, Spain) was equipped with a precision detector (Amherst, MA), a 2-angle laser scattering detector 2040, an IR5 infrared detector, and a 4-capillary viscometer (both from PolymerChar). Data collection was performed using PolymerChar's Instrument Control software and data acquisition interface. The system was equipped with an online solvent degassing unit and pumping system from Agilent Technologies (Santa Clara, CA).

[0111] The injection temperature was controlled at 150°C. The columns were three 10-micron "mixed-type B" columns from Polymer Laboratories (Shropshire, UK). The solvent was 1,2,4-trichlorobenzene. Samples were prepared at a concentration of "0.1 g polymer in 50 mL of solvent". Both the chromatographic solvent and the sample preparation solvent contained "200 ppm butylated hydroxytoluene (BHT)". Both solvent sources were bubbled with nitrogen. The vinyl polymer sample was gently stirred at 160°C for three hours. The injection volume was 200 μL, and the flow rate was 1 mL / min. The GPC column assembly was calibrated by running 21 "narrow molecular weight distribution" polystyrene standards. The standards had molecular weights (MW) ranging from 580 to 8,400,000 g / mol, and were contained in six "cocktail" mixtures. Each standard mixture had at least a tenfold interval between individual molecular weights. The standard mixtures were purchased from Polymer Laboratories. Polystyrene standards are prepared as follows: for molecular weights equal to or greater than 1,000,000 g / mol, 0.025 g in 50 mL solvent is used; and for molecular weights less than 1,000,000 g / mol, 0.050 g in 50 mL solvent is used.

[0112] Polystyrene standards were dissolved at 80°C for 30 minutes with gentle stirring. A narrow standard mixture was run first, minimizing degradation in descending order of "highest molecular weight component". The peak molecular weight of the polystyrene standards was converted to the molecular weight of polyethylene using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Letters, 6, 621 (1968)).

[0113] M_polyethylene = A x (M_polyethylene) B (Equation 1)

[0114] Where M is the molecular weight, A has a value of 0.4316, and B equals 1.0.

[0115] Calculate the number-average molecular weight (Mn(conv gpc)), weight-average molecular weight (Mw-conv gpc), and z-average molecular weight (Mz(conv gpc)) according to the following equations 2 to 4.

[0116] (Equation 2)

[0117] (Equation 3)

[0118] (Equation 4)

[0119] In Equations 2 through 4, RV is the column retention volume (linear interval), collected at “1 point per second”, IR is the IR detector signal from the IR5 measurement channel of the GPC instrument minus the baseline, in volts, and LogM PE The equivalent MW of polyethylene is determined by Equation 1. The data was calculated using GPC One software (version 2.013H) from Perimocha.

[0120] Differential scanning calorimetry

[0121] Differential scanning calorimetry (DSC) can be used to measure the melting and crystallization properties of polymers over a wide temperature range. For example, the TA Instruments Q1000DSC, equipped with an RCS (Refrigerant Cooling System) and an autosampler, is used to perform this analysis. During testing, a nitrogen purge gas flow of 50 ml / min is used. Each sample is melted and pressed into a thin film at approximately 175°C; the molten sample is then allowed to cool to room temperature (approximately 25°C). A 3–10 mg sample of “6 mm diameter” is extracted from the cooled polymer, weighed, placed in a light aluminum pan (approximately 50 mg), and rolled up until stopped. Analysis is then performed to determine its thermal properties.

[0122] The thermal behavior of the sample was determined by slowly raising and lowering the sample temperature to create a heat flow contrast with the temperature distribution. First, the sample was rapidly heated to 180°C and held isothermally for 3 minutes to remove its thermal history. Next, the sample was cooled to -40°C at a cooling rate of 10°C / min and held isothermally at -40°C for 3 minutes. The sample was then heated to 150°C (this is the “second heating” ramp) at a heating rate of 10°C / min. The cooling and second heating curves were recorded. The cooling curve was analyzed by setting a baseline endpoint from the start of crystallization to -20°C. The heating curve was analyzed by setting a baseline endpoint from -20°C to the melting endpoint. The measured values ​​were the peak melting temperature (Tm), peak crystallization temperature (Tc), heat of fusion (Hf) (in Joules / gram), and the crystallinity % of the polyethylene sample calculated using Equation 5: Crystallinity % = ((Hf) / (292 J / g)) × 100 (Equation 5).

[0123] The heat of fusion (Hf) and peak melting temperature are reported from the second heating curve. The peak crystallization temperature is measured from the cooling curve.

[0124] The present invention also relates to the following embodiments:

[0125] 1. A thermoplastic adhesive composition comprising:

[0126] At least one maleic anhydride-grafted vinyl polymer;

[0127] At least one ethylene / α-olefin / non-conjugated diene interpolymer with a molecular weight distribution (MWD) ≥ 2.5, wherein MWD = Mw / Mn, where Mw is the weight-average molecular weight and Mn is the number-average molecular weight, both of which are measured by gel permeation chromatography.

[0128] Very low density polyethylene (VLDPE) has a density ranging from 0.885 to 0.915 g / cm³. 3 Within the range.

[0129] 2. The thermoplastic adhesive composition according to claim 1 further comprises at least one ethylene alkyl (meth)acrylate copolymer, wherein the alkyl group comprises one to four carbon atoms.

[0130] 3. The thermoplastic adhesive composition according to any of the preceding claims, wherein the density of the ethylene alkyl (meth)acrylate copolymer is from 0.930 to 0.960 g / cc.

[0131] 4. The thermoplastic adhesive composition according to any of the preceding claims, wherein the thermoplastic adhesive composition comprises 20 to 40% by weight of ethylene alkyl (meth)acrylate copolymer.

[0132] 5. The thermoplastic adhesive composition according to any of the preceding claims, wherein the maleic anhydride-grafted vinyl polymer comprises one or more of maleic anhydride-grafted linear low-density polyethylene, maleic anhydride-grafted polyethylene elastomer, or combinations thereof.

[0133] 6. The thermoplastic adhesive composition according to any of the preceding claims, wherein the maleic anhydride-grafted vinyl polymer has a density of less than 0.900 g / cc and a melt index (I2) of 1 to 20 g / 10 min.

[0134] 7. The thermoplastic adhesive composition according to any of the preceding claims, wherein the thermoplastic adhesive composition comprises 10 to 40% by weight of a maleic anhydride-grafted vinyl polymer.

[0135] 8. The thermoplastic adhesive composition according to any of the preceding claims, wherein the α-olefin of the ethylene / α-olefin / non-conjugated diene interpolymer is propylene, and the non-conjugated diene of the ethylene / α-olefin / non-conjugated diene interpolymer is ethylidene-norbornene.

[0136] 9. The thermoplastic adhesive composition according to any of the preceding claims, wherein the thermoplastic adhesive composition comprises 15 to 35% by weight of an ethylene / α-olefin / non-conjugated diene interpolymer.

[0137] 10. The thermoplastic adhesive composition according to any of the preceding claims, wherein the melt index (I2) of the VLDPE is 2 to 8 g / 10 min.

[0138] 11. The thermoplastic adhesive composition according to any of the preceding claims, wherein the thermoplastic adhesive composition comprises 15 to 50% by weight of the VLDPE.

[0139] 12. The thermoplastic adhesive composition according to any of the preceding claims, wherein the ethylene / α-olefin / non-conjugated diene interpolymer has a crystallinity of 7 to 20%, as measured by differential scanning calorimetry.

[0140] Example

[0141] The following examples illustrate the features of this disclosure, but are not intended to limit the scope of this disclosure.

[0142] Table 2 includes a list of the commercial polymers and additives used in comparative example A of the adhesive layer and examples 1 and 2 of the present invention, which are listed in Table 3 below.

[0143] Table 2

[0144]

[0145] Furthermore, Examples 1 and 2 of the present invention include NORDEL™ IP 3720P (EPDM) with a MWD of 3-4, a crystallinity of 14% as measured by differential scanning calorimetry (DSC), and a Mooney viscosity (ML) as measured by ASTM D1646. 1+4 The value is 20. NORDEL™ IP 3720P is commercially available from Dow Chemical Company (Midland, Michigan).

[0146] Table 3 lists the comparative adhesive layer formulations used in the three-bubble films in Table 3 below (Comparative Example A) and two adhesive layer formulations of the present invention (Examples 1 and 2 of the present invention). The main difference between Examples 1 and 2 of the present invention is that Example 1 does not include ethylene alkyl (meth)acrylate copolymers.

[0147] Table 3

[0148]

[0149] The adhesive layer formulations in Table 3 comprise 13 layers of triple bubble film produced by a triple bubble process. Table 4 below provides the layer composition of the 13 layers of triple bubble film. As shown below, the performance of adhesive example A and adhesive examples 1 and 2 of the present invention were measured and compared by including these adhesive compositions as adhesive layers in layer 11 or layer 2.

[0150] Table 4

[0151]

[0152] Three-bubble membrane material

[0153] The following are the compositions used in the triple bubble film layers listed in Table 4 above.

[0154] PET is polyethylene terephthalate commercially available from Dufor (Zevenaar, Netherlands) under the name Cumastretch FX.

[0155] PA is a blend of the following materials: 90% by weight of nylon 6 with a melting point of 220°C and a melt flow rate of 25 g / 10 min at a load of 5 kg at 275°C, according to ASTM D1238, commercially available from EMS-Grivory (Sumter, South Carolina, USA) as F40; and 10% by weight of Selar. ® PA 3426 amorphous nylon resin is available from DuPont.

[0156] EVOH is available from Nippon Goshei as Soarnol TM AT4403 commercially obtained ethylene vinyl alcohol.

[0157] PO-1 is a random polypropylene copolymer with a density of 0.900 g / cm³. 3 It has a melt index (MI) of 5.5 g / 10 min at 230°C and a load of 2.16 kg, a melting point of 128°C, and a Vicat softening point of 103°C. It is commercially available from LyondelBasell as Adsyl 6C30F.

[0158] PO-2 is a polymer blend of the same type as the following sealants, without additives.

[0159] Tie-1 is a modified vinyl acrylate resin available from DuPont under the trademark Bynel® 22E780.

[0160] Adhesive-2 is an anhydride-modified linear low-density polyethylene, commercially available from DuPont under the trademark Bynel® 41E687.

[0161] The sealant is a 70 wt% vinyl-1-octene plastide produced by solution polymerization using a metallocene catalyst, with a density of 0.902 g / cm³. 3 The I2 concentration is 3 g / 10 min, and the melting point is 96°C. ° C, commercially available from Borealis (Vienna, Austria) under the product name Queo 0203; and 30 wt% of metallocene-catalyzed ethylene-hexene copolymer, commercially available from ExxonMobil Chemicals (Houston, Texas, USA) under the product name Exceed. TM Obtained from 1018 commercial purchase; and some additives, such as slip or anti-stick additives.

[0162] Three-bubble process

[0163] The co-extruded multilayer films in Table 4 were produced on a three-bubble (3B) production line (available from Kuhne Anlagenbau GmbH, St. Augustine, Germany) using the materials, thicknesses, and extrusion temperatures listed in Table 3 above, as well as the procedures and production line speeds described in International Patent Application Publication Nos. WO2007 / 099214 and WO2016 / 100277. Specific conditions for co-extruded multilayer films comprising the thermoplastic adhesive compositions described herein include: orienting the film by exposing the second bubble to a temperature of 90°C; and annealing the film by exposing the third bubble to temperatures of 60°C (for shrinkable films) and 100°C (for non-shrinkable films), respectively.

[0164] Layer 1 is the outer surface layer of three tubular bubbles, layer 13 is the inner surface layer of three tubular bubbles, and layers 2 to 12 are the inner layers of the multilayer film. When the continuous co-extruded layers of the multilayer film contain the same material, such as in layers 3 to 6, the continuous co-extruded layers appear as a single layer in the final film structure. The co-extruded multilayer film includes a polyester outer layer at layer 1 and gas-barrier triplet layers PA / EVOH / PA at layers 8, 9, and 10.

[0165] Adhesion test

[0166] Adhesive strength was measured using the following method. After extrusion, the film from Table 4 was conditioned under ambient conditions for at least 24 hours, and then cut longitudinally into strips with a transverse width of 15 mm.

[0167] For comparative membrane A and membranes 1 and 2 of the present invention, layers 1 to 10 were manually separated from layers 12 to 13 at one 15 mm end of the strip. The separated ends of the two layers were fixed to a tensile testing machine, and delamination continued by mechanically separating the ends. During mechanical delamination, layers 1 to 10 and layers 12 to 13 were at an angle of 180° to each other, and the separation speed at the ends was 100 mm / min. The force required to delaminate the membranes under these conditions was measured and recorded as adhesive strength in Newtons per 15 mm.

[0168] For comparison membrane B and membranes 3 and 4 of the present invention, layer 1 (PET) was manually separated from layers 3 to 13 at a 15 mm end of the strip. The separated ends of the two layers were fixed to a tensile testing machine, and the separation continued by mechanically separating the two ends. During the mechanical separation process, layer 1 (PET) and layers 3 to 13 were at a 180° angle to each other, and the separation speed of the two ends was 100 mm / min.

[0169] Figure 1 The adhesive strength of comparative bonding examples and bonding examples 1 and 2 of the present invention when used to bond polyamide (PA) to polyethylene (PO-2) is shown. As shown in the figure, films 1 and 2 of the present invention, which include bonding examples 1 and 2 of the present invention respectively, have adhesive strength greater than 2.5 N / 15 min, while comparative film A, which includes the comparative bonding example, has an undesirable adhesive strength of less than 2.0 N / 15 min.

[0170] Figure 2 The adhesive strength of comparative bonding examples and bonding examples 1 and 2 of the present invention when used to bond polyester (PET) to polypropylene (PO-1) is shown. As shown in the figure, films 3 and 4 of the present invention, which include bonding examples 1 and 2 of the present invention respectively, both have an adhesive strength of about 3 N / 15 min, both of which are higher than comparative film B, which includes the comparative bonding examples.

[0171] The adhesive properties of films 3 and 4 of the present invention are noteworthy because polyesters are known to react very poorly with maleic anhydride; however, the combination of maleic anhydride-grafted vinyl polymer (Fusabond® N525) with other components—ethylene / α-olefin / non-conjugated diene interpolymer (NORDEL™ IP 3720P EPDM), VLDPE (FLEXOMER™ DFDB-9042), and optionally ethylene alkyl (meth)acrylate copolymer (Elvaloy® 1224AC)—improves the adhesion between the various polymer layers.

[0172] It will be apparent to those skilled in the art that various modifications can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter. Therefore, this specification is intended to cover modifications and variations of the described embodiments, provided that such modifications and variations are within the scope of the appended claims and their equivalents.

Claims

1. A thermoplastic adhesive composition comprising: 20 wt% to 35 wt% of at least one maleic anhydride-grafted vinyl polymer, said at least one maleic anhydride-grafted vinyl polymer having a density of less than 0.900 g / cc and a melt index I2 of 1 to 5 g / 10 min, said melt index I2 being measured according to D1238 at 190°C and 2.16 kg; 1 wt% to 40 wt% of at least one ethylene / α-olefin / non-conjugated diene interpolymer with a molecular weight distribution (MWD) ≥ 2.5, wherein MWD = Mw / Mn, where Mw is the weight-average molecular weight and Mn is the number-average molecular weight, both of which are measured by gel permeation chromatography. 20 wt% to 50 wt% of very low density polyethylene (VLDPE), with a density of 0.885 to 0.905 g / cm³. 3 Within the range, and the melt index I2 is 3 to 6 g / 10 min; and Based on the total weight of the thermoplastic adhesive composition, up to 40 wt% of at least one ethylene alkyl (meth) acrylate copolymer, wherein the alkyl group comprises one to four carbon atoms.

2. The thermoplastic adhesive composition according to claim 1, wherein, The density of the ethylene alkyl (meth) acrylate copolymer is 0.930 to 0.960 g / cc.

3. The thermoplastic adhesive composition according to any of the preceding claims, wherein, The thermoplastic adhesive composition comprises 20 to 40% by weight of ethylene alkyl (meth)acrylate copolymer.

4. The thermoplastic adhesive composition according to any of the preceding claims, wherein, The maleic anhydride-grafted vinyl polymer includes one or more of maleic anhydride-grafted linear low-density polyethylene, maleic anhydride-grafted polyethylene elastomer, or combinations thereof.

5. The thermoplastic adhesive composition according to any of the preceding claims, wherein, The maleic anhydride-grafted vinyl polymer has a density of 0.860 to 0.900 g / cc and a melt index I2 of 2 to 4 g / 10 min.

6. The thermoplastic adhesive composition according to any of the preceding claims, wherein, The α-olefin in the ethylene / α-olefin / non-conjugated diene interpolymer is propylene, and the non-conjugated diene in the ethylene / α-olefin / non-conjugated diene interpolymer is ethylidene-norbornene.

7. The thermoplastic adhesive composition according to any of the preceding claims, wherein, The thermoplastic adhesive composition comprises 15 to 35% by weight of ethylene / α-olefin / non-conjugated diene interpolymer.

8. The thermoplastic adhesive composition according to any of the preceding claims, wherein, The ethylene / α-olefin / non-conjugated diene interpolymer has a crystallinity of 7 to 20%, as measured by differential scanning calorimetry.

9. A multilayer film formed by a three-bubble process from a thermoplastic adhesive composition according to any of the preceding claims.

Images