Recoverable solventless adhesives

Abstract

The present invention discloses a solvent-free lamination adhesive composition comprising (a) a polyurethane prepolymer composition wherein the prepolymer has an NCO% of less than 10%, the polyurethane prepolymer composition comprising the reaction product of (i) at least 20% by weight, based on the weight of the prepolymer composition, of an aromatic isocyanate, (ii) no more than 10% by weight, based on the weight of the prepolymer composition, of a natural oil polyol, and (iii) at least 60% by weight, based on the weight of the prepolymer composition, of polypropylene glycol; and (b) a hydroxyl functional co-reactant composition comprising: (i) from 80% to 100% by weight, based on the weight of the co-reactant composition, of a natural oil polyol, (ii) from 0% to 20% by weight, based on the weight of the co-reactant composition, of a hydrophobic polyether polyol, and (iii) from 0% to 2% by weight, based on the weight of the co-reactant composition, of a phosphate adhesion promoter; wherein the solvent-free lamination adhesive composition can be directly mechanically recovered for use in polyolefin laminates. Also disclosed is a laminate produced using the disclosed adhesive.

Description

Technical Field

[0001] The present disclosure relates to solventless laminating adhesives. More particularly, the present disclosure relates to solventless laminating adhesives having improved mechanical recyclability. Background Art

[0002] Polyurethane-based adhesives are widely used in the packaging industry for flexible packaging, including flexible food packaging. Solvent-based polyurethane adhesives are applied via gravure or flexographic printing systems, while solvent-free systems are applied using five-roller systems. If flexible packaging is used for food products, bond strength and resistance to sealing conditions are essential.

[0003] Traditional flexible packaging designs are based on lamination of functional layers such as polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), metallized PET oriented polypropylene (OPP), aluminum foil and nylon / polyimide with sealable layers such as low density polyethylene (LDPE) or cast polypropylene (CPP). Due to the absence of economical and technically effective multi-layer separation and subsequent process for recycling of the single film, traditional flexible packaging is non-recyclable. Traditionally used laminating adhesives include acrylic or polyurethane-based adhesives. Due to the chemical differences between the polyolefin backbone of the laminating adhesive and the film and the highly cross-linked nature of the adhesive, adhesives are incompatible with polyolefin film materials, and therefore the combination of different polyolefin films laminated with such traditional adhesives is challenging for recycling.

[0004] Therefore, there is a need for an adhesive that can enable a fully recyclable laminate structure having all of the beneficial properties described above (ie, good performance and the achievement of recyclable packaging). Summary of the Invention

[0005] The present invention discloses a solventless laminating adhesive composition comprising (a) a polyurethane prepolymer composition, wherein the NCO% of the prepolymer is less than 10%, the polyurethane prepolymer composition comprising the reaction product of: (i) at least 20 wt. % of an aromatic isocyanate, based on the weight of the prepolymer composition; (ii) no more than 10 wt. % of a natural oil polyol, based on the weight of the prepolymer composition; and (iii) at least 60 wt. % of a polypropylene glycol, based on the weight of the prepolymer composition. (b) a hydroxyl-functional co-reactant composition comprising: (i) 80% to 100% by weight of a natural oil polyol, based on the weight of the co-reactant composition, (ii) 0% to 20% by weight of a hydrophobic polyether polyol, based on the weight of the co-reactant composition, and (iii) 0% to 2% by weight of a phosphate adhesion promoter, based on the weight of the co-reactant composition; wherein the solventless laminating adhesive composition is capable of being directly mechanically recycled for use in polyolefin laminates. Also disclosed is a laminate produced using the disclosed adhesive. DETAILED DESCRIPTION

[0006] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not specifically disclosed. For the avoidance of any doubt, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term "consisting essentially of excludes from the scope of any subsequently recited component, step, or procedure any other component, step, or procedure, except those that are not essential to operability. The term "consisting of excludes any component, step, or procedure not specifically recited or listed.

[0007] The numerical ranges disclosed herein include all values ​​from the lower limit to the upper limit, and include the lower limit and the upper limit. For ranges containing exact values ​​(e.g., a range of 1 to 2 or 3, 5, 6 or 7), any subrange between any two exact values ​​is included (e.g., the above range 1 to 7 includes subranges of 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6, etc.).

[0008] The term "composition" refers to a mixture of materials comprising the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0009] An "isocyanate" is a chemical substance that contains at least one isocyanate group in its structure. An isocyanate group is represented by the formula: N=C=O, or abbreviated as "NCO." Isocyanates containing more than one, or at least two, isocyanate groups are "polyisocyanates." An isocyanate with two isocyanate groups is a diisocyanate, and an isocyanate with three isocyanate groups is a triisocyanate, and so on. Isocyanates can be aromatic or aliphatic.

[0010] A "polyisocyanate" is a molecule containing at least two isocyanate groups.

[0011] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers (whether of the same or different types). Thus, the general term polymer encompasses the term "homopolymer," which is typically used to refer to polymers prepared from only one type of monomer, as well as "copolymer," which refers to polymers 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. Thus, the general term interpolymer includes copolymers and polymers prepared from more than two different types of monomers, such as terpolymers.

[0012] As used herein, "polyolefin" refers to an olefin-based polymer. As used herein, "olefin," which may also be referred to as "alkene," refers to a linear, branched, or cyclic compound comprising carbon and hydrogen and having at least one double bond. As used herein, when a polymer or copolymer, such as a polyolefin elastomer, is referred to as comprising an olefin, the olefin present in the polymer or copolymer is the polymerized form of the olefin.

[0013] As used herein, the term "polyethylene" refers to a polymer comprising greater than 50% by weight of units derived from ethylene monomer, and optionally one or more comonomers. This may include 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-site catalyzed linear low density polyethylene, including both linear and substantially linear low density resins (m-LLDPE); medium density polyethylene (MDPE); and high density polyethylene (HDPE).

[0014] A "polyether" is a chemical compound containing two or more ether linkages in the same linear chain of atoms.

[0015] A "polyester" is a chemical compound containing two or more ester linkages in the same linear chain of atoms.

[0016] A "polyol" is an organic compound containing multiple hydroxyl (OH) groups. In other words, a polyol contains at least two OH groups. Non-limiting examples of suitable polyols include diols having two OH groups, triols having three OH groups, and tetraols having four OH groups.

[0017] "Polyester polyols" are compounds that contain polyester and hydroxyl functional groups in the backbone structure of the compound.

[0018] "Polyether polyols" are compounds containing polyether and hydroxyl functional groups in the backbone structure of the compound.

[0019] Unless thickness is specifically specified, "film" (including when referring to a "film layer" in a thicker article) includes any thin, flat, extruded, blown, or cast thermoplastic article having a generally consistent and uniform thickness.

[0020] A "polymer film" is a film made of a polymer or a polymer mixture. A polymer film typically consists of 80 weight percent (wt%) of one or more polymers.

[0021] Laminated films prepared using adhesives

[0022] Laminated films produced using adhesives may comprise a polyolefin / polyolefin structure. Laminated films produced using adhesives may comprise polyethylene / polyethylene. Laminated films produced using adhesives may comprise HDPE / LDPE. Polyethylene / polyethylene structures may have a bond strength greater than or equal to 1000 g / 25.4 mm. Polyolefin / polyolefin structures may have a bond strength between 1000 g / 25.4 mm and 2500 g / 25.4 mm, inclusive of all values ​​and subranges. For example, the polyethylene / polyethylene substrate layer may have a thickness of 3000 g / 25.4 mm, 2500 g / 25.4 mm, 2400 g / 25.4 mm, 2300 g / 25.4 mm, 2200 g / 25.4 mm, 2100 g / 25.4 mm, 2000 g / 25.4 mm, 1900 g / 25.4 mm, 1800 g / 25.4 mm, 1700 g / 25.4 mm, 1600 g / 25.4 mm, 1500 g / 25.4 mm, g / 25.4 mm or an upper limit of 1400 g / 25.4 mm to a lower limit of 1300 g / 25.4 mm, 1400 g / 25.4 mm, 1500 g / 25.4 mm, 1600 g / 25.4 mm, 1700 g / 25.4 mm, 1800 g / 25.4 mm, 1900 g / 25.4 mm, 2000 g / 25.4 mm, 2200 g / 25.4 mm, or 2400 g / 25.4 mm.

[0023] The laminate produced using the adhesive may comprise a polyolefin / polyolefin structure. The polyolefin / polyolefin structure may comprise a BOPP / / BOPP sealing structure and have a bond strength greater than or equal to 230 g / 25.4 mm. The polyolefin substrate layer may comprise a BOPP / / BOPP sealing structure and have a bond strength of 230 g / 25.4 mm to 450 g / 25.4 mm, including all internal values ​​and subranges. For example, the polyolefin substrate layer may comprise a BOPP / / BOPP sealing structure and have a bond strength of 600 g / 25.4 mm, 450 g / 25.4 mm, 430 g / 25.4 mm, 410 g / 25.4 mm, 390 g / 25.4 mm, 370 g / 25.4 mm, 350 g / 25.4 mm, 330 g / 25.4 mm, 310 g / 25.4 mm, 290 g / 25.4 mm, 270 g / 25.4 mm The bonding strength may be an upper limit of 4 mm or 250 g / 25.4 mm to a lower limit of 230 g / 25.4 mm, 250 g / 25.4 mm, 270 g / 25.4 mm, 290 g / 25.4 mm, 310 g / 25.4 mm, 330 g / 25.4 mm, 350 g / 25.4 mm, 370 g / 25.4 mm, 390 g / 25.4 mm, 410 g / 25.4 mm or 430 g / 25.4 mm.

[0024] Laminates produced using the adhesive may have a static or dynamic coefficient of friction (COF) of 0.150 to 0.400.

[0025] The polyolefin laminate produced using the adhesive can have a recyclability of less than or equal to 33%. The laminate produced using the adhesive can have a recyclability of 1.5% to 33%. All internal values ​​and subranges are included and disclosed. For example, the laminate produced using the adhesive can have an upper limit of 25%, 23%, 21%, 19%, 17%, 15%, 13%, 11%, 9%, 7%, 5% or 3% to a lower limit of 1.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22% or 24%.

[0026] Polyethylene laminates produced using the adhesive can have a HAAKE melt index after compounding of 1.0 g / 10 min to 4.5 g / 10 min at a temperature of 210° C., including all values ​​and subranges therein. For example, a laminate produced using the adhesive can have a HAAKE melt index after compounding of 4.5, 4.3, 4.1, 3.9, 3.7, 3.5, 3.3, 3.1, 2.9, 2,7, 2.5, 2.3, 2.1, 1.9, 1.7, 1.5, 1.3, or 1.1 to a lower limit of 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, or 4.4.

[0027] Laminates produced using the adhesive may have a molecular weight M of 41,000 g to 43,000 g after HAAKE compounding. n All internal values ​​and subranges are disclosed. For example, a laminate produced using the adhesive may have a molecular weight M of 41,000 g to 42,000 g or 42,000 g to 43,000 g after HAAKE compounding. n .

[0028] Laminates produced using the adhesive may have a molecular weight M of 165,500 g to 172,000 g after HAAKE compounding. w All values ​​and subranges therein are included. For example, a laminate produced using the adhesive may have a molecular weight M of 165,500 g to 168,000 g or 168,000 g to 172,000 g after HAAKE compounding. w .

[0029] Laminates produced using the adhesive may have an M of 457,500 g to 480,000 g after HAAKE compounding. z All values ​​and subranges therein are included. For example, a laminate produced using the adhesive may have a molecular weight M of 457,500 g to 465,000 g or 465,000 g to 480,000 g after HAAKE compounding. z .

[0030] Laminates produced using the adhesive may have a molecular weight M of 100,000 g to 110,000 g after HAAKE compounding. p All values ​​and subranges therein are included. For example, a laminate produced using the adhesive may have a molecular weight M of 100,000 g to 106,000 g or 106,000 g to 110,000 g after HAAKE compounding. p .

[0031] Laminates produced using the adhesive may have a PDI (M) of 4.00 to 4.05 after HAAKE compounding. w / M n ). All values ​​and subranges therein are included. For example, a laminate produced using an adhesive may have a PDI (M) of 4.00 to 4.02 or 4.02 to 4.05. w / M n ).

[0032] Polyolefin substrate layer

[0033] The disclosed polyolefin substrate layer is made of an olefin-based polymer. The polyolefin substrate layer may include a vinyl polymer. Common forms of polyethylene known in the art include, but are not limited to: low-density polyethylene (LDPE); linear low-density polyethylene (LLDPE); ultra-low-density polyethylene (ULDPE); very-low-density polyethylene (VLDPE); single-site-catalyzed linear low-density, including linear and substantially linear low-density resins (m-LLDPE); medium-density polyethylene (MDPE); and high-density polyethylene (HDPE). For example, the polyolefin substrate layer may include one or more polyolefin layers, such as HDPE, LDPE, LLDPE, MDO PE, BOPE, and mixtures thereof.

[0034] Additionally, as used herein, the term "LDPE" may also be referred to as "high pressure ethylene polymer" or "highly branched polyethylene" and is defined to mean a polymer that is partially or completely 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. Pat. No. 4,599,392). LDPE resins typically have a density in the range of 0.916 g / cm3 to 0.940 g / cm3.

[0035] As used herein, the term "LLDPE" may include resins made using Ziegler-Natta catalyst systems, as well as resins made using single-site catalysts including, but not limited to, dimetallocene catalysts (sometimes referred to as "m-LLDPE"), phosphinimines, and constrained geometry catalysts, and resins made using post-metallocene, molecular catalysts including, but not limited to, bis(biphenylphenoxy) catalysts (also known as polyvalent aryloxyether catalysts). LLDPE includes linear, substantially linear, or heterogeneous ethylene-based copolymers or homopolymers. LLDPE contains less long-chain branching than LDPE and includes substantially linear ethylene polymers (as further defined in U.S. Patents 5,272,236; 5,278,272; 5,582,923; and 5,733,155); homogeneously branched ethylene polymers (such as those described in U.S. Patent 3,645,992); heterogeneously branched ethylene polymers (such as those prepared according to the process disclosed in U.S. Patent 4,076,698); and blends thereof (such as those disclosed in U.S. Patent 3,914,342 or U.S. Patent 5,854,045). LLDPE resins can be prepared via gas-phase, solution-phase, or slurry polymerization, and any combination thereof, using any type of reactor or reactor configuration known in the art. LLDPE resins can be prepared via gas-phase, solution-phase, or slurry polymerization, and any combination thereof, using any type of reactor or reactor configuration known in the art.

[0036] Additionally, as used herein, the term "HDPE" refers to polyethylene having a density of about 0.940 g / cm3 or greater, which is typically produced using Ziegler-Natta catalysts, chromium catalysts, or even metallocene catalysts. The polyolefin film substrate layer may be a multilayer film including an outer layer comprising an ethylene-based polymer.

[0037] Polyethylene polymers suitable for use in the present disclosure may be commercially available. Suitable commercial polyethylene polymers include, but are not limited to: AGILITY TM (For example, AGILITY TM 1000、AGILITY TM 1001 and AGILITY TM 1021) INNATE TM ST50、ELITE TM 5940、ELITE TM 5960、DOW TM LDPE 6211 and DOW TM LDPE 7511, these polymers are available from The Dow Chemical Company.

[0038] The disclosed polyolefin substrate layer is made of an olefin-based polymer. The polyolefin substrate layer may include a propylene-based polymer. Common forms of polypropylene known in the art include, but are not limited to, BOPP and CPP films;

[0039] The polyolefin substrate layer used to make the recyclable laminate structure of the present disclosure may include a single layer (monolayer) made of one or more polyolefins, olefin polymers, or ethylene vinyl acetate (EVA); or ethylene vinyl alcohol (EVOH), or the recyclable laminate structure may include a multilayer structure made of one or more polyolefin layers.

[0040] The polyolefin substrate layer of the present disclosure can be a multilayer film containing more than one layer. As used herein, "multilayer film" means any film having more than one layer. For example, a multilayer film can have two, three, four, five or more layers. A multilayer film can be described as having layers represented by letters to help describe the layers. For example, a two-layer film having two different polyolefin film layers can be represented as A / B; and a three-layer film having a core layer B and two outer layers A and C can be represented as A / B / C. Similarly, a structure having two core layers B and C and two outer layers A and D would be represented as A / B / C / D. The polyolefin film can be a coextruded film having an odd number of layers from 3 to 35, such as from 3 to 11 or from 3 to 7. For example, the polyolefin substrate layer can be a three-layer multilayer film composed of three polyethylene layers.

[0041] The polyolefin substrate layer may be a multilayer film consisting of one or more of the following HDPE, LLDPE and LDPE layers; a PP film, ie a biaxially oriented PP (BOPP) film layer or a machine direction oriented PE (MDO PE) or biaxially oriented PE (BOPE).

[0042] The thickness of the polyolefin substrate layer may be, for example, 8 (μm) to 125 μm, 20 μm to 100 μm, or 25 μm to 50 μm.

[0043] The polyolefin substrate layer may have a thickness less than or equal to (≤) 1 mm, such as ≤ 900 μm, ≤ 800 μm, ≤ 700 μm, ≤ 600 μm, ≤ 500 μm, ≤ 400 μm, ≤ 300 μm, or even ≤ 200 μm. The polyolefin substrate layer may have a thickness greater than or equal to (≥) 1 μm, ≥ 5 μm, ≥ 10 μm, ≥ 20 μm, ≥ 30 μm, ≥ 40 μm, or even ≥ 50 μm. As will be appreciated by those skilled in the art, in a multilayer film, the thickness of different layers may be the same or different; and the layer thickness may be selected based on the disclosure herein by techniques known to those skilled in the art.

[0044] The polyolefin substrate layer can be produced from a low-density polymer. The polyolefin substrate layer can be a polyethylene / polyethylene film or a polypropylene / polypropylene film. The polyolefin substrate layer can be blown or coextruded.

[0045] Solvent-free laminating adhesives

[0046] The solvent-free laminating adhesive may have a Hansen solubility factor, calculated as described below, of less than or equal to 21. The solvent-free laminating adhesive may have a Hansen solubility factor, calculated as described below, of 16 to 21. All values ​​and subranges therein are included and disclosed. For example, the solvent-free laminating adhesive may have a Hansen solubility factor of 21, 20, 19, 18, or 17, to a lower limit of 16, 17, 18, 19, or 20.

[0047] It is contemplated that two components, an isocyanate component and a polyol component, are employed in the present disclosure. It is also contemplated that the isocyanate component and the polyol component of the disclosed adhesive composition can be prepared separately and, if necessary, stored until the adhesive composition is desired to be used. The NCO index (the number of moles of NCO functional groups to hydroxyl functional groups) of the mixed adhesive can be 1.0 to 1.5, or 1.1 to 1.3. The mixing ratio of the isocyanate component to the polyol component can be 100:80-100:30 or 100:70-100:40.

[0048] The adhesive composition can be directly mechanically recycled for use in polyolefin laminates. The performance change of the polyolefin laminate coated with the adhesive composition after direct mechanical recycling should not exceed 33% when compared to the performance of the substrate layer without the adhesive dispersion composition. This is referred to as having a "recyclability" of 25%. Properties that can be tested to determine recyclability include, but are not limited to, the following properties of the laminate: (1) mechanical properties (e.g., tensile modulus), and (2) IR absorption properties. If desired, other properties of the film present in the multilayer laminate structure of recycled material, such as clarity and gel content, can be measured to further determine the recyclability of the laminate film structure.

[0049] The adhesive compositions of the present disclosure may include one or more additional optional conventional ingredients or additives including, but not limited to, catalysts, tackifiers, plasticizers, rheology modifiers, tackifiers, antioxidants, fillers, colorants, pigments, surfactants, polymers (including, for example, thermoplastic resins other than those discussed herein above), dehydrating agents (including, for example, silanes), benzoyl chloride, other polyols (including, for example, aliphatic polyols), ultraviolet indicators, and combinations of two or more of these.

[0050] The adhesive composition may include, for example, an adhesion promoter. Non-limiting examples of suitable adhesion promoters include coupling agents such as silane coupling agents, titanate coupling agents, and aluminate coupling agents; epoxy resins, phosphoric acid, polyphosphoric acid, and phosphate esters.

[0051] Examples of silane coupling agents that can be used in the present disclosure include, but are not limited to, aminosilanes such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; epoxysilanes such as β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, γ-glycidoxypropyl-trimethoxysilane, and γ-glycidoxypropyltriethoxysilane; vinylsilanes such as vinyltri(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane; hexamethyldisilazane; γ-mercaptopropyltrimethoxysilane; and mixtures thereof.

[0052] Examples of titanate coupling agents useful in the present disclosure include, but are not limited to, tetraisopropoxytitanium, tetra-n-butoxytitanium, butyl titanate dimer, tetrastearyl titanate, titanium acetylacetonate, titanium lactate, tetraoctyl titanate, titanium lactate, tetrastearyl titanium; and mixtures thereof.

[0053] Examples of epoxy resins that can be used in the present disclosure include, but are not limited to, various readily available epoxy resins such as bisphenol a-epichlorohydrin (epi-bis) type epoxy resins, novolac type epoxy resins, β-methylepichlorohydrin type epoxy resins, cyclic oxirane type epoxy resins, glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, polyethylene glycol ether type epoxy resins, glycol ether type epoxy resins, epoxidized fatty acid ester type epoxy resins, polycarboxylate type epoxy resins, aminoglycidyl type epoxy resins, resorcinol type epoxy resins; and mixtures thereof.

[0054] The adhesion promoter may be a phosphate compound or epoxy silane ((3-glycidoxypropyl)-trimethoxysilane). Phosphoric acid may be incorporated into the polyol component, while epoxy silane may be incorporated into the isocyanate component. Both epoxy silane and phosphoric acid may be incorporated into the polyol component.

[0055] When used, the amount of optional components may be 0 wt % to 15 wt %, 0.01 wt % to 10 wt %, or 0.1 wt % to 5 wt %, based on the total amount of components in the adhesive composition.

[0056] Adhesive polyurethane prepolymer

[0057] The isocyanate in the isocyanate component can be, for example, an isocyanate monomer, a polyisocyanate (eg, dimer, trimer, etc.), an isocyanate prepolymer, and a mixture of two or more of the foregoing. "Polyisocyanate" is any compound containing two or more isocyanate groups.

[0058] The polyurethane prepolymer composition may comprise at least 20% by weight of an aromatic isocyanate based on the weight of the prepolymer. The polyurethane prepolymer composition may comprise from 20% to 50% by weight based on the weight of the prepolymer composition. All internal values ​​and subranges are disclosed. For example, the polyurethane prepolymer composition may comprise an upper limit of 50%, 45%, 40%, 35%, 30% or 25% by weight to a lower limit of 20%, 25%, 30%, 35%, 40% or 45% by weight based on the weight of the prepolymer composition.

[0059] Aromatic-based isocyanates useful in the present disclosure may include, for example, one or more polyisocyanate compounds, including, but not limited to, for example, 1,3-phenylene diisocyanate and 1,4-phenylene diisocyanate; 1,5-naphthylene diisocyanate; 2,4'-diphenylmethane diisocyanate (2,4'-MDI); 4,4'-diphenylmethane diisocyanate (4,4'-MDI); 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 3,3'-dimethyl-4,4'-biphenyl diisocyanate (TODI) and isomers thereof; polymeric isocyanates; and mixtures of two or more thereof.

[0060] Examples of some commercial aromatic components that can be used in the present disclosure include, but are not limited to, ISONATE, available from The Dow Chemical Company. TM 125M, ISONATE TM 143L, ISONATE TM 50OP, ADCOTTE TM L76-204, COREACTANT CT TM and CATALYST F TM DESMODUR purchased from The Covestro Company TM E 2200 / 76; and mixtures thereof.

[0061] The polyurethane prepolymer composition may include no more than 10 wt % of the natural oil polyol, based on the weight of the prepolymer composition. The polyurethane prepolymer may comprise from 0.1 wt % to 10 wt % based on the weight of the prepolymer composition. All internal values ​​and subranges are disclosed. For example, the polyurethane prepolymer may comprise 10 wt %, 9.5 wt %, 9.0 wt %, 8.5 wt %, 8.0 wt %, 7.5 wt %, 7.0 wt %, 6.5 wt %, 6.0 wt %, 5.5 wt %, 5.0 wt %, 4.5 wt %, 4.0 wt %, 3.5 wt %, 3.0 wt %, 2.5 wt %, 2.0 wt %, 1.5 wt %, 1.0 wt %, or more, based on the weight of the prepolymer composition. %, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6.0 wt%, 6.5 wt%, 7.0 wt%, 7.5 wt%, 8.0 wt%, 8.5 wt%, 9.0 wt%, or 9.5 wt%. Examples of natural oils suitable for use in the present disclosure include, but are not limited to, castor oil, rapeseed oil, and palm kernel oil.

[0062] The polyurethane prepolymer composition may comprise at least 60% by weight of polypropylene glycol based on the weight of the prepolymer composition. The polyurethane prepolymer composition may comprise from 60% to 80% by weight of polypropylene glycol based on the weight of the prepolymer. All internal values ​​and subranges are inclusive. For example, the polyurethane prepolymer composition may comprise an upper limit of 80%, 75%, 70%, or 65% by weight to a lower limit of 60%, 65%, 70%, or 75% by weight of polypropylene glycol.

[0063] The NCO% of the prepolymer can be less than or equal to 12% based on the weight of the prepolymer. The NCO% of the prepolymer can be from 1% to 12%. All internal values ​​and subranges are disclosed. For example, the NCO% of the prepolymer can be from an upper limit of 12%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, or 2% to a lower limit of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0064] Adhesive Hydroxyl Functional Co-Reactant

[0065] The adhesive hydroxyl-functional co-reactant may comprise 80% to 100% of a natural oil polyol, based on the weight of the co-reactant composition. All internal values ​​and subranges are disclosed. For example, the adhesive hydroxyl-functional co-reactant may comprise an upper limit of 100%, 95%, 90%, or 85% to a lower limit of 80%, 85%, 90%, or 95% of a natural oil polyol, based on the weight of the co-reactant composition. Examples of natural oils suitable for use in the present disclosure include, but are not limited to, castor oil, rapeseed oil, and palm kernel oil.

[0066] The adhesive hydroxyl-functional coreactant composition can include from 0% to 20% by weight of a hydrophobic polyether polyol, based on the weight of the coreactant composition, including all values ​​and subranges therein. For example, the adhesive hydroxyl-functional coreactant can include an upper limit of 20%, 15%, 10%, or 5% by weight of a hydrophobic polyether polyol, to a lower limit of 0%, 5%, 10%, or 15% by weight, based on the weight of the coreactant composition. Suitable hydrophobic polyether polyols include, but are not limited to, polypropylene glycol, polybutylene glycol, or polypentane glycol.

[0067] Suitable commercial examples include, but are not limited to, VORANOL TM CP 450 and Vorapel T5001.

[0068] The adhesive hydroxyl functional coreactant composition can include 0% to 2% by weight of the phosphate adhesion promoter based on the weight of the coreactant composition. All internal values ​​and subranges are included. For example, the coreactant composition can include an upper limit of 2%, 1.8%, 1.6%, 1.4%, 1.2%, 1.0%, 0.8%, 0.6%, 0.4%, or 0.2% by weight to a lower limit of 0%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, or 1.8% by weight of the phosphate adhesion promoter based on the weight of the coreactant composition. Suitable commercial examples include, but are not limited to, those available from DOW TM Chemical's MOR-FREE TM 88-138.

[0069] Adhesives and laminate formation

[0070] The solventless laminating adhesive composition can be produced by mixing, blending, mixing or any other method known in the art a polyurethane prepolymer composition comprising the reaction product of at least 20 wt % of an aromatic isocyanate, based on the weight of the prepolymer composition, no more than 10 wt % of a natural oil polyol, based on the weight of the prepolymer composition, and at least 60 wt % of a polypropylene glycol, based on the weight of the prepolymer composition, wherein the NCO% of the prepolymer is less than 10%, with a hydroxyl-functional co-reactant composition comprising from 80 wt % to 100 wt % of a natural oil polyol, based on the weight of the co-reactant composition, from 0 wt % to 20 wt % of a hydrophobic polyether polyol, based on the weight of the co-reactant composition, and from 0 wt % to 2 wt % of a phosphate adhesion promoter, based on the weight of the co-reactant composition, in the ratios described above; wherein the solventless laminating adhesive so produced is capable of being directly mechanically recycled for use in polyolefin laminates.

[0071] Generally speaking, the polyurethane prepolymer composition and the hydroxyl-functional coreactant composition can be prepared separately from each other, and the components can be stored in separate containers. Optional additives can be present in the polyurethane prepolymer composition or the hydroxyl-functional coreactant composition or both. Suitable containers for storing each component can be, for example, drums, cans, bags, barrels, cans, cylinders, bottles, barrels or tubes. The two components can be mixed with each other before applying the adhesive composition, or the two components can be mixed only during application.

[0072] Adhesive can be applied to the surface of at least one base material and can be carried out by conventional means, such as by using a roller coater, a scraper or an extrusion device and technology. Adhesive composition can be applied with 1 or larger level (in grams per square meter of dry composition) in one embodiment, and with 2 or larger level in another embodiment. Adhesive composition can be applied with 7 or still less level (in grams per square meter of dry composition) in one embodiment, and with 5 or still less level in another embodiment.

[0073] Another embodiment of the present invention is directed to a method for bonding at least a first substrate to at least a second substrate, the method comprising the steps of: (a) mixing a polyurethane prepolymer composition and a hydroxyl-functional co-reactant composition as described above to form an adhesive, (b) applying the adhesive of step (a) to at least one of the surfaces of the substrates to be bonded, and (c) contacting (or joining) the first and second substrates to be bonded together with the adhesive.

[0074] The recyclable laminate structures disclosed herein can be used in packaging applications such as manufacturing a variety of packaging materials and products. Non-limiting examples of uses for the disclosed recyclable laminate structures include bulk packaging for food grains / beans, packaging for seeds, packaging for lentils and grains, packaging for fertilizers, packaging for oilseeds, packaging for sugar, packaging for salt, packaging for pharmaceuticals, packaging for other foods, and packaging for personal care items such as bath salts, detergent pods, etc. The recyclable laminate structures can also be used as wrappers for baby wipes, feminine hygiene products, cereal bars, protein bars, cheese, and confectionery products.

[0075] Test Method

[0076] Hansen solubility calculation

[0077] Hansen Solubility Parameter (HSP), Arithmetic Distance (R a ), geometric distance (R b ) and the calculation of the aliphatic carbon ratio (ACR) are described in the "SYSTEMS, METHODS, AND NON- TRANSITORYCOMPUTER-READABLE MEDIUM OF PREDICTING A COMPATIBILITY OF AN ADHESIVE OR COATING COMPOSITION AND POLYOLEFIN POLYMERS” In brief, the model works as follows. For each component in the adhesive composition, the number of moles of functional groups is calculated. (Functional groups can be found in DW van Krevelen's book "Properties of Polymers" 4th edition, completely revised Listed in Table 7.12 of , purchased from Elsevier: Amsterdam, 2009, ebook ISBN: 9780080915104. )

[0078] Then, the values ​​of the group contributions are calculated, including the molar attraction function (F t ), polar component (F p ), molar volume (V), Lydersen correction of solvent (Δ T ) and Lydersen correction of polymers (Δ T (p) ) or a combination thereof. All values ​​and equations are in the "SYSTEMS,METHODS,AND NON-TRANSITORYCOMPUTER- READABLE MEDIUM OF PREDICTING A COMPATIBILITY OF AN ADHESIVE OR COATING COMPOSITION AND POLYOLEFIN POLYMERS” Finally, calculate HSP, R a and R b .

[0079] While the HSP of the polyurethane adhesive or coating composition is less than or equal to 22.7 and the ACR of the polyurethane adhesive or coating composition is greater than or equal to 6.9, the HSP and ACR values ​​may be different for adhesive or coating compositions based on chemistries other than polyurethane.

[0080] When the arithmetic distance (R a ) is less than or equal to 12 and the ACR of the polyurethane adhesive or coating composition is greater than or equal to 6.9, for adhesives or coating compositions based on chemistries other than polyurethane, the ACR and R a The value can be different.

[0081] When the geometric distance (R b ) is less than or equal to 6 and the ACR of the adhesive or coating composition is greater than or equal to 6.9, for adhesives or coating compositions based on chemistries other than polyurethanes, the ACR and R b The value can be different.

[0082] T-peel bond strength

[0083] Three 1-inch strips of each laminate were tested at a rate of 10 inches / minute using an Instron tensile tester with a 200N load cell. High and average strengths were reported along with the failure modes. In the case of film tear and stretch, high values ​​were reported, while in the other failure modes, average T-peel bond strengths were reported. Typical failure modes include:

[0084] AF - Adhesive Failure (adhesion to primary substrate)

[0085] AT - Adhesive Transfer (bonding to secondary substrates)

[0086] AS - Adhesive Cracking (Cohesive Failure of Adhesive)

[0087] FT-film tear (substrate stretch or failure)

[0088] T-tunneling

[0089] In-bag boiling test

[0090] The 9-inch by 11-inch cured laminate was folded over to form a double layer, so that the PE film of one layer was in contact with the PE film of the other layer. The edges were then trimmed with a paper cutter to obtain a folded sheet measuring approximately 5 inches by 7 inches. The edges were then heat-sealed to form a pouch with interior dimensions of 4 inches by 6 inches, and the pouch was filled through the open edge with 100 mL of a 1 / 1 / 1 sauce blend consisting of equal parts by weight of ketchup, vinegar, and vegetable oil. The pouch was then sealed in a manner that minimized air entrapment and carefully immersed in boiling water for either thirty or sixty minutes. After boiling, the extent of bulging, delamination, or leakage was compared to the marked pre-existing defects. The bag was then emptied, and at least three 1-inch strips were cut from the pouch, and the T-peel bond strength was measured as quickly as possible.

[0091] COF

[0092] The COF of the laminated films was tested after a curing time of 21 days using a TMICOF tester in a controlled room at 25°C and 50% humidity according to ASTM D1894.

[0093] Primary aromatic amines (PAA)

[0094] After the samples were cured at 25°C, 50% RH for 2 or 3 days, the laminate structures were tested for primary aromatic amine ("PAA") decay. The cured laminate structures were folded to form a double layer so that the polyethylene film of one layer was in contact with the polyethylene film of the other layer. The edges were then trimmed with a paper cutter to obtain a folded sheet of approximately 6.5 inches by 7 inches. The edges were then heat sealed to form pouches with interior dimensions of 5.5 inches by 5.6 inches. The pouches were then filled with 100 mL of 3% acetic acid. The pouches were extracted at 70°C in an air-circulating oven for 2 hours. After quenching the pouches in cold tap water, the test solution was allowed to equilibrate at room temperature and 100 mL of the test solution was transferred to a beaker. The amount of primary aromatic amine extracted into the 3% acetic acid solution was determined by a classical colorimetric method.

[0095] Recyclability

[0096] Recyclability was evaluated by comparing the mechanical properties of the laminated structures containing adhesive to films without adhesive after the HAAKE compounding process described below and pressing into sheets. Mechanical properties that varied within ±25% between the experimental and control samples were defined as recyclable.

[0097] The Haake compounding process involves mixing and compressing sheet molding of the film (laminated or control) in an RS5000 equipped with a Haake Rheomix 3000 mixer with a 25% GF Teflon liner and a cam-type rotor. The mixer is attached to an RS5000 torque rheometer drive unit, which is controlled by System 5PC-based control / data acquisition software designed to operate the RS5000 drive.

[0098] Film samples were melt blended in a heated mixer at 160°C for PE laminates and 190°C for BOPP laminates for 20-25 minutes. Mixing speed was a maximum of 5-20 rpm, with a nitrogen purge block to limit sulfur oxidation. Once melt blending was complete, the samples were quickly removed and cooled in the cooling platens of a hydraulic carver at 20,000 psi for approximately 3 minutes.

[0099] Compressed sheet samples were prepared using 15-16 gram Haake remolded samples in a 188°C carver press with a 4.5" x 4.5" x 0.035 die set. The sample was heated in the upper platen of the carver press for the first 3 minutes, then moved to the lower platen and cooled to 20°C for 3 minutes. Air bubbles were preferably avoided, and widths of 1 / 8" or less were desirable.

[0100] The mechanical properties of the control sample and the inventive sample were tested on an Instron tensile tester according to ASTM D 1708. The results are reported in Tables 11 and 12 below.

[0101] Melt flow rate

[0102] Melt flow rate (MFR) was measured at the HHD ASTM laboratory using ASTM standard D1238, Method B, and a Tinius Olsen Plastometer MP993 with a 9.55 mm diameter and 162 mm long cylinder. A 9.55 mm diameter die with a 2.0955 mm center hole diameter and 8 mm length and a 9.474 mm diameter piston were used. Samples of at least 2.8 grams were used. A 2.16 kg piston weight was used to measure polymer flow at 190°C for PE samples and 210°C for BOPP samples using a thermostatically controlled heated steel cylinder.

[0103] Example

[0104] The materials used are listed below in Table 1. All commercial samples were purchased from DOW Inc.

[0105] Table 1: Materials

[0106]

[0107]

[0108] Prepolymer synthesis

[0109] Experimental prepolymer compositions 1, 2 and 3 (PP 1, PP 2 and PP 3) are shown in Table 2 below. A 3 L three-necked flask was dried and purged with N2 and connected to a condenser, an overhead mixer, a thermocouple temperature controller and a nitrogen bubbler. A given amount of ISONATE TM 125M Isocyanate and / or ISONATE TM 50OP MDI was loaded into the reactor and a given amount of VORANOL was added under mixing. TM 220-56N is loaded into the reactor, and then castor oil or modified castor oil POLYCIN TMGR-50 was loaded into the reactor. After bubbling N2 through the reactor for several minutes, the reactor was gradually heated to 78°C and then maintained at this temperature for two hours as the reaction proceeded. After two hours, the product was poured into a glass bottle and characterized as shown in Table 3.

[0110] Table 2: Prepolymer (PP) formulations of the present invention

[0111]

[0112] Table 3: Properties of the prepared prepolymers

[0113]

[0114] The co-reactant compositions 1 and 2 (CC 1 and CC 2) of the present invention are listed below in Table 4. These compositions were mixed by a high speed mixer at 1800 rpm for 1 minute.

[0115] Table 4: Co-reactant compositions

[0116]

[0117] HSP, R a and R b The example calculations are in the section called "SYSTEMS, METHODS, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM OF PREDICTING A COMPATIBILITY OF AN ADHESIVE OR COATING COMPOSITION AND POLYOLEFINPOLYMERS" is given in the application, in which Dow's polyurethane adhesive " The mixing ratio of 102E / Coreactant CT is 100:5.2.

[0118] The solubility parameters calculated as described above are shown in Table 5 below.

[0119] Table 5: Calculated Hansen Solubility Parameters

[0120]

[0121] Laminated samples were prepared using a Nordmecanica LaboCombi pilot laminator. The disclosed formulations were first applied to HDPE or BOPP primary films, followed by lamination with LDPE GF-19 or BOPP sealing secondary films. Coat weights were maintained within the typical application range for solventless laminating adhesives; specifically, 1.0 to 1.2 lb / ream. The resulting laminates were cured in a controlled room (25°C, 50% RH). Bond strength was measured on HDPE / / LDPE and BOPP / / BOPP sealing structures after 1, 7, 14, and 28 days, as shown in the table below.

[0122] Table 6: Adhesive properties in HDPE / / LDPE structures (g / 25.4 mm)

[0123]

[0124] *Too strong to separate for testing

[0125] Table 7: Adhesive properties of BOPP / / BOPP seal structure (g / 25.4mm)

[0126]

[0127]

[0128] Table 8: Effect of adhesive on 7-day COF of HDPE and LDPE films in laminated structures

[0129]

[0130] Table 9: Effect of adhesive on 7-day COF of BOPP and BOPP sealing films in laminated structures

[0131]

[0132]

[0133] Table 10: PAA decay results for IE 3 in HDPE / / GF-19 and BOPP / / BOPP seal structures

[0134]

[0135] Recyclability

[0136] Recyclability was evaluated by comparing the mechanical properties of the laminated structures containing adhesive to films without adhesive after the HAAKE compounding process described below and forming compressed sheets. Mechanical properties that varied within ±25% between the experimental and control samples were defined as recyclable.

[0137] The Haake compounding process involves mixing and compressing sheet molding of the film (laminated or control) in an RS5000 equipped with a Haake Rheomix 3000 mixer with a 25% GF Teflon liner and a cam-type rotor. The mixer is attached to an RS5000 torque rheometer drive unit, which is controlled by System 5PC-based control / data acquisition software designed to operate the RS5000 drive.

[0138] Film samples were melt blended in a heated mixer at 160°C for PE laminates and 190°C for BOPP laminates for 20-25 minutes. Mixing speed was a maximum of 5-20 rpm, with a nitrogen purge block to limit sulfur oxidation. Once melt blending was complete, the samples were quickly removed and cooled in the cooling platens of a hydraulic carver at 20,000 psi for approximately 3 minutes.

[0139] Compressed sheet samples were prepared using 15-16 gram Haake remolded samples in a 188°C carver press with a 4.5" x 4.5" x 0.035 die set. The sample was heated in the upper platen of the carver press for the first 3 minutes, then moved to the lower platen and cooled to 20°C for 3 minutes. Air bubbles were preferably avoided, and widths of 1 / 8" or less were desirable.

[0140] The mechanical properties of the control sample and the inventive sample were tested on an Instron tensile tester according to ASTM D 1708. The results are reported in Tables 11 and 12 below.

[0141] Table 11: Recyclability of HDPE / / LDPE films using comparative and inventive samples

[0142]

[0143]

[0144] *For the control sample, the change in mechanical properties is defined as "0". For the other samples, changes in mechanical properties were observed compared to the control.

[0145] Table 12: Recyclability of BOPP laminates using inventive and comparative samples

[0146]

[0147] *For the control sample, the change in mechanical properties is defined as "0". For the other samples, changes in mechanical properties were observed compared to the control.

[0148] The melt flow rate was measured as described above in the test procedure. The results are reported in Table 13 below.

[0149] Table 13: Melt index of laminated samples after HAAKE compounding process

[0150]

[0151] The molecular weight of the BOPP samples before and after HAAKE compounding was measured as described above in the test procedure. The results are reported in Table 14 below.

[0152] Table 14: Molecular weight (Daltons) of BOPP / BOPP laminate samples after HAAKE compounding process

[0153]

Claims

1. A solvent-free laminating adhesive composition, comprising: a. A polyurethane prepolymer composition comprising the reaction product of the following components: i. at least 20% by weight, based on the weight of the prepolymer composition, of an aromatic isocyanate, ii. not more than 10 wt. % of a natural oil polyol, based on the weight of the prepolymer composition, and iii. at least 60 wt.% polypropylene glycol, based on the weight of the prepolymer composition, wherein the NCO% of the prepolymer is less than 10%; b. a hydroxyl-functional coreactant composition comprising: i. 80% to 100% by weight, based on the weight of the co-reactant composition, of a natural oil polyol, ii. 0% to 20% by weight, based on the weight of the co-reactant composition, of a hydrophobic polyether polyol, and iii. 0% to 2% by weight, based on the weight of the co-reactant composition, of a phosphate adhesion promoter; The solvent-free laminating adhesive composition can be directly mechanically recycled for use in polyolefin laminates.

2. The solventless laminating adhesive composition according to any preceding claim, wherein the Hansen Solubility Parameter calculated as disclosed in the specification is less than 21.

3. The polyurethane prepolymer composition of any preceding claim, wherein the aromatic isocyanate comprises 20 to 50 weight percent, based on the weight of the prepolymer composition.

4. The polyurethane prepolymer composition of any preceding claim, wherein propylene glycol comprises 60 to 80 weight percent, based on the weight of the prepolymer composition.

5. The polyurethane prepolymer composition according to any preceding claim, wherein the NCO is from 5% to 10%.

6. The solventless laminating adhesive composition according to any preceding claim, wherein the Hansen Solubility Parameter calculated as disclosed in the specification is from 16 to 21.

7. The polyurethane prepolymer of any preceding claim, wherein the natural oil polyol comprises from 0.1 wt% to 10 wt% based on the weight of the prepolymer composition.

8. A laminate produced using an adhesive according to any preceding claim.

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