Recyclable solvent-free adhesive

Abstract

Disclosed herein is a solventless laminating adhesive composition for polyolefin laminates, the solventless laminating adhesive composition comprising: (a) a polyurethane prepolymer composition, the polyurethane prepolymer composition comprising the reaction product of (i) at least 20 wt% aromatic isocyanate, based on the weight of the prepolymer composition, (ii) no more than 10 wt% 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 prepolymer NCO% is less than 10%, and (b) a hydroxyl-functional co-reactant composition, the hydroxyl-functional co-reactant composition comprising: (i) 80-100 wt% natural oil polyol, based on the weight of the co-reactant composition, (ii) 0-20 wt% hydrophobic polyether polyol, based on the weight of the co-reactant composition, and (iii) 0-2 wt% phosphate adhesion promoter, the solventless laminating adhesive composition being directly mechanically recyclable. Laminates made using the disclosed adhesive are also disclosed.

Description

[Technical Field]

[0001] This disclosure relates to solventless lamination adhesives. More particularly, this disclosure relates to solventless lamination adhesives with improved mechanical recyclability. [Background technology]

[0002] Introduction Polyurethane 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 application systems, while solventless systems are applied using five-roller application systems. When flexible packaging is used with food, adhesive strength and seal integrity are essential.

[0003] Conventional flexible packaging designs are based on functional layers such as polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), metallized PET-oriented polypropylene (OPP), aluminum foil, and nylon / polyimide laminated with sealable layers such as low-density polyethylene (LDPE) or cast polypropylene (CPP). Conventional flexible packaging is not recyclable because there is no economically practical and technically efficient process for separating the layers and subsequently recycling the individual films. Traditionally used laminating adhesives include either acrylic-based or polyurethane-based adhesives. Combinations of different polyolefin films laminated with such conventional adhesives are difficult to recycle due to the highly crosslinked nature of the adhesives, as well as chemical differences between the laminating adhesive and the polyolefin backbone of the films, resulting in the adhesives being incompatible with polyolefin film materials.

[0004] Therefore, there is a need for an adhesive that allows for a fully recyclable laminate construction with all the beneficial properties mentioned above, namely, good performance and the viability of recyclable packaging. Summary of the Invention

[0005] Disclosed herein is a solventless laminating adhesive composition for polyolefin laminates, the solventless laminating adhesive composition comprising: (a) a polyurethane prepolymer composition, the polyurethane prepolymer composition comprising the reaction product of (i) at least 20 wt% aromatic isocyanate, based on the weight of the prepolymer composition, (ii) no more than 10 wt% 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 prepolymer NCO% is less than 10%, and (b) a hydroxyl-functional co-reactant composition, the hydroxyl-functional co-reactant composition comprising: (i) 80-100 wt% natural oil polyol, based on the weight of the co-reactant composition, (ii) 0-20 wt% hydrophobic polyether polyol, based on the weight of the co-reactant composition, and (iii) 0-2 wt% phosphate adhesion promoter, the solventless laminating adhesive composition being directly mechanically recyclable for polyolefin laminates. Laminates made using the disclosed adhesive are also disclosed. DETAILED DESCRIPTION OF THE INVENTION

[0006] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional component, step, or procedure, whether or not it is specifically disclosed. For the avoidance of doubt, all compositions claimed through the use of the term "comprising" may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless otherwise stated to the contrary. In contrast, the term "consisting essentially of" excludes from the scope of any succeeding description 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 delineated or listed.

[0007] Numerical ranges disclosed herein include all values ​​between and including the lower and upper limits. Ranges containing explicit values ​​(e.g., ranges from 1 to 2, or 3 to 5, 6, or 7) include any subranges between any two explicit values ​​(e.g., the range 1 to 7 above includes subranges 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 that comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

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

[0010] A "polyisocyanate" is a molecule that contains 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 generic term polymer encompasses the term "homopolymer," which is commonly used to refer to a polymer prepared from only one type of monomer, as well as "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 polymerization of at least two different types of monomers. Thus, the generic term interpolymer includes copolymers and polymers prepared from three or more different monomers, such as terpolymers.

[0012] As used herein, "polyolefin" refers to an olefin-based polymer. As used herein, "olefin," sometimes referred to as "alkene," refers to a linear, branched, or cyclic compound containing 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 containing greater than 50% by weight of units derived from ethylene monomers and, optionally, one or more comonomers. This may include polyethylene homopolymer or copolymer (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 (m-LLDPE), which includes both linear and substantially linear low-density resins, medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

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

[0015] A "polyester" is a compound containing two or more ester linking groups 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, which have two OH groups, triols, which have three OH groups, and tetraols, which have four OH groups.

[0017] A "polyester polyol" is a compound that contains polyester and hydroxyl functional groups in the backbone structure of the compound.

[0018] A "polyether polyol" is a compound that contains polyether and hydroxyl functional groups in the backbone structure of the compound.

[0019] "Film" includes any thin, flat, extruded, blown, or cast thermoplastic article having a generally consistent and uniform thickness, unless it has an explicitly specified thickness, including when referring to a "film layer" of a thicker article.

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

[0021] Laminated film manufactured using adhesives Laminated films produced using adhesives can include polyolefin / polyolefin structures. Laminated films produced using adhesives can include polyethylene / polyethylene. Laminated films produced using adhesives can include HDPE / LDPE. Polyethylene / polyethylene structures can have adhesive strengths of 1000 g / 25.4 mm or greater. Polyolefin / polyolefin structures can have adhesive strengths of 1000 to 2500 g / 25.4 mm. All internal values ​​and subranges are included. For example, a polyethylene / polyethylene substrate layer may have an adhesive strength of an upper limit of 3000, 2500, 2400, 2300, 2200, 2100, 2000, 1900, 1800, 1700, 1600, 1500, or 1400 g / 25.4 mm to a lower limit of 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2200, or 2400 g / 25.4 mm.

[0022] Laminates manufactured using the adhesive may include a polyolefin / polyolefin structure. The polyolefin / polyolefin structure may include a BOPP / / BOPP seal structure and have an adhesive strength of 230 g / 25.4 mm or greater. The polyolefin substrate layer may include a BOPP / / BOPP seal structure and have an adhesive strength of 230 to 450 g / 25.4 mm. All internal values ​​and subranges are included. For example, the polyolefin substrate layer may include a BOPP / / BOPP seal structure and have an adhesive strength of from an upper limit of 600, 450, 430, 410, 390, 370, 350, 330, 310, 290, 270, or 250 g / 25.4 mm to a lower limit of 230, 250, 270, 290, 310, 330, 350, 370, 390, 410, or 430 g / 25.4 mm.

[0023] Laminates made using the adhesive may have a static or kinetic coefficient of friction (COF) of 0.150 to 0.400.

[0024] Polyolefin laminates produced using adhesives may have recyclability properties of 33% or less. Laminates produced using adhesives may have recyclability properties of 1.5% to 33%. All internal values ​​and subranges are included and disclosed. For example, laminates produced using adhesives may have recyclability properties from upper limits of 25%, 23%, 21%, 19%, 17%, 15%, 13%, 11%, 9%, 7%, 5%, or 3% to lower limits of 1.5%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, or 24%.

[0025] Polyethylene laminates produced using the adhesives may have a melt index after HAAKE compounding of 1.0 to 4.5 g / 10 min at a temperature of 210°C. All internal values ​​and subranges are included. For example, laminates produced using the adhesives may have a melt index after HAAKE 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 at upper limits to 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 at lower limits.

[0026] Laminates produced using the adhesive have a molecular weight M of 41,000 to 43,000 g after HAAKE compounding. n All internal values ​​and subranges are disclosed. For example, laminates made using the adhesive may have a molecular weight M of 41,000 to 42,000 g or 42,000 to 43,000 g after HAAKE compounding. n may have:

[0027] Laminates produced using the adhesive have a molecular weight M of 165,500g to 172,000g after HAAKE compounding. w All internal values ​​and subranges are included. For example, a laminate produced using the adhesive may have a molecular weight M of 165,500 to 168,000 g or 168,000 to 172,000 g after HAAKE compounding. w may have:

[0028] Laminates produced using the adhesive have a molecular weight M of 457,500 to 480,000 g after HAAKE compounding. z All internal values ​​and subranges are included. For example, a laminate produced using the adhesive may have a molecular weight M of 457,500 to 465,000 g or 465,000 to 480,000 g after HAAKE compounding. z may have:

[0029] Laminates produced using the adhesive have a molecular weight M of 100,000 to 110,000 g after HAAKE compounding. p All internal values ​​and subranges are included. For example, a laminate produced using the adhesive may have a molecular weight M of 100,000 to 106,000 g or 106,000 to 110,000 g after HAAKE compounding. p may have:

[0030] Laminates produced using the adhesive have a PDI (M) of 4.00-4.05 after HAAKE compounding. w / M n All internal values ​​and subranges are included. For example, a laminate made using the adhesive may have a PDI (M) of 4.00 to 4.02 or 4.02 to 4.05. w / M n ).

[0031] Polyolefin base layer The disclosed polyolefin substrate layer is made from an olefin-based polymer. The polyolefin substrate layer may include an ethylene-based polymer. Common forms of polyethylene known in the art include, but are not limited to, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), single-site catalyzed linear low-density polyethylene (m-LLDPE), including both linear and substantially linear low-density resins, 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, MDOPE, BOPE, and mixtures thereof.

[0032] Furthermore, 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 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 peroxide (see, e.g., U.S. Pat. No. 4,599,392). LDPE resins typically have densities ranging from 0.916 g / cm to 0.940 g / cm.

[0033] The term "LLDPE," as used herein, can include resins made using Ziegler-Natta catalyst systems, as well as resins made using single-site catalysts, including, but not limited to, bis-metallocene catalysts (sometimes referred to as "m-LLDPE"), phosphinimine, and constrained geometry catalysts, and post-metallocene molecular catalysts, including, but not limited to, bis(biphenylphenoxy) catalysts (also referred to as polyaryloxy ether 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. Patent Nos. 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 No. 3,645,992; heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Patent No. 4,076,698; and blends thereof (such as those disclosed in U.S. Patent No. 3,914,342 or U.S. Patent No. 5,854,045). LLDPE resins can be made 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 made via gas phase, solution phase, or slurry polymerization, and any combination thereof, using any type of reactor or reactor configuration known in the art.

[0034] Additionally, as used herein, the term "HDPE" generally refers to polyethylene prepared using a Ziegler-Natta catalyst, a chromium catalyst, or even a metallocene catalyst and having a density of about 0.940 g / cm or greater. The polyolefin substrate layer can be a multilayer film, including outer layers comprising an ethylene-based polymer.

[0035] Suitable polyethylene polymers for use in the present disclosure may be commercially available. Suitable commercially available polyethylene polymers include, but are not limited to, AGILITY™ (e.g., AGILITY™ 1000, AGILITY™ 1001, and AGILITY™ 1021), INNATE™ ST 50, ELITE™ 5940, ELITE™ 5960, DOW™ LDPE 6211, and DOW™ LDPE 7511, all available from The Dow Chemical Company.

[0036] The disclosed polyolefin substrate layer is made from an olefin-based polymer. The polyolefin substrate layer may include a propylene-based polymer. Common forms of polyethylene known in the art include, but are not limited to, BOPP and CPP films.

[0037] The polyolefin substrate layer used to make the recyclable laminate structures of the present disclosure may comprise a single layer (monolayer) made from one or more polyolefins, olefin polymers, or ethylene vinyl acetate (EVA), or may comprise ethylene vinyl alcohol (EVOH), or the recyclable laminate structures may comprise a multilayer structure made from one or more polyolefin layers.

[0038] The polyolefin substrate layer of the present disclosure may be a multilayer film containing more than one layer. As used herein, "multilayer film" refers to any film having multiple layers. For example, a multilayer film may have two, three, four, five, or more layers. A multilayer film may be described as having layers designated by letters to aid in describing the film. For example, a two-layer film having two different polyolefin film layers may be designated as A / B, and a three-layer film having a core layer B and two outer layers A and C may be designated as A / B / C. Similarly, a structure having two core layers B and C and two outer layers A and D would be designated as A / B / C / D. The polyolefin film may also 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 may be a three-layer multilayer film composed of three layers of polyethylene.

[0039] The polyolefin substrate layer may be a multilayer film composed of one or more layers of HDPE, LLDPE, and LDPE, a PP film, a biaxially oriented PP (BOPP) film layer, or a machine-direction oriented PE (MDO PE) or biaxially oriented PE (BOPE) film.

[0040] 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.

[0041] The polyolefin substrate layer may have a thickness of ≦1 mm, for example, ≦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 of ≧1 μm or more, ≧5 μm, ≧10 μm, ≧20 μm, ≧30 μm, ≧40 μm, or even ≧50 μm. As will be understood by those skilled in the art, in a multilayer film, the thicknesses of different layers may be the same or different, and the layer thicknesses may be selected by techniques known to those skilled in the art based on the disclosure herein.

[0042] The polyolefin substrate layer can be made of 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.

[0043] Solvent-free laminating adhesive The solventless lamination adhesive may have a Hansen Solubility Factor of 21 or less, calculated as described below. The solventless lamination adhesive may have a Hansen Solubility Factor of 16 to 21, calculated as described below. All internal values ​​and subranges are included and disclosed. For example, the solventless lamination adhesive may have a Hansen Solubility Factor of an upper limit of 21, 20, 19, 18, or 17 to a lower limit of 16, 17, 18, 19, or 20.

[0044] The present disclosure contemplates the use of two components: an isocyanate component and a polyol component. It is also contemplated that the isocyanate component and polyol component of the disclosed adhesive composition can be prepared separately and, if desired, stored until it is desired to use the adhesive composition. The NCO index (moles of NCO functional groups relative 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 to 100:30 or 100:70 to 100:40.

[0045] The adhesive composition may be directly mechanically recyclable for polyolefin laminates. Polyolefin laminates coated with the adhesive composition should have a performance change of 33% or less after direct mechanical recycling compared to the performance of a substrate layer that does not contain the adhesive dispersion composition. This is said to have a "recyclability characteristic" of 25%. Properties that can be tested to determine the recyclability characteristic include, but are not limited to, (1) mechanical properties (e.g., tensile modulus) and (2) IR absorption characteristics of the laminate. Other properties, such as the clarity and gel content of the film present in the multi-layer laminate structure of recycled materials, can also be measured as needed to further determine the recyclability of the laminate film structure.

[0046] The adhesive compositions of the present disclosure may include one or more additional optional conventional components or additives, including, but not limited to, for example, catalysts, tackifiers, plasticizers, rheology modifiers, adhesion promoters, antioxidants, fillers, colorants, pigments, surfactants, polymers (including, for example, thermoplastic resins other than those discussed hereinabove), dehydrating agents (including, for example, silanes), benzoyl chloride, other polyols (including, for example, aliphatic polyols), ultraviolet light indicators, and combinations of two or more thereof.

[0047] 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.

[0048] Examples of silane coupling agents useful in the present disclosure include, but are not limited to, aminosilanes such as γ-aminopropyltriethoxysilane, γ-aminopropyl-trimethoxysilane, 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 vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane; hexamethyldisilazane; γ-mercaptopropyl-trimethoxysilane; and mixtures thereof.

[0049] 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, tetraoctylene glycol titanate, titanium lactate, tetrastearoxytitanium; and mixtures thereof.

[0050] Examples of epoxy resins useful in the present disclosure include, but are not limited to, a variety of 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, polyglycol ether type epoxy resins, glycol ether type epoxy resins, epoxidized fatty acid ester type epoxy resins, polycarboxylic acid ester type epoxy resins, aminoglycidyl type epoxy resins, resorcinol type epoxy resins, and mixtures thereof.

[0051] The adhesion promoter can be a phosphate ester compound or an epoxy silane ((3-glycidyloxypropyl)-trimethoxysilane). The phosphoric acid can be incorporated into the polyol component, while the epoxy silane can be incorporated into the isocyanate component. Both the epoxy silane and the phosphoric acid can be incorporated into the polyol component.

[0052] When used, the amount of optional components can be 0% to 15% by weight, 0.01% to 10% by weight, or 0.1% to 5% by weight, based on the total amount of components in the adhesive composition.

[0053] Adhesive polyurethane prepolymer The isocyanate in the isocyanate component can be, for example, an isocyanate monomer, a polyisocyanate (e.g., a dimer, trimer, etc.), an isocyanate prepolymer, or a mixture of two or more thereof. A "polyisocyanate" is any compound containing two or more isocyanate groups.

[0054] The polyurethane prepolymer composition may comprise at least 20 weight percent aromatic isocyanate, based on the weight of the prepolymer. The polyurethane prepolymer composition may comprise 20 to 50 weight percent, based on the weight of the prepolymer composition. All internal values ​​and subranges are disclosed. For example, the polyurethane prepolymer composition may comprise from a lower limit of 50, 45, 40, 35, 30, or 25 weight percent to an upper limit of 20, 25, 30, 35, 40, or 45 weight percent, based on the weight of the prepolymer composition.

[0055] Aromatic isocyanates useful in the present disclosure can include, for example, one or more polyisocyanate compounds, including, but not limited to, 1,3- 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.

[0056] Some examples of commercially available aromatic components useful in the present invention include, but are not limited to, ISONATE™ 125 M, ISONATE™ 143L, ISONATE™ 50OP, ADCOTTE™ L76-204, COREACTANTCT™, and CATALYST F™, available from The Dow Chemical Company; DESMODUR™ E 2200 / 76, available from The Covestro Company; and mixtures thereof.

[0057] The polyurethane prepolymer composition may include up to 10 wt. % of a natural oil polyol based on the weight of the prepolymer composition. The polyurethane prepolymer may comprise 0.1 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 from an upper limit of 10, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, 6.0, 5.5, 5.0, 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, 1.5, 1.0, or 0.05 wt. % to a lower limit of 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, or 9.5 wt. % based on the weight of the prepolymer composition. Examples of natural oils suitable for use in the present disclosure include, but are not limited to, castor oil, rapeseed, and palm kernel oil.

[0058] The polyurethane prepolymer composition may comprise at least 60 wt. % polypropylene glycol, based on the weight of the prepolymer composition. The polyurethane prepolymer composition may comprise 60 to 80 wt. % polypropylene glycol, based on the weight of the prepolymer. All internal values ​​and subranges are included. For example, the polyurethane prepolymer composition may comprise from an upper limit of 80, 75, 70, or 65 wt. % polypropylene glycol to a lower limit of 60, 65, 70, or 75 wt. % polypropylene glycol.

[0059] The NCO% of the prepolymer can be 12% or less, based on the weight of the prepolymer. The NCO% of the prepolymer can be 1-12%. 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%.

[0060] Adhesive Hydroxyl-Functional Coreactants The adhesive hydroxyl-functional coreactant may comprise 80 to 100% natural oil polyol, based on the weight of the coreactant composition. All internal values ​​and subranges are disclosed. For example, the adhesive hydroxyl-functional coreactant may comprise an upper limit of 100, 95, 90, or 85% to a lower limit of 80, 85, 90, or 95% natural oil polyol, based on the weight of the coreactant composition. Examples of natural oils suitable for use in this disclosure include, but are not limited to, castor, rapeseed, and palm kernel oil.

[0061] The adhesive hydroxyl-functional coreactant composition may comprise 0 to 20 weight percent hydrophobic polyether polyol, based on the weight of the coreactant composition. All internal values ​​and subranges are included. For example, the adhesive hydroxyl-functional coreactant may comprise an upper limit of 20, 15, 10, or 5% to a lower limit of 0, 5, 10, or 15% hydrophobic polyether polyol, based on the weight of the coreactant composition. Suitable hydrophobic polyether polyols include, but are not limited to, polypropylene glycol, poly 1,2-butylene glycol, or poly 1,2-pentylene glycol.

[0062] Suitable commercially available examples include, but are not limited to, VORANOL™ CP 450 and Vorapel T5001.

[0063] The adhesive hydroxyl-functional coreactant composition may include 0 to 2 weight percent phosphate adhesion promoter, based on the weight of the coreactant composition. All internal values ​​and subranges are included. For example, the coreactant composition may 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 weight percent 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 weight percent phosphate adhesion promoter, based on the weight of the coreactant composition. Suitable commercially available examples include, but are not limited to, MOR-FREE™ 88-138, available from DOW™ Chemical.

[0064] Adhesive and Laminate Formation The solventless laminating adhesive composition can be made through mixing, admixing, blending, or any other process known in the art, a polyurethane prepolymer composition comprising the reaction product of at least 20 wt% aromatic isocyanate, based on the weight of the prepolymer composition, no more than 10 wt% natural oil polyol, based on the weight of the prepolymer composition, and at least 60 wt% polypropylene glycol, based on the weight of the prepolymer composition, wherein the NCO% of the prepolymer is less than 10%, together with a hydroxyl-functional co-reactant composition comprising, in the ratios above, 80-100 wt% natural oil polyol, based on the weight of the co-reactant composition, 0-20 wt% hydrophobic polyether polyol, based on the weight of the co-reactant composition, and 0-2 wt% phosphate adhesion promoter, based on the weight of the co-reactant composition, and the solventless laminating adhesive so made is directly mechanically recyclable for polyolefin laminates.

[0065] Generally, the polyurethane prepolymer composition and the hydroxyl-functional coreactant composition can be prepared separately from one another, and the components can be stored in separate containers. Optional additives can be present in either the polyurethane prepolymer composition or the hydroxyl-functional coreactant composition, or both. Suitable containers for storing each component can be, for example, drums, hobs, bags, buckets, cans, jars, bottles, cartridges, or tubes. The two components can be mixed together before application of the adhesive composition, or the two components can be mixed only during application.

[0066] Application of the adhesive to the surface of at least one substrate can be accomplished by conventional means, such as using a roll coater, doctor blade, or extrusion equipment and process. The adhesive composition can be applied at a level of 1 or more, in one embodiment, and 2 or more, in grams of dry composition per square meter. The adhesive composition can be applied at a level of 7 or less, in another embodiment, and 5 or less, in grams of dry composition per square meter.

[0067] Another embodiment of the present invention relates to a process for adhering at least a first substrate to at least a second substrate, comprising: (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 adhered; and (c) contacting (or joining) the first and second substrates to one another to form an adhesive bond.

[0068] The recyclable laminate structures of the present disclosure can be used, for example, in packaging applications to produce a variety of packaging materials and products. Non-limiting examples of uses for the disclosed recyclable laminate structures include bulk packaging for food grains / pulses, seed packaging, lentil and cereal packaging, fertilizer packaging, oilseed packaging, sugar packaging, salt packaging, pharmaceutical packaging, other food packaging, and personal care items such as bath salts and detergent pods. The recyclable laminate structures can also be used as wrappers for baby wipes, feminine hygiene products, cereal bars, protein bars, cheese, and confectionery products.

[0069] Test Method Hansen Solubility Calculation Hansen's solubility parameter (HSP), arithmetic distance (R a ), geometric distance (R bThe calculation of the molecular weight, molecular weight, and aliphatic carbon ratio (ACR) is described in the application entitled "SYSTEMS, METHODS, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM OF PREDICTING A COMPATIBILITY OF AN ADHESIVE OR COATING COMPOSITION AND POLYOLEFIN POLYMERS." Briefly, the model works as follows: For each component in the adhesive composition, calculate the number of moles of functional groups. (Functional groups are specified in Table 7.12 of DW van Krevelen's book "Properties of Polymers," 4th ed., Completely Revised Edition, available from Elsevier: Amsterdam, 2009, ebook ISBN: 9780080915104.)

[0070] Then, the molar attraction function (F t ), polar components (F p ), molar volume (V), Lydersen correction for the solvent (Δ T ), and the Lydersen correction for polymers (Δ T (p) ), or a combination thereof, group contribution values ​​are calculated. All values ​​and formulas are found in Figure 4 of the application entitled "SYSTEMS, METHODS, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM OF PREDICTING A COMPATIBILITY OF AN ADHESIVE OR COATING COMPOSITION AND POLYOLEFIN POLYMERS." Finally, HSP, R a , and R b is calculated.

[0071] Where the HSP of a polyurethane adhesive or coating composition is 22.7 or less and the ACR of a polyurethane adhesive or coating composition is 6.9 or more, the HSP and ACR values ​​may be different for adhesive or coating compositions based on chemicals other than polyurethane.

[0072] Arithmetic distance (R a ) is 12 or less and the ACR of the polyurethane adhesive or coating composition is 6.9 or more, the ACR and R a The values ​​can be different.

[0073] Geometric distance (R b ) is 6 or less and the ACR of the adhesive or coating composition is 6.9 or more, for adhesive or coating compositions based on chemicals other than polyurethane, the ACR and R b The values ​​can be different.

[0074] T-peel adhesive strength An Instron tensile tester equipped with a 200 N load cell is used to test three 1-inch strips per laminate at a rate of 10 in / min. The high and average strengths are recorded along with the failure mode. For film tear and elongation, the high value is reported; for other failure modes, the average T-peel adhesion strength is reported. Typical failure modes include: AF - Adhesion failure (primary adhesive) AT-Adhesive Transfer (Secondary Adhesive) AS - Adhesion Separation (Cohesive Failure of Adhesive) FT-film tearing (stretching or breaking of the substrate) T-tunnel.

[0075] Boil-in-Bag Test The 9" x 11" cured laminate was folded to form a double layer, with the PE film of one layer in contact with the PE film of the other layer. The edges were then trimmed with a paper cutter to obtain a folded piece approximately 5" x 7" in size. The edges were then heat-sealed to form a pouch with an internal size of 4" x 6", and the pouch was filled through the open edge with 100 mL of a 1 / 1 / 1 sauce blend of equal parts by weight of ketchup, vinegar, and vegetable oil. The pouch was then sealed to minimize air entrapment and carefully immersed in boiling water for 30 or 60 minutes. After boiling, the degree of tunneling, delamination, or leakage was compared with the marked existing defects. The bag was then emptied, and at least three 1" strips were cut from the pouch and the T-peel adhesion strength was measured as soon as possible.

[0076] COF The COF of the laminated film is tested according to ASTM D1894 using a TMI COF tester in a controlled room at 25°C and 50% humidity after 21 days of curing time. Primary Aromatic Amine (PAA) After the samples are cured at 25°C and 50% RH for 2 or 3 days, the laminated structures are tested for primary aromatic amine ("PAA") degradation. The cured laminated structures are folded over to form a double layer, with one layer of polyethylene film in contact with the other. The edges are then trimmed with a paper cutter to obtain folded pieces approximately 6.5 inches by 7 inches. The edges are then heat-sealed to form pouches with an internal size of 5.5 inches by 5.6 inches. The pouches are then filled with 100 mL of 3% acetic acid. These pouches are extracted for 2 hours at 70°C in an air-circulating oven. After quenching the pouches with cold tap water, the test solution is allowed to equilibrate at room temperature, and 100 mL of the test solution is transferred to a beaker. The amount of primary aromatic amine extracted into the 3% acetic acid solution is determined using a classical colorimetric method.

[0077] Recyclability Recyclability is assessed by comparing the mechanical properties of the laminate structure containing the adhesive with a film containing no adhesive after the HAAKE compounding process and compression into a sheet as described below. Recyclability is defined as a variation in mechanical properties between the experimental and control samples within ±25%.

[0078] The Haake compounding process involves mixing and compressing a sheet compact of film (either laminate or control) in an RS5000 equipped with a Haake Rheomix 3000 mixer equipped with 25% GF Teflon bushings and a cam-type rotor. The mixer is attached to an RS5000 torque rheometer drive unit and controlled by System 5 PC-based control / data acquisition software designed to operate the RS5000 drive.

[0079] Film samples are melt blended in a heated mixer at 160°C for PE laminates and 190°C for BOPP laminates for 20-25 minutes. The mixing speed is a maximum of 5-20 rpm with a nitrogen purge block to limit sulfur oxidation. Once melt blending is complete, the samples are quickly removed and cooled in the cooling platens of a Carver hydraulic press at 20,000 psi for approximately 3 minutes.

[0080] Compressed sheet samples are prepared using 15-16 gram Haake remolded samples in a Carver press at 188°C with a 4.5" x 4.5" x 0.035" chase. The sample is heated on the upper platen of the Carver press for the first 3 minutes, then transferred to the lower platen and cooled to 20°C over 3 minutes. Air bubbles are preferably avoided, and a width of 1 / 8 inch or less is desirable.

[0081] The mechanical properties of both the control and inventive samples were tested on an Instron tensile tester according to ASTM D1708. The results are reported in Tables 11 and 12 below.

[0082] Melt Flow Rate Melt flow rate is tested in the HHD ASTM lab using ASTM standard D1238 method B using 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 bore diameter and 8 mm length is used with a 9.474 inch diameter piston. A sample weight of at least 2.8 grams is used. A thermostatically controlled heated steel cylinder is used to measure polymer flow at 190°C for PE samples and 210°C for BOPP samples using a 2.16 kg weighted piston. [Example]

[0083] The materials used are listed below in Table 1. All commercial samples are available from DOW Inc.

[0084] [Table 1]

[0085] Prepolymer Synthesis Experimental prepolymer compositions 1, 2, and 3 (PP1, PP2, and PP3) are shown in Table 2 below. A 3-L three-neck flask was dried, purged with N2, and connected to a condenser, overhead mixer, thermocouple temperature controller, and nitrogen bubbler. A given amount of ISONATE™ 125M isocyanate and / or ISONATE™ 50 OP MDI was charged, and a given amount of VORANOL™ 220-56N was then added to the reactor, followed by castor oil or modified castor oil POLYCIN™ GR-50, with mixing. After bubbling N2 through the reactor for several minutes, the reactor was gradually heated to 78°C and then maintained at this temperature for 2 hours as the reaction proceeded. After 2 hours, the product was placed in a glass bottle and characterized as shown in Table 3.

[0086] [Table 2]

[0087] [Table 3]

[0088] Coreactant compositions 1 and 2 (CC1 and CC2) of the present invention are listed below in Table 4. These compositions were mixed in a high speed mixer at 1800 rpm for 1 minute.

[0089] [Table 4]

[0090] HSP, R a , and R b An example of the calculation of is given in the application entitled "SYSTEMS, METHODS, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM OF PREDICTING A COMPATIBILITY OF AN ADHESIVE OR COATING COMPOSITION AND POLYOLEFIN POLYMERS" for Dow's polyurethane adhesive "ADCOTE® 102E / Coreactant CT" at a mix ratio of 100:5.2.

[0091] The solubility parameters calculated as above are shown in Table 5 below.

[0092] [Table 5]

[0093] Laminated samples were prepared using a Nordmeccanica LaboCombi pilot laminator. The disclosed formulation was first applied to an HDPE or BOPP primary film, followed by lamination of an LDPE GF-19 or BOPP seal secondary film. Coating weights were maintained within the typical solventless lamination adhesive application range, specifically 1.0-1.2 lbs / ream. The resulting laminates were cured in a controlled room (25°C, 50% RH). The HDPE / LDPE and BOPP / BOPP seal constructions were tested for adhesive strength after 1, 7, 14, and 28 days, as shown in the table below.

[0094] [Table 6] * Too strong to be isolated for testing

[0095] [Table 7]

[0096] [Table 8]

[0097] [Table 9]

[0098] [Table 10]

[0099] Recyclability Recyclability is evaluated by comparing the mechanical properties of the adhesive-containing laminate structure with those of the adhesive-free film after the HAAKE compounding process and the compressed sheet prepared as described below. Recyclability is defined as a variation of ±25% in mechanical properties between the experimental and control samples.

[0100] The Haake compounding process involves mixing and compressing a sheet compact of film (either laminate or control) in an RS5000 equipped with a Haake Rheomix 3000 mixer equipped with 25% GF Teflon bushings and a cam-type rotor. The mixer is attached to an RS5000 torque rheometer drive unit and controlled by System 5 PC-based control / data acquisition software designed to operate the RS5000 drive.

[0101] Film samples are melt blended in a heated mixer at 160°C for PE laminates and 190°C for BOPP laminates for 20-25 minutes. The mixing speed is a maximum of 5-20 rpm with a nitrogen purge block to limit sulfur oxidation. Once melt blending is complete, the samples are quickly removed and cooled in the cooling platens of a Carver hydraulic press at 20,000 psi for approximately 3 minutes.

[0102] Compressed sheet samples are prepared using 15-16 gram Haake remolded samples in a Carver press at 188°C with a 4.5" x 4.5" x 0.035" chase. The sample is heated on the upper platen of the Carver press for the first 3 minutes, then transferred to the lower platen and cooled to 20°C over 3 minutes. Air bubbles are preferably avoided, and a width of 1 / 8 inch or less is desirable.

[0103] The mechanical properties of both the control and inventive samples were tested on an Instron tensile tester according to ASTM D1708. The results are reported in Tables 11 and 12 below.

[0104] [Table 11] * The change in mechanical properties of the control sample was defined as "0", and the changes in the other samples were compared with the control.

[0105] [Table 12] * The change in mechanical properties of the control sample was defined as "0", and the changes in the other samples were compared with the control.

[0106] Melt flow rate is measured as described in the test procedure above, and the results are reported in Table 13 below.

[0107] [Table 13]

[0108] The molecular weights of the BOPP samples before and after HAAKE compounding are measured as described above in the test procedures, and the results are reported in Table 14 below.

[0109] [Table 14]

Claims

1. 1. A solventless laminating adhesive composition comprising: a. a polyurethane prepolymer composition, i. at least 20 weight percent, based on the weight of the prepolymer composition, of an aromatic isocyanate; ii. 10 wt.% or less of a natural oil polyol, based on the weight of the prepolymer composition; and iii. At least 60 wt.%, based on the weight of the prepolymer composition, of a reaction product of polypropylene glycol; a polyurethane prepolymer composition, wherein the prepolymer has an NCO% of less than 10%; b. a hydroxyl-functional co-reactant composition comprising: i. 80 to 100 wt. % natural oil polyol, based on the weight of the co-reactant composition; ii. 0 to 20 wt. % of a hydrophobic polyether polyol, based on the weight of the coreactant composition; and iii. a hydroxyl-functional co-reactant composition comprising 0 to 2 wt. % of a phosphate adhesion promoter, based on the weight of the co-reactant composition; A solventless laminating adhesive composition that is directly mechanically recyclable for polyolefin laminates.

2. 10. The solventless lamination adhesive composition of claim 1, having a Hansen Solubility Parameter calculated as disclosed herein of less than 21.

3. 3. The polyurethane prepolymer composition of claim 1, 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 of claims 1 to 3, wherein the propylene glycol comprises 60 to 80 wt% based on the weight of the prepolymer composition.

5. 5. The polyurethane prepolymer composition according to claim 1, wherein the NCO is 5 to 10%.

6. 6. The solventless lamination adhesive composition of any of claims 1 to 5, having a Hansen Solubility Parameter calculated as disclosed herein of 16 to 21.

7. The polyurethane prepolymer of any of claims 1 to 6, wherein the natural oil polyol comprises 0.1 to 10 wt % based on the weight of the prepolymer composition.

8. A laminate produced using the adhesive according to any one of claims 1 to 7.

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