WO2025029423A1

WO2025029423A1 - Polycarbodiimide based adhesive composition

Info

Publication number: WO2025029423A1
Application number: PCT/US2024/036355
Authority: WO
Inventors: James M. CABRERA; Manesh Nadupparambil Sekharan; Nolan T. MCDOUGAL; Yinzhong Guo
Original assignee: Dow Global Technologies Llc
Priority date: 2023-07-31
Filing date: 2024-07-01
Publication date: 2025-02-06

Abstract

The present disclosure provides an adhesive composition. In an embodiment, the adhesive composition includes a reaction product formed from (A) a carbodiimide (CDI) component and (B) a CD I reactive component (r-CDI) selected from the group consisting of (i) a polycarboxylic acid functional polyester resin, and (ii) an amine functional resin. The present disclosure also provides a laminate with the present adhesive composition disposed between a first substrate and a second substrate.

Description

POLYCARBODIIMIDE BASED ADHESIVE COMPOSITION

BACKGROUND

[0001] Adhesive compositions for laminates play an important role in the food and packaging industries. Most flexible food packaging utilizes multilayer films having barrier layers, and/or printable layers (polyethylene terephthalate, metalized polypropylene, polyamide, foil, polyethylene, polypropylene, etc.) and/or sealable layers (polyethylene, polypropylene, oriented polypropylene, etc.). These different film layer types are typically bonded together with an adhesive composition to form a laminate structure. A common adhesive for food packaging laminates is isocyanate-based polyurethane. However, while isocyanate-based laminating adhesives have great adhesive performance, use of isocyanate-based laminating adhesives carry toxicity, environmental concerns, and health risks. Isocyanates are hazardous to human health and can be sensitizing which complicates their manufacturing and handling.

[0002] Food packaging laminates adhere non-porous films together, such as films composed of foil, polyethylene, polyester, and polypropylene. As such, the curing chemistry for the lamination process is limited to chemical reactions that do not produce byproducts, such as water, a by-product for the polycondensation of polyester, and/or alcohol, a by-product in silanization chemistry. Due to the need to eliminate by-products during cure, the options for crosslinkable polymers for food-packaging laminate adhesives are limited.

[0003] While isocyanate functional groups provide a convenient way of crosslinking, isocyanates as laminate adhesives have disadvantages and limitations. The use of aromatic isocyanates run the risk of forming primary aromatic amines (PAAs) from isocyanate group react with moisture if the reactive adhesive is not fully cured with polyols during curing. PAAs are carcinogenic and are therefore a health risk and require close monitoring for food-contact packaging applications. In addition to the safety concerns, isocyanate-based cure technology has performance limitations at high humidity conditions including short pot life, out-gassing between high barrier films, anti-seal issue, and poor compatibility with digital inks.

[0004] In view of the health risks and performance limitations in using isocyanates, the art recognizes the need to develop adhesive compositions with non-isocyanate functional groups to be used for curing during curing stage. In particular, the art recognizes the need to develop adhesive compositions with non-isocyanate functional groups to be used for curing during curing stage for food-contact packaging applications.

SUMMARY

[0005] The present disclosure provides an adhesive composition. In an embodiment, the adhesive composition includes a reaction product formed from (A) a carbodiimide (CDI) component and (B) a CDI reactive component (r-CDI) selected from the group consisting of (i) a polycarboxylic acid functional polyester resin, and (ii) an amine functional resin.

[0006] The present disclosure also provides a laminate. In an embodiment, the laminate includes a first substrate, a second substrate, and an adhesive composition disposed between the first substrate and the second substrate. The adhesive composition includes a reaction product formed from (A) a carbodiimide (CDI), and (B) a CDI reactive component (r-CDI) selected from the group consisting of (i) a polycarboxylic acid functional polyester resin and (ii) an amine functional resin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1A is an infrared (IR) spectrograph of an NCO-terminated prepolymer used for preparing a carbodiimide component in accordance with an embodiment of the present disclosure (CDI-1).

[0008] FIG. IB is an IR spectrograph of a carbodiimide formed from the NCO-terminated prepolymer of FIG. 1A, in accordance with an embodiment of the present disclosure (CDI-1).

[0009] FIG. 2A is an infrared (IR) spectrograph of an NCO-terminated prepolymer used for preparing a carbodiimide component in accordance with an embodiment of the present disclosure (CDI-2).

[0010] FIG. 2B is an IR spectrograph of a carbodiimide formed from the NCO-terminated prepolymer of FIG. 1A, in accordance with an embodiment of the present disclosure (CDI-2). DEFINITIONS

[0011] Any reference to the Periodic Table of Elements is that as published by CRC Press, Inc., 1990-1991. Reference to a group of elements in this table is by the new notation for numbering groups.

[0012] For purposes of United States patent practice, the contents of any referenced patent, patent application or publication are incorporated by reference in their entirety (or its equivalent US version is so incorporated by reference) especially with respect to the disclosure of definitions (to the extent not inconsistent with any definitions specifically provided in this disclosure) and general knowledge in the art.

[0013] The numerical ranges disclosed herein include all values from, and including, the lower and upper value. For ranges containing explicit values (e.g., a range from 1, or 2, or 3 to 5, or 6, or 7), any subrange between any two explicit values is included (e.g., the range 1-7 above includes subranges 1 to 2; 2 to 6; 5 to 7; 3 to 7; 5 to 6; etc.).

[0014] Unless stated to the contrary, implicit from the context, or customary in the art, all parts and percents are based on weight and all test methods are current as of the filing date of this disclosure.

[0015] "Alkyl" refers to a saturated linear, cyclic, or branched hydrocarbon group. Nonlimiting examples of suitable alkyl groups include, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, i-butyl (or 2-methylpropyl), etc. In an embodiment, the alkyls have 1 to 20 carbon atoms. [0016] An "amide" is a compound containing an N— C=O moiety in its structure.

[0017] An "amine" refers to a compound containing: NR1R2R3, where each of Ri, R2 and R3 is independently selected from hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl (including pyridines), substituted aryl, heteroaryl, substituted heteroaryl, alkoxy, aryloxy, silyl, and combinations thereof.

[0018] An "aryl" (or "aryl group") refers to an aromatic substituent which may be a single aromatic ring or multiple aromatic rings which are fused together, linked covalently, or linked to a common group such as a methylene or ethylene moiety. The aromatic ring(s) may include phenyl, naphthyl, anthracenyl, and biphenyl, among others. In an embodiment, aryls have from 1 to 200 carbon atoms, or from 1 to 50 carbon atoms, or from 1 to 20 carbon atoms. [0019] The term "composition" refers to a mixture of materials which comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0020] 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 the same is specifically disclosed. In order to avoid 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 succeeding recitation any other component, step, or procedure, excepting those that are not essential to operability. The term "consisting of" excludes any component, step, or procedure not specifically delineated or listed. The term "or," unless stated otherwise, refers to the listed members individually as well as in any combination. Use of the singular includes use of the plural and vice versa.

[0021] An "ether group" is a moiety containing an oxygen atom bonded to two alkyl or aryl groups. "Substituted ether group," refers to an ether in which one or more hydrogen atom bound to any carbon of the alkyl or aryl is replaced by another group such as a phosphate, a hydroxy, and combinations thereof.

[0022] A "hydrocarbon" is a compound that contains only hydrogen and carbon atoms. The hydrocarbon can be (i) branched or unbranched, (ii) saturated or unsaturated, (iii) cyclic or acyclic, and (iv) any combination of (i)-(iii)- Nonlimiting examples of hydrocarbons include alkyls, aryls, alkanes, alkenes, and alkynes.

[0023] An "isocyanate" is a compound that contains at least one isocyanate group in its structure. An isocyanate group is represented by the formula: — N=C=O. A "polyisocyanate" (or "multifunctional isocyanate") is an isocyanate containing more than one, or at least two, isocyanate groups. A polyisocyanate having two isocyanate groups is a diisocyanate and an isocyanate having three isocyanate groups is a triisocyanate, etc. Isocyanates include aromatic isocyanates, aromatic polyisocyanates, aliphatic isocyanates and aliphatic polyisocyanates.

[0024] A "phenyl group" is an aromatic hydrocarbon with the formula CgHs. One of the carbon atoms is bonded to a substituent and the other five carbon atoms are bonded to hydrogen atoms. The phenyl group has the Structure (A):

Structure (A)

[0025] A "polyester" is a compound containing two or more ester linkages in the same linear chain of atoms.

[0026] A "polyester polyol" is a compound that is a polyester and a polyol. Nonlimiting examples of suitable polyester polyols include polycondensates of diols, polyols (e.g., triols, tetraols), dicarboxylic acids, polycarboxylic acids (e.g., tricarboxylic acids, tetracarboxylic acids), hydroxycarboxylic acids, lactones, and combinations thereof. The polyester polyols can also be derived from, instead of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides, or corresponding polycarboxylic esters of lower alcohols.

[0027] A "polymer" is a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term polymer thus embraces the term "homopolymer" (employed to refer to polymers prepared from only one type of monomer, with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term "interpolymer," which includes copolymers (employed to refer to polymers prepared from two different types of monomers), terpolymers (employed to refer to polymers prepared from three different types of monomers), and polymers prepared from more than three different types of monomers. Trace amounts of impurities, for example, catalyst residues, may be incorporated into and/or within the polymer. It also embraces all forms of copolymer, e.g., random, block, etc. It is noted that although a polymer is often referred to as being "made of" one or more specified monomers, "based on" a specified monomer or monomer type, "containing" a specified monomer content, or the like, in this context the term "monomer" is understood to be referring to the polymerized remnant of the specified monomer and not to the unpolymerized species. In general, polymers herein are referred to has being based on "units" that are the polymerized form of a corresponding monomer.

[0028] A "polyol" is an organic compound containing multiple hydroxyl (—OH) groups. In other words, a polyol contains at least two hydroxyl groups. Nonlimiting examples suitable polyols include diols (which contain two hydroxyl groups) and triols (which contain three hydroxyl groups).

TEST METHODS

[0029] Acid value (or acid number) is measured following the procedure in Table A below. Units for acid value are mg KOH/g.

Table A --Acid value determination

[0030] Bond strength. 180° Bond strength was measured on 1" strips of laminate samples at a pulling rate of 10"/min using an Instron tensile tester with a 200 N loading cell. Three strips were tested for each sample and the high and mean bond strength were recorded together with the failure mode. In case of film tear and film stretch, the high value was reported. In all other failure modes, the mean value was reported. Typical failure modes include: AF - Adhesive failure (adhesive on the primary film)

AT - Adhesive transfer (adhesive on the secondary film)

AS - Adhesive split (adhesive on both sides of the laminate, cohesive failure of the adhesive)

FT - Film tear

[0031] Gel Permeation Chromatography (GPC). Weight average molecular weight (Mw) and number average molecular weight (Mn) are measured using a gel permeation chromatography (GPC) system. The "Z average molecular weight"(Mz) is the third moment average molar mass. Mz is measured using a gel permeation chromatography (GPC) system. Mw, Mn, and Mz are calculated according to the following Equations (l)-(3):

Equation (1) Equation (2) Equation (3) wherein Wfi is the weight fraction of the i-th component and Mi is the molecular weight of the i- th component. Polydispersity is calculated in accordance with the following Equation (4): Equation (4)

[0032] The content of species having a Mw less than 500 g/mol, and a Mw less than 1000 g/mol for a polyol is measured using the "GPC One" software from PolymerChar Inc. using the following Equation (5): Equation (5)

wherein W is the weight fraction of the j-th component with a molecular weight lower than 500 g/mol or 1,000 g/mol, respectively.

[0033] Hydroxyl number (or OH Number) is a measure of the number of hydroxyl groups present in a component or a composition. The OH Number is the number of milligrams of potassium hydroxide required to neutralize the hydroxyl groups in one gram of a substance (mg KOH/g). The OH Number is determined in accordance with DIN 53240.

[0034] Isocyanate weight percent. Compounds having isocyanate groups may be characterized by the parameter "%NCO" which is the amount of isocyanate groups by weight based on weight of the compound. The parameter %NCO is measured in accordance with ASTM D 2572-97. Results are reported in weight percent (or "%") based on total weight of the component.

[0035] Viscosity is measured at 25°C in accordance with ASTM D2196. Viscosity is reported in millipascal seconds (mPa-s).

DETAILED DESCRIPTION

The present disclosure provides an adhesive composition. The adhesive composition contains the reaction product of (A) a carbodiimide component (CDI) and (B) a carbodiimide reactive component (r-CDI). The r-CDI component (B) is a resin selected from (i) a carboxyl functional polyester resin, and (ii) an amine functional resin.

A. Carbodiimide Component (CDI)

[0036] The adhesive composition contains the (A) carbodiimide (CDI) component. The CDI component has a structure of Structure 1

(Structure 1)

R_rN=C=N- R₂ wherein Ri and R₂ can be the same or different,

Ri is a phenyl group ("Ph") or a Ph-CH₂-aryl moiety, and

R₂ is Ph, or a Ph-CH₂-a ryl moiety.

[0037] In an embodiment, the CDI component is component is formed from an NCO- terminated prepolymer. The NCO-terminated prepolymer can include an aromatic isocyanate, an aliphatic isocyanate, a polyol, and combinations thereof.

[0038] In an embodiment, the NCO-terminated prepolymer is an aromatic isocyanate. An "aromatic isocyanate" is an isocyanate containing one or more aromatic rings. Nonlimiting examples of suitable aromatic isocyanates include isomers of methylene diphenyl dipolyisocyanate (MDI) such as 4,4'-MDI, 2,4'-MDI, and 2, 2'-MDI; modified MDI such as carbodiimide modified MDI or allophanate modified MDI; isomers of toluenedipolyisocyanate (TDI) such as 2,4-TDI, and 2,6-TDI; isomers of naphthalene-dipolyisocyanate (NDI) such as 1, 5-NDI; isomers of phenylene dipolyisocyanate (PDI), such as 1,3-PDI and 1,4- PDI; and combinations thereof.

[0039] In an embodiment, the NCO-terminated prepolymer is an aliphatic isocyanate. An "aliphatic isocyanate" is an isocyanate that is void of, or contains no, aromatic rings. Aliphatic isocyanates include cycloaliphatic isocyanate, in which the chemical chain is ring-structured. In an embodiment, the aliphatic isocyanate contains from 3, or 4, or 5, or 6 to 7, or 8, 10, 12, or 13, or 14, or 15, or 16 carbon atoms in the linear, branched, or cyclic alkylene residue. Nonlimiting examples of suitable aliphatic isocyanates include cyclohexane diisocyanate; methylcyclohexane diisocyanate; ethylcyclohexane diisocyanate; propylcyclohexane diisocyanate; methyldiethylcyclohexane diisocyanate; propane diisocyanate; butane diisocyanate; pentane diisocyanate; hexane diisocyanate; heptane diisocyanate; octane diisocyanate; nonane diisocyanate; nonane triisocyanate; decane di- and tri-isocyanate; undecane di- and tri-isocyanate; dodecane di- and tri-isocyanate; isophorone diisocyanate; hexamethylene diisocyanate; diisocyanatodicyclohexylmethane; 2-methylpentane diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; norbornane diisocyanate; xylylene diisocyanate; isomers, dimers, and/or trimers thereof; and combinations thereof.

[0040] In an embodiment, the isocyanate is a polyfunctional isocyanate. In another embodiment, the polyfunctional isocyanate is selected from a di-isocyanate, a tri-isocyanate, and combinations thereof. In a further embodiment, the polyfunctional isocyanate is a diisocyanate.

[0041] In an embodiment, the NCO-terminated prepolymer is a multi-functional NCO- terminated prepolymer. A "multi-functional NCO-terminated prepolymer" is the reaction product of an isocyanate and at least one polyol. The isocyanate bonds to a polyol in a chemical reaction to form the multi-functional NCO-terminated prepolymer. The isocyanate can be any aliphatic isocyanate and/or aromatic isocyanate as disclosed above. Nonlimiting examples of suitable polyols used to form multi-functional NCO-terminated prepolymer include polyester polyols, polyether polyols, aliphatic polyols, and combinations thereof.

[0042] In an embodiment, the GDI component is formed by converting the isocyanate groups of the NCO-terminated prepolymer into carbodiimide groups using a catalyst. The catalyst is a cyclic phosphorous compound, e.g., substituted phospholene-l-oxide, phosphetane 4-oxide, 1,3-diazaphospholidine oxide, 1,3-dimethylphospholine-l-oxide, 1- ethyl-3-methylphospholine-l-oxide, l-phenyl-3-methylphospholine-l-oxide, 1- phenylphospholene-l-oxide, l,3,2-diazaphospholidine-2-oxide, 3-methyl-l-phenyl-2- phospholene-l-oxide, and combinations thereof. In a further embodiment, the catalyst is 3- methyl-phenyl-2-phospholene-l-oxide.

[0043] The conversion of the isocyanate groups to carbodiimide groups lowers the weight percent of the isocyanate in the prepolymer from an initial range from 5 wt% to 20 wt% of isocyanate groups to a final range of isocyanate groups in the CDI component to less than 1 wt%. In an embodiment, the CDI component has less than 1 wt% isocyanate, or 0 wt% or from greater than 0 wt% to 0.5 wt%, or 0 wt% or from greater than 0 wt% to 0.3 wt%, or 0 wt% or from greater than 0 wt% to 0.1 wt% isocyanate content. Weight percent is based on total weight of the CDI component.

[0044] In an embodiment, the CDI component is formed from an NCO-terminated prepolymer and has one, some, or all of the following properties:

(i) weight average molecular weight (Mw) from 600 g/mol to 500,000 g/mol, or from 600 g/mol to 100,000 g/mol, or from 600 g/mol to 6000 g/mol, or from 600 g/mol to 1000 g/mol; and/or

(ii) an isocyanate content of 0 wt%, or from greater than 0 wt% to less than 0.5 wt%, or from greater than 0 wt% to less than 0.1 wt%; and/or

(iii) a viscosity from 500,000 mPa.s to 2,000,000 mPa.s at 25°C.

[0045] The CDI component may comprise two or more embodiments disclosed herein.

B. Carbodiimide reactive component (B)

[0046] The adhesive composition contains (B) the carbodiimide reactive component (or "r-CDI"). The r-CDI is a carboxyl functional polyester resin, an amine functional resin polyol component, and combinations thereof.

[0047] In an embodiment the r-CDI component is the polycarboxylic acid functional polyester resin ("PAFP"). The polycarboxylic acid functional polyester resin was synthesized by polyesterification of two or more diols with two or more dicarboxylic acids with excess mol% of the dicarboxylic acids. The PAFP is a polyester with terminal carboxylic acid functional groups at each chain-end. In a further embodiment, the PAFP resin has one, some, or all of the following properties:

(i) a weight average molecular weight, Mw, from 400 g/mol to 3000 g/mol; or from 500g/mol to 2000g/mol; and/or

(ii) an acid value from 0.1 mg KOH/g to 200 mg KOH/g; and/or

(iii) a viscosity a viscosity at 25°C from 500 mPa-s to 100,000 mPa-s.

[0048] In an embodiment, the r-CDI component is the amine functional resin. The amine functional resin has a terminal amine functional group at each chain-end. The terminal amine can be a primary amine or a secondary amine. In a further embodiment, the amine functional resin is a polyetheramine having a terminal amine functional group at each chain-end.

C. Adhesive composition

[0049] The adhesive composition is prepared by adding the CDI component (A) and the r-CDI component (B) to a polar solvent and mixing to obtain a homogeneous solution. A "polar solvent" is a substance capable of dissolving another substance (solute) to form a uniformly dispersed mixture (solution) at the molecular or ionic level; the solvent composed of molecules in which positive and negative electrical charges are permanently separated, as opposed to nonpolar molecules in which the charges coincide. Nonlimiting examples of polar solvents include alcohols, ketones and esters. In an embodiment, the polar solvent is an ester. Nonlimiting examples of suitable esters include butyl acetate and ethyl acetate. In a further embodiment, the solvent is ethyl acetate.

[0050] The CDI component (A) and the r-CDI component (B) are completely dissolved, or substantially dissolved, and are combined, or otherwise mixed, in the solvent at a temperature from 15°C to 45°C, or from 20°C to 25°C for a period from 10 minutes to 30 minutes. The GDI component (A) and the r-CDI component react in the polar solvent; the adhesive composition is the reaction product of (A) the CDI component; (B) the r-CDI component. In an embodiment, the adhesive composition has a solids content from 20 wt% to 45 wt%, or from 30 wt% to 40 wt%, or 35 wt%, based on the total weight of the adhesive composition and the solvent.

[0051] In an embodiment, the adhesive composition includes

(A) from 40 wt% to 60 wt% of the CDI component; and

(B) from 60 wt% to 40 wt% of the polycarboxyl acid functional polyester resin, based on total weight of the adhesive composition (and solvent removed).

[0052] In an embodiment, the adhesive composition includes

(A) from 40 wt% to 60 wt% of the CDI component; and

(B) from 60 wt% to 40 wt% of the amine-functional resin, based on total weight of the adhesive composition (and solvent removed).

D. Laminate

[0053] The present disclosure provides a laminate. The laminate includes a first substrate, a second substrate, and an adhesive layer between the first substrate and the second substrate. The adhesive layer is formed from the present adhesive composition. The adhesive composition may be any adhesive composition with the CDI component (A) and the r-CDI component (B) as disclosed herein.

[0054] The laminate includes a first substrate and a second substrate. The first substrate and the second substrate may be the same or different. In an embodiment, the first substrate and the second substrate are the same, such that they have the identical compositions and identical structures.

[0055] In an embodiment, the first substrate and the second substrate are compositionally distinct and/or structurally distinct from one another.

[0056] It is understood that the below description referring to a "substrate" refers to the first substrate and the second substrate, individually and/or collectively.

[0057] A nonlimiting example of a suitable substrate is a film. The film may be a monolayer film or a multilayer film. The multilayer film contains two layers, or more than two layers. For example, the multilayer film can have two, three, four, five, six, seven, eight, nine, ten, eleven, or more layers. In an embodiment, the multilayer film contains only two layers, or only three layers. [0058] In an embodiment, the film is a monolayer film with one, and only one, layer.

[0059] In an embodiment, the film includes a layer containing a component selected from ethylene-based polymer, propylene-based polymer (PP), polyamide (such as nylon), polyester, ethylene vinyl alcohol (EVOH) copolymer, polyethylene terephthalate (PET), ethylene vinyl acrylate (EVA) copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, ethylene butyl acrylate copolymer, ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, an ionomer of ethylene acrylic acid, an ionomer of methacylic acid, maleic anhydride grafted ethylene-based polymer, a polylactic acid (PLA), a polystyrene, a metal foil, a cellulose, cellophane, nonwoven fabric, and combinations thereof. A nonlimiting example of a suitable metal foil is aluminum foil. Each layer of a multilayer film may for formed from the same component, or from different components.

[0060] In an embodiment, the film includes a layer containing metal foil.

[0061] In an embodiment, the film is a monolayer film having a single layer that is an ethylenebased polymer layer. In a further embodiment, the film is a monolayer film having a single layer that is a polyethylene layer.

[0062] The substrate, and further the film, is a continuous structure with two opposing surfaces.

[0063] In an embodiment, the substrate has a thickness from 5 pm, or 10 pm, or 15 pm, or 20 pm to 25 pm, or 30 pm, or 40 pm, or 50 pm, or 100 pm, or 200 pm, or 300 pm, , or 400 pm, or 500 pm.

[0064] In an embodiment, the first substrate is a film having a layer that is a metal foil layer; and the second substrate is a monolayer film having a single layer that is an ethylene-based polymer layer (such as low density polyethylene (LDPE)) or a propylene-based polymer layer (such as polypropylene).

[0065] The first substrate may comprise two or more embodiments disclosed herein.

[0066] The second substrate may comprise two or more embodiments disclosed herein. [0067] The adhesive composition is applied between the first substrate and the second substrate, such as with a Nordmeccanica Labo Combi laminator, for example.

[0068] Nonlimiting examples of suitable application methods include brushing, pouring, spraying, coating, rolling, spreading, and injecting.

[0069] In an embodiment, the adhesive composition is applied between the first substrate and the second substrate at a coat weight from 0.5 grams per square meter (g/m²) to 5.0 g/m². [0070] In an embodiment, the adhesive composition is uniformly applied on the first substrate, on the second substrate, or on both first and second substrates, the solvent is evaporated to form an adhesive layer, and then the adhesive layer is brought into contact with the second substrate. A "uniform application" is a layer of the composition that is continuous (not intermittent) across a surface of the substrate, and of the same, or substantially the same, thickness across the surface of the substrate. In other words, a composition that is uniformly applied to a substrate directly contacts the substrate surface, and the composition is coextensive with the substrate surface.

[0071] The adhesive composition and the first substrate are in direct contact with each other. The term "directly contacts," as used herein, is a layer configuration whereby a substrate is located immediately adjacent to a two-component solvent-based adhesive composition, or an adhesive layer and no intervening layers, or no intervening structures, are present between the substrate and the two-component solvent-based adhesive composition, or the adhesive layer. The adhesive composition directly contacts a surface of the first substrate. The structure containing the first substrate and the adhesive composition has the following Structure (D):

First Substrate / Adhesive Composition Structure (D)

[0072] In an embodiment, the Structure (D) is dried to form an adhesive layer in direct contact with the first substrate. In a further embodiment, the Structure (D) is dried by passing it through an oven at a temperature sufficient to evaporate all, or substantially all, of the solvent from the adhesive composition. Then, the adhesive layer is contacted with the second substrate to form a laminate. The first substrate is in direct contact with the adhesive layer and the second substrate is in direct contact with the adhesive layer and the laminate has the following Structure (E): First Substrate / Adhesive Layer I Second Substrate Structure (E).

[0073] In an embodiment, the adhesive layer and the second substrate are in direct contact with each other. The adhesive layer directly contacts a surface of the second substrate.

[0074] The adhesive layer of Structure (E) is formed from curing, or drying the adhesive composition. The adhesive composition is formed from mixing and reacting the (A) CDI component and the (B) r-CDI component in the presence of (C) the polar solvent (and subsequent removal of the solvent), as disclosed above.

[0075] The laminate includes the first substrate in direct contact with the adhesive layer, and the second substrate in direct contact with the adhesive layer.

[0076] The present disclosure also provides an article containing the laminate. Nonlimiting examples of suitable articles include packages, bags, pouches, deep-drawn cans, and containers. [0077] In an embodiment, the laminate contacts a comestible. A "comestible" is an edible food item.

[0078] By way of example, and not limitation, some embodiments of the present disclosure will now be described in detail in the following Examples.

EXAMPLES

[0079] Materials used to prepare the inventive examples ("IE") are provided in Table 1 below.

Table 1- Materials

A. Preparation of carbodiimide component (Al )

[0080] Inside a glovebox, a jar was charged with NCO-terminated prepolymer (PACACEL L75- 191) (100 g, 100 mol%, 13% NCO). The jar was then charged with phenyl isocyanate (19 g, 50 mol%) and 3-methyl-l-phenyl-2-phospholene-l-oxide (295 mg, 0.25 wt%, 85% pure). The mixture was then heated at 80°C and stirred at 1000 rpm for 22 hours to form the carbodiimide component with 8.9 wt% carbodiimide content, based on the total weight of the CDI component A (hereafter referred to as "CDI-l").

[0081] FT-IR in FIGS. 1A-1B confirmed the loss of the isocyanate peak (2257 cm ^-1) in FIG. 1A and increase of the carbodiimide peak (2106, 2132 cm'¹) in FIG IB. After completion of the reaction, the mixture was cooled to room temperature and stored in the glovebox.

[0082] Calculation for wt% carbodiimide ("NCN"), based on total weight CDI-l, is provided below (NCO is isocyanate and PhNCO is phenyl isocyanate).

Moles of NCO in Pacacel L75-191 = (Mass of Pacacel L75-191 x %NC0)/MW (NCO)

= (100 g x 13%)/42 g/mol = 0.31 mmol

Moles of NCO in PhNCO = Mass of PhNCO/MW (PhNCO)

= 19 g/119.1 g/mol = 0.16 mmol

In this reaction every 2 moles of NCO generates 1 mol of NCN and 1 mol of CO₂ ^:

Moles of NCN in final polymer = Total moles of NCO in mixture/2

= (0.31 mmol + 0.16 mmol)/2 = 0.24 mmol

Mass of NCN in final polymer = (Moles of NCN) x MW (NCN)

= 0.24 mmol x 40 g/mol = 9.6 g of NCN

Moles of CO₂ formed = (Moles of NCN) x MW (CO₂)

= 0.24 mmol x 44 g/mol = 10.6 g

Total Mass of final polymer = (Mass of Pacacel L75-191 + Mass of PhNCO) - Mass of CO₂

= (100 g + 19 g) - 10.6 g = 108.4 g

Wt % NCN in final polymer = (Mass of NCN/Total Mass of final polymer) x 100% = (9.6 g/108.4 g) x 100% = 8.9 wt% B. Preparation of NCO-terminated prepolymer

[0083] In a pre-heated (60°C) round bottom flask of 3000 mL under N2 atmosphere, ISONATE™ 125M was added, previously melted in a water-bath. A polyether polyol (Voranol PUP 2025) was pre-heated to 50°C and added to the heated ISONATE™ 125M to form a reaction mixture.

[0084] The reaction mixture was stirred, until exothermic phenomena were completed. Then, the reaction mixture was heated to 80-85°C. The reaction mixture was maintained under constant stirring at 80°C for 1.5 hours. Residual %NCO was determined via titration. The reaction mixture was cooled to 40-50°C and transferred to metallic cans. The metallic cans were filled with nitrogen to prevent reaction with moisture and stored in a freezer until the stripping step.

[0085] The resulting reaction product mixture (RPA) was then subjected to distillation without solvent as follows: evaporator temperature of 175°C, condenser temperature of 45°C, pressure of 0.04 mbar, feed rate of 0.6 to 1.2 kg/hour, wiper speed of 360 U/minute, using a laboratory-scale UIC KDL 5 distillation device, using a single pass, thereby forming the NCO-terminated prepolymer. The properties of the NCO-terminated prepolymer are shown in Table B below.

[0086] Table B -NCO-terminated prepolymer properties (weight percent based on total weight of NCO-terminated prepolymer). The NCO-terminated prepolymer is substantially void of free isocyanate monomer (less than 0.15 wt% free MDI, or 0.13 wt% free MDI) as shown in Table B below.

Table B

C. Preparation of carbodiimide component (A2)

[0087] Inside a glovebox, a jar was charged with the NCO-terminated prepolymer of Table B.

(100 g, 100 mol%, 2.7% NCO). The jar was then charged with phenyl isocyanate (3.8 g, 50 mol%) and 3-methyl-l-phenyl-2-phospholene-l-oxide (295 mg, 0.25 wt%, 85% pure). The mixture was then heated at 80 °C and stir at 1000 rpm for 17 hours (h) to form the carbodiimide component with 1.9 wt% carbodiimide content, based on the total weight of the CDI component A (hereafter referred to as "CDI-2").

[0088] FT-IR in FIGS. 2A-2B confirmed formation of CDI-2 by the loss of the isocyanate peak (2261 cm'¹) in FIG. 2A and increase of the carbodiimide peak (2111, 2137 cm'¹) in FIG 2B. After completion of the reaction, the mixture was cooled to room temperature and stored in the glovebox.

[0089] Calculation for wt% NCN, based on total weight CDI-2, is provided below.

Moles of NCO in NCO-terminated prepolymer of Table B = (Mass of NCO-terminated prepolymer of Table B x %NC0)/MW (NCO)

= (100 g x 2.7%)/42 g/mol = 0.064 mmol

Moles of NCO in PhNCO = Mass of PhNCO/MW (PhNCO)

= 3.8 g/119.1 g/mol = 0.032 mmol

In this reaction every 2 moles of NCO generates 1 mol of NCN and 1 mol of CO?^:

Moles of NCN in final polymer = Total moles of NCO in mixture/2

= (0.064 mmol + 0.032 mmol)/2 = 0.048 mmol

Mass of NCN in final polymer = (Moles of NCN) x MW (NCN)

= 0.048 mmol x 40 g/mol = 1.9 g of NCN

Moles of CO2 formed = (Moles of NCN) x MW (CO2)

= 0.048 mmol x 44 g/mol = 2.1 g

Total Mass of final polymer = (Mass of NCO-terminated prepolymer of Table B + Mass of PhNCO) - Mass of CO2

= (100 g + 3.8 g) - 2.1 g = 101.7 g

Wt% NCN in final polymer = (Mass of NCN/Total Mass of final polymer) x 100%

= (1.9 g/101.7 g) x 100% = 1.9 wt%

D. Preparation of carbodiimide reactive component (B)

1. Carboxyl functional polyester resin

[0090] The PAFP resin was synthesized by polyesterification of diols (neopentyl glycol and 1,6 hexane diol) with dicarboxylic acids (isophthalic acid and adipic acid) with excess mol% of the dicarboxylic acids. The raw materials in Table 2 below were combined and were heated to 150°C gradually, then the temperature was gradually increased and water is removed. After most of the water was removed, a vacuum was applied to the reaction system to continually remove the reacting water while gradually increasing the reaction temperature to 220°C and increasing the vacuum pressure to 20mm Hg. The final acid value of the resin was determined to be 153 mg KOH/gm of resin.

[0091] The composition of the PAFP resin is provided in Table 2 below.

[0092] Table 2 (hereafter referred to as "r-CDI-1")

E. Preparation of adhesive composition

[0093] Two different adhesive compositions were prepared at various ratios of GDI component (A) (either CDI-1 or CDI-2) to r-CDI component (B).

[0094] 35 wt% CDI-1 solution in ethyl acetate and 35 wt% CDI-2 solution in ethyl acetate each was mixed with a respective amount of r-CDI-1 (PAFP resin) and additional ethyl acetate using a Flextrak mixer to obtain a homogeneous solution of the adhesive composition with 35 wt% solids.

[0095] 35 wt% of CDI-1 solution in ethyl acetate and 35 wt% of CDI-2 solution in ethyl acetate each was mixed with a respective amount of r-CDI-2 (amine functional resin, Jeffamine SD 2001) and additional ethyl acetate using a Flextrak mixer to obtain a homogeneous solution with 35 wt% solids. Table 3

F. Preparation of laminates

[0096] Laminated samples were prepared using a heated-roll hand laminator. The adhesive composition was first coated onto a polyester film using a Meyer bar #2 to achieve dry adhesive coat weight in the range of 1.0-1.1 Ib/ream. The primary substrate was then dried in a 90 °C oven for 2 minutes to remove the solvent (ethyl acetate) before it was laminated to a polyethylene sealant film with nip temperature at 150 °F and pressure at 40 psi. The formed laminates were placed under 2 lb weight to cure at room temperature for 7 days. Bond strengths were tested after 1 day of curing.

[0097] Table 4A - polyester/CDI-1 and r-CDI-l/polyethylene

[0098] Table 4B- polyester/CDI-2 and r-CDI-l/polyethylene

[0099] Table 5A - polyester/CDI-1 and r-CDI-2/polyethylene

[00100] Table 5B - polyester/CDI-2 and r-CDI-2/polyethylene

G. Results

[00101] The bond strength after one day cure demonstrates that Adhesive compositionlA, Adhesive compositionlB, Adhesive composition2A and Adhesive composition2B each is suitable as a laminating adhesive.

[00102] It is specifically intended that the present disclosure not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.

Claims

1. An adhesive composition comprising: a reaction product formed from

(A) a carbodiimide (CDI) component; and

(B) a CDI reactive component (r-CDI) selected from the group consisting of

(i) a polycarboxylic acid functional polyester resin, and

(ii) an amine functional resin.

2. The adhesive composition of claim 1 wherein the CDI component has a Structure 1

(Structure 1)

R_rN=C=N- R₂ wherein

Ri and R₂ are the same or different,

Ri is selected from the group consisting of a phenyl group ("Ph"), and a Ph-CH₂-aryl moiety, and

R₂ is selected from the group consisting of a phenyl group ("Ph"), and a Ph-CH₂-aryl moiety.

3. The adhesive composition of any of claims 1-2 wherein the carbodiimide component is formed from an NCO-terminated prepolymer.

4. The adhesive composition of any of claims 1-3 wherein the CDI component has a weight average molecular weight (Mw) from 600 g/mol to 500,000 g/mol.

5. The adhesive composition of any of claims 1-4 wherein the CDI component has an isocyanate content less than 0.1 wt %.

6. The adhesive composition of any of claims 1-5 wherein the polycarboxylic acid functional polyester is a reaction product resin is a reaction product of a polyesterification of two or more diols with two or more dicarboxylic acids.

7. The adhesive composition of claim 6 wherein the adhesive composition comprises

(A) from 40 wt% to 60 wt% of the GDI component; and

(B) from 60 wt% to 40 wt% of the polycarboxylic acid functional polyester resin, based on total weight of the adhesive composition.

8. The adhesive composition of any of claims 1-5 wherein the amine functional resin comprises polyetheramine having a terminal amine at each chain end.

9. The adhesive composition of claim 8 wherein the adhesive composition comprises

(A) from 40 wt% to 60 wt% of the GDI component; and

(B) from 60 wt% to 40 wt% of the amine-functional resin, based on total weight of the adhesive composition.

10. A laminate comprising: a first substrate; a second substrate; and an adhesive composition disposed between the first substrate and the second substrate, the adhesive composition comprising a reaction product formed from

(A) a carbodiimide (GDI); and

(B) a GDI reactive component (r-CDI) selected from the group consisting of

(i) a polycarboxylic acid functional polyester resin and

(ii) an amine functional resin.