Solvent-free lamination adhesive kit, laminated adhesive, retort bag, methods of providing a multilaminated structure and making the kit, laminated adhesive structure and use of the kit

Description

"Solvant-free laminating adhesive kit, laminated adhesive, retort bag, methods for providing a multi-layered structure and for making the kit, laminated adhesive structure and uses of the kit"

[0001] The application claims priority over application EP 22209746.1, which is incorporated herein by reference. Field of Invention

[0002] The present invention relates to solvent-free two-pack adhesives and to the use of said adhesives in providing laminates for retort applications. Fundamentals of the Invention

[0003] Retorting is a well-known process in the packaging industry, where hermetically sealed bags containing moist food are processed at high temperatures, typically above 100 °C, to cook and sterilize the food.

[0004] Solvent-based adhesives are used in retort applications because they provide the bond strength between the layers of the packaging laminate under the retort process conditions that is necessary to ensure the integrity of the laminate without delamination failures. In particular, solvent-based adhesives have high resistance to thermal degradation, partly because solvent-based adhesives allow the use of higher molecular weight starting materials, which build stronger networks that are less susceptible to the formation of migratable small molecule species after thermolysis. The solvent maintains an adequate viscosity of the composition for use in lamination, which would otherwise be increased as a result of incorporating high molecular weight materials.

[0005] Therefore, it is desirable to provide an alternative solvent-free adhesive for retort applications to eliminate the need Petition 870260046201, dated 05 / 15 / 2026, page 10 / 120 2 / 44 of removal and handling of volatile solvents, such as ethyl acetate and methyl ethyl ketone (MEK). Furthermore, higher laminating press speeds are achievable with solvent-free adhesives.

[0006] Solvent-free adhesives are known in the art. However, without the presence of a solvent, the molecular weight of the components must be limited in order to provide a composition with a viscosity suitable for use in lamination and, although low molecular weight species can provide low viscosity compositions, they can also migrate through the composition and contaminate the food with which they come into contact.

[0007] One method for providing lower viscosity adhesive compositions and also reducing the amounts of migratable species present in adhesives is to remove residual isocyanate monomer, for example, using evaporation techniques. EP3176196 refers to a single-pack lamination adhesive comprising aromatic isocyanate polyurethane prepolymers, wherein the amount of free diisocyanate monomer in the polyurethane prepolymer is reduced to less than 0.1% (w / w) using a thin-film evaporator. The residual diisocyanate monomer is removed under pressures of 10 Pa (0.1 mbar) or less at 140 °C. However, EP3176196 does not disclose two-pack adhesives, which have different requirements than single-pack adhesives, such as those according to the present invention comprising aliphatic polyurethane prepolymers.Furthermore, document EP3176196 does not disclose that these adhesive compositions are suitable for the preparation of flexible packaging laminates for the manufacture of shrink bags.

[0008] US5202001 discloses the use of a thin-film evaporator to remove an aromatic diisocyanate (TDI - toluene diisocyanate) from an isocyanate-functionalized polyurethane prepolymer. The use of isocyanates Petition 870260046201, dated 05 / 15 / 2026, page 11 / 120 The use of 3 / 44 aromatics in the production of polyurethane prepolymers is undesirable due to the risks associated with the generation of potentially harmful primary aromatic amines, which can be produced under retort conditions. Furthermore, US5202001 does not refer to adhesive compositions and does not disclose adhesives according to the present invention, comprising aliphatic polyurethane prepolymers. Additionally, US5202001 does not disclose the use of adhesives in the preparation of shrink-wrap laminates.

[0009] A number of prior art documents refer to the reduction of the amount of residual diisocyanate monomers present in polyurethane prepolymers by distillation in the presence of what are referred to as inert solvents. In this regard, US20030065124 discloses the removal of free diphenylmethane diisocyanate (MDI) by means of reduced pressure distillation using a clean film evaporator. The process employs dimethyl phthalate as the inert solvent, having a boiling point below that of MDI. Similarly, WO2018013688 refers to polyurethane prepolymers prepared from aromatic paraphenylene diisocyanate (PPDI), from which the free monomer is also removed using a clean film evaporator. In this case, dimethyl adipate is used as the inert solvent.

[00010] Neither document US20030065124 nor document WO2018013688 refers to adhesive compositions and therefore does not disclose a two-pack adhesive according to the present invention comprising aliphatic polyurethane prepolymers. These documents also do not disclose the use of such an adhesive in the preparation of laminates suitable for retort applications. Furthermore, in contrast to the aliphatic polyurethane isocyanate functional prepolymers of the present invention, the polyurethane prepolymers of US20030065124 and WO2018013688 are prepared using solvents, i.e., they are not solvent-free. Petition 870260046201, dated 05 / 15 / 2026, p. 12 / 120 4 / 44

[00011] CN110922929 refers to a one-package functional polyurethane prepolymer adhesive with isocyanate, which can be used to manufacture flexible laminates. CN110922929 does not refer to two-package adhesives and does not disclose the reduction of the amount of free isocyanate monomer to less than 0.1% (w / w) of the polyurethane prepolymer component. Furthermore, there is no instruction on how to maintain the viscosity of the disclosed compositions at a level suitable for use in a laminating machine while also removing residual isocyanate monomer. CN110922929 does not disclose the use of a clean film evaporator. Additionally, CN110922929 does not teach that the use of aliphatic polyurethane precursors would provide laminated adhesives with improved bond strength under retort conditions.Furthermore, the compositions of a CN110922929 package include significant amounts of catalyst to function, resulting in a significantly reduced shelf life that is unsuitable for use in a two-pack adhesive kit.

[00012] CN102604583B refers to solvent-free two-pack adhesives that can be used in the manufacture of flexible laminates that can withstand boiling. However, CN102604583B does not disclose the reduction of the amount of free isocyanate monomer to less than 0.1% (w / w) of the polyurethane prepolymer component, nor does it teach how the viscosity of the disclosed compositions could be maintained at a level suitable for use in a laminating machine while also removing residual isocyanate monomer. Furthermore, CN102604583B does not disclose the use of a clean film evaporator. Additionally, a reactive silane is an essential component of the CN102604583B adhesive. Finally, CN102604583B does not evaluate the disclosed adhesives under retort conditions.

[00013] To the best of the inventors' knowledge, the successful use of solvent-free two-pack lamination adhesives comprising pre Petition 870260046201, dated 05 / 15 / 2026, page 13 / 120 5 / 44 aliphatic polyurethane polymers comprising a free isocyanate monomer content of less than 0.1% (w / w) and suitable for retort applications have not been disclosed. Therefore, the solvent-free laminating adhesive kit of the present invention is advantageous at least in this respect. Other advantages associated with the solvent-free laminating adhesive kit of the present invention are described in this document. Summary of the Invention

[00014] The present invention provides a solvent-free laminating adhesive kit comprising an isocyanate-functionalized aliphatic polyurethane prepolymer comprising monomeric units derived from aliphatic isocyanate monomers and a polyol crosslinker. The amount of free isocyanate monomer present in the polyurethane prepolymer is less than or equal to 0.1% (w / w) of said prepolymer. The aliphatic isocyanate monomers are diisocyanates selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, methylene dicyclohexyl diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, pentamethylene diisocyanate and combinations thereof.

[00015] The adhesive kit of the invention is a two-package adhesive kit, that is, it comprises the functional isocyanate prepolymer in addition to a polyol crosslinker.

[00016] The invention further provides a laminated adhesive comprising the components of the solvent-free laminating adhesive kit of the invention mixed into a single composition. The invention also provides a retort pouch comprising a laminated adhesive formed from the components of the kit of the invention.

[00017] The invention further provides a method for supplying a multi-layered structure, comprising forming a laminated adhesive from the components of the invention's kit and applying Petition 870260046201, dated 05 / 15 / 2026, page 14 / 120 6 / 44 of the composition in a flexible film.

[00018] The invention further provides a method for making the kit of the invention, comprising the steps of a) reacting an aliphatic isocyanate with a polyester and / or polyether polyol to obtain an isocyanate-functionalized aliphatic polyurethane prepolymer comprising monomeric units derived from aliphatic isocyanate monomers; b) reducing the residual isocyanate monomer present in the prepolymer to less than 0.1% (w / w) of the prepolymer; and c) introducing a polyol crosslinker into the kit.

[00019] The invention further provides the use of the invention kit to form a laminated adhesive. The invention also provides the use of the invention kit to improve the bond strength under retort conditions of a multilayer structure formed from a flexible film and a laminated adhesive formed from the invention kit. The improvements relate to a multilayer structure formed from the same flexible film and a laminated adhesive that is not formed from the invention kit. The bond strength is the strength required to separate at least two layers of the multilayer structure that are joined with said adhesive and is measured at room temperature (25 C°) and 100 mm / min. Detailed Description of the Invention Definitions

[00020] Aromatic monomer = a monomer in which the polymerizable functional group is directly attached to an aromatic group.

[00021] Aliphatic monomer = a monomer in which the polymerizable functional group(s) is / is not directly attached to an aromatic group.

[00022] Aromatic isocyanates = isocyanates comprising at least one isocyanate group (-NCO) directly attached to an aromatic ring. Petition 870260046201, dated 05 / 15 / 2026, page 15 / 120 7 / 44

[00023] Aliphatic isocyanates = isocyanates in which the isocyanate group(s) (-NCO) is / is / are not directly attached to an aromatic ring. Aliphatic isocyanates include alicyclic isocyanates. Aliphatic isocyanates may thus include aromatic rings provided that the isocyanate group(s) is / is / are not directly attached to the aromatic ring, for example, xylylene diisocyanate.

[00024] Aromatic polyurethane = polyurethane formed from aromatic isocyanates. A person skilled in the art would appreciate that it is the identity of the isocyanate alone (being aliphatic or aromatic) that dictates the nature of the polyurethane as being aliphatic or aromatic. For the purposes of the present invention, aliphatic polyurethane prepolymers are derived from 95 mol% or more of aliphatic isocyanate monomers, relative to the total moles of isocyanate monomers incorporated into the prepolymer.

[00025] Aliphatic polyurethane = polyurethane formed from aliphatic isocyanates. A person skilled in the art would appreciate that it is the identity of the isocyanate alone (being aliphatic or aromatic) that dictates the nature of the polyurethane as being aliphatic or aromatic. For the purposes of the present invention, aliphatic polyurethane prepolymers are derived from 95 mol% or more of aliphatic isocyanate monomers, relative to the total moles of isocyanate monomers incorporated into the prepolymer.

[00026] Aromatic-aliphatic polyurethane = polyurethane formed from aromatic and aliphatic isocyanates. For the purposes of the present invention, aromatic-aliphatic polyurethane prepolymers are derived from more than 5 mol% to less than 95 mol% of aromatic isocyanate monomers and more than 5 mol% to less than 95 mol% of aliphatic isocyanate monomers relative to the total moles of isocyanate monomers incorporated into the prepolymer.

[00027] Aromatic carboxylic acid = a carboxylic acid Petition 870260046201, dated 05 / 15 / 2026, page 16 / 120 8 / 44 comprising at least one acid group (-COOH) directly attached to an aromatic ring.

[00028] Aliphatic carboxylic acid = a carboxylic acid in which the carboxylic acid group(s) (-COOH) is / is not directly attached to an aromatic ring. Aliphatic carboxylic acids include alicylic carboxylic acids. Aliphatic carboxylic acids may thus include aromatic rings provided that the carboxylic acid group(s) is / is not directly attached to the aromatic rings.

[00029] Free isocyanate monomer = a monomeric isocyanate species that has not undergone a reaction with a comonomer, for example, a polyol. Unreacted starting material from the polymerization reaction, for example, that used to form the polyurethane prepolymer.

[00030] Solvent-free = comprising 5% by weight or less of any solvent.

[00031] Retort bag = Type of food packaging made from a flexible plastic laminate.

[00032] Retort conditions = methods of cooking and sterilizing food in retort packaging, typically involving heating to high temperatures, for example, 115 to 125 °C for a period of time, for example, 20-60 minutes.

[00033] Two-component adhesive = an adhesive composition comprising two components, with one component inducing the crosslinking agent of the other component.

[00034] Package adhesive = an adhesive composition comprising one component, which normally undergoes cross-linking through reaction with residual moisture: PET = Polyethylene Terephthalate PE = Polyethylene Petition 870260046201, dated 05 / 15 / 2026, page 17 / 120 9 / 44 ALU = Aluminum CPP = Cast Polypropylene OPA = Nylon AlOx = Aluminum oxide SiOx = Silicon dioxide OPP = Oriented Polypropylene Ope = Oriented Polyethylene LDPE = Low-Density Polyethylene LLDPE = Linear Low-Density Polyethylene VM-PET = Vacuum Metallized Polyethylene Terephthalate Methylene dicyclohexyl diisocyanate includes the isomers: 1-isocyanato-1-[(1-isocyanatocyclohexyl)methyl]cyclohexane and 4,4-diisocyanatodicyclohexylmethane Xylene diisocyanate includes its regioisomers.

[00035] Unless otherwise indicated, all ranges include their respective endpoints. For example, a range from 3 to 9 includes the endpoints 3 and 9. However, when an endpoint is defined as being more than one value and / or less than another value, the range does not include the respective endpoints.

[00036] Unless otherwise indicated, % by weight (w / w) refers to the mass of the component in question in relation to all components present in the composition.

[00037] The % by weight (w / w) of free isocyanate monomer is the mass of said species in relation to the total mass of the polyurethane prepolymer that is derived from said monomer. The Present Invention

[00038] The present invention provides an improved two-package solvent-free laminating adhesive kit comprising a pre Petition 870260046201, dated 05 / 15 / 2026, page 18 / 120 10 / 44 aliphatic polyurethane polymer. The adhesive kit of the invention is suitable for the preparation of flexible packaging laminates that can be used in retort applications.

[00039] To the best of the inventors' knowledge, this is the first reported instance of the use of solvent-free aliphatic two-package laminating adhesives in the preparation of flexible laminates for retort applications, with the laminates withstanding thermal processing temperatures of 100 °C or more.

[00040] The solvent-free two-package lamination adhesive kit of the present invention comprises a functional aliphatic isocyanate polyurethane prepolymer produced from aliphatic isocyanate monomers, such as diisocyanates. The amount of residual monomer in the polyurethane prepolymer for use in the invention is less than 0.1% (w / w) of said prepolymer. The amount of residual monomer can be reduced using an evaporator (e.g., clean film evaporator). The adhesive of the present invention is particularly suitable for the preparation of flexible packaging laminates used in the manufacture of shrink-wrapped, pasteurizable, and boilable bags.

[00041] The invention kit can therefore be used to improve the bond strength under retort conditions of a multilayer structure formed from a flexible film and a laminated adhesive formed from the components of the invention kit. The improved bond strength refers to the increased resistance to delamination of said laminated structure compared to a comparative laminated structure formed from the same flexible film and a laminated adhesive that is not formed from the components of the invention kit.

[00042] Retort conditions include heating to 100 °C or more for a period of 20 minutes, such as heating to 120 °C for 30 Petition 870260046201, dated 05 / 15 / 2026, page 19 / 120 11 / 44 minutes or 135 °C for 20 minutes. Retort conditions induce pressure differentials between the pressure inside the retort bag and atmospheric pressure, which can put the adhesives used to seal the retort bag under stress. For example, the low retort test might involve heating a retort bag in an autoclave at about 120 °C for at least 30 minutes, where the autoclave is at a pressure of about 150 kPa (1.5 bar). The high retort test might involve heating a retort bag in an autoclave at about 135 °C for at least 20 minutes, where the autoclave is at a pressure of about 260 kPa (2.6 bar). Advantages Associated with the Present Invention

[00043] The inventors have discovered that incorporating an aliphatic polyurethane prepolymer for use in the invention, comprising monomeric units derived from aliphatic isocyanate monomers, into a solvent-free laminating adhesive provides adhesives with improved bonding under retort conditions. The improvements are observed in relation to comparative adhesives comprising aromatic polyurethane prepolymers comprising monomeric units derived from aromatic isocyanate monomers.

[00044] The adhesive kit of the invention is also improved in relation to comparative adhesive kits comprising polyurethane prepolymers comprising residual isocyanate monomer content above that required by the present invention.

[00045] The two-package solvent-free aliphatic laminating adhesive kit of the present invention is suitable for preparing flexible packaging laminates that are resistant to retort conditions of >100 °C for periods of >10 minutes (i.e., form seals that do not fail under said conditions). To date, two-package solvent-free laminating adhesives have found widespread use in less demanding applications, Petition 870260046201, dated 05 / 15 / 2026, page 20 / 120 12 / 44 but failed in retort applications.

[00046] Furthermore, a consequence of using aliphatic isocyanate monomers in the preparation of adhesives for use in the present invention is that the risk associated with the generation of harmful primary aromatic amines is removed. Such aromatic amines can be produced when adhesives comprising polyurethane prepolymers formed from aromatic diisocyanates are placed under retort conditions. The use of an aliphatic isocyanate-based adhesive reduces the risk of forming primary aromatic amines under retort conditions.

[00047] An additional advantage is that the amount of free diisocyanate monomer in the polyurethane prepolymer component of the two-pack adhesive kit of the invention is less than 0.1% (w / w), based on the weight of the polyurethane prepolymer. This is important with regard to the hazards related to the prepolymer. In particular, reducing the free diisocyanate monomer content in the polyurethane prepolymer to less than 0.1% (w / w) ensures that the risks associated with monomeric isocyanates (e.g., diisocyanates, such as hexamethylene diisocyanate) can be mitigated, insofar as, according to the current Classification, Labelling and Packaging Guidelines for Substances and Mixtures (CLP), the prepolymer is free from any labelling related to the risks associated with free diisocyanate monomer.This is advantageous because it allows for easier handling of the adhesive kit of the invention compared to conventional two-package laminating adhesive kits / compositions that comprise larger amounts of residual isocyanates. Reducing the amount of free monomeric isocyanates, such as xylylene diisocyanate, present in an adhesive, for example, by using a clean film evaporator, has not been previously reported.

[00048] Furthermore, even if monomers are used Petition 870260046201, dated 05 / 15 / 2026, page 21 / 120 13 / 44 of aliphatic isocyanate, providing primary aliphatic amines when subjected to retort conditions, reducing the amounts of free isocyanate monomer to less than 0.1% (w / w) minimizes the risks associated with the presence of migratable species in adhesive compositions.

[00049] Solvent-free laminating adhesives do not comprise organic solvents or water in order to reduce viscosity to a level such that the material can be applied with a laminating machine at temperatures of <90 °C, for example, <80 °C. However, as a result of the aforementioned advantages, the inventors have found a way to produce solvent-free adhesives where the viscosity required for use in a laminating machine at the aforementioned temperatures can be achieved by controlling the molecular weight of the components and without the problems typically associated with the presence of low molecular weight / small molecule migratable components.

[00050] The solvent-free laminated adhesive kit of the invention comprises 5% by weight or less of any solvent. Preferably, the solvent-free laminated adhesive kit comprises 3% by weight or less of any solvent, and more preferably 1% by weight or less of any solvent. Even more preferably, the solvent-free laminated adhesive kit of the invention is substantially solvent-free.

[00051] Furthermore, the inventors also discovered that incorporating a polyester polyol comprising monomeric units derived from a mixture of aromatic monomers and aliphatic monomers into the polyurethane prepolymer for use with the invention improves its mechanical properties.

[00052] The two-component adhesive kit of the invention provides adhesives with the added advantages of having a stronger bond, better chemical resistance, and faster curing, when compared to Petition 870260046201, dated 05 / 15 / 2026, page 22 / 120 14 / 44 analogous adhesive compositions of a package. Single-pack adhesives cure using only the moisture present in the substrate and the air. Typically, single-pack adhesives work well with paper-to-film laminated substrates. However, with film-to-film lamination or film-to-aluminum lamination, for example, the development of the reaction and bond strength of single-pack adhesives can be very slow, as there is not as much moisture available and / or it is difficult for moisture to reach the isocyanate.

[00053] In addition, a catalyst (e.g., ethyl morpholine, DMDEE = 2,2-Dimorpholinodiethyl ether or another compound containing a tertiary amine or a metal salt) is typically added to single-pack adhesives to compensate for slower cure rates, making the isocyanate group more reactive / sensitive to moisture. A two-pack adhesive does not require a catalyst, meaning that the amounts of migratable species may be even further reduced compared to comparable single-pack adhesives. Instead, the isocyanate groups in two-pack adhesives react with a polyol that is intimately blended into the polyurethane prepolymer and provides readily available reactive sites. However, the isocyanate groups of the polyurethane prepolymers in two-pack adhesives may also react with residual moisture. Aliphatic polyurethane prepolymer

[00054] Polyurethanes with NCO end groups are typically obtained by reacting polyfunctional alcohols with an excess of polyisocyanate monomer(s). Generally, diisocyanates are used to obtain a prepolymer with a molecular weight and viscosity compatible with use in a laminating machine at temperatures of 80-90 °C. This is because diisocyanates (as opposed to the more functional isocyanates) are only capable of reacting with two polyol species and therefore do not form Petition 870260046201, dated 05 / 15 / 2026, page 23 / 120 15 / 44 cross-tabulations.

[00055] The polyurethane prepolymer for use in the present invention is characterized by having a viscosity at 80 °C ranging from 800 mPas to 20,000 mPas, or preferably 1,000 mPas to 10,000 mPas, or more preferably 2,000 mPas to 7,000 mPas.

[00056] The polyurethane prepolymer for use in the present invention preferably has a content of reactive isocyanate groups (%NCO) ranging from 3% to 16%, or more preferably from 5% to 10%.

[00057] Those skilled in the art will appreciate that, although the advantages associated with the present invention derive from the use of an aliphatic polyurethane precursor comprising monomeric units derived from aliphatic isocyanates, this does not preclude the presence of a small amount of non-aliphatic isocyanate in the prepolymer, provided that such amount does not affect these advantageous properties. Consequently, for the purposes of the present invention, an aliphatic polyurethane prepolymer is derived from 95 mol% or more of aliphatic isocyanate monomers, relative to the total moles of isocyanate monomers incorporated in the prepolymer. Preferably, the aliphatic polyurethane prepolymer for use in the invention is derived from more than 98 mol%, more preferably more than 99 mol%, of aliphatic isocyanate monomers, relative to the total moles of isocyanate monomers incorporated in the prepolymer.More preferably, the only isocyanate monomers incorporated into the aliphatic polyurethane prepolymer for use in the invention are aliphatic isocyanate monomers.

[00058] A certain amount of residual diisocyanate monomers (due to the use of a stoichiometric excess) will remain present in the reaction mixture at the end of the reaction, regardless of the reaction time. The aliphatic polyurethane prepolymer for use in the invention is functionalized with isocyanate, such that NCO groups Petition 870260046201, dated 05 / 15 / 2026, page 24 / 120 16 / 44 reactive elements are attached to the prepolymer. The aliphatic polyurethane prepolymer for use in the invention comprises at least two isocyanate groups per prepolymer. The aliphatic polyurethane prepolymer for use in the invention is preferably difunctionalized with isocyanate groups, such as wherein the aliphatic polyurethane prepolymer for use in the invention is linear and comprises an isocyanate group at either end.

[00059] The polyurethane prepolymer for use in the invention may comprise three or more isocyanate groups per prepolymer, such as four or more, or five or more isocyanate groups per prepolymer.

[00060] The polyurethane prepolymer is preferably linear. For the purposes of the present invention, a linear polyurethane prepolymer is typically derived from bifunctional isocyanates and bifunctional polyols, such that each isocyanate-derived moiety is covalently linked to a maximum of two polyols and each polyol-derived moiety is covalently linked to a maximum of two isocyanates. A linear polyurethane prepolymer may comprise monomeric components that are themselves branched, such as a branched glycol.

[00061] The aliphatic polyurethane prepolymer for use in the invention is preferably derived from a polyester polyol and more preferably from a polyester polyol comprising monomeric units derived from aromatic monomers, such as aromatic dicarboxylic acids.

[00062] It is preferred that of the polyol components used to make the polyurethane prepolymer for use in the invention, at least 50% by weight be polyester polyols, such as at least 60% by weight, at least 70% by weight, more preferably at least 80% by weight, or at least 90% by weight be polyester polyols. It is more preferably that all the polyols used to make the polyurethane prepolymer for use in the invention Petition 870260046201, dated 05 / 15 / 2026, page 25 / 120 17 / 44 are polyester polyols. The inventors found that polyester polyols provide desirable high-temperature mechanical properties to polyurethane prepolymers for use in the invention.

[00063] The molar ratio of the NCO groups of the aliphatic isocyanate monomers used to make the polyurethane prepolymer for use in the invention to the HO groups of the polyol used to make the polyurethane prepolymer for use in the invention may be from 5:1 to 2:1. Preferably, the molar ratio of the NCO groups of the aliphatic isocyanate monomers used to make the polyurethane prepolymer for use in the invention to the HO groups of the polyol used to make the polyurethane prepolymer for use in the invention is from 4:1 to 2:1, as well as from 3:1 to 2:1.

[00064] The ratio of NCO:OH groups of the isocyanates and polyols used to make the prepolymer for use in the two-pack adhesive kits of the invention may be lower than that required for single-pack adhesives that rely on residual moisture content to cure. Without wishing to be limited by theory, a lower NCO:OH ratio may be used when making polyurethane prepolymers for use in two-pack adhesives; the lower ratio results in higher molecular weight and viscosity polyurethane prepolymers, which may function effectively when combined with a polyol crosslinker. In contrast, a higher NCO:OH ratio should be used when making polyurethane prepolymers for use in single-pack adhesives; the excess NCO provides lower molecular weight polyurethane prepolymers and therefore sufficiently low viscosity for use in single-pack adhesive applications.Excess isocyanate monomer should then be removed from the adhesive packaging after use. Reduction of free isocyanate monomer content

[00065] Even at room temperature, diisocyanates, such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), di Petition 870260046201, dated 05 / 15 / 2026, page 26 / 120 Toluene isocyanate (TDI) and diphenylmethane diisocyanate (MDI) have significant vapor pressures. This gives rise to serious health risks during application, as these species are toxic due to their sensitizing and irritating actions. Users are legally required to implement specific measures to protect personnel during use, involving significant additional equipment, such as those designed to maintain breathable air and / or keep these substances at concentrations below the maximum permitted in the workplace. Users are therefore required to install expensive protective equipment for personnel exposed to such product vapors and / or aerosols developed by the dynamic application conditions in rotating machinery.

[00066] Reagents of this type are regulated by hazardous substances legislation and must be labeled as hazardous materials. The labeling obligation is accompanied by the requirement to take special packaging and transport measures.

[00067] Many polyurethane adhesives of the art comprise more than 0.1% (w / w) (the limit prescribed by the CLP Regulation, below which the product is not considered hazardous) of residual isocyanate monomer (generally volatile diisocyanates such as free TDI, MDI or other isocyanate monomers). In particular, when a molar excess of isocyanate functional groups is used relative to the hydroxyl functional groups of the polyol, an excess of free isocyanate monomer will remain in the reaction mixture after the formation of the polyurethane prepolymer. Unless additional processing steps are taken to remove this excess free monomer, more than 0.1% (w / w) of free isocyanate monomer will remain in the prepolymer, requiring the aforementioned safety precautions.Furthermore, if prepolymers comprising more than 0.1% (w / w) of free isocyanate monomer are used as adhesives for food packaging, the contamination of food products with isocyanate monomers can occur. Petition 870260046201, dated 05 / 15 / 2026, page 27 / 120 Migrable 19 / 44 isocyanates may also result.

[00068] The solvent-free laminating adhesive kit of the present invention comprises an aliphatic isocyanate-functional polyurethane component having an amount of free isocyanate monomer less than or equal to 0.1% (w / w) relative to said prepolymer. For example, the isocyanate-functional polyurethane component preferably comprises less than 0.1% (w / w) or 0.08% (w / w) or less of free isocyanate monomer. The polyurethane prepolymer undergoes additional processing steps described herein in order to reduce the amount of free isocyanate monomer to that required by the present invention.

[00069] The low amounts of free monomeric isocyanate monomer required by the present invention can be achieved by removing unreacted isocyanate monomer from the polyurethane prepolymer using an evaporator (e.g., a clean film evaporator). The evaporator can be used at temperatures of 100-250 °C, preferably 120-200 °C, and more preferably 140-180 °C. The evaporator can operate under a pressure of less than 500 Pa (5 mbar), preferably less than 50 Pa (0.5 mbar), and more preferably less than 10 Pa (0.1 mbar). The evaporator can be operated for a total contact time of less than 30 min, preferably less than 15 min, and more preferably less than 5 min. The evaporator can be operated at a pressure of 10 Pa (0.1 mbar) or less and at a temperature of 140 °C–180 °C. Making the polyurethane prepolymer for use in the invention

[00070] The polyurethane prepolymer for use in the present invention can be obtained by a process comprising the following protocol: a) react an aliphatic diisocyanate with a polyester polyol and / or a polyether polyol, each with a number-average molecular weight (Mn) of Petition 870260046201, dated 05 / 15 / 2026, page 28 / 120 20 / 44 <1000 g / mol, in an NCO:OH molar ratio greater than 2.0:1.0; i. optionally using a catalyst; and ii. optionally using an acid compound, to obtain an NCO-terminated prepolymer; and b) subject the NCO-terminated prepolymer obtained in step a) to one or more extraction stages, using a series of one or more clean film evaporators and / or short path evaporators.

[00071] Steps a) and b) are conducted in accordance with known operating procedures and conditions.

[00072] The final polyurethane prepolymer thus obtained has the following characteristics after removal of the free isocyanate monomer: - %NCO >7% - A viscosity at 50 °C of < 30,000 mPas - A free diisocyanate monomer in <0.1% by weight.

[00073] The method of making the polyurethane prepolymer for use in the invention preferably does not require a solvent. In other words, the polyurethane prepolymer for use in the invention can be formed using only the reagents that are themselves incorporated into the prepolymer. Aliphatic isocyanates for use in the manufacture of prepolymer of POLYURETHANE

[00074] The aliphatic isocyanates used for the preparation of the isocyanate-functionalized aliphatic polyurethane prepolymer for use in the invention are selected from the group consisting of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methane dicyclohexyl diisocyanate, xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), pentamethylene diisocyanate (PDI) and combinations of any of the foregoing. Petition 870260046201, dated 05 / 15 / 2026, page 29 / 120 21 / 44

[00075] Preferably, the aliphatic isocyanate monomer for use in the invention is a diisocyanate selected from the group consisting of isophorone diisocyanate (IPDI) and its isomeric mixtures, 1,6-hexane diisocyanate (HDI), xylylene diisocyanate (XDI) and combinations thereof. More preferably, the aliphatic isocyanate monomer for use in the invention is xylylene diisocyanate (XDI).

[00076] The aliphatic isocyanates for use in the invention comprise isocyanate groups that are not directly attached to an aromatic ring. Consequently, the aliphatic isocyanates for use in the invention may comprise aromatic groups, provided that the isocyanate groups are not directly attached. POLYOL FOR MAKING POLYURETHANE PREPOLYMER FOR USE IN THE INVENTION

[00077] The polyol for use in the manufacture of the isocyanate-functionalized aliphatic polyurethane prepolymer for use in the invention may be selected from the group consisting of a polyester polyol, a polyether polyol and combinations thereof. The polyol for use in the invention is preferably a polyester polyol and more preferably a polyester polyol comprising monomeric units derived from aromatic monomers.

[00078] The polyester polyol for use in the invention was selected to provide a desirable combination of properties. In particular, the polyol is selected so that when incorporated into the polyurethane prepolymer for use in the invention, the polyurethane prepolymer has desirable mechanical properties at high temperatures and a final viscosity that is suitable for use in a laminating machine at 80-90 °C.

[00079] The inventors have found that a polyester polyol particularly preferred for use in the invention is characterized as follows: 1. It comprises a mixture of dicarboxylic acids. Petition 870260046201, dated 05 / 15 / 2026, p. 30 / 120 22 / 44 aromatics and aliphatics; and / or 2. comprises a mixture of linear and branched short-chain glycols; and / or 3. has an OH ion number ranging from 110 to 400 mgKOH / g; and / or 4. It has a viscosity ranging from 500 to 10,000 mPas at 23 °C.

[00080] Although the polyester polyol for use in the invention may comprise other components, such as polyether segments, it is preferred that at least 50 mol% of the monomeric units present be polyester monomeric units, such as at least 60 mol%, at least 70 mol%, preferably at least 80 mol%, or more preferably at least 90 mol% of the monomeric units present be polyester monomeric units. The polyester polyol for use in the invention may comprise only polyester monomeric units.

[00081] When used to formulate the laminating adhesive of the invention, the inventors found that a polyurethane prepolymer made with a polyester polyol backbone is advantageous because the resulting polyurethane prepolymer exhibits improved mechanical properties (e.g., tear resistance) at typical temperatures used for return processes (100-135 °C).

[00082] The polyester and / or polyether polyols for use in the invention are preferably linear. In the context of the invention, a linear polyester polyol is derived from bifunctional (and optionally also monofunctional) monomers, such that each monomer unit can react with a maximum of two other monomers. In other words, the maximum functionality of the monomers is two. For example, a dicarboxylic acid and a diol make a linear polyester. Aromatic and Aliphatic Monomers

[00083] When used to formulate the prepolymer of Petition 870260046201, dated 05 / 15 / 2026, page 31 / 120 23 / 44 polyurethane for use in the invention, a polyester polyol comprising at least 10% by weight of monomeric units derived from aromatic monomers is preferred. More preferably, at least 20% by weight of the monomeric units of the polyester polyol are derived from aromatic monomers. This is because, in general, polyurethane prepolymers derived from such polyols exhibit improved mechanical properties at typical temperatures for the retorting process and, in particular, improved bond strength under retort conditions. Without wishing to be limited by theory, the inventors postulate that the improvements relate to greater hydrolysis resistance and higher glass transition temperature (Tg) of these polyester polyols.

[00084] Polyurethanes made with a polyester polyol backbone are generally more viscous than those made with a polyether backbone; and polyester polyols containing aromatic rings in the backbone are even more viscous than pure aliphatic polyester polyols. The inventors have found that incorporating a mixture of aliphatic and aromatic groups into the polyester polyol for use in the invention provides polyurethane prepolymers with enhanced mechanical properties and viscosities suitable for use in adhesive laminate applications.

[00085] The polyester polyol for use in the invention can be derived from 10 to 55% by weight of aromatic monomers, preferably 15 to 45% by weight, and more preferably 15 to 35% by weight, such as 20 to 30% by weight of aromatic monomers, relative to the total weight percentage of the polyester polyol. The aromatic monomers are preferably aromatic dicarboxylic acids, such as isophthalic acid.

[00086] The polyester polyol for use in the invention can be derived from 45% to 90% by weight of aliphatic monomers, preferably 55% to 85% by weight, and more preferably 65% ​​to 85% by weight. Petition 870260046201, dated 05 / 15 / 2026, page 32 / 120 24 / 44 weight of aliphatic monomers, relative to the total weight percentage of the polyester polyol. The aliphatic monomers are preferably aliphatic dicarboxylic acids, such as sebacic acid. The aliphatic monomers are also preferably aliphatic polyols, such as aliphatic glycols and diols. POLYOLS USED TO MAKE POLYESTER POLYOL

[00087] The polyol used to make the polyester polyol is preferably a glycol and / or diol. The glycols and diols used to make the polyester polyol are preferably selected from the group consisting of neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, monoethylene glycol and their combinations.

[00088] The polyester polyol for use in the invention may comprise 15 to 35% of monomeric units derived from aromatic dicarboxylic acids and 65 to 85% by weight of monomeric units derived from aliphatic dicarboxylic acids and aliphatic glycols and diols.

[00089] The polyester polyol for use in the invention can be formed from 10 to 55% by weight of aromatic monomers, preferably 15 to 45% by weight, and more preferably 15 to 35% by weight, such as 20 to 30% by weight of aromatic dicarboxylic acids relative to the total amount of monomers used to form the polyester polyol. The polyester polyol for use in the invention can be formed from 45% by weight to 90% by weight of aliphatic dicarboxylic acids and aliphatic glycols and diols, preferably 55 to 85% by weight, and more preferably 65 to 85% by weight of aliphatic dicarboxylic acids and aliphatic glycols and diols, relative to the total amount of monomers used to form the polyester polyol.

[00090] The aromatic dicarboxylic acids used for the preparation of polyester polyol are preferably selected from the list consisting of terephthalic acid, isophthalic acid, phthalic anhydride, and combinations thereof. The aliphatic dicarboxylic acids used for the preparation of Petition 870260046201, dated 05 / 15 / 2026, p. 33 / 120 25 / 44 polyol polyesters are preferably linear C2-C14 dicarboxylic acids, such as linear C2-C14 dicarboxylic acids selected from the group consisting of succinic acid, glutaric acid, adipic acid, sebacic acid, azelaic acid and combinations thereof.

[00091] The weight ratio of aromatic dicarboxylic acids: The ratio of aliphatic dicarboxylic acids incorporated into the polyol can be from 10:1 to 1:10, preferably 4:1 to 1:4, and more preferably 2:1 to 1:2. The weight ratio of aromatic:aliphatic dicarboxylic acids incorporated into the polyol for use in the invention can be from 1.5:1 to 1:1.5, such as being incorporated in substantially equal weight percentages. Short-Chain Glycols

[00092] Short-chain glycols suitable for the preparation of the polyester polyol for use in the invention include, but are not limited to, linear C1-C6 diols, such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and combinations thereof. Short-chain glycols comprising alkyl substituents are also suitable for the preparation of the polyester polyol for use in the invention and are preferably selected from the C1-C6 diols: 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, neopentyl glycol, 1,3-methylpentanediol, 2-methyl-1,3-propanediol and combinations thereof.

[00093] The glycols for use in the invention preferably have a molecular weight of less than 500 gmol-1, such as less than 300 gmol-1 and preferably less than 200 gmol-1.

[00094] The percentage weight ratio of linear:branched short-chain glycols incorporated into the polyol for use in the invention may be 10:1 to 1:10, preferably 4:1 to 1:4, and more preferably 2:1 to 1:2. The weight ratio of dicarboxylic acids of linear:branched short-chain glycols incorporated into the polyol for use in the invention may be Petition 870260046201, dated 05 / 15 / 2026, page 34 / 120 26 / 44 1.5:1 to 1:1.5, as incorporated in substantially equal weight percentages. Polyurethane prepolymer additives

[00095] The polyurethane prepolymer for use in the invention can be used as is (i.e., in the form provided from the method mentioned above) or after the addition of additives such as adhesion promoters, viscosity and rheology regulators, water scavengers, anti-skin agents and anti-bubble agents.

[00096] In particular, the use of an adhesion promoter, for example, silane-containing groups that react with isocyanate groups (such as 3-aminopropyltriethoxysilane), is advantageous when the adhesive system is to be used on metal or metallized substrates, such as aluminum. Such an adhesion promoter can also be incorporated into the polyol crosslinking agent. However, such a component is not essential for the adhesive kit of the invention. The inventors found that the adhesive of the invention works well under retort conditions, even in the absence of a silane additive that reacts with isocyanates. Consequently, the functional polyol crosslinking agent for use in the invention may not comprise a silane compound capable of reacting with isocyanates. Optional additional aliphatic polyisocyanate(s)

[00097] The polyurethane prepolymer for use in the invention may also be formulated with the addition of one or more additional aliphatic polyisocyanates to further reduce the viscosity of the final system, i.e., an additional aliphatic polyisocyanate(s) may be incorporated into part a) of the kit of the invention. The additional aliphatic polyisocyanate(s) for use in the invention may be of low viscosity, i.e., the additional aliphatic polyisocyanate(s) for use in the invention may have a viscosity at 23 °C of 3,000 mPas or less, preferably 2,000 mPas Petition 870260046201, dated 05 / 15 / 2026, p. 35 / 120 27 / 44 or less, as well as 1,000 or less, or 500 or less.

[00098] The additional aliphatic polyisocyanate(s) is / are preferably selected from the group consisting of aliphatic polyisocyanate trimers (i.e., isocyanurates), aliphatic polyisocyanate allophanates, aliphatic polyisocyanate oligomers, aliphatic polyisocyanate biuretes, aliphatic polyisocyanate urethdiones, and combinations thereof.

[00099] Specific examples of these compounds include hexamethylene diisocyanate (HDI) trimers (e.g., POLURENE MT100, POLURENE MT100LV, POLURENE MT100LLV, Wanhua's Wannate HT 100 and Wannatye HT 600), hexamethylene diisocyanate (HDI) allophanates, hexamethylene diisocyanate biuret, urethdione / allophanate-modified HDI oligomers, and HDI oligomers (e.g., Polurgreen MT 100 01, Polurgreen MT 100 LV 01, Polurgreen MT 100 LLV 01, Tolonate HDT, Tolonate HDT LV, Tolonate HDT LV2, Tolonate XFLO 100, Basonat HI, Basonat HI-2000, Basonat HA3000, Desmodur ULTRA N 3300, Desmodur ULTRA N 3600, Desmodur ULTRA N 3900, Desmodur XP2860). An allophanate is an isocyanate dimer. [000100] More preferably, the additional aliphatic polyisocyanate(s) is / are selected from the group consisting of aliphatic polyisocyanate trimers, such as HDI trimer, aliphatic polyisocyanate allophanates, such as HDI allophanate, and combinations thereof. Even more preferably, the additional aliphatic polyisocyanate(s) is / are an aliphatic polyisocyanate trimer, such as HDI trimer. [000101] The aliphatic polyurethane prepolymer for use in the invention may be incorporated into a composition comprising the additional polyisocyanate(s) for use in the invention. The ratio in % by weight of the polyurethane prepolymer for use in the invention to the polyisocyanate(s) Petition 870260046201, dated 05 / 15 / 2026, page 36 / 120 28 / 44 additional(s) for use in the invention may be from 8:1 to 1:1, more preferably from 5:1 to 2:1, and even more preferably from 3:1 to 2:1. Catalysts [000102] If desired, the urethane formation reaction can be accelerated by adding suitable catalysts during the preparation phase. Suitable catalysts for the urethane formation reaction are known and comprise amines and organometallic compounds. However, such a component is not essential for the adhesive kit of the invention. The inventors have found that the adhesive of the invention works well under retort conditions, even in the absence of a catalyst. Consequently, the polyurethane prepolymer for use in the invention (and kit of the invention) may not comprise a catalyst. [000103] Examples of suitable catalysts for use in the invention include triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N-tetramethyldiamine methyl ether, bis(dimethylaminopropyl)urea, N-methyl or N-ethylmorpholine, N,N'-dimorpholinodiethyl ether (DMDEE), N-cyclohexylmorpholine, N,N,N',N'tetramethylethylenediamine, N,N,N',N'-tetramethylbutylenediamine, N,N,N',N'tetramethyl-1,6-hexanediamine, pentamethyldiethylenetriamine, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, N-hydroxypropylimidazole, 1-azabicyclo-[2,2,0]-octane, 1,4-diazabicyclo[2,2,2]octane (DABCO), alkanolamines such as triethanolamine, triisopropanolamine, N-methyl and N-ethyl diethanolamine, dimethylaminoethanol, 2-(N,N'-dimethylaminoethoxy)ethanol, N,N',N-tris(dialkylaminoalkyl)hexahydrothiazines such as N,N',N-tris-(dimethylaminopropyl)-hexahydrotazine, tetraalkylammonium hydroxides such as tetramethylammonium hydroxide,alkaline hydroxides such as sodium hydroxide, alkaline alcoholates such as sodium methylate, alkaline salts of long-chain fatty acids, iron(II) chloride, zinc chloride, lead octoate, tin salts, Petition 870260046201, dated 05 / 15 / 2026, p. 37 / 120 29 / 44 such as tin dioctate, tin diethylhexanoate, dibutyltin dilaurate, dibutyldilauryltin mercaptide, titanium compounds such as titanium (IV) butylate, organometallic compounds of tin, lead, iron, titanium, bismuth and zirconium, tin oxides and sulfides and bismuth carboxylates. [000104] The polyurethane prepolymer adhesive obtained as described above, characterized by a free monomer below 0.1% by weight (“free monomer”), does not require hazard labeling as it is completely safe for the user and does not contain substances liable to migrate from the packaging into the food (primary aromatic amines and cyclic esters), even when the packaged product has a long shelf life. Polyol crosslinker [000105] The polyol crosslinking agent for use in the kit of the present invention may be any polyol suitable for curing the isocyanate-functionalized aliphatic polyurethane prepolymer for use in the invention. [000106] The polyol crosslinking agent for use in the kit of the present invention may be selected from linear or branched polyethers and / or linear or branched polyester polyols. The polyol crosslinking agent for use in the invention may be a mixture of polyester polyol and polyether polyol. The polyol crosslinking agent for use in the invention is preferably a polyester polyol. [000107] The polyol crosslinking agent for use in the invention may be a polyester polyol formed from glycols and dicarboxylic acids. The glycol may be selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, tetramethylene glycol, polyethylene glycol (including methyl ether thereof), polypropylene glycol (including methyl ether thereof) and polybutylene glycol (including methyl ether thereof). The dicarboxylic acid may be selected Petition 870260046201, dated 05 / 15 / 2026, page 38 / 120 30 / 44 of the group consisting of aliphatic dicarboxylic acids malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, aspartic acid, malic acid and the aromatic dicarboxylic acids terephthalic acid and isophthalic acid. Polyester polyol can also be derived from non-glycol polyols, including trimethylolpropane. [000108] The polyol crosslinking agent for use in the invention may be a polyester polyol comprising tertiary amine groups in the backbone. [000109] The polyol crosslinking agent, for example, polyester polyol, for use in the invention may have a number average molecular weight of 200 to 10,000 Da, preferably 400 to 5,000 Da, and more preferably 500 to 2,000 Da. [000110] The polyol crosslinking agent for use in the invention can be incorporated into a crosslinking composition (as part b) further comprising a polyether monool (i.e., comprising a single hydroxyl substituent, for example, polypropylene glycol monoalkyl ether). The polyether monool is preferably selected from a list consisting of polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, polybutylene glycol monoalkyl ether, and combinations thereof. For example, the polyol crosslinking agent for use as part b) in the invention can be incorporated into a crosslinking composition further comprising polypropylene glycol monomethyl ether. [000111] The polyether monool can have a number average molecular weight of 200 to 2000 Da, such as 200 to 1000 Da, or 200 to 500 Da. [000112] When present, the polyether monool (e.g., polypropylene glycol monoalkyl ether) may be incorporated into the polyol crosslinking agent composition of part b) in an amount of up to 50%. Petition 870260046201, dated 05 / 15 / 2026, p. 39 / 120 31 / 44 by weight relative to the total weight of both the polyol crosslinking agent and the polyether monool, for example, up to 40% by weight. In other words, the % by weight ratio of the polyol crosslinking agent from part b) to the polyether monool (when present) can be from 100:0 to 50:50, such as 80:20 to 50:50, or 70:30 to 60:40, such as approximately 60:40. [000113] The invention kit comprises aliphatic polyurethane prepolymer and, optionally, additional polyisocyanate as part a) and polyol crosslinker as part b). The weight % ratio of part a) to part b) can be from 5:1 to 1:2, and preferably from 4:1 to 1:1, and more preferably from 3:1 to 1:1. Laminates [000114] There is a significant market related to adhesive-formed multiplication laminates for retort applications. Typical structures include the following substrate combinations: PET / CPP, PET / Al / CPP, PET / Al / OPA / CPP, PET-SiOx / CPP, PET-AlOx / CPP, OPA / CPP, OPA / LDPE, PET / Al / LDPE, VM-PET, AlOx-PET, SiOx-PET, AlOx-OPP, SiOx-OPP, AlOx-OPE, SiOx-OPE, AlOx-OPA, SiOx-OPA, PET / OPA / Al / CPP, OPA / VM-PET / LDPE, PET / OPA / CPP, PET / OPA-SiOx / CPP, PET / OPAAlOx / CPP, PET-SiOx / OPA / CPP, PET-AlOx / OPA / CPP, OPP / CPP, OPPSiOx / OPA / CPP, OPP-AlOx / OPA / CPP. OPE-SiOx / OPA / CPP, OPEAlOx / OPA / CPP, OPA-SiOx / OPA / CPP, OPA-AlOx / OPA / CPP. [000115] The adhesive kit of the invention can be used with any of the substrates mentioned above to form laminates. Retort conditions [000116] The adhesive lamination kit of the invention provides laminates with improved bond strength under retort conditions compared to comparable laminates. Retort conditions involve placing a sealed retort package under temperatures for a Petition 870260046201, dated 05 / 15 / 2026, p. 40 / 120 32 / 44 time period. For example, retort conditions may involve heating a package from 115 °C to 150 °C for 10 to 60 minutes, such as heating a package from 120 °C to 140 °C for 20 to 35 minutes. Retort conditions may involve pressures of 150 to 400 kPa (1.5 to 4 bar), such as 150 to 300 kPa (1.5 to 3 bar). Retort conditions may involve heating at 120 °C for 30 minutes at 150 kPa (1.5 bar) or heating at 135 °C for 20 minutes at 260 kPa (2.6 bar). Examples [000117] The invention is defined by the following non-limiting examples, which further illustrate the invention and are not intended to, nor should they be construed to, limit the scope of the invention. Testing methods [000118] Free diisocyanate monomer content (e.g., %HDI, %XDI): Determined by gas chromatography with an internal standard according to ASTM D3432. Expressed as % by weight relative to the total amount of polyurethane prepolymer. [000119] Reactive NCO group content (%NCO): Determined by back titration with an excess of n-butylamine acid according to ASTM D2572. [000120] Viscosity: Determined using a Brookfield Mod. LVDVII rotational viscometer according to ASTM D1084 at the specified temperature. Unless otherwise indicated, viscosity is measured at 23 °C. [000121] Hydroxyl Value (OH Number): The number of milligrams of potassium hydroxide required to neutralize the acetic acid absorbed in the acetylation of one gram of a chemical substance containing free hydroxyl groups. The standard procedure as defined in ISO 46291:2016(E) is used to determine the Hydroxyl Value. [000122] - Molecular Weight: Petition 870260046201, dated 05 / 15 / 2026, page 41 / 120 33 / 44 a) The molecular weight of non-polymeric or oligomeric compounds (i.e., defined monomeric species) is defined and calculated from the molecular structure of the compound. This is usually provided by the monomer supplier's data sheet or can be found on the European Chemicals Agency (ECHA) website; b) Oligomeric and polymeric species typically comprise a chain length distribution and therefore a molecular weight distribution. Consequently, unless otherwise indicated, the molecular weight of oligomeric and polymeric species (as well as components existing as a mixture of species with individual molecular weights above 500 Da (and thus having a distribution – e.g., vegetable oils)) is measured by Gel Permeation Chromatography (GPC) conducted on a Hewlett-Packard 1050 Series HPLC system equipped with two Ultrastyragel GPC columns, 103 and 104 A (5 μm mixed, 300 mm x 19 mm, Waters Millipore Corporation, Milford, MA, USA) and THF as the mobile phase. The column temperature is 40 °C. The molecular weight is calculated by comparison with a polystyrene standard. Those skilled in the art will appreciate that this definition of molecular weight applies to polymeric materials that typically have a molecular weight distribution.Unless otherwise indicated, the molecular weight reported here for oligomers and polymers is the number-average molecular weight. [000123] - Bond strength is the strength required to separate a multilayer structure formed from a flexible film and a laminated adhesive formed from the components of an adhesive kit. The multilayer structure comprises at least two layers bonded with the laminated adhesive. Bond strength is measured at room temperature (25°C) and at 100 mm / min. All other parameters are in accordance with ASTM D3330-F (the 90° peel test). Petition 870260046201, dated 05 / 15 / 2026, page 42 / 120 34 / 44 [000124] Improved bond strength refers to an increase in the delamination resistance of a laminated structure made from a flexible film and a laminated adhesive formed from the components of the invention kit compared to a comparative laminated structure formed from the same flexible film but using a laminated adhesive that is not formed from the components of the invention kit. Example 1: Synthesis of polyester polyol [000125] The polyester polyol of Example 1 is prepared by mixing the following diols and dicarboxylic acids and reacting them in a typical condensation polymerization using an esterification reactor and well-known esterification conditions. Table 1: Reagents used to prepare the polyester polyol of example 1 Components % Range Isophthalic acid 20-30 Sebacic acid 20-30 Monoethylene glycol 10-20 Neopentyl glycol 5-15 1,6-hexanediol 5-15 3-methyl-1,5-pentanediol 5-15 [000126] Example 1 is a typical polyester polyol obtained from reagents incorporated in the quantities above and has the following characteristics: OH- ion concentration = 265 mg KOH / g Viscosity at 23 °C = 3,000 mPas. Example 2: Synthesis of NCO-terminated polyurethane prepolymer [000127] 550 parts of xylylene diisocyanate (XDI) are added to a 1-liter reaction flask equipped with a stirrer and reflux condenser, flowing continuously with nitrogen. The mixture is heated to 50 °C and 450 parts of polyester polyol A from Example 1 (OH-terminated polyester polyol with 2 functional groups and a number-mean Mw of 420 g / mol) Petition 870260046201, dated 05 / 15 / 2026, p. 43 / 120 35 / 44 are added dropwise to the mixture over 240 minutes under stirring, monitoring the reaction mixture temperature and adjusting the polyol addition rate to ensure it never exceeds 60 °C. [000128] At the end of the addition, the mixture is heated to 80 °C for hours until the % of NCO is about 15.5%. [000129] The product thus obtained is distilled in a thin-film evaporator at a pressure of about 10 Pa (0.1 mbar) and a temperature of 140 °C to remove unreacted monomer. 760 parts of a colorless, transparent liquid with the following characteristics are obtained: %NCO = 7.6% Viscosity at 50 °C = 18,700 mPas %XDI = 0.04% by weight. Example 3: Preparation of solvent-free aliphatic isocyanate prepolymer with a residual monomer level of less than 0.1%. [000130] 700 parts of Example 2 are mixed with 300 parts of a low-viscosity HDI trimer with a residual HDI content of <0.1% (Polurgreen MT 100 LV 01) and 1000 parts of a colorless transparent liquid with the following characteristics were obtained: %NCO = 12.3% Viscosity at 40 °C = 11,000 mPas %XDI = 0.04% %HDI = 0.04%. [000131] Example 3 is a solvent-free aliphatic isocyanate prepolymer with a residual monomer level of less than 0.1% by weight, prepared following the method described above. Its performance was evaluated on PET (12 pm) / aluminum (8 pm) / cast polypropylene (CPP) (60 pm) triplex structures, compared to solvent-free aromatic adhesives. Petition 870260046201, dated 05 / 15 / 2026, p. 44 / 120 36 / 44 The laminates using the adhesives described in Table 2 below were produced on a Labo Combi 400 laminator made by the Nordmeccanica Group, under the following conditions: Coating weight: 2.5 g / m2 / dry; Adhesive roller speed: 80; Adhesive roller temperature: 50 °C; Application Roller Temperature: 50 °C; Tension Releaser A: 23 N; Tension releaser B: 20 ​​N; Tension Rewinder (Laminated): 28 N; Casing head pressure: 300 kPa (3 bar); Tightening pressure: 300 kPa (3 bar); Nip temperature 50 °C. [000132] The laminates were cured at 20 °C for 20 days. Table 2: Comparative and inventive adhesive systems and mixing ratios Sample Base (NCO) Hardener (OH) Mixing Ratio (mass) Description 1 (Comparative) NS4158A HA328B 100 : 50 High-performance solvent-free aliphatic commercial adhesive 2 (Comparative) ZA1000 ZB301 100 : 40 Ultra-low monomer-free commercial solvent-free aromatic adhesive 3 Example 3 MP40 100 : 70 Multi-polyol-cured solvent-free aliphatic shrink adhesive prototype 4 Example 3 MP70 100 : 85 5 Example 3 HA450B 100 : 60 6 Example 3 ZB301 100 : 60 [000133] Sunlam NS-4158A (polyurethane polyisocyanate) / HA-328 (polyester polyol) is a 2-component, solvent-free, partially aromatic laminating adhesive that can be processed at 50°C. The prepolymer Petition 870260046201, dated 05 / 15 / 2026, p. 45 / 120 37 / 44 polyurethane (NS-4158A) is aromatic, meaning that the polyurethane comprises monomeric units derived from aromatic isocyanates. [000134] Sunlam ZA-1000 (polyisocyanate polyurethane) / ZB301 (propylene glycol-based polyester polyol, trimethylol propane combined with adipic acid, containing a small amount of a tetraol with tertiary amines in its backbone) is a commercial two-component, solvent-free (<0.1% by weight) aromatic isocyanate monomer laminating adhesive that can be processed at 50-55 °C. The polyurethane (ZA-1000) is aromatic, i.e., the polyurethane comprises monomeric units derived from aromatic isocyanates. [000135] MP40 is a 60 / 40 mixture of DIC Dry HA930 (Polyol Polyester (DIC Graphics Corporation) and Smack MP-40 (Kao Corporation). Smack MP-40 is a polypropylene glycol monomethyl ether with a molecular weight of approximately 260 Da. [000136] MP70 is a 60 / 40 mixture of DIC Dry HA930 (Polyol Polyester (DIC Graphics Corporation) and Smack MP-70 (Kao Corporation). Smack MP-70 is a polypropylene glycol monomethyl ether with a molecular weight of approximately 450 Da. [000137] Sunlam HA450B is a commercial solvent-free polyester polyol based on monoethylene glycol, neopentyl glycol, trimethylolpropane combined with isophthalic and adipic acids, which is generally used in combination with aromatic isocyanate-functionalized prepolymers. [000138] ZB301 is a solvent-free polyester polyol. [000139] The bond resistances measured at room temperature, expressed in N / 15mm, and measured at 100mm / min, between Aluminum and CPP were recorded subsequent to various heat treatments; the results are presented in the table below: Petition 870260046201, dated 05 / 15 / 2026, page 46 / 120 38 / 44 Table 3: Bond strength of selected adhesives before and after pasteurization and retort. Sample Initial Bond Strength Bond strength after pasteurization test (95 °C for 1 h) Bond strength after low retort test (121 °C for 30 min) Bond strength at room temperature after high retort test (135 °C for 20 min) 1 5.2 (Ad-Al) 2.7 (Ad-Al) 0.5 (Ad-Al) Delamination 2 10 (Alu-F) 1.6 (Ad-Al) 0.5 (Ad-Al) Delamination 3 9.5 (Alu-F) 4.4 (Alu-F) 5 ​​(Ad-Al) 4.1 (Ad-Al) 4 9.5 (Alu-F) 4.0 - 4.6 (Ad-Al and AluF) 3.6 - 4 (Ad-Al and AluF) 3.1 (Ad-Al) 5 10 (Alu-F) 3.6 - 4.2(Ad-Al and Alu-F) 4.5 (Ad-Al and Alu-F) 4.3 - 4.6 (Ad-Al and AluF) 6 11.5 (Alu-F) NA 7.8 (Ad-Al) 5 (Ad-Al) Alu-F = aluminum failure / Ad-Alu = adhesive failure. [000140] Comparative Examples (Samples 1 and 2), prepared using aromatic-based polyisocyanate prepolymers with standard or ultra-low levels of free monomer, failed the high retort test and nearly failed the low retort test. The laminates that survived the low retort process, maintaining their appearance and showing no delamination, ended up with almost no bond strength and are therefore unsuitable for use in retort applications. [000141] The four samples based on the Inventive Example (i.e., samples 3, 4, 5 and 6) cured with various polyol crosslinkers and survived low and high retort processes, maintaining their appearance and integrity, while exhibiting adequate bond strength. [000142] The present invention has been described in detail, including the various embodiments thereof. However, it will be perceived by those skilled in the art, upon consideration of the present disclosure, that they may make modifications and / or improvements to this invention which fall within the scope and spirit of the invention. Petition 870260046201, dated 05 / 15 / 2026, p. 47 / 120 39 / 44 Numbered Embodiments of the Invention [000143] The invention is defined by the following numbered embodiments, which form part of the description: 1. A solvent-free laminating adhesive kit comprising: a) an aliphatic polyurethane prepolymer functionalized with isocyanate comprising monomeric units derived from aliphatic isocyanate monomers; and b) a polyol crosslinker, wherein the amount of free isocyanate monomer present in the polyurethane prepolymer is less than or equal to 0.1% (w / w) of said prepolymer; 2. The kit of embodiment 1, wherein the aliphatic isocyanate monomers are diisocyanates selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, methylene dicyclohexyl diisocyanate, xylylene diisocyanate, tetramethyl xylene diisocyanate, pentamethylene diisocyanate and combinations thereof; optionally wherein the aliphatic isocyanate monomers are diisocyanates selected from the group consisting of isophorone diisocyanate, 1,6-hexane diisocyanate, xylylene diisocyanate and combinations thereof; 3. The kit, according to any previous embodiment, in which the isocyanate-functionalized aliphatic polyurethane prepolymer is difunctionalized with isocyanate groups, optionally in which the isocyanate-functionalized aliphatic polyurethane prepolymer is linear and functionalized with an isocyanate group at each end; 4. The kit, according to any of the previous options, in which i) The aliphatic polyurethane prepolymer functionalized with isocyanate has a viscosity at 80 °C between 800 mPa and 20,000 mPas, as Petition 870260046201, dated 05 / 15 / 2026, p. 48 / 120 40 / 44 between 1,000 mPas and 10,000 mPas, or between 2,000 mPas and 7,000 mPas; where viscosity is measured according to the method described in the description; and / or ii) the isocyanate-functionalized aliphatic polyurethane prepolymer has an isocyanate group content (%NCO) between 3% and 16%, such as between 5% and 10%; and / or iii) the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from more than 80 mol% of aliphatic isocyanates, relative to the total moles of isocyanates incorporated in the prepolymer, such as more than 90 mol%, or more than 95 mol% of aliphatic isocyanates, relative to the total moles of isocyanates incorporated in the prepolymer; and / or d) wherein the only isocyanates incorporated into the isocyanate-functionalized aliphatic polyurethane prepolymer are aliphatic isocyanates; 5. The kit, according to any previous embodiment, in which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from a polyester polyol and / or a polyether polyol; optionally in which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from a polyester polyol comprising monomeric units derived from aromatic monomers; 6. The kit for modality 5, in which i) the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from at least 50% by weight of polyester polyol relative to the total amount of polyols incorporated in said prepolymer; and / or ii) the polyester polyol comprises monomeric units derived from a mixture of aromatic and aliphatic dicarboxylic acids; and / or iii) the polyester polyol comprises between 10 and 55% by weight of monomeric units derived from aromatic monomers, as well as between 15 and 45% by weight, or between 15 and 35% by weight of monomeric units derived from aromatic monomers; Petition 870260046201, dated 05 / 15 / 2026, page 49 / 120 41 / 44 7. The kit for modes 5 or 6, in which i) the polyester polyol comprises between 45% and 90% by weight of monomeric units derived from aliphatic monomers, as well as between 55% and 85% by weight, or between 65% and 85% by weight of monomeric units derived from aliphatic monomers; and / or wherein the polyester polyol comprises monomeric units derived from a mixture of linear and branched glycols; optionally, wherein the linear and branched glycols have a molecular weight of less than 500 gmol-1, as well as less than 200 gmol-1; and / or ii) the polyester polyol and / or polyether polyol each have a number average molecular weight of less than 1000 g / mol; and / or iii) the polyester polyol and / or polyether polyol is linear; 8. The kit, according to any of the previous options, in which i) the polyol crosslinking agent does not comprise a silane compound capable of reacting with isocyanates, such as an aminosilane; and / or ii) the polyurethane prepolymer is incorporated into a composition further comprising an additional polyisocyanate; optionally wherein said additional polyisocyanate is selected from the group consisting of a hexamethylene diisocyanate trimer, a hexamethylene diisocyanate allophanate or combinations thereof; 9. A laminated adhesive comprising the components of the solvent-free laminating adhesive kit according to any previous embodiment mixed into a single composition; 10. A retort bag comprising laminated adhesive of embodiment 9; 11. A method for providing a multilayered structure comprising i) to form a laminated adhesive from the components of the kit of Petition 870260046201, dated 05 / 15 / 2026, page 50 / 120 42 / 44 any of the options 1 to 8 or provide the laminated adhesive of option 9; and ii) application of the laminated adhesive to a flexible film; 12. The method of modality 11, where: i) the flexible film is selected from the group consisting of polyethylene terephthalate, Nylon, aluminum, oriented polypropylene, cast polypropylene, low-density polyethylene, linear low-density polyethylene, vacuum-modified polyethylene terephthalate, aluminum oxide polyethylene terephthalate, silicon oxide polyethylene terephthalate, aluminum oxide-oriented polypropylene, silicon oxide-oriented polypropylene, aluminum oxide-oriented polyethylene, silicon oxide-oriented polyethylene, aluminum oxide-Nylon and silicon oxide-Nylon and any film coated therewith; and / or ii) the method further comprises applying the adhesive at press speeds exceeding 50 m / min or exceeding 100 m / min; 13. A method for making the kit for any previous modality that comprises the steps of a) reacting an aliphatic isocyanate with a polyester and / or polyether polyol to obtain an isocyanate-functionalized aliphatic polyurethane prepolymer comprising monomeric units derived from aliphatic isocyanate monomers; b) reduce the residual isocyanate monomer present in the prepolymer to less than 0.1% (w / w) of the prepolymer; c) introduce a polyol crosslinker into the kit; 14. The method of modality 13, where: i) Aliphatic isocyanate monomers are diisocyanates selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, methylene dicyclohexyl diisocyanate, xylylene diisocyanate, tetramethyl xylene diisocyanate, pentamethylene diisocyanate and their Petition 870260046201, dated 05 / 15 / 2026, page 51 / 120 43 / 44 combinations; and / or ii) the aliphatic isocyanate monomers are diisocyanates selected from the group consisting of isophorone diisocyanate, 1,6-hexane diisocyanate, xylylene diisocyanate and combinations thereof; and / or iii) the amount of isocyanate monomer is reduced by extracting the prepolymer using a series of one or more thin-layer evaporators and / or molecular evaporators; 15. The method, according to modalities 13 or 14, in which i) the isocyanate-functionalized aliphatic polyurethane prepolymer is the isocyanate-functionalized aliphatic polyurethane prepolymer according to any of embodiments 3 to 6; and / or ii) step a) comprises reacting the aliphatic isocyanate with a polyester polyol; optionally, wherein the polyester polyol is the polyester polyol according to embodiments 6 or 7; and / or iii) prior to step a), the method further comprises the step of reacting a mixture of aromatic and aliphatic dicarboxylic acids with at least one polyol to form the polyester polymer; optionally wherein the at least one polyol is a mixture of linear and branched glycols, optionally wherein the linear and branched glycols have a molecular weight of less than 500 gmol-1, such as less than 200 gmol-1; 16. The method of any of the modalities from 13 to 15, which is solvent-free; 17. Use of the kit, according to any previous embodiment, to form a laminated adhesive; optionally, wherein the laminated adhesive is part of a retort packaging, such as a pouch; 18. Use of the kit, according to any previous embodiment, to improve the bond strength under retort conditions of a multilayer structure formed from a flexible film and a laminated adhesive. Petition 870260046201, dated 05 / 15 / 2026, p. 52 / 120 44 / 44 formed from the components of said kit; optionally, where the retort conditions comprise heating at 100 °C or more for a period of 20 minutes, such as heating at 120 °C for 30 minutes or 135 °C for 20 minutes.

Claims

1. SOLVENT-FREE LAMINATION ADHESIVE KIT, characterized by comprising: (a) a composition comprising: (i) an aliphatic polyurethane prepolymer functionalized with isocyanate comprising monomeric units derived from aliphatic isocyanate monomers, wherein an aliphatic polyurethane prepolymer is formed from aliphatic isocyanate monomers, wherein the identity of the isocyanate alone dictates whether the polyurethane is aliphatic or aromatic, and wherein an aliphatic isocyanate monomer is one in which the isocyanate group(s) is / are directly linked to an aromatic ring; wherein the aliphatic isocyanate monomers are diisocyanates selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, methylene dicyclohexyl diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, pentamethylene diisocyanate and combinations thereof;wherein the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from a polyester polyol and / or a polyether polyol; wherein the molar ratio of the NCO groups of the aliphatic isocyanate monomers to the HO groups of the polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived is from 5:1 to 2:1; and (ii) an additional aliphatic polyisocyanate selected from the group consisting of aliphatic polyisocyanate trimers, aliphatic polyisocyanate allophanates, aliphatic polyisocyanate biuretes, aliphatic polyisocyanate oligomers, aliphatic polyisocyanate urethdiones and combinations thereof; and (b) a polyol crosslinker, wherein the polyol crosslinker is a linear or branched polyether polyol and / or a linear or branched polyester polyol;wherein the amount of free isocyanate monomer present in the polyurethane prepolymer is less than or equal to 0.1% (w / w) of said prepolymer; wherein the amount of free isocyanate monomer is determined according to the method described in the description; and wherein the polyol crosslinking agent does not comprise a silane additive capable of reacting with isocyanates.

2. A KIT, according to claim 1, characterized in that the aliphatic isocyanate monomers are diisocyanates selected from the group consisting of isophorone diisocyanate, 1,6-hexane diisocyanate, xylylene diisocyanate and combinations thereof, such as in which the aliphatic isocyanate monomers are xylylene diisocyanate.

3. KIT, according to any one of claims 1 to 2, characterized by: (i) the isocyanate-functionalized aliphatic polyurethane prepolymer being difunctionalized with isocyanate groups, optionally wherein the isocyanate-functionalized aliphatic polyurethane prepolymer is linear and functionalized with an isocyanate group at each terminus; and / or (ii) the isocyanate-functionalized aliphatic polyurethane prepolymer having a viscosity at 80°C of 800 mPa to 20,000 mPa, such as 1,000 mPa to 10,000 mPa, or 2,000 mPa to 7.000 mPas; wherein viscosity is measured according to the method described in the description; and / or (iii) the isocyanate-functionalized aliphatic polyurethane prepolymer has an isocyanate group content (%NCO) of 3% to 16%, such as 5% to 10%; and / or (iv) the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from equal to or greater than 95 mol% of aliphatic isocyanate monomers, relative to the total isocyanate monomers incorporated in the prepolymer; and / or (v) the only isocyanate monomers incorporated in the isocyanate-functionalized aliphatic polyurethane prepolymer are aliphatic isocyanate monomers; and / or Petition 870260046201, dated 05 / 15 / 2026, p.55 / 120 3 / 9 (vi) the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from a polyester polyol comprising monomeric units derived from aromatic monomers; and / or (vii) the isocyanate-functionalized aliphatic polyurethane prepolymer is derived from at least 50% by weight of polyester polyol relative to the total amount of polyols incorporated in the prepolymer.

4. A KIT, according to any one of claims 1 to 3, characterized in that: (i) the polyester polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived comprises monomeric units derived from aromatic dicarboxylic acids and monomeric units derived from aliphatic dicarboxylic acids; and / or (ii) the polyester polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived is itself derived from 10 to 55% by weight of aromatic dicarboxylic acids, such as 15 to 45% by weight, or 15 to 35% by weight of aromatic dicarboxylic acids; and / or (iii) the polyester polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived is itself derived from 10% by weight to 55% by weight of aliphatic dicarboxylic acids, such as 15% to 45% by weight, or 15% to 35% by weight of aliphatic dicarboxylic acids;and / or (iv) the polyester polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived comprises monomeric units derived from a mixture of linear and branched glycols; optionally, wherein the linear and branched glycols have a molecular weight of less than 500 gmol-1, such as less than 200 gmol-1; and / or (v) the polyester polyol and / or polyether polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived has a number average molecular weight equal to or less than 1000 g / mol; and / or Petition 870260046201, dated 15 / 05 / 2026, page 56 / 120 4 / 9 (vi) the polyester polyol and / or polyether polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived is linear.

5. A KIT, according to any one of claims 1 to 4, characterized in that: (i) the molar ratio of the NCO groups of the aliphatic isocyanate monomers to the HO groups of the polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived is from 4:1 to 2:1, or from 3:1 to 2:1; and / or (ii) the polyol crosslinking agent being a linear or branched polyester polyol, or the polyol crosslinking agent being a mixture of at least one linear or branched polyester polyol and at least one linear or branched polyether polyol.

6. A KIT, according to any one of claims 1 to 5, characterized in that the polyol crosslinker is a polyester polyol formed from one or more glycols and one or more dicarboxylic acids; optionally wherein: (i) one or more glycols are selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, tetramethylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, the methyl ether derivatives of any of the above glycols and combinations thereof; and / or (ii) the dicarboxylic acid is selected from the group consisting of aliphatic dicarboxylic acids: malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, aspartic acid, malic acid and aromatic dicarboxylic acids: terephthalic acid, isophthalic acid and combinations thereof;and / or (iii) the polyester polyol of the polyol crosslinking agent is derived from non-glycol polyols, such as trimethylolpropane.; 7. KIT, according to any one of claims 1 to 6, characterized in that: (i) the polyol crosslinker of the polyol crosslinker being a polyester polyol comprising tertiary amine groups in the main structure; and / or (ii) the additional aliphatic polyisocyanate having a viscosity at 23°C of 3,000 mPas or less, such as 2,000 mPas or less, 1,000 or less, or 500 or less; and / or (iii) the additional aliphatic polyisocyanate being selected from the group consisting of hexamethylene diisocyanate trimer, hexamethylene diisocyanate allophanate, hexamethylene diisocyanate biuret and combinations thereof; and / or (iv) the ratio in % by weight of the polyurethane prepolymer to the additional polyisocyanate in the composition comprising the additional aliphatic polyisocyanate is 8:1 to 1:1, such as 5:1 to 2:1, or 3:1 to 2:

1.

8. LAMINATED ADHESIVE, characterized by comprising the components of the solvent-free laminating adhesive kit, as defined in any one of claims 1 to 7, mixed into a single composition.

9. Retort bag, characterized by comprising the laminated adhesive, as defined in claim 8.

10. METHOD FOR PROVIDING A MULTILAYER STRUCTURE, characterized by comprising: (a) forming a laminated adhesive from the kit components, as defined in any one of claims 1 to 7, or providing the laminated adhesive, as defined in claim 8; and (b) applying the laminated adhesive to a flexible film.

11. METHOD, according to claim 10, characterized by: Petition 870260046201, dated 05 / 15 / 2026, page 58 / 120 6 / 9 (i) the flexible film being selected from the group consisting of polyethylene terephthalate, Nylon, aluminum, oriented polypropylene, cast polypropylene, low-density polyethylene, linear low-density polyethylene, vacuum-modified polyethylene terephthalate, aluminum oxide-polyethylene terephthalate, silicon oxide-polyethylene terephthalate, aluminum oxide-oriented polypropylene, silicon oxide-Nylon oriented polyethylene, aluminum oxide-Nylon and silicon oxide-Nylon and any film coated therewith; and / or (ii) the method comprising applying the adhesive at press speeds greater than 50 m / min or greater than 100 m / min.

12. LAMINATED ADHESIVE STRUCTURE, characterized by being the result of the method as defined in any one of claims 10 to 11.

13. STRUCTURE, according to claim 12, characterized by being suitable for the preparation of retort pouches in which no delamination failures occur under retort conditions of 100°C or more.

14. METHOD FOR MAKING THE KIT, as defined in any one of claims 1 to 14, characterized by comprising the steps of: (a) reacting aliphatic isocyanate monomers with a polyester polyol and / or polyether polyol to obtain an isocyanate-functionalized aliphatic polyurethane prepolymer comprising monomeric units derived from said aliphatic isocyanate monomers; wherein an aliphatic polyurethane prepolymer is formed from aliphatic isocyanates, wherein the identity of the isocyanate alone dictates whether the polyurethane is aliphatic or aromatic, wherein an aliphatic isocyanate is one in which the isocyanate group(s) is / are directly attached to an aromatic ring;wherein the aliphatic isocyanate monomers are diisocyanates selected from the group consisting of hexamethylene diisocyanate, Petition 870260046201, dated 05 / 15 / 2026, page 59 / 120 7 / 9 isophorone diisocyanate, methylene dicyclohexyl diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, pentamethylene diisocyanate and combinations thereof; wherein the molar ratio of the NCO groups of the aliphatic isocyanate monomers to the HO groups of the polyol from which the isocyanate-functionalized aliphatic polyurethane prepolymer is derived is from 5:1 to 2:1; (b) reduce the residual isocyanate monomer present in the aliphatic polyurethane prepolymer to less than 0.1% (w / w) of the prepolymer;(c) introduce an additional aliphatic polyisocyanate selected from the group consisting of aliphatic polyisocyanate trimers, aliphatic polyisocyanate allophanates, aliphatic polyisocyanate biuretes, aliphatic polyisocyanate oligomers, aliphatic polyisocyanate urethdiones and combinations thereof; and (d) introduce a polyol crosslinker into the kit, wherein the polyol crosslinker is a linear or branched polyether polyol and / or a linear or branched polyester polyol; wherein the polyol crosslinker does not comprise a silane additive capable of reacting with isocyanates.

15. METHOD, according to claim 14, characterized by: (i) the aliphatic isocyanate monomers being diisocyanates selected from the group consisting of isophorone diisocyanate, 1,6-hexane diisocyanate, xylylene diisocyanate and combinations thereof; and / or (ii) the amount of isocyanate monomer being reduced by extracting the prepolymer using a series of one or more clean film evaporators and / or short path evaporators; and / or (iii) the isocyanate-functionalized aliphatic polyurethane prepolymer being the isocyanate-functionalized aliphatic polyurethane prepolymer as defined in claim 3; and / or (iv) step (a) comprising reacting the aliphatic isocyanate with a Petition 870260046201, dated 05 / 15 / 2026, p. 60 / 120 8 / 9 polyester polyol, optionally wherein the polyester polyol is the polyester polyol as defined in claim 4.

16. METHOD, according to any one of claims 14 to 15, characterized in that: (i) prior to step (a), the method further comprises the step of reacting a mixture of aromatic and aliphatic dicarboxylic acids with at least one polyol to form the polyester polyol; optionally wherein the at least one polyol is selected from the group consisting of neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, monoethylene glycol and combinations thereof; and / or (ii) the kit being solvent-free.

17. USE OF THE KIT, as defined in any one of claims 1 to 7, characterized in that it is for forming a laminated adhesive; optionally wherein the laminated adhesive is part of a retort packaging, such as a pouch.

18. USE OF THE KIT, as defined in any one of claims 1 to 7 or 17, characterized in that it improves the bond strength under retort conditions of a multilayer structure formed from a flexible film and a laminated adhesive formed from said kit in relation to a multilayer structure formed from said flexible film and a laminated adhesive not formed from the kit of the invention, wherein the bond strength is the strength required to separate at least two layers of the multilayer structure that are joined with said adhesive and is measured at room temperature (25°C) and at 100 mm / min; optionally wherein the retort conditions comprise heating at 100°C or more for a period of 20 minutes, such as heating at 120°C for 30 minutes at 150 kPa (1.5 bar) or heating at 135°C for 20 minutes at 260 kPa (2.6 bar); and / or Petition 870260046201, dated 05 / 15 / 2026, page.61 / 120 9 / 9 optionally where the retort conditions comprise placing the multi-layered structure in an autoclave with an internal pressure of 150 kPa (1.5 bar) to 300 kPa (3 bar), as well as 150 kPa (1.5 bar) or 260 kPa (2.6 bar).