TWO-COMPONENT WATER-BASED LAMINATING ADHESIVE AND ITS USE FOR BONDING SUBSTRATES AND FOAMS

Abstract

A two-component, water-based polyurethane dispersion adhesive comprises an anionic polyester-polyurethane resin and a solvent-free, liquid aliphatic polyisocyanate crosslinking agent. The dispersion can be reactivated one or more times for bonding the edges of a flexible sheet material to a substrate having a main surface, a peripheral surface, and a border connecting the main and peripheral surfaces.

Description

TWO-COMPONENT WATER-BASED LAMINATION ADHESIVE AND ITS USE FOR BONDING SUBSTRATES AND FOAMS FIELD OF INVENTION This disclosure relates to a two-component, water-based polyurethane dispersion adhesive and the use of this adhesive for bonding flexible sheet materials such as polyurethane foams to substrates, especially polymeric substrates such as those found in automotive interiors. More specifically, this disclosure relates to a two-component, water-based polyurethane adhesive that can be reactivated. BRIEF DESCRIPTION OF RELATED TECHNOLOGY Automotive upholstery applications, such as those used in car interiors, often involve bonding flexible sheet materials such as foams, leather substrates, and similar polymeric substrates like polypropylene (PP) or acrylonitrile butadiene styrene (ABS). Water-based adhesives for such applications can offer low or zero levels of volatile organic compounds (VOCs). Furthermore, water-based adhesives can offer ease of processing and good heat dissipation, making them suitable for use in production plants. Many automotive upholstery applications involve placing flexible sheet materials such as foams onto substrate surfaces, around substrate edges, and over a peripheral substrate surface. In many cases, the peripheral surfaces are angled relative to the main surface. An aqueous adhesive is typically applied to these substrate surfaces and edges, followed by the placement of a flexible sheet material over them, for example, by wrapping or partially wrapping a single piece of flexible sheet material over the surfaces, edges, and peripheral surfaces. Unless adequate contact between the foam and the substrate surfaces and edges is maintained during the drying and curing of the aqueous adhesive, the foam will separate from one of the substrate surfaces and / or the edge, resulting in failure.Maintaining sufficient contact during the long drying and curing times required by waterborne adhesives is often difficult, especially for substrates that have complex and changing edge geometries. freo L Ln / Lznz / E / YILI BRIEF DESCRIPTION OF THE INVENTION The disclosed two-component, water-based polyurethane adhesive dispersions not only offer excellent structural bonding properties but also provide the ability to reactivate the adhesive one or more times by heating above a reactivation temperature. Reactivation of the adhesive allows for wrapping the edges, according to a customer's specification, of a layer of flexible sheet material, such as a foam, including a polymeric foam such as polyurethane foam, onto a substrate, around the edges of the substrate, and over a peripheral surface of the substrate without the disadvantages of currently used adhesives. In one aspect of the present invention, a method for bonding a flexible sheet material to a substrate includes: provide a substrate having a main surface, a peripheral surface arranged angularly to the main surface, and an edge connecting the main surface and the peripheral surface; provide a single piece of flexible sheet material having first and second portions; provide a two-component, water-based polyurethane dispersion; freo L Ln / įZРZ / B / YILI apply the water-based polyurethane dispersion to part or all of the main surface and, optionally, to part or all of the peripheral surface of the substrate; remove water from the applied water-based polyurethane dispersion to form a dry polyurethane adhesive layer on the surfaces; apply a first heating cycle to activate the polyurethane adhesive layer on the main surface; Place the first portion of the flexible sheet material on the activated adhesive on the main surface to glue the first portion of material to the main surface; Optionally, cool the polyurethane adhesive and substrate surfaces below the adhesive activation temperature; apply a second heating cycle to heat the polyurethane adhesive layer on an edge and / or on the peripheral surface above the reactivation temperature and reactivate the adhesive on the edge and / or on the peripheral surface; Place a second portion of the material layer over the heated and reactivated adhesive at the edge and / or peripheral surface to bond the second portion of material to the edge and peripheral surface; and optionally, cool the polyurethane adhesive and substrate surfaces below the adhesive activation temperature. In one embodiment, the substrate can be a plastic or a substrate containing plastic, such as polypropylene (PP) or a substrate containing acrylonitrilebutadiene-styrene (ABS). freo L LO / ίΖΠΖ / Ε / ΥΙΛΙ In one embodiment, the flexible sheet material may comprise a flexible sheet foam material, such as a polyurethane foam material, a flexible leather sheet, a polymeric film or sheet, a fabric, and combinations thereof. In one mode, the first heating cycle can be carried out after the first portion of material is placed on the main surface. In one embodiment, the first heating cycle may comprise heating the polyurethane adhesive layer and the main surface in an oven at approximately 60°C to approximately 80°C for approximately 2 to approximately 4 minutes. In one embodiment, the second heating cycle may include exposing the edge and peripheral surface of the substrate and the polyurethane adhesive layer on the edge and peripheral surface to a temperature of approximately 200°C to approximately 300°C for approximately 30 seconds or less than 30 seconds before placing a second portion of the material layer over the heated and reactivated adhesive on the edge and peripheral surface. In one embodiment, the second heating cycle may include exposing the edge and peripheral surface of the substrate; the polyurethane adhesive layer on the edge and peripheral surface of the substrate and the second portion of the material on the edge and peripheral surface of the substrate to a temperature of approximately 200 °C to approximately 300 °C from approximately 2 seconds to approximately 4 seconds. In one embodiment, the second heating cycle may include heating the second portion of the material and the peripheral surface of the substrate in an oven at approximately 60°C to approximately 80°C for a time of approximately 15 seconds to approximately 30 seconds. In one embodiment, the second heating cycle may include heating the polyurethane adhesive layer to a temperature of approximately 55°C to approximately 85°C, or preferably from approximately 55°C to approximately 65°C. In one embodiment, a component of the two-component water-based polyurethane dispersion adhesive may comprise: a solvent-free liquid aliphatic polyisocyanate crosslinking agent; an anionic polyester-polyurethane resin; water; and optionally one or more additives. After the second heating cycle, the cured polyurethane adhesive can have a peel strength of approximately 4 kgf (kilogram-force) to approximately 5 kgf. freo L Ln / Lznz / E / YILI In one embodiment, one component of the two-component, water-based polyurethane dispersion adhesive may comprise a water-free, solvent-free, liquid aliphatic polyisocyanate crosslinking agent and, optionally, one or more additives. The water-free, solvent-free, liquid aliphatic polyisocyanate crosslinking agent may comprise hexamethylene diisocyanate or a 1,6-hexamethylene diisocyanate trimer (HDI-biuret). Brief Description of the Drawings Referring now to the drawings, where similar elements are numbered similarly in the different Figures: FIG. 1 is a schematic diagram illustrating the steps of the structural bonding process and the steps of the reactivation bonding process for one embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION The word "around" or "approximately", as used herein in relation to a numerical value, refers to the numerical value ±10%, preferably ±5% and more preferably ±1% or less. This document describes the formulation and performance of new classes of two-component, water-based polyurethane dispersion adhesives for bonding a polymeric primer, such as polypropylene, to a flexible sheet material, such as polyurethane foam. The disclosed adhesive not only offers improved structural bonding properties but also the ability to reactivate one or more times after subsequent heating. Reactivation of an adhesive is an important property required for applications such as edge wrapping. In general, bonding to plastic substrates is difficult due to the low surface energy (less than approximately 30 dynes / cm) of plastic substrates. Water-based adhesives are even more difficult to bond because the surface tension (ST) of water (approximately 72 dynes / cm) is greater than the surface energy of plastic substrates. According to Young's equation, an adhesive can wet a substrate surface as long as the contact angle (Θ) is less than 90°. Lowering the surface tension of a water-based adhesive to less than that of the plastic surface will typically lead to a lower contact angle, resulting in better wettability. The surface tension of two-component, water-based polyurethane dispersion adhesives can be reduced by using a surfactant. The surface energy of untreated polypropylene is low.The surface energy of such low-energy plastic substrates can be increased by various surface treatment methods such as flame treatment, corona treatment, plasma treatment, chemical etching, etc. In this way, a water-based polyurethane dispersion can be useful for bonding plastic substrates such as polypropylene, acrylonitrile-butadiene-styrene, and similar materials. freo L Ln / Lznz / E / YILI The two-component, water-based polyurethane dispersion adhesives described herein can bond, for example, flexible sheet polyurethane (PU) foam material to a polypropylene (PP) substrate, including a treated PP substrate. These two-component, water-based polyurethane dispersion adhesives desirably possess a reactivation property, allowing for additional bonding after a second heating cycle, such as in edge-wrapping applications that are critical in vehicle door trim. For example, door trim applications often involve two heating cycles: one to bond flexible foam material to the flat surface of a part (substrate), and a second to bond the flexible foam material around the edges and to the peripheral surface of that substrate. The polyurethane adhesive dispersions described herein are particularly useful for bonding polyurethane foam to a polypropylene substrate, such as in door trim applications. This utility is enhanced by the adhesive's ability to reactivate after a second or subsequent heating. Reactivation is the ability of an adhesive to transition from a cooled, non-sticky state to a heated, sticky state. Once the adhesive cross-links, it can no longer be reactivated. Typical current water-based products for bonding polyurethane foam to treated polypropylene have the following drawbacks: 1. Lack of reactivation function (one or multiple times), making it unsuitable for edge wrapping applications. 2. The use of organic solvents such as N-methyl-2-pyrrolidone (NMP) and ethanol in the formulation, which contributes to volatile organic compounds and thus poses unwanted environmental problems. The disclosed compositions are water-based, preferably substantially solvent-free, and can be reactivated multiple times by reheating. In one embodiment, the adhesive is a two-component (2K) water-based polyurethane adhesive that is substantially free of organic solvents such as N-methyl-2-pyrrolidone (NMP), ethanol, and other volatile organic compounds. As used herein, "substantially free" means that the individual components and the mixed adhesive dispersion contain less than 1% by weight of an organic solvent, preferably less than 0.1% by weight of an organic solvent, and more preferably no (0% by weight) organic solvent, based on the weight of the individual component or the mixed dispersion, respectively. The disclosed composition comprises Part A and Part B. Part A is a water-based polyurethane dispersion formulation. Part B is a crosslinking agent formulation. In one embodiment, the Part-A component comprises one or more polyurethane and water dispersions. The Part-A component may optionally comprise additives selected from surfactant, copolymer, colorant, dye, biocide, defoamer, and rheology modifier. Table 1 illustrates some properties of one embodiment of the Part-A composition. freo L LO / ίΖΠΖ / Ε / ΥΙΛΙ Table 1 Composition Properties: Part-A Property Specifications Solids content 43 to 47% Viscosity (@ 25 °C and 10 rpm) 5000 to 9000 mPa.s pH 7.5 to 9.5 In one embodiment, the Part-B component comprises a crosslinking agent that is reactive with the Part-A component. Part-B may comprise one or more aliphatic polyisocyanates. In one embodiment, the Part-B component may comprise a solvent-free liquid aliphatic polyisocyanate crosslinking agent. In another embodiment, the Part-B component may comprise hexamethylene diisocyanate or a 1,6-hexamethylene diisocyanate trimer (HDI-biuret). Table 2 illustrates some properties of the Part-B component. Table 2 Inventive Composition of Part-B Formulation Raw Material NCO Content HDI Monomer Content Aliphatic Polyisocyanate1 21.8 ± 0.6 < 0.25 Part A is mixed with Part B to form a water-based polyurethane dispersion. The mixing of Part A and Part B initiates a crosslinking or curing reaction. This reaction is the primary curing reaction. The polyurethane dispersion adhesives disclosed are not moisture-curable adhesives and are not moisture-curable hot-melt adhesives. The relative amounts of the components of Part A and Part B may be varied as needed to achieve the desired properties, but may be in the range of 80 to 99% by weight of the Part A component and 1 to 20% by weight of the Part B component. Preferably, the relative amounts of the components of Part A and Part B are in the range of 93 to 97% by weight of Part A and 3 to 7% by weight of Part B. Table 3 illustrates some properties of a water-based polyurethane dispersion adhesive shortly after mixing Part A and Part B. freo L Ln / Lznz / E / YILI Table 3 Properties of Mixed Product of Compositions: Part-A and Part-B Property Specifications Solids content 44 to 48% by weight Water content 52 to 56% by weight Mixed Viscosity (@ 25 °C and 10 rpm) 5500 to 9500 mPa.s pH 7.5 to 9.5 Heat activation temperature range: 55 to 85 °C; Bonding temperature: 60 °C; Shelf life: 2 to 4 hours The mixed dispersion can be applied to part or all of a main surface, edges, and peripheral surfaces of the substrate to be bonded. The water is drawn off from the dispersion onto the substrate to form a polyurethane adhesive layer on the substrate surfaces and edges. This polyurethane adhesive layer can be cooled to a non-sticky state and stored if desired. A first heating cycle is performed to heat the polyurethane adhesive layer on the main substrate surface and, optionally, on the peripheral surface and edges of the substrate. In some variations, the first heating cycle also dries the water from the applied adhesive. Typically, the polyurethane adhesive layer is heated to between 55°C and 85°C. Heating the polyurethane adhesive layer causes activation, making the adhesive tacky. A portion of flexible sheet material is then placed over the activated polyurethane adhesive layer and the main substrate surface. In one variation, the material (PU foam) is placed over the tacky polyurethane adhesive layer and the main substrate surface.In this variation, the adhesive, along with the main substrate and the adhesive layer, is heated to activate the adhesive, and the composite material is applied onto the tacky polyurethane adhesive. Cooling of the polyurethane adhesive layer bonds the material to the substrate surface. After the first heating cycle, the peripheral surface and edges of the substrate are typically free of the material and not bonded to it. In one variation, the adhesive, along with the main substrate, is heated to activate the PU adhesive. The composite material (PU foam) is also heated and applied over the tacky polyurethane adhesive. Cooling the polyurethane adhesive layer bonds the material to the substrate surface. After the main surface bonds to the material, the peripheral surfaces and substrate edges are exposed to secondary heating (a second heating cycle) to reactivate the polyurethane adhesive layer. The material can then be wrapped around the edges and over the peripheral surfaces using simple manual pressure. After the adhesive cools, the material bonds from the main surface, over the edges, and onto the substrate's peripheral surface. The foam then wraps around the edges during secondary heating, and the adhesive reactivates to create a strong bond around the substrate's periphery. The second heating cycle can be performed 10 to 30 minutes after the first heating cycle. The polyurethane adhesive layer can be reactivated a third or more times if necessary. The variants of this adhesive exhibit some or all of the following advantages over known adhesives, which are, but are not limited to: The disclosed compositions are water-based adhesives and environmentally friendly. The disclosed compositions have a low level of VOCs because they do not contain organic solvents. The disclosed compositions are mixed and applied at room temperature (approximately 20°C), offering energy savings to a user. The disclosed Part-A and Part-B can be mixed by simple stirring at room temperature, thus offering ease of preparation. The disclosed compositions can be used for edge wrapping applications by reactivating the adhesive once or multiple times. Reactivation allows the disclosed adhesives to combine the benefits of low VOCs, low energy use, and environmental friendliness of a water-based adhesive, while at the same time providing the rapid initial tack of a solvent-based adhesive and short contact times to bond. Reactivation allows an adhesive to be applied to a substrate and that component to be stored. The stored component is subsequently reactivated, and the flexible sheet material is laid over the reactivated freo L Ln / Lznz / E / YILI adhesive. Part-A Preparation Initially, the following premixes were made. A. Alkali Premix: 5% alkaline NaOH was prepared by adding 50 gm of NaOH to a one liter volumetric flask and diluted with water. B. Antifoam Premix: 0.05% antifoam was added to the anionic high molecular weight polyester-polyurethane dispersion and stirred for 10 minutes. C. Premix-Color: 0.07% water-based blue color was added to the water and stirred for 10 minutes. A two-liter cylindrical flask equipped with a top stirrer was charged with the anionic high molecular weight polyester-polyurethane dispersion in water and the anionic high molecular weight polyester-polyurethane dispersion in water and stirred for 10 minutes. Two percent water was added to this mixture, and it was stirred for another 10 minutes. The non-foaming, non-ionic surfactant was added to this mixture at a slower rate to avoid foaming and stirred for 10 minutes. The vinyl acetate-ethylene copolymer was added slowly (for at least 10 minutes). In this step, the pH was ideally maintained above approximately 8.0. The pH was adjusted by adding the Alkali Premix (A.). The biocide was added to the mixture and stirred for 10 minutes. The Color Premix (C) was added to the mixture and mixed for 10 minutes. The Antifoam Premix (B) was added to the mixture and mixed.The rheology modifier was added until the desired Brookfield viscosity was achieved, within the range of 5000 to 9000 cP. The final pH was adjusted to be between approximately 8 and approximately 9. Part-B Preparation Part B contained only aliphatic polyisocyanate and was used as received. Because Part B is sensitive to moisture, it was stored properly sealed and under a nitrogen blanket to exclude moisture. A thin sheet of flexible polyurethane foam was used as the flexible sheet material. This material is often used to cover interior automotive panels. A polypropylene structure was used as the main substrate, edge, and peripheral substrate. The surface energy of the bonding surfaces of the polypropylene substrate was increased by either flame or corona treatment. freo L Ln / Lznz / E / YILI Application method for dispensing a mixed polyurethane adhesive dispersion on a substrate Mix Part B is mixed with Part A to create an adhesive product prior to application. Typically, 5 parts by weight of the curing agent (e.g., Part B) are added to 100 parts by weight of the resin dispersion (e.g., Part A). A homogeneous mixture is achieved by directly adding the curing agent from Part B to the resin from Part A at room temperature with simple stirring. Adhesive bonding process and temperature The mixed product can be sprayed onto a substrate surface that will be glued or onto the surfaces of both substrates that will be glued. After the mixed product is applied to the bonding surface, it dries through water evaporation. Drying can be done at room temperature or accelerated by placing it in an infrared oven or a conventional oven at approximately 40°C until all the water is removed. The dried polyurethane adhesive layer must be free of water. The substrate and the coated product can be heated in an oven at a temperature of approximately 60 °C to approximately 80 °C for approximately 2 minutes to approximately 4 minutes (first heating cycle). The heated bonding surfaces of the substrates were pressed together and bonded. Bonding pressures of 0.6 to 1.0 N / mm² are suitable. Reactivation process (second heating cycle) Adhesive reactivation can be performed using any suitable heating method, for example, but not limited to, either by heating with a hot air gun or heating in an oven. In the first case, the part is exposed to a temperature of approximately 200°C to approximately 300°C for a very short time, such as approximately 2 to approximately 4 seconds, and in the second case, it is heated to a temperature of approximately 60°C to approximately 80°C for approximately 15 to approximately 30 seconds. The polyurethane foam was wrapped around the edges of the adhesive-coated PP or ABS (main) substrate. The bonding line temperature was observed to be approximately 55°C to approximately 65°C for the reactivation process. Adhesive failure resistance The adhesive's resistance to failure was measured after 24 hours. The foam substrate was cut by making a cross and then peeled off using an Imada push-pull caliper. The adhesion of the remaining foam to the substrate was recorded as substrate failure. This is a good result, as the foam failed (e.g., it tore or separated) but the adhesive did not. An undesirable result is adhesion failure, where the foam did not fail (e.g., it did not tear or separate), but the adhesive failed to bond the components under the test conditions. Adhesion was also checked on cured / bent surfaces. Table 5 shows the adhesion comparisons for formulations F1 and F4. Formulations F2 and F3 had a mixed failure mode. The only formulations that had 100% substrate failure were formulations F1 and F4. However, reactivation could not be achieved for formulation F4.The bonding line temperature for structural bonding as well as for reactivation was approximately 55°C to approximately 65°C. freo L Ln / Lznz / E / YILI Different resin dispersions (Part-A) were prepared as shown below in Table 4. Compositions are expressed in % by weight. Table 4 Formulation for Composition of Part-A Component Description Formulation No. F1 F2 F3 F4 Anionic high molecular weight polyester-polyurethane dispersion1 40 20 60 80 Anionic high molecular weight polyester-polyurethane dispersion2 40 60 20 0 Water 6 6 6 6 Non-foaming non-ionic surfactant 3 (A) (A) (A) (A) Vinyl acetate-ethylene copolymer4 Water-based dye (blue) Biocide Antifoam Rheology modifier5 Dispercoll U56 available from Covestro (Surfynol 440)(from Evonik, formerly Air Products) Vinnapas EP 605 A available from Wacker Chemie AG (Acrysol ASE 60) (from DOW) The properties of the Part-B component of the sample material are shown below in Table 5. Table 5 Inventive Composition of Formulation of Part-B freo L Ln / Lznz / Ε / ΥΙΛΙ Raw Material NCO Content HDI Monomer Content Aliphatic Polyisocyanate1 21.8 ± 0.6 < 0.25 Desmodur DN available from Covestro The peel resistance, failure mode, and reactivation possibility of each formulation are shown below in Table 6. Table 6 Formulation No. F1 F2 F3 F4 95% by weight of Part A F1 F2 F3 F4 5% by weight of Part BBBBB Cured Adhesive Property Peel Strength (kgf) 4 to 5 1.5 to 2.8 not determined 4 to 5 Failure Mode Substrate Failure Adhesion Failure Mixed Failure Mode Substrate Failure Reactivation possible possible not possible not possible The peel strength and failure mode of a mixed product of Part-A F1 with 5% and 4% of Part-B are shown below in Table 7. freo L Ln / Lznz / E / YILI Table 7 Formulation / Specification Fl Fl Part A (Fl) 95% by weight 96% by weight Percentage of Part-B 5% by weight 4% by weight Peel strength (kgf) 4 to 5 0.8 to 1.7 Failure mode Substrate failure Adhesion failure With reference to the modality in Figure 1, the following elements are shown: substrate main surface of substrate mixed adhesive flexible sheet material (PU foam) peripheral surfaces of substrate With reference to the embodiment in Figure 1, the following steps are shown. Part A and Part B of the adhesive are mixed to form a two-component, water-based polyurethane dispersion adhesive 6. A substrate 2 is provided having a main surface, a peripheral surface 10 arranged at an angle to the main surface, and a rim connecting the main surface 4 and the peripheral surfaces 10. Optionally, one or more of the surfaces 4 and 10 may be pretreated. The two-component, water-based polyurethane dispersion adhesive 6 is applied to the substrate surfaces 4 and 10 and the rim. The adhesive 6 is dried to remove water and form a dry, activated polyurethane adhesive layer on the substrate surfaces 4 and 10 and the rim.A first portion of a single piece of flexible sheet material 8 is placed over the activated adhesive 6 on the main surface 4 to bond the first portion of material 8 to the main surface 4. Optionally, the adhesive 6 and the substrate surfaces 4, 10 can be cooled below the adhesive activation temperature. Heat is applied to the substrate edges and peripheral surfaces 10 to reactivate the adhesive 6 at the edges and on the peripheral surfaces 10. A second portion of the flexible sheet material 8 is wrapped from the substrate surface 4 over the heated and reactivated adhesive at the substrate edges and on the peripheral surfaces 10 to bond the second portion of material 8 to the substrate edges and the peripheral surfaces 10. The substrate, adhesive, and bonded flexible sheet material are cooled below the adhesive activation temperature. Although several embodiments of the present inventive technology are illustrated and / or specifically described herein, it will be appreciated that modifications and variations of the present inventive technology may be made by those skilled in the art without departing from the spirit and intended scope of the inventive technology. Furthermore, any embodiment or aspect of the invention as described in the claims or specification may be used with or without limitation. Furthermore, the modalities or aspects of the invention or inventive technology described herein may be combined in any manner and in any combination and be within the scope of the present invention.

Claims

1. A method for bonding a flexible sheet material to a substrate, comprising: providing a substrate having a main surface, a peripheral surface disposed at an angle to the main surface, and an edge connecting the main surface and the peripheral surface; providing a flexible sheet material having a second portion extending from a first portion; providing a first component of a two-component, water-based polyurethane dispersion adhesive; providing a second component of the two-component, water-based polyurethane dispersion adhesive; mixing the first component and the second component to form a mixed two-component, water-based polyurethane dispersion adhesive; applying the mixed adhesive to a portion of the main surface and, optionally, to a portion of the peripheral surface and / or the edge;Dry the applied adhesive to form a dry polyurethane adhesive layer on the main surface and, optionally, on the peripheral surface and / or edge; apply a first heating cycle to activate the polyurethane adhesive layer on the main surface; position the first portion of the flexible sheet material onto the activated adhesive on the main surface to bond the first portion of material to the main surface; optionally, cool the polyurethane adhesive and the substrate surfaces below the adhesive activation temperature; apply a second heating cycle to heat the polyurethane adhesive layer on an edge and / or peripheral surface above the reactivation temperature and reactivate the adhesive on the edge and / or peripheral surface;Place the second portion of the flexible sheet material onto the heated and reactivated adhesive at the edge and / or peripheral surface to bond the second portion of material to the edge and peripheral surface; and optionally, cool the polyurethane adhesive and substrate surfaces below the adhesive activation temperature.

2. The method of claim 1, wherein the substrate is polymeric. freo L Ln / Lznz / E / YILI 3. The method of claim 1 or 2, wherein the substrate is composed of polypropylene (PP) or acrylonitrile-butadiene-styrene (ABS).

4. The method of any of claims 1 to 3, wherein the flexible sheet material comprises a flexible polyurethane foam material.

5. The method of any of claims 1 to 4, wherein the step of applying the first heating cycle comprises heating the main surface and the first portion of flexible sheet material disposed on the main surface to approximately 60 °C to approximately 80 °C for approximately 2 to approximately 4 minutes.

6. The method of any of claims 1 to 5, wherein the step of applying the first heating cycle comprises heating the main surface and the first portion of heated flexible sheet material disposed on the main surface to approximately 60°C to approximately 80°C for approximately 2 to approximately 4 minutes.

7. The method of any of claims 1 to 6, wherein the step of arranging a second portion of the flexible sheet material over the heated and reactivated adhesive comprises wrapping unsecured portions of the flexible sheet material over the edge and over the peripheral surface.

8. The method of any of claims 1 to 7, wherein the steps of applying the second heating cycle and arranging a second portion of the flexible sheet material over the heated and reactivated adhesive comprise exposing the peripheral surface to a temperature of approximately 200 °C to approximately 300 °C for approximately 30 seconds or less, then wrapping the second portion of material over the edges and over the heated peripheral surface.

9. The method of any one of claims 1 to 8, wherein the steps of applying the second heating cycle and placing the second portion of material on the rim and on the peripheral surface and heating the second portion of material placed and the peripheral surface to approximately 60 °C to approximately 80 °C for approximately 15 seconds to approximately 30 seconds and subsequently wrapping the layer of material around the heated peripheral surface.

10. The method of any of claims 1 to 9, wherein the step of applying the second heating cycle comprises exposing the peripheral surface to a temperature of approximately 55 °C to approximately 85 °C.

11. The method of any of claims 1 to 10, wherein the first component comprises at least one polyurethane resin dispersion and the second component comprises a solvent-free, water-free liquid aliphatic polyisocyanate crosslinking agent.

12. The method of any of claims 1 to 11, wherein the first component and the second component are mixed prior to use to initiate a crosslinking reaction.

13. The two-component water-based polyurethane dispersion adhesive of any of claims 1 to 12, wherein: the first component comprises: an anionic water-based polyester-polyurethane resin dispersion, water, and optionally one or more additives; the second component comprises: one or more solvent-free, water-free liquid aliphatic polyisocyanate crosslinking agents, and optionally one or more additives; wherein a dry, non-adhesive mixture of the first and second components can be reactivated to an adhesive state by exposure to a temperature above a reactivation temperature.

14. The adhesive composition of claim 13, wherein the reactivation temperature is from approximately 55 °C to approximately 85 °C. freo L Ln / Lznz / E / YILI 15. The adhesive composition of claim 13 or 14, wherein the solvent-free, water-free liquid aliphatic polyisocyanate crosslinking agent comprises hexamethylene diisocyanate or a 1,6-hexamethylene diisocyanate trimer (HDI-biuret).