Polyurethane adhesives laminating

Laminated film consisting of glycol-modified polyethylene terephthalate (PETG), polyvinylidene chloride (PVDG), and polyethylene (PE) with a polyurethane adhesive. 

The second major classification of common polyurethane adhesives is the two-component system. Two-component polyurethane adhesives are widely used where fast cure speeds are critical, as on OEM (original equipment manufacturers) assembly lines that require quick fixture of parts, especially at ambient or low bake temperatures. Two-component urethanes are required in laminating applications where no substrate moisture is available or where moisture cannot penetrate through to the adhesive bond. Two-component urethanes are also useful where CO2 (generated by a one-component moisture cure) or a volatile blocking agent would interfere with the adhesive properties. 

Over the last four decades there have been a number of attempts to wed the unique benefits of polyurethane adhesives with the benefits of other adhesive systems. These attempts have led to the reporting of a variety of urethane hybrids. Early work focused on simple blends for example, in 1964 Union Carbide blended organic isocyanates with ethylene-vinyl acetate copolymers [66]. These blends were used as an adhesive interlayer in glass laminations, particularly safety glass laminates. Similarly, polylurethane poxy blends for safety glass laminates were reported in 1970 [67]. 

Many interior fittings (e.g., instrument panel, door and sidewall panels, package trays, seat linings, boot carpetings, rear window shelves, etc.) are often manufactured by vacuum drawing and laminating the cover sheet material (leatherette, textile, leather, etc.) onto the trim panel. The use of hot-melt (also cross-linking) adhesives and water-based polyurethane adhesives (with hardener) is state of the art for this type of component production. 

This paper aims at explaining the reaction between the HMR coupling agent and one-component polyurethane adhesives used for wood lamination. 

The predominant failure mode in bonded joints was cohesive failure of the adherend. Only in those adhesively bonded joints with the polyurethane adhesive (1897) was a cohesive failure of the adhesive encountered. No adhesive failures were detected, indicating that the surface treatments performed had been sufficient. The quality of adhesive layers was in general satisfactory. However, in joints of laminates with a woven roving or a uni-directional surface layer (Table 7) the adhesive layers were thick and of poor quality, having large voids. With laminates of a uni-directional surface layer, this... 

Lamination of Paper and Board. Adhesives based on starch, dextrin, glutin and poly(vinyl alcohol), and also emulsion adhesives, mainly polyfvinyl acetate), are used for the lamination of paper and board. Only when high initial tack and a lay-flat effect are required are hot glues based on glutin still in use. Starch-based adhesives modified with silicate, casein-stabilized copolymer dispersions, and rubber latices are used in the lamination of paper to aluminum foils. Modified polyacrylate solutions and reactive polyurethane adhesives are used mainly for paper-to-plastic lamination. 

Adhesives for Laminated Films. Laminated films are currently produced by two techniques lamination and extrusion. In lamination, the low-viscosity adhesive solution is applied by rolls to one of the films in a thickness of a few micrometers and dried. The two films are then combined in the laminator. The adhesives used are either two-component or one-component, moisture-cross-linking polyurethane adhesives, depending on requirements (type of film, sterilization resistance, sealing seam strength, etc.). Besides the traditional solvent-based systems developments have been made in the direction of solvent-free systems (high-solids products) and of polyurethane emulsion-based systems. 

Manufacture of Polyethylene Sacks. The one-component and two-component polyurethane adhesives used for the production of laminated films (see above) are used for this purpose, depending on the type of machine. 

In the next paper, Illinger, Lewis and Barr find that the morphological structure of polyurethane adhesives affects both the optical clarity and the energy-absorbing properties of acrylic-poly-urethane adhesive-polycarbonate laminates. The morphological structure of the adhesive is in turn related to the composition of the hard and soft segments of the blocked polyurethane adhesives. 

Acrylic/polycarbonate laminates for windshield applications fabricated using transparent flexible polyurethane adhesive interlayers have demonstrated resistance to impact up to 100% greater than polycarbonate, currently considered the best commercially available transparent impact-resistant material. 

Film overlay laminations (furniture) and sole attaching (footwear) are other applications for polyurethane adhesives (Table 15). 

Chapter 8 Adhesives for packaging and paper, bookbinding, by P. Cognard Chapter 9 Polyurethane adhesives for laminating and packaging, by J. F. Lecam, Bostik-Findley... 

With elastic polyurethane adhesives, almost all construction materials are laminated together, such as concrete, wood, ceramics, plastic, and metal. Thus, completely new design possibilities arise. When bonding steps, parquet, or tiles, two advantages come into play, namely, the impact sound insulation and the background-balancing property of the adhesive (Brunner 1996). 

This effect is utilized in furniture lamination, in which the polyurethane dispersion is usually mixed with a reactive crosslinking agent The polyurethane adhesive is applied using a spray gun. After the adhesive has dried, a blocldng-resistant film forms, and the fiberboard elements can be stacked. They are then pressed with the decorative sheet at 60-80 °C, for example in a membrane press. On coohng, recrystallization produces a rapid increase in strength. This is necessary to counter the re-... 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

The large volume applieations for moisture-euring polyurethanes are diseussed briefly in the applieations seetion below. These adhesive offer superior low temperature, high temperature, and speeifie adhesion performanee in comparison to conventional hot melts. These attributes have allowed them to excel in various product assembly applications, including structures such as windows, doors, furniture, and automotive headlamps and trim. Newer applications include bookbinding, fabric laminating, and assembly of athletic shoes. 

Various elastic elements are added to disposable sanitary products. Strands of lycra, natural rubber, polyurethane foam, and other elastic laminates are applied to provide good fit and avoid leakage. These are attached with adhesives. While non-PSA formulas such as polybutene-based [64] and polyamide [65] adhesives have shown utility, as well as benefits in terms of resistance to baby oils and lotions, adhesives based on styrenic block copolymers still dominate. SBC-based... 

The market for polyurethane thermoplastic adhesives is small, but growing. TPU s are used to produce some solvent-borne adhesives and also are used in laminating textiles and films for labels and emblems. In addition, they are being considered as an alternative to solvent-borne adhesives in the shoe market. 

Copolymers of ethylene with up to 15-20% acrylic or methacrylic acid offer improved adhesion, abrasion resistance, toughness, and low-temperature flexibility compared to EVA. Applications include extrusion coatings on aluminum foil for pouches, wire and cable, packaging film, laminations with metal and glass fibers (building and automotive products) and polyurethane (carpet backing). 

Recently a solvent-free dual-cure laminating adhesive based on the combination of polyurethane chemistry and EB cure was developed that exhibits improved properties compared to laminates prepared by either method alone. ... 

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