Paper adhesion polyethylene

In extmsion coating a polymer is extmded from a slot die into the nip of two roUs where it is bonded to a substrate under pressure (Fig. 6). A corona discharge may be appUed to the substrate just prior to the nip to enhance adhesion. Polyethylene or ionomer are the most common resins used in extmsion coatings. They provide improved moisture barrier (on paper), or sealabUity (on foU, polypropylene, or polyester). When a second substrate is introduced to the nip, laminated stmctures may be produced. 

Use Pressure-sensitive and hot-melt adhesives, bonding of paper to polyethylene, laminating adhesive, tackifier and plasticizer for coatings, heat sensitizer for rubber latex, pigment binder in textile finishing and printing inks, protective colloid in emulsions. 

Reduced adhesion between, for instance, paper and polyethylene surface films or between paper and toner, due to a decreased surface energy of the paper surface. 

Silicone products dominate the PSA release finer market, but Wemer-type chromium complexes such as stearato chromic chloride [12768-56-8] are also used. Various substrates are used, including coated PCraft papers and polyethylene or polyester films. Silicone coatings that cross-link to form a film are used in various forms such as solvent and solventless dispersions, and emulsions. Technical requirements include good release, no contamination of the adhesive. 

Junnila J, Savolainen A, Forsberg D. Adhesion improvements between paper and polyethylene by pretreatment of substrate. TAPPI polymers, laminations and coatings conference. Orlando 1989. 

Ethylene-propylene elastomers are also used as additives (10-15%) for waxes used in paper coating. EPMs are preferred because of the absence of gel and greater UV stability, and because they confer greater self-adhesion of the paper and higher impermeability. In direct competition to this type of paper are polyethylene and polypropylene film. 

The Nitro-dur system, marketed by Key Pharmaceuticals, Inc., contains nitroglycerin in acryUc-based polymeric adhesives with a cross-linking agent for polymer stabiUty. This depot of dmg provides a continuous source of active ingredient. An impermeable backing prevents release of nitroglycerin away from the skin. The systems are individually sealed in a paper polyethylene-foil pouch (81). 

Mention may also be made of an application in which careful control of polymer morphology has led to the production of novel materials. By treatment of solutions of high-density polyethylene, products are obtained with a celluloselike morphology and which are known as, fibrides or synthetic wood pulp. They are used for finishing paper and special boards to impart such features as sealability and improved wet strength. They are also reported to be used for such diverse applications as tile adhesives, thixotropic agents, battery separators and teabags ... 

Solvent-home urethanes are still widely used to bond leather and athletic shoes. The OEM automotive market uses some solvent-home urethanes together with chlorosulfonated polyethylene as a primer. Some urethane solvent-home packaging adhesives are used for cap liners and for paper and foil lamination. Some textile laminating applications are still based on solvent-home urethanes. 

On occasion the polyethylene has been blamed for odors caused by other parts of the container design such as screw cap liners, printing inks on the bottle exterior, adhesives used to laminate polyethylene to paper, and the fiberboard or the lining of material used in the separate exterior overpack in which a polyethylene container is held. Careful selection of all of these related materials is always advisable with liquid food products. 

There are four major types of barrier materials used now in the US for military purposes a)Water-proof b)Greaseproof c)Water-vapor-proof and d) Combinations of a,b c. Almost all the barrier materials in use today are composed of several layers or plies. The plies are usually cemented together with suitable adhesives(/< mi anrs) to form a laminated structure, although several other methods of making multi-ply sheets are also used. Materials used for making plies include kraft paper, cotton scrim, aluminum foil, polyethylene, cellulose acetate, Mylar, etc... 

Materials may exhibit a tainting odor from the polymers, monomers, additives, adhesives, or process. Packaging related taints, as reported from the Nestle s Central Packaging Laboratory over a 4-year period (1996-2000) were related to solvents (28%), degraded polyethylene (PE) (24%), styrene (15%), halogenated phenols (15%), degraded paper (3%),... 

A new approach was proposed for making effective helmets which could replace the former British army steel helmet. Essentially the new helmet used modified phenolic resins reinforced with nylon, and the crown cap inside was thermoformed from polyethylene. Formerly the crown cap was attached to the steel by rivets—not an appropriate method for fixing polyethylene to reinforced plastics. Instead a method was developed with a hot-melt adhesive based on ethylene-vinyl acetate copolymers cast as film on release paper. For assembly, the cast film is cut in advance to match the intricate shape required and activated by heat to bond under light pressure subsequently, a further heat activation is employed to fix the crown cap in place (Figure 52 illustrates this). 

Again, many cartons used for the packing of food products comprise paper laminated with polyethylene, the bonds being by means of simple adhesives which are effective only if the plastic has been treated suitably in advance. 

Vinylidene Chloride Copolymer Latex. Vinylidene chloride polymers are often made in emulsion, but usually are isolated, dried, and used as conventional resins. Stable latices have been prepared and can be used diiecdy for coatings (171—176). The principal applications for these materials are as barrier coatings on paper products and, more recently, on plastic films. The heat-seal characteristics of VDC copolymer coatings are equally valuable in many applications. They are also used as binders for paints and nonwoven fabrics (177). The use of special VDC copolymer latices for barrier laminating adhesives is growing, and the use of vinylidene chloride copolymers in flame-resistant carpet backing is well known (178—181). VDC latices can also be used to coat polyethylene terephthalate) (PET) bottles to retain carbon dioxide (182). 

The final thickness of epoxy tape or film adhesives is on the order of 5 to 15 mils. These adhesives may be soft and tacky, or stiff and dry, depending on their formulation. The soft and tacky products are valuable in products requiring application to contoured or vertical surfaces. If the product is especially tacky, a release liner (e.g., polyethylene film, coated paper) is generally used to keep the film from blocking. The stiff and dry products are generally used for flat surfaces where speed and ease of application are required. 

Reswax [Borden], TM for a series of wax-resin blends used as coatings and hot-melt adhesives in paper conversion. The polymers used include butyl rubber, polyisobutylene, chlorinated rubber, polyethylene, and styrene copolymers. 

It can be seen that most containers and almost aU film materials arc potentially includwi in the 6 categories. There are several cautionary points to be observed. Except for poly(ethylene terephthalate), PET, containers arc not the predominant use for any one polymer. For poly (vinyl chloride), PVC, consumer-indentifiable containers are less than 10% of the total. TTie identification on products is not always very prominently displayed. It can take some effort to ascertain that a given grocery bag is either No. 2 (HDPE), high-density polyethylene, or No. 4 (LDPE), low-density polyethylene. And there is a problem with composite products. Even the symbol on the base of a 2-liter soda bottle is somewhat ambiguous. The symbol is No. 1 (PETE). While it is true that the clear bottle is, indeed, PET, the base (placwi over the round bottom of the bottle) is itself No. 2 (HDPE). Also, the bottle usually will contain small amounts of paper (label) and poly(vinyl acetate) (adhesive) in addition to a metal cap with a copolymer liner. 

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