Packaging hot melt

Pentaerythritol in rosin ester form is used in hot-melt adhesive formulations, especially ethylene—vinyl acetate (EVA) copolymers, as a tackifier. Polyethers of pentaerythritol or trim ethyl ol eth an e are also used in EVA and polyurethane adhesives, which exhibit excellent bond strength and water resistance. The adhesives maybe available as EVA melts or dispersions (90,91) or as thixotropic, one-package, curable polyurethanes (92). Pentaerythritol spko ortho esters have been used in epoxy resin adhesives (93). The EVA adhesives are especially suitable for cellulose (paper, etc) bonding. 

The seam closure on a folding carton is typicahy made using a latex, poly(vinyl acetate), vinyl acetate copolymer, or hot-melt adhesive (27). The choice of adhesive depends on a number of factors, including the nature of any coating used on the package and the production speeds required. 

Thermoplastic block copolymers were used for pressure-sensitive and hot-melt rubber adhesives as from the middle sixties. These adhesives found application in packaging, disposable diapers, labels and tapes, among other industrial markets. The formulation of these adhesives generally includes an elastomer (generally containing styrene endblocks and either isoprene, butadiene or ethylene-butylene midblocks) and a tackifier (mainly a rosin derivative or hydrocarbon resin). 

One key consideration in developing radiation curable adhesive systems is the thermal stability and volatility of any photoinitiators used. These chemicals are designed for liquid systems where these issues do not arise. Few of the commercial photoinitiators have adequate thermal stability at the highest hot melt temperatures (180-200°C) and many are too volatile. Reduced application temperatures and special antioxidant packages are often required. 

The primary non-woven applications for hot melts are in disposable articles such as diapers and sanitary napkins (see Fig. 22). These articles are made by high speed processes and are immediately packaged in sealed plastic bags, thus they are prime candidates for hot melt use. The applications are broken down into three categories, requiring three different types of adhesives construction, elastic attachment, and garment attachment. 

Case and carton sealing is a high volume application for hot melt adhesives. Typical formulas use 20-30% wax, 25-40% polymer, and 35-55% tackifier resin. The basic requirements for packaging adhesives will be described followed by formulating guidelines for specific market areas. The focus of this discussion will be on EVA and EnBA-based systems, which are the most common. 

Polyethylene and polypropylene are used as carpet backing and as hot melts in packaging. 

Choi, W.Y., Lee, C.M., and Park, H.J. (2006). Development of biodegradable hot-melt adhesive based on poly-[epsilon]-caprolactone and soy protein isolate for food packaging system. LWT Food Sci. Technol. 39(6), 591-597. 

The adhesive may be solvent or water-based, hot-melt, coldseal or heatseal and pressure sensitive or chemically reactive. So the solidification process may occur via drying of water or solvent-based adhesives, by cooling of hot-melt and heat-seal adhesives, or by curing of chemically-reactive systems. With two notable exceptions - self-adhesive labels used on items of fruit or vegetables, and heat-sealable layers on packaging films - adhesives are in general not intended to touch the packaged food directly. 

Flexible packaging laminates Chemically reactive systems water-based hot-melts tie-layers Indirect... 

Presented here are only the methods that the author has tested in practice on plastics wastes. The first attempts were undertaken in 1986 in a small pilot unit that dealt with wastes of polyolefin films used for packaging. Those wastes were nonpigmented, transparent and rather clean. They were provided by waste collectors in blocks of approximately 30 kg, intended for factories producing regenerated granules (recyclate). The intention was to show the potential of producing a polyolefin wax to be used in polish applications or in hot-melt glues from those wastes. 

In using a bottom load case packer for a packaging operation, the containers are accumulated and unitized into the selected case pattern. As the unitized load is indexed onto the lift platform, a case blank is unfolded from the case magazine over the product. The lift platform raises the product into the opened case. The case is indexed out of the loading area and is top and bottom sealed by a hot melt glue system. The bottom load case packer is the best type of case packer for containers that require stacking, pads, or automatic case insertion. 

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