It is well known that the polyamides generally do not melt within a commercially acceptable temperature range. Therefore, a polyamide melt is usually mixed with a suitable meltable polymer(s) and then extruded to produce a fibrous non-woven material. However, such a method is not suitable for the manufacture of films, tapes, packaging films, etc. Because polyamides generally have extremely low solubility in organic solvents, it is often necessary to use a solvent to dissolve the polyamide to produce a solution. The solvent is then removed from the solution to produce a polyamide-containing film. Since the solubility of the polyamide varies with the solvent and with the concentration of the polyamide in the solution, the solution must be adjusted to produce a film with a desirable concentration of polyamide.
In the manufacture of biaxially-oriented non-wovens, it is often desirable to apply an adhesive to one surface of the non-woven material and then to adhere the non-woven material to another surface to produce a laminate having a desired strength. For example, a polyamide-containing non-woven material is sometimes laminated to a film of a polyolefin, such as polyethylene or polypropylene, to produce a laminate having a greater moisture barrier than the polyamide alone. To this end, the surface of the polyamide-containing non-woven material can be coated with a thermoplastic adhesive, such as polyethylene, and the coated polyamide-containing non-woven material is then adhered to the film, for example, by calendering, and then further calendered to produce a laminate. Since aqueous solutions of polyamides are notoriously difficult to uniformly apply to the surface of a polyamide-containing non-woven, a dry adhesive, such as an organic solvent-based polyethylene, must usually be applied to the surface of the non-woven material to produce a laminate.
Biaxially-oriented polyamide films are also used to produce films for packaging food products. For example, biaxially-oriented polyamide films are often used to wrap food products, such as meats or cheeses, in packages for retail sale. In such uses, it is desirable to maintain the film integrity during the process of packaging and wrapping. That is, the film must maintain its structural integrity so that the film does not tear and remains sealed as the food
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