F. Parodi and R. Alessio, "Polymeric Compositions Rapidly Heatable Under Electromagnetic Irradiation, Their Uses and Processing Methods", World Pat. Appl. WO-2004-048463 (A1) (Jun. 10, 2004; to F. Parodi);  Australian Pat. Appl. AU-2003-288732 (A1) (Jun. 18, 2004; to F. Parodi);  Italian Pat. IT-1,334,163 (May 24, 2006; to F. Parodi) [published as Ital. Pat. Appl. ITGE20020104 (A1) (May 23, 2004)].

ABSTRACT:  Thermoplastic polyolefin compositions capable of undergoing particularly rapid and uniform heating under microwave irradiation, or under simultaneous microwave and infrared irradiation.  Processes for conversion of such thermoplastic compositions into semifinished articles, and subsequent and fast hot conversion thereof into finished articles of various type under microwave irradiation, or under simultaneous microwave and infrared irradiation.

SUMMARY:   This patent application claims thermoplastic polyolefin compositions capable of undergoing particularly rapid heating under microwave irradiation.  Processes for conversion of such thermoplastic compositions into semifinished pieces, and subsequent , super-fast hot conversion thereof into finished articles of various type under microwave irradiaton, or under combined microwave + infrared irradiation,  are described as well.

The thermoplastic polyolefin compositions of the invention camprise:  a) a polyolefin-type polymer (such as polyethylene, polypropylene, related copolymers and terpolymers), or a mixture of different polymers of this kind;  b) a modest amount of a finely dispersed metal powder (e.g. aluminum, brass or bronze), or a mixture of different metal powders;  c) a suitable organic additive, i.e. a triaryl-, triarylmethyl-, aryl-diarylmethyl-, or also diaryl-arylmethyl-phosphine or amine;  d) a mono- or polybasic protic acid, of polymeric or non-polymeric type;  e) optional additives of known use in polymeric compositions, selected among mineral fillers, pigments, reinforcing fibers, light and heat stabilizers, etc.  Such polyolefin compositions are designed to be used as polymeric materials for the following applications, implying accelerated hot post-processing operations by means of mechanical stresses imposed under simultaneous microwave irradiation (or, even more rapidly and efficiently, under combined microwave + infrared irradiation) in conventional, tunnel or closed-chamber, industrial UHF devices:

i)  continuous fabrication of nets, grids, geo-nets and geo-grids by uni- or biaxial hot stretching of polymeric slabs, planar network structures or suitable tridimensional preforms, made of thermoplastic polyolefins, bearing holes, depressions, cavities and/or protrusions;

ii)  hot stretching, bending, folding and other geometrical deformations of extruded bars, rods, pipes, tubes, sheets, slabs, etc.;

iii)  fast hot conversion of the end portions of pipes into bell-and-spigot joints;

iv)  welding materials for fast joining of articles, parts or components made of polyolefin materials.

The proprietary system of additives c) + d) endows the novel polymeric materials with a surprisingly strong microwave heatability, even with low fractions of metal fillers, while promoting the prompt and optimal dispersion of metal particles within the molten polyolefin matrix during the mixing operations in extruders, and ensuring at the same time excellent mechanical end-properties of the finished, solid articles.