Process for preparing novel sheet-like structures

A process for preparing a porous, sheet-like structure composed of polyolefin microflakes is provided. The product is unique in that it can be prepared from inexpensive polyolefins and is useful as a synthetic paper. Moreover, when subjected to shrinking treatment, unwoven cloths and leathers of high quality are obtained. The process comprises ejecting via an orifice, a mixture of a polyolefin, an oligomer (A) (essentially a linear polyester oligomer having two vinyl or vinylidene groups on its molecular terminals), a surfactant and a solvent into air to form microflakes, forming the latter into a sheet by the conventional wet process, and finally irradiating the resulting sheet with electron beams (dose rate 0.1 to 50 Mrad/sec, absorbed dose 0.5 to 10 Mrad) to cross-link the polyolefin with the oligomer (A). In one example (parts by weight), a mixture of isotactic polypropylene (10), high density polyethylene (5), oligomer A (3), nonipol (nonionic surfactant) (0.2) and methylene chloride (85) is ejected through an orifice into air to form microflakes; the latter is formed into a sheet by the conventional paper-making process in the presence of methylene chloride as a medium. Finally, the sheet is irradiated with electron beams (dose rate 3 Mrad/sec, absorbed dose 2 Mrad) to obtain a tough synthetic paper useful for packagings. (Kaichi, S.)