| 摘要 |
<p>1,199,224. Cross-linking polymers. IMPERIAL CHEMICAL INDUSTRIES Ltd. 21 April, 1969 [15 May, 1968], No. 23171/68. Heading C3P. Shaped articles of cross-linked polymeric material are prepared by subjecting a shaped article of a crystalline polymer containing a thermally activatable cross-linking agent to a pressure sufficient to cause a rise of at least 10‹ C. in the crystalline melting point of the polymer, and heating the article while under pressure to a temperature below the crystalline melting point of the polymer at the applied pressure and at which cross-linking will occur. Specified polymers are polyethylene, polypropylene, polyamides and polyesters, e.g. nylon 66 and polyethylene terephthalate. Preferred cross-linking agents for polyolefins are peroxides, optionally with non-conjugated polyenes, e.g. polyunsaturated esters and poly-α- alkenyl aromatic hydrocarbons. The article may be a sheet, film, fibre, pipe or pipe fitting, and the pressure may be applied via a liquid or gaseous medium, particularly water. Some cross-linking may be effected at temperatures above the crystalline melting point. Examples describe the cross-linking of polyethylene in the presence of (1 and 2) dicumyl peroxide and (3,4 and 8 to 11) di-t. butyl peroxide; and of polypropylene with (7) 1,1,4,4,7,7-hexamethyl cyclo-4,7-diperoxynonane.</p> |
