Abstract: Process for producing flexible PVC irrigation pipe by extruding a plasticized PVC composition containing a melt strength-enhancing aid and a chemical blowing agent and (a) the extruded melt being expanded by foaming thereof immediately on leaving the die into a substantially closed-cell extrudate of outer diameter greater than the die orifice with the extrudate surfaces being substantially unpunctured, (b) drawing down the extrudate in the atmosphere causing rupturing of the foam cell walls of the extrudate to form a substantially open-cell extrudate having punctured surfaces, and (c) when the extrudate has been drawn down to a degree which is prior to any cellular collapse which would lead to the formation of water-impervious pipe, cooling the extrudate by passing it through a cooling means in order to prevent said collapse. Preferably the extrudate passes through a tubular guide into a water bath in step (c).

Abstract: Foamable vinyl chloride polymer composition containing as a foam stabilizer an alkyl acrylate polymer.