Method for producing polyethylene-based resin foam sheet and polyethylene-based resin foam sheet

Abstract

A method for producing a polyethylene-based resin foam sheet and a polyethylene-based resin foam sheet are provided without depending on an inorganic substance and a chemical blowing agent, and the method enables production of a good polyethylene-based resin foam sheet. In a first way of the method including extrusion-foaming a foamable resin melt containing a polyethylene-based resin and a physical blowing agent to produce a polyethylene-based resin foam sheet, one or more organic physical blowing agents selected from hydrocarbons having 3 to 5 carbon atoms and dialkyl ethers having an alkyl group having 1 to 3 carbon atoms and nitrogen are used as a physical blowing agent, and adjustment is performed so that the total (A+B) of the amount A of the organic physical blowing agents added and the amount B of the nitrogen added is 0.5 mol or more and 5 mol or less per kg of a resin component, the amount B of the nitrogen added is 0.1 mol or more and 0.4 mol or less per kg of the resin component, and the ratio (A/B) of the amount A of the organic physical blowing agents added to the amount B of the nitrogen added is 2 or more and 18 or less. The polyethylene-based resin foam sheet of the present invention has a density of 20 kg/m3 or more and 100 kg/m3 or less and an average of the number of cells of 0.5 cells/mm or more and 5 cells/mm or less in the thickness direction, the foam sheet has an ash content of less than 0.1 mass % (including 0), and the ash content includes sodium at a proportion of 10 mass % or less (including 0).

Dependencies are inferred from the claim text.