Extruded polyolefin foam in thicker grades and plank and process therefor

The foam of claim I wherein said blowing agent is about 70 percent propane and 30 percent by weight of isobutane, normal butane, or a mixture of iso- and normal butane.

An extruded polyolefin foam having a thickness of at least about 12 mm and a density of from about 20 to 65 kg/m3, wherein said polyolefin is selected from the group consisting of low density polyethylene, polypropylene, and mixtures thereof, wherein said foam is expanded by a blowing agent comprising from 25 to 100 percent propane and from 0 to 75 percent isobutane, normal butane, or mixtures thereof, and wherein the force required to cut the foam is at least 10 percent less than that of foams prepared from the same polyolefins using a blowing agent of 100% isobutane, normal butane, or mixtures thereof for foam samples of comparable size and density.

An extruded polyolefin foam having a thickness of at least about 12 mm and a density of from about 20 to 65 kg/m3, wherein said polyolefin is selected from the group consisting of low density polyethylene, polypropylene, and mixtures thereof, wherein said foam is expanded by a blowing agent comprising from 25 to 100 percent propane and from 0 to 75 percent isobutane, normal butane, or mixtures thereof, and wherein the force required to bend the foams is at least 5% higher than that for foams prepared from the same polyolefins using a blowing agent of 100% isobutane, normal butane, or mixtures thereof for foam samples of comparable size and density.

A process for producing an extruded low density polyolefin foam having a thickness of at least about 12 mm, said process comprising the steps of:

• a) mixing a blowing agent with a plasticized polyolefin resin selected from the group consisting of low density polyethylene, polypropylene, and mixtures thereof, wherein the blowing agent is selected from the group consisting of 100 percent by weight of propane and blends of propane with up to about 75% by weight of normal butane, isobutane, or a mixture of normal butane and isobutane;
• and
• b) extruding the mixture of resin and blowing agent so as to produce a foam plank having a compressive strength about one hour after extrusion of from about 8 to 45 psig at 25 percent compression by unit volume.

An extruded polyolefin foam having a nominal thickness of at least about 12 mm and a density of from about 20 to 65 kg/m3, wherein said polyolefin is selected from the group consisting of low density polyethylene, polypropylene, and mixtures thereof, wherein said foam is expanded by a blowing agent comprising from about 25 to 100 percent by weight of propane and from about 0 to 75 percent by weight of isobutane, normal butane, or a mixture of isobutane and normal butane, and wherein said foam has a compressive strength one hour after extrusion of about 8 to 20 psig at about 25 percent compression by unit volume.