Polymeric foam powder processing techniques, foam powders products, and foams produced containing those foam powders

Abstract

This relates variously to techniques for comminuting polymeric foams, to techniques for preparing polymeric foams containing that comminuted foam, and to the resulting comminuted foam powder and polymeric foams. The procedures may be used on foams containing production contaminants such as polyolefins, paper, and foam skins and on other foams containing consumer contaminants such as wood, metal, leather, etc. The comminuted foam powder, with or without contaminants, preferably is screened or sifted to obtain a foam powder having a particle size of about 2 mm or less.

Description

FIELD OF THE INVENTION [0001] This invention relates variously to techniques for comminuting polymeric foams, to techniques for preparing polymeric foams containing that comminuted foam, and to the resulting comminuted foam powder and product polymeric foams. The procedures may be used on foams containing production contaminants such as polyolefins, paper, and foam skins and on other foams containing consumer contaminants such as wood, metal, leather, etc. BACKGROUND OF THE INVENTION [0002] Polymeric foams include a wide variety of materials, generally forming two-phase systems having a solid polymeric phase and a gaseous phase. The continuous phase is a polymeric material and the gaseous phase is either air or gases introduced into or formed during the synthesis of the foam. Some of these gases are known as “blowing agents.” Some syntactic polymeric foams contain hollow spheres. The gas phase of syntactic foams is contained in the hollow spheres that are dispersed in the polymeric ...

AI Technical Summary

Benefits of technology

[0018] This invention provides novel methods and devices for polymeric foam processing, particularly methods for comminuting (e.g., milling, pulverizing, or grinding) polymeric foams, preferably those containing with production and, perhaps, post-consumer contaminants. These novel methods and devices reduce excessive heating of polymeric foam during processing and improve the processing of polymeric foam products containing a variety of contaminants.

[0024] In another variation of the present invention a novel feed rate control method is employed for controlling the rate at which polymeric foam pieces are fed to a mill. This novel method uses, e.g., the mill's power consumption, to control the rate at which conveying equipment feeds foam pieces to the mill.

Problems solved by technology

Typical foam manufacturing processes result in polymeric foam wastes.

Post-consumer waste often contains contamination from other materials that were used in a fabricated part with the foam or from materials the foam was exposed to during its useful lifetime.

In addition to being reversibly deformable, flexible foams tend to have limited resistance to applied load and tend to have mostly open cells.

“Semi-rigid” or “semi-flexible” foams are those that can be deformed, but may recover their original shape slowly, perhaps incompletely.

Used foam objects, such as automobile cushioning materials, may be contaminated with grease or oil contaminants that destabilize the formation of new foam.

Foam trimmings containing polymeric foam skin waste material, which is typically formed in slabstock on the outside of a foam bun, are difficult to grind effectively using conventional grinding conditions that are most suitable for grinding polymeric foam.

The thermal insulating properties of foam make it difficult continuously to grind the foam in relatively long production runs because the grinding temperature tends to increase as grinding is continued, potentially resulting in thermal degradation of the polymeric foam.

Production contaminants result in increased grinding temperatures.

Furthermore, foam pieces and foam powder are difficult materials to handle in large quantities because these products bridge readily in various processing equipment.

Moreover foam powder tends to coat the surfaces of processing equipment such as conveyers, mills and screens.

It is also difficult to grind production foam trimmings for re-use as foam powder because they are typically contaminated with production contaminants such as plastic film or sheeting (often of polymers such as polystyrene or polyolefins such as polyethylene and polypropylene), plastic netting, or paper, which are used in slabstock production.

These plastics may coat the grinding surfaces of the comminution equipment because of the heat generated during grinding processes.

Paper contamination hinders comminution of foam, particularly when comminuting to obtain very small foam particles, because the grinding properties of paper are very different from those of polymeric foam.

Large particles of these contaminants cause processing difficulties with subsequent foam production and cause quality problems with the resulting foam.

These problems include: high viscosity of PUR-foam ingredients that include mixtures, such as slurries, of foam powder and active-hydrogen compounds, poor cell structure in the resulting foam, visibility of the larger foam particles, and poor quality and feel of the foam.

Foam scrap that is contaminated with adhesives is difficult to process using conventional techniques for comminuting and conveying the resulting foam pieces or foam powder.

Adhesives present in foam powder that is used to prepare new foam can destabilize the polymer foam during its formation.

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