Extruded polymer foam with filler particles and method

Abstract

A thermosetting foam, preferably polyisocyanurate or polyurethane foam, is prepared in an extruder which permits the incorporation of high levels of filler particles. The method includes introducing polyol, isocyanate and filler particles to an extruder screw for mixing. In conjunction with extruding, a catalyst is added. The catalyst may be added either in a last extruder barrel or with the extruder head. Foam with filler particle content in excess of 12% made be readily made. Filler particles, such as aluminum trihydrate, perlite, carbon black, diatomaceous earth, polyiso powders, ammonium phosphate, fly ash, barium sulfate, calcium silicate, and calcium carbonate, may be used. The process described is preferably used for making foam boards or bunstock.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe invention relates to foamed polymer material, methods for producing polymer foams, and, particularly, to a method for extruding polymer foam material, such as polyisocyanurate and polyurethane foams, using a screw-type extruder. The extruded polymer foams contain substantial amounts of filler particles.2. Description of the Prior ArtPolymer foams, such as polyisocyanurate and polyurethane foams, have not previously been able to be produced using an extruder. The foaming material "firms" in the extruder and blocks the equipment. Additionally, use of filler materials has been limited using conventional methods to produce foam sheets.U.S. Pat. No. 3,466,705, (Richie) describes an apparatus for extruding foamable thermoplastic material, such as polystyrene, preferably in tubular form. Richie discloses that the apparatus can be used for thermosetting materials, such as polyurethanes, but that steam or hot water would have a damaging...

AI Technical Summary

Benefits of technology

Polymer foam board is disclosed which includes high levels of filler material, such as 15%-20% by weight filler particles, or higher. Polyisocyanurate or polyurethane foam is made using a screw-type extruder for mixing the components of the composition. Isocyanate and polyol are introduced into a screw of an extruder. Filler particles are also introduced in the extruder screw. The isocyanate, polyol, and filler particles are mixed together with a foaming agent and, optionally, a surfactant with the extruder to produce a high quality dispersion. The mixture is cooled via a cooling manifold of the screw extruder and the addition of the various components in the mixture. Cooling inhibits reaction of the mixed components within the screw.

The filler particles included in the thermoset foams produced in accordance with the invention maintain the mechanical or insulative characteristics of the resultant extruded foam as compared to the properties of the extruded foam without filler particles. However, with some fillers improved characteristics result. For example, carbon black can improve the insulation properties of the foam as set forth in the Soukup and Gluck patents, supra. Ammonium phosphate can improve flame-retardant properties. Overall, the addition of filler particles makes the resultant foam more economical to produce and the process enables the use of more filler materials in the production of suitable foam board insulation.

Different filler particles can be used in the same foam. For example, carbon black and another type filler particle, which is less expensive, can be used to gain the insulative effect of the carbon black while increasing costs savings. Aluminum trihydrate, perlite, ammonium phosphate and calcium carbonate are preferred filler materials, used either as the sole filler material or with carbon black. Other filler materials include carbon black, fly ash, diatomaceous earth, polyiso powder, barium sulfate, melamine and calcium silicate. The filler particles added to the polyol / isocyanate mixture in the extruder reduce the cost of the resultant extruded thermoset foam, since the filler particles are lower in cost than polyol and / or polyisocyanate.

Problems solved by technology

Polymer foams, such as polyisocyanurate and polyurethane foams, have not previously been able to be produced using an extruder.

Additionally, use of filler materials has been limited using conventional methods to produce foam sheets.

Richie discloses that the apparatus can be used for thermosetting materials, such as polyurethanes, but that steam or hot water would have a damaging effect and therefore are not used.

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