Rolled rigid foam

Details Rolled rigid foam Rolled rigid foam

1999-03-22

2001-05-08

Kuhns, Allan R. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Pore forming in situ

Composite article making

C264S046300, C264S046500, C264S048000, C264S050000, C264S053000, C264S054000, C264S154000

Reexamination Certificate

active

06228296

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the production of rolled, rigid foams, particularly polyurethane and polyisocyanurate foams.
2. Description of the Prior Art
It is known to prepare foam laminates of the kind comprising a rigid layer of foam sandwiched between two skins. These foams, such as the polyurethanes and polyisocyanurates, have been very well accepted for many years because of their well-known advantages and widespread usefulness for structural, insulating and/or decorative purposes.
The rigid foams have excellent structural strength coupled with a relatively low density, and, in their sandwich-type constructions, their rigidity makes them particularly suitable for building purposes. Also, because of their generally closed cell, or substantially closed cell structure, they are superior heat insulators. The presence of the isocyanurate ring structure in the polyisocyanurate foams provides these foams with excellent high temperature properties, particularly an outstanding resistance to deformation at high temperatures.
Although these lightweight faced panels of the prior art are thus of considerable value as rigid and unbent insulating materials, this utilization leaves unaddressed the many areas where curved insulation is needed. If, for example, the highly insulating closed cell polyisocyanurate foams were available as rolled goods, the market for such foams could profitably expand to applications not currently exploited, such as pipe, tank and duct wrap. Furthermore, having such foams in a rolled form would contribute significantly to their manageability in use. A roll of foam would be much easier to transport and handle than the same amount of foam in the form of a number of discrete rigid panels.
OBJECTS OF THE INVENTION
It is accordingly an object of the present invention to provide a rigid, especially closed cell, foam plastic in a rolled form for use as an insulating material.
It is another object of the present invention to provide an apparatus and method for the continuous and efficient manufacture of a rolled, rigid foam plastic.
SUMMARY OF THE INVENTION
The foregoing and other objects of the invention have been achieved by the process and apparatus of the present invention for the continuous production of a rolled, rigid plastic foam structure, wherein a foam-forming mixture is deposited from a dispenser onto a moving carrier, which suitably is a flexible material, and converted to a rigid foam, and the rigid foam is thereafter rolled. Another moving flexible material is advantageously placed over the deposited mixture so that the finished product will have a plastic foam core sandwiched between outer facing materials. The apparatus includes a conveyor assembly for continuously advancing the facing materials, which must be pliable, i.e., capable of being bent or rolled without fracturing, and means for regulating the amount of foam forming mixture which is deposited to provide only enough for formation, after foaming and curing, of a finished foam product having a maximum thickness of less than 1 inch. The width of the rigid foam product can vary widely from about 1 foot to 4 feet or more, depending on the width of the carrier and a predetermined setting of the regulating means. The foam product is formed continuously and its length for eventual use will depend on wherever the product is cut after foaming and curing.
The inventive process is distinguished from a process involving the addition of a foam-forming mixture to a stationary mold which is curved for formation of a rounded foam. The rigid foams formed on the conveyor must not be so thick that rolling them results in breakage. Applicants have found this maximum thickness for workability to be advantageously less than ½ inch, more advantageously less than ¼ inch. That rigid polymer-based foams which have a high closed-cell content can be thus produced is surprising in that the foams' rigidity would seem to prevent such rolling The inventive foams are desirably greater than 75, preferably 80, and more preferably 85, percent closed-cell according to ASTM D2856-A. The rollable polymeric foams which are producible in accordance with the invention can be easily determined through routine experimentation. Polyurethane and polyisocyanurate foams comprise preferred rigid foam plastics of the invention.
The facers of the invention are conveniently flexible material which is in the form of continuous or semicontinuous sheets fed from rolls. A wide variety of materials are employable as the facers, and can be any of the flexible sheet materials conventionally employed in laminated foam insulation products. Such facing materials include, but are not limited to, metals, paper, paperboard, plastics, fiber glass, textiles, asphalt-saturated felts, asphalt fiber glass sheets, metallized plastics, coated plastics and coated papers. The facers may be made from combinations of these materials. In some cases, adhesion can be improved by coating the facing materials before lamination with conventional coating compositions such as vinyl or epoxy compounds. Particularly suitable facers for use in the invention are metallized and coated polymer films, such as metallized and coated polyesters, plain polymer films, papers, and coated papers. Various protective and/or decorative materials may be used on or in the facing materials to make them waterproof, fireproof, etc.
The foamable chemical mixture, which is capable of being formed into a rollable rigid foam, is suitably deposited on the lower facer from a mixing head or other appropriate device which traverses either partially or completely across the width of the facer. The mixture also can be laid down by a stationary device.
After deposition of the foamable mixture and optional application of the upper facer, the resultant composite advances into an expansion zone wherein the foam-forming mixture expands to a cured state. The expansion can be the “free rise” type, such as disclosed in U.S. Pat. No. 4,028,158, where the thickness of the composite is controlled by a gap which is preferably provided by the nip of two rotating rolls. The nip of the two rotating rolls serves as a means for metering the amount of the foamable mixture. Other nip-defining means, as, e.g., the combination of a doctor blade and a fixed plate, or the gap provided by thermal means, such as described in U.S. Pat. No. 5,817,260, also can be employed. The expansion also can be restrained, such as where the foamable material and facer(s) are directed between a pair of spaced conveyor belts which preferably are positioned apart a distance less than the thickness the combination of foam and facer(s) would otherwise ordinarily reach if allowed to foam unrestrictedly.
In the expansion zone, the foamable mixture/facer(s) composite is advantageously subjected to the influence of heat controllably added by the circulation of hot air and cured to a rigid foam structure. In this manner, the resulting faced foam body or slab has two major, relatively flat, parallel surfaces after foaming and curing.
The resulting rigid product is next edge trimmed, and rolled upon itself or on a core to produce a rolled rigid foam which is conveniently sized in finite lengths for shipping. The faced foam must be sufficiently thin so that it can be readily rolled up to form a desirable cylindrical package of insulating material. The product may be perforated to promote water vapor transmission. Faced foams having a thickness of less than 1 inch, preferably less than ¾ inch, and more preferably a thickness in the range of approximately ⅛″-¼″ have been found to yield superior rolled products of the invention.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described with reference to the accompanying drawing which is a side schematic elevation of an apparatus suitable for producing a rolled, rigid foam laminate in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a conve

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