Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Process of treating scrap or waste product containing solid...
Reexamination Certificate
2000-12-21
2003-12-30
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Process of treating scrap or waste product containing solid...
C521S049000, C521S050000, C521S050500, C521S061000, C521S099000, C521S155000, C521S170000
Reexamination Certificate
active
06670404
ABSTRACT:
FIELD OF THE INVENTION
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
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 phase. These spheres can be made of a variety of materials including glass, metal, carbon and polymers. Other materials such as fillers, reinforcing agents, and flame retardants can be used to obtain specific foam properties. Polymeric foams, open-celled or closed-cell, are usually classified as flexible, semi-flexible, semi-rigid, or rigid. Flexible foams, foams that recover after deformation, are typically used in carpet backing, bedding, furniture and automotive seating. Rigid foam, foams that do not recover after deformation, are used in thermal insulation, packaging, and load bearing components. Examples of polymers commonly used in foams include epoxy, fluoropolymer, latex, polyisocyanurate, polyimide, polyolefin, polystyrene, polyurethane, poly(vinyl chloride) (PVC), silicone, and urea-formaldehyde.
Typical foam manufacturing processes result in polymeric foam wastes. For example, commercial procedures resulting in large quantities of polyurethane foam produce slabstock in a continuous pouring process. The resulting cast buns are often cut, for example, in pieces that are 1 to 2.5 m wide, 1.5 m high, and as long as 70 m. Foam buns are also made in boxes using batch processes. In either process, the outside of the bun is lined with a paper and/or plastic release sheet, and a layer of foam skin is formed there. The buns generally require trimming of the top and sides before the buns are cut or sliced for commercial use. These top and side trimmings include a foam waste product containing production contaminants.
By “production contaminant” we mean to include materials that are co-produced or used in the manufacture of slabstock or box foam, and are typically present in the scrap trimmed from the sides, top, and bottom of slabstock or box foam. Examples of production contaminants are those foam skins discussed above. Additionally, the term includes the release sheets or separators also discussed above, that are, e.g., of paper, paper coated with wax or polyolefin, and also may be of film, sheet, or netting made from polymer materials such as polyethylene, polypropylene, polystyrene, or other polyolefins. We will generically nominate the release sheets containing some amount of any polymer as “polymeric sheets”. The skin material in trimmed scrap (or, “foam skins”) is quite different in consistency and density from the desired foam product. The skin material is a tougher, more rubbery product, and has a higher density than the desired foam product. Foam skins are layers of non-foam or very high density foam that are formed during the foam polymerization procedures. Foam skin is also present in scrap such as “mushrooms” of material from foam molding operations that escape the mold. Foam skin is also found in off-spec molded parts.
Trimmings also result from foam fabrication processes in which useful shapes are cut from the buns. This type of waste is called fabrication scrap, and it generally contains lower amounts of production contaminants than waste from trimming buns.
Polymeric foam waste is also present in many discarded foam-containing products such as furniture, automobile seats, thermal insulation foams, and packaging foams. This type of waste is called “post-consumer waste”. 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. These “consumer contaminants” include wood, ferrous metal, non-ferrous metal, textiles, leather, glass, dirt, oil, grease, adhesives, minerals, and plastics.
“Polyurethane” (PUR) describes a general class of polymers prepared by polyaddition polymerization of diisocyanate molecules and one or more active-hydrogen compounds. “Active-hydrogen compounds” include polyfunctional hydroxyl-containing (or “polyhydroxyl”) compounds such as diols, polyester polyols, and polyether polyols. Active-hydrogen compounds also include polyfunctional amino-group-containing compounds such as polyamines and diamines. An example of a polyether polyol is a glycerin-initiated polymer of ethylene oxide or propylene oxide.
“PUR foams” are formed via a reaction between one or more active-hydrogen compounds and a polyfunctional isocyanate component, resulting in urethane linkages. As defined here, PUR foam also includes polyisocyanurate (PIR) foam, which is made with diisocyanate trimer, or isocyanurate monomer. PUR foams are widely used in a variety of products and applications. These foams may be formed in wide range of densities and may be of flexible, semi-flexible, semi-rigid, or rigid foam structures. Generally speaking, “flexible foams” are those that recover their shape after deformation. In addition to being reversibly deformable, flexible foams tend to have limited resistance to applied load and tend to have mostly open cells. “Rigid foams” are those that generally retain the deformed shape without significant recovery after deformation. Rigid foams tend to have mostly closed cells. “Semi-rigid” or “semi-flexible” foams are those that can be deformed, but may recover their original shape slowly, perhaps incompletely. A foam structure is formed by use of so-called “blowing agents.” Blowing agents are introduced during foam formation through the volatilization of low-boiling liquids or through the formation of gas during the reaction. For example, a reaction between water and isocyanate forms CO
2
gas bubbles in PUR foam. This reaction generates heat and results in urea linkages in the polymer. Additionally, surfactants may be used to stabilize the polymer foam structure during polymerization. Catalysts are used to initiate the polymerization reactions forming the urethane linkages and to control the blowing reaction for forming gas. The balance of these two reactions, which is controlled by the types and amounts of catalysts, is also a function of the reaction temperature.
Effective recycling technologies are highly desirable in order to re-use the foam waste, to maximize the raw material resources of these foams, to reduce or to eliminate the adverse environmental impact of polymeric foam waste disposal, and to make polymeric foam production more cost-effective.
It is desirable to recycle flexible PUR foam by reducing that foam scrap to particles having a maximum particle size of about 2 mm and introducing the comminuted particles in making new flexible PUR foam, see for example U.S. Pat. No. 4,451,583, to Chesler. In the Chesler process, the comminuted particles are added to the reaction mixture for the new PUR, or to one of the reactive liquid components such as the polyhydroxyl compounds, and then new flexible foam is prepared in a conventional manner. Cryogenic grinding is disclosed in the '583 patent as a preferred grinding technique for forming the required foam scrap particle size.
U.S. Pat. No. 5,411,213, to Just, shows a process for grinding polymers such as PUR by adding an anti-agglomeration or partitioning agent and subjecting the material to a compressive shear force using for example a two-roll mill. In another technique, disclosed in U.S. Pa
Martel Bryan
Stone Herman
Villwock Robert
Cooney Jr. John M.
Mobius Technologies, Inc.
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