Polymeric foam powder processing techniques, foam powders products, and foams produced containing those foam powders
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.
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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 CO2 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. Pat. No. 4,304,873, to Klein, micro-bits of flexible PUR foam are prepared by subjecting shredded flexible PUR foam and a cooling fluid, such as water, to repeated impact by a plurality of impact surfaces. In yet another technique, U.S. Pat. No. 5,451,376, to Proska et al, discloses a PUR foam comminution process and apparatus wherein a fine comminution is carried out by forcing a mixture of coarsely comminuted material and one of the liquid PUR reaction components through one or more nozzles.
Used foam objects, such as automobile cushioning materials, may be contaminated with grease or oil contaminants that destabilize the formation of new foam. U.S. Pat. No. 5,882,432, to Jody et al, describes a process for directly removing oil or grease contaminants from large PUR foam pieces.
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. The papers may also be coated with a polymer. 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 often cause foam pieces or foam powder to adhere to each other and to conveying and/or processing equipment such as mills. Adhesives present in foam powder that is used to prepare new foam can destabilize the polymer foam during its formation.
Cost-effective improved techniques, methods, and equipment for processing polymeric foam to achieve improved integration of polymeric foam and foam powder processing steps, utilization of a wider range of foam compositions for comminution and re-use in new foam, improved control and reliability of processing equipment and methods, reduction of operating and materials costs and improvements in resource utilization are all desirable. Particularly, a need exists for improved processing techniques and devices for (1) comminuting polymeric foam including production contaminants such as polymeric foam skins, polymeric sheet, or paper, (2) preventing or reducing excessive heating of polymeric foam during comminution, (3) processing foam products containing a wide variety of production and consumer contaminants and (4) using foam powder prepared from polymeric foam including production and consumer contaminants as an ingredient in new foam.
None of the documents cited above disclose the inventive processes and foam products described herein.
SUMMARY OF THE INVENTION
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.
Polymeric foams containing production contaminants are comminuted on a two-roll mill. The resulting comminuted foam powder is quenched both to cool the comminuted foam powder and the comminution process equipment.
In one variation of the present invention, a novel collection chamber is employed variously for collecting polymeric foam powder from a two-roll mill and for quenching the comminuted foam powder by means of a gaseous cooling medium.
Another variation of the invention involves a novel sifter for screening polymeric foam powder. The device employs a cylindrical screening tube and beater bars for separating foam particles from larger foam pieces.
The PUR foam powder prepared from PUR foam containing production contaminants such as PUR foam skins, polymeric sheets (often of polyethylene, polypropylene, or polystyrene), and paper (perhaps coated) is subsequently used in the preparation of new PUR foam.
In yet another variation of the present invention, a novel energy optimizing method for a two-roll mill is employed wherein the fastest roll is driven, for example, by an electric motor while the slowest roll is indirectly driven by the first roll through friction between the two rolls.
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.
The inventive procedure includes procedures for removing oil and grease from foam powder and either removing adhesive contaminants from polymeric foam powder or destroying the adhesive property of these contaminants.
BRIEF DESCRIPTION OF THE DRAWINGS
DESCRIPTION OF THE INVENTION
While describing the invention and its variations, certain terminology will be utilized for the sake of clarity. It is intended that such terminology includes the recited variations as well as all equivalent variations.
Processing module 200 (
Should the polymeric foam be contaminated with adhesive, the foam should first be treated to remove the adhesive properties. This permits effective conversion of the foam scrap into foam powder. Appropriate treatment techniques include solvent washing or subjecting the adhesively contaminated foam to microwave, infrared, or UV radiation.
Foam products and articles are introduced (not shown) into the size reduction equipment of step 212 using any of the techniques that are well known to those of ordinary skill in the art such as feeding the foam articles manually into the fragmentation equipment or using hoppers and/or conveyors. It will be understood that a preliminary size reduction step (not shown) may be executed prior to step 212 in order to reduce the foam articles to a size that is suitable for the fragmentation equipment of step 212.
Desirably, the size of the small foam pieces resulting from step 212 is less than about 10 cm. Preferably, this size is less than about 2 cm. A specific size range is obtained by operating the size reduction equipment of step 212 at the required operating parameters, followed by a screening step 214 (
Storage facilities for executing optional storage step 220 may include storage bins, boxes and silos such as are used for bulk solids storage. Preferably, a foam piece discharge method is provided according to the present invention for facilitating the discharge of foam pieces from the storage equipment of step 220, as compared with conventional discharge methods. Equipment adapted for executing the inventive discharge method is illustrated in
Optionally, the moving conveying surface has protrusions 238 (
Returning for a moment to conveying step 218, one or more fans may be used to blow or to convey foam pieces through a conduit or duct in the inventive process by means of a gaseous flow. For example, two fans may be used in combination with a cyclone. Suitable equipment for conveying foam pieces or foam powder employing a cyclone and two fans are shown in
Pneumatic conveying techniques often include steps for separation of the conveying gas from the material that is conveyed. A convenient place for doing so is at the point where the conveyed material is discharged from the conveying process. Cyclones may be utilized to remove the excess air but when foam is to be conveyed, foam pieces and foam powder may coat the inside walls of the cyclone. Additionally, foam pieces and foam powder are prone to plug the cyclone material outlet. Such coating and plugging difficulties associated with the use of foam in cyclones, can be alleviated by using an elongated flexible element 283, see
The conveying devices and procedure shown in
Alternative First Comminution Step
As shown in
Subsequent to fragmenting step 252, the materials are sorted in a sorting step 254 to remove the noted contaminants in a contamination removing step 256. These sorting methods include any techniques that are well known to those of ordinary skill in the art. For example, ferrous metals may be removed via magnets. Non-ferrous metals can be magnetically separated following the induction of eddy currents in these metals. Post-consumer contaminants such as wood, fiber, leather, plastic and glass can be removed using conventional elutriation methods wherein the pieces are for example separated by gravity in an upwardly flowing gas, e.g. air, stream.
The foam pieces that are thus obtained may be screened and recycled according to size in steps 258 and 260. (
Milling Step Controller
As shown in processing sequence 300, illustrated in
In addition to the use of roll mill current draw or power consumption as the measure of foam conveyance rate to a mill, other similar indicia may be employed. For instance, when hydraulic motors are used to power the conveying devices, hydraulic pressure or hydraulic fluid flow rate may be used.
Process-Contaminant-Containing Foam Powder
Foam pieces resulting from the methods of processing module 200 are comminuted employing a comminution step 314, see
The resulting material, the foam powder, may comprise or consist essentially of particles of PUR foam and any one or more of the production contaminants. We have found that the process is quite consistent in producing commninuted foam particles having any one of the production contarinants. Desirably, the foam powder is produced from at least some flexible pur foam, preferably 5% or 10% by weight or more, but containing little if any rigid or semi-rigid foam. Of course, it is possible to accrue the benefits of the process using the rigid and semirigid foam, but other processes deal suitably with rigid foams.
Quench Milling Step
Foam powder is discharged from the mill in discharging step 316, depicted in
In the present invention, a gaseous cooling medium such as make-up conveying air is preferably injected or sucked into the pneumatic conveying system to quench the foam powder in step 318 as the foam powder is discharged from the mill. Alternatively, the gaseous cooling medium such as air can be added to the pneumatic conveying system anywhere within the recirculation loop. A preferred method of adding the air is to provide an inlet for air with a baffle for flow control in a section of duct with pressure less than atmospheric pressure, for example, before a fan. For instance, we have found that for net foam comminution rates of about 450 kg/hr (990 lb./hr.) employing quenching air flow rates of about 42.5 m3/min (1500 cu. ft./min.) air at ambient temperature in a duct with a diameter of 20 cm (8 in.) results in a highly turbulent flow providing effective cooling of the foam powder. Again, the cooling medium flow preferably is in turbulent flow.
Examples of suitable cooling media include: gases such as air, nitrogen, carbon dioxide or mixtures of these gases, gases such as these that additionally include droplets or vapor of liquids such as water, alcohols, ketones, alkanes, or halogenated solvents. The droplets are added for evaporative cooling. Preferably, droplets used in these media should have a droplet size of about 0.06 mm or less. It is also preferable to cool the gaseous cooling medium to a temperature below ambient prior to using in the present process.
Before proceeding to a discussion of the quenching concept, the comminution step is considered. Comminution step 314 may be carried out by using an inventive two-roll mill as shown in
The speed reduction on the slow roll 313 may be achieved by mechanical braking in the depiction in
On to the quench feature of this inventive device.
An example of a quench feature is employed in the
Scraper bars 440 and 442 are positioned such that they contact (or nearly contact) cylindrical surfaces 424 and 432 respectively. The scraper bars are intended to remove substantially all of the foam that may adhere to either of rollers 426 and 428. Our process operates in an optimum fashion when substantially all of the comminuted foam falls into the lower chamber. The scraper bars can be fitted through slots, such as slot 443, in the end walls of the chamber. Inlet 444 in end wall 434 is provided for introducing a gaseous cooling medium while outlet 446 in end wall 438 provides a discharge for polymeric foam powder that is discharged when polymeric foam pieces are comminuted on rolls 426 and 428. It will be understood that the positioning of the inlet and outlet are merely illustrative. Alternatively, the inlet and/or the outlet can be positioned in the side walls or in the bottom of the chamber. Alternatively, an auger can be mounted in the bottom of the chamber, for example in alignment with inlet 444 and outlet 446 to assist in discharging foam powder from the chamber.
As shown in
As noted in
In any event, foam powder screening step 324 (
An axle 388 is positioned substantially along the central axis of housing 378 such that it extends from screen tensioning flange 385 through housing 378 and inlet section 376. Axle 388 rotates and is centered using, e.g., a bearing 358 in inlet section 376. A drive mechanism, e.g., electric motor, steam turbine, etc. perhaps with attendant gearbox, is rotates axle 388. Axle 388 is supported in a bearing 389 that is attached to tensioning flange 385, for example using a spider bearing. Bearing 389 is preferably chosen so that the axle 388 may slide axially within. This allows the bearing 389 to be an integral part of screen tensioning flange 385, simple assembly and disassembly of the unit, and simple access to the bearing for service or replacement.
The area surrounding bearing 389 within tensioning flange 385 provides a foam powder discharge outlet 410. A foam powder discharge collection cap 412 (
A foam powder feed mechanism 390 such as a screw or auger is mounted to axle 388. Feed mechanism 390 extends into housing 378. Central to the operation of this device is a generally cylindrical screen assembly or tube 391. Screen assembly 391 is made up of a suitably sized screen material and generally will be attached to flanges or rings 392 and 393 to provide overall cylindrical form to the screen assembly 391 and to provide attachment points for mounting and stretching of the screen. Flange 393 of the screening assembly is attached to tensioning flange 385.
Suitable screening materials include organic fabrics such as polyester and nylon as well as metal such as stainless steel mesh. A typical screening tube has a length-to-diameter ratio of in the range of 0.1 to 3, preferably in the range of 0.2 to 2.
Situated on the axle 388 is a beater assembly that is positioned inside the screening tube 391. The beater assembly includes one or more beater bars 395, 396, and 397 that are attached to and rotate with axle 388. The beater bars are generally positioned substantially parallel to the interior of the screening tube 391 and to the axis of the axle 388. Of course, the beater bars may be helical with respect to the axle 388 at an angle of zero degrees to 60 degrees to the axle 388. The beater bars are preferably adjustably attached to the brackets in order to provide for an adjustable gap width between the bars and the interior of screening tube 391. The beater bars may be constructed of a variety of materials such as metals, rubber and plastic, or a combination of materials such as metal and rubber.
Clearly, the size of the slots 414 shown in the
Another useful aspect of the invention is shown in
To optimize the operation of the inventive screening device 374, we have found that it is preferable to screen mixtures of both fine and coarse foam powder and foam pieces such that the mixture has a particle size range such that less than about half of the feed material comprises particles that are small enough to pass through the screen and the major portion of the feed material comprises foam particles having a particle size that doesn't pass through the screen. Qualitatively speaking, the beater bars via the larger particles “wipe” the screen and push the smaller particles through the screen openings.
Foam particles in the target size range are discharged from the screening equipment of step 324 (
In another variation of the present invention, a gaseous cooling medium is injected or sucked into foam powder as it is discharging from the mill, as schematically illustrated in
Sifter 408 (
Optionally, some amount of additional cooling medium may be introduced in conduits 406 and 414, and in sifter 408, using for example a centrifugal or an open-face fan. Alternatively a cyclone (not shown) may be utilized in conduit 406 and/or conduit 414 for enhanced cooling of the foam powder. These cyclones can be utilized by expelling gaseous cooling medium, which has been heated by foam powder, through the top of the cyclone, and introducing additional gaseous cooling medium at a lower temperature after the cyclone, for example at the material outlet at the cyclone bottom. This gaseous cooling medium exchange is accomplished while conveying the foam powder through the respective cyclones. Examples of suitable cooling media include those discussed above.
Processing sequence 520, illustrated in
In a preferred variation of the present invention, the final washing is carried out using a solvent that functions as a foam blowing agent when the foam powder is subsequently used in new foam. Methylene chloride, pentane, acetone and liquid carbon dioxide are examples of suitable liquids that can dissolve oil and grease, and are blowing agents in some foam systems such as PUR. Methylene chloride is preferred. In this inventive example, the final washing step can be carried out using a solvent that is a blowing agent. A solvent removal similar to step 526 (
Preparing Mixtures With Foam Powder
Processing module 400 (
The blending step typically results in the introduction of air, causing the formation of foam or air bubbles in the mixture. It is undesirable to have air bubbles in the blend when this is subsequently polymerized and it is thus desirable to deaerate the blend. The liquid blend may be deaerated during the storing step by keeping the blend in storage, preferably with low intensity stirring, until the air bubbles have escaped from the blend. Alternatively, continuous deaeration can be achieved through continuous centrifuging (not shown) of the blend in a vacuum,environment between steps 536 and 538 (
Generally, it is desirable to use an in-line mixer in blending step 536, thereby avoiding the incorporation of air in the blend. High shear mixers are preferred for use in blending step 536.
Processing sequence 540, shown in
In an alternative method (not shown) foam powder is added under vacuum to continuous blending step 536 (
Typically, the mill discharge is conveyed in a conveying step 584 to a storing step 586. Alternatively, the mill discharge is fed to a screen (not shown) that allows a predetermined particle size fraction to pass for conveying (not shown) to a storing step (not shown), while returning (not shown) the oversize fraction to the comminution step. Generally, it is desirable to deaerate the mill discharge using such deaeration techniques as have been described in connection with
Processing module 500 (
The foam powder may also be added to one or more liquids of processing step 614, shown in
As described in connection with
We have also found that the addition of a low concentration of active-hydrogen compounds (e.g., 0.01% to 5.0% by weight of polyol), to the polymeric foam pieces and polymeric foam powders, generally on the outside of the foam powder particles or pieces, results in improved material handling properties. Specifically, upon such addition, we have found that the foam pieces and foam powder are less prone to form a coating, also known as plating, on the surfaces of processing equipment. Indeed, in most instances, the plating is eliminated. Further, problems with handling due to static electricity are minimized. The active-hydrogen compound may be misted on the foam pieces or foam powder as it is transported in the processing equipment. Preferably, it is added to air used for pneumatic conveying or cooling of these foam products
A wide variety of polymeric foams including production contaminants may be processed using our inventive methods and devices of our invention. For example, if a PUR foam is processed, suitable polymerizable liquids for blending with foam powder include polyfunctional isocyanates or active-hydrogen compounds such as polyhydroxyl compounds, hydroxyl-terminated polyesters, and hydroxyl-terminated polyethers. On the other hand, if a polyimide foam is processed, a suitable polymerizable liquid for blending with foam powder includes acetic anhydride. The foam powder and acetic anhydride blend may subsequently be used to prepare a new foam by mixing and heating the blend with solid polyamide, 4-benzoyl pyridine, and glass microspheres. The present techniques may also be employed to prepare polyisocyanurate foam, wherein suitable polymerizable liquids for blending with foam powder include isocyanurates and active-hydrogen compounds because these compounds can be used to prepare polyisocyanurate foam.
The level of PUR foam powder that may be included in a new PUR foam typically ranges from about 3% to about 60% by weight. The methods, techniques, and devices of the present invention are suitable for comminuting and processing PUR foam containing foam skins and/or polymer sheet and/or paper at levels ranging from 0.1%, preferably from about 0.5%, to about 75% particularly when processing PUR bun trmmings. The resulting newly formed PUR foam can thus include processing or production contaminants at levels ranging from 0.003%, preferably from about 0.015% to about 65%, generally preferable is an amount in the ranges of 20% to 65%, 20% to 50%, 20% to and any sub-range up to that 65%. It is an advantage of this process that extremely large amounts of those polymeric foam skins may be included. New PUR foam can be made with foam powder in a wide range of density and hardness. For example, flexible slabstock foam that contains foam powder with production contaminants typically has a density in the range of about 13 to about 70 kg/m3. The hardness of this foam (as determined by the 25% IFD test in method ASTM D3574) is typically about 25 to 200 N/323 cm2. Foams with higher density and hardness are also possible; however, these have less commercial significance.
Flexible-slabstock polyurethane foam production scrap was obtained from trimming the skins from foam buns. The scrap contained dense skin material and polyethylene film, with the balance being polyurethane foam of varying density. This scrap material was first reduced to pieces with a size of approximately 1 cm. The foam pieces were then comminuted on 56-cm-diameter, 152-cm-length counter-rotating rolls such as those shown in
Flexible-slabstock polyurethane foam production scrap was obtained from trimming the skins from buns of foam made with polyether polyols. The scrap material included 2.3% by weight of high-density polyethylene film with a thickness of about 25 microns, and 30% by weight of dense skin material, with the balance being polyurethane foam of varying density. This scrap material was first reduced to pieces with a size of approximately 3 cm by means of a rotary grinder. The foam pieces were then comminuted on 30-cm-diameter, 45-cm-length counter-rotating rolls such as those shown in
A slurry sample was prepared by mixing 15 parts of the fine polyurethane powder described in Example 1 with 100 parts of VORANOL® 3137 polyether polyol from The Dow Chemical Company. This polyol is a liquid polyhydroxyl compound having a viscosity of about 460 centipoise at a temperature of 25° C.
The beneficial size reduction effects which are obtained by high-shear mixing of polyurethane powder in a polyhydroxyl compound are illustrated in
The results are shown in the graphs depicted in
Pieces of polyurethane foam with a size of approximately 1 cm were loaded into a bin. The bin had a 1 ft2 open area on the bottom that was covered with a screen. The screen had both 4-inch by 4-inch openings and 1-inch by 1-inch openings in it. The foam chunks did not fall out of the opening in the screen when the bin was at rest. The bin was then agitated sinusoidally in a direction parallel to the screen at a frequency of about 3 Hz and an amplitude of about four inches. While the bin was agitated, the foam chunks fell out through the screen at a rate of about 4 ft3/min. When the agitation was stopped, flow of the foam chunks also stopped.
A slurry of 16.7% by weight of the fine powder described in Example 1 in VORANOL 3137 was prepared. The slurry contained 10 volume percent air as shown by volume change upon settling for 48 hours. The slurry was pumped one-pass through a Cornell D-16 Versator at 10 gpm and a vacuum of −27 in. Hg (about 0.01 bar absolute pressure). The resulting slurry contained no measurable entrained air.
The fine powder described in Example 1 was mixed into polyol under an atmosphere of carbon dioxide from which the air had been purged. The resulting slurry had less than 12.6% entrained gas bubbles by volume (presumably carbon dioxide). An identical slurry mixed under air, without CO2, had 16% entrained gas bubbles by volume (presumably air).
96. A powder having a maximum particle size of 2 mm, comprising a contaminant powder of a contaminant and at least 5% by weight of a comminuted polyurethane foam powder, wherein the contaminant is selected from the group consisting of polymer sheeting, and paper, further wherein the comminuted polyurethane foam powder is a powder of flexible reversibly deformable foam having a majority of open cells.
97. The powder of claim 96 containing substantially no rigid polyurethane foam.
98. The powder of claim 96 containing said contaminants in the range from about 0.1% to about 75% by weight.
99. The powder of claim 96 containing said contaminants in the range from about 0.5% to about 75% by weight.
100. The powder of claim 96 wherein said comminuted polyurethane foam powder has been comminuted from polyurethane foam having cells with cell walls.
101. The powder of claim 100 wherein said comminuted polyurethane foam powder has substantially no remaining cells.
102. The powder of claim 96 having a particle size ranging from about 0.001 mm to about 2 mm.
103. The powder of claim 96 having a particle size ranging from about 0.001 mm to about 0.25 mm.
104. The powder of claim 96 having a particle size ranging from about 0.001 mm to about 0.150 mm.
105. The powder of claim 96 having a particle size ranging from about 0.001 mm to about 0.045 mm.
106. The powder of claim 96 having a particle size ranging from about 0.001 mm to about 0.020 mm.
107. The powder of claim 96 having a particle size ranging from about 0.001 mm to about 0.010 mm.
108. The powder of claim 96 wherein the contaminated polymeric foam comprises polyurethane foam that is contaminated with polyurethane foam skins.
109. The powder of claim 96 wherein the contaminated polymeric foam comprises polyurethane foam that is contaminated with polymeric sheet.
110. The powder of claim 109 wherein the polymeric sheet comprises a polymer selected from polyethylene, polypropylene, and polystyrene.
111. The powder of claim 110 wherein the polymeric sheet comprises polyethylene.
112. The powder of claim 111 wherein the polymeric sheet comprises polyethylene with a softening point less than about 135° C.
113. The powder of claim 96 wherein the contaminated polymeric foam comprises polyurethane foam that is contaminated with paper.
114. The powder of claim 96 consisting essentially of comminuted polyurethane and polyurethane foam skins having a size between 0.001 mm and about 2 mm.
115. The powder of claim 114 consisting essentially of particles having a size between 0.001 mm and about 0.25 mm.
116. The powder of claim 114 consisting essentially of particles having a size between 0.001 mm and about 0.150 mm.
117. The powder of claim 114 consisting essentially of particles having a size between 0.001 mm and about 0.045 mm.
118. The powder of claim 114 consisting essentially of particles having a size between 0.001 mm and about 0.020 mm.
119. The powder of claim 114 consisting essentially of particles having a size between 0.001 mm and about 0.010 mm.
120. The powder of claim 96 consisting essentially of comminuted polyurethane and polymeric sheeting and having a particle size between 0.001 mm and about 2 mm.
121. The powder of claim 120 consisting essentially of comminuted polyurethane and polymeric sheeting and having a particle size between 0.001 mm and about 0.25 mm.
122. The powder of claim 120 consisting essentially of comminuted polyurethane and polymeric sheeting and having a particle size between 0.001 mm and about 0.150 mm.
123. The powder of claim 120 consisting essentially of comminuted polyurethane and polymeric sheeting and having a particle size between 0.001 mm and about 0.045 mm.
124. The powder of claim 120 consisting essentially of comminuted polyurethane and polymeric sheeting and having a particle size between 0.001 mm and about 0.020 mm.
125. The powder of claim 120 consisting essentially of comminuted polyurethane and polymeric sheeting and having a particle size between 0.001 mm and about 0.010 mm.
126. The powder of claim 120 wherein the polymeric sheeting comprises a polymer selected from polyethylene and polypropylene and polystyrene.
127. The powder of claim 126 wherein the polymeric sheet comprises polyethylene.
128. The powder of claim 127 wherein the polymeric sheet comprises polyethylene with a softening point less than about 135° C.
129. The powder of claim 96 consisting essentially of comminuted polyurethane and paper and having a particle size between 0.001 mm and about 2 mm.
130. The powder of claim 96 consisting essentially of comminuted polyurethane and paper and having a particle size between 0.001 mm and about 0.25 mm.
131. The powder of claim 96 consisting essentially of comminuted polyurethane and paper and having a particle size between 0.001 mm and about 0.150 mm.
132. The powder of claim 96 consisting essentially of comminuted polyurethane and paper and having a particle size between 0.001 mm and about 0.045 mm.
133. The powder of claim 96 consisting essentially of comminuted polyurethane and paper and having a particle size between 0.001 mm and about 0.020 mm.
134. The powder of claim 96 consisting essentially of comminuted polyurethane and paper and having a particle size between 0.001 mm and about 0.010 mm.
160. The powder of claim 96 further comprising a powder of a polyurethane foam skin of said flexible reversibly deformable foam.