U.S. patent application number 11/711654 was filed with the patent office on 2007-07-05 for polymeric foam powder processing techniques, foam powders products, and foam produced containing those foam powders.
This patent application is currently assigned to Mobius Technologies, Inc.. Invention is credited to Bryan Martel, Herman Stone, Robert Villwock.
Application Number | 20070155843 11/711654 |
Document ID | / |
Family ID | 22626289 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070155843 |
Kind Code |
A1 |
Martel; Bryan ; et
al. |
July 5, 2007 |
Polymeric foam powder processing techniques, foam powders products,
and foam 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.
Inventors: |
Martel; Bryan; (Grass
Valley, CA) ; Villwock; Robert; (Grass Valley,
CA) ; Stone; Herman; (Williamsville, NY) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
1650 TYSONS BOULEVARD
SUITE 400
MCLEAN
VA
22102
US
|
Assignee: |
Mobius Technologies, Inc.
Grass Valley
CA
|
Family ID: |
22626289 |
Appl. No.: |
11/711654 |
Filed: |
February 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11133281 |
May 20, 2005 |
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11711654 |
Feb 28, 2007 |
|
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10698436 |
Nov 3, 2003 |
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11133281 |
May 20, 2005 |
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09748307 |
Dec 21, 2000 |
6670404 |
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10698436 |
Nov 3, 2003 |
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60172081 |
Dec 23, 1999 |
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Current U.S.
Class: |
521/50 |
Current CPC
Class: |
B29K 2711/14 20130101;
B29K 2023/12 20130101; Y02W 30/62 20150501; C08J 9/35 20130101;
C08G 2110/005 20210101; B29K 2705/00 20130101; B29L 2031/44
20130101; C08J 3/12 20130101; B29K 2705/12 20130101; B29L 2031/7322
20130101; C08G 2110/0008 20210101; B29K 2105/06 20130101; B29K
2105/04 20130101; B02C 25/00 20130101; C08J 2375/04 20130101; B02C
4/28 20130101; B29K 2023/06 20130101; B29K 2075/00 20130101; B02C
4/04 20130101; B29B 17/0404 20130101; Y02W 30/52 20150501; B02C
4/42 20130101; B29B 2017/0484 20130101; B29C 44/3461 20130101; B29B
17/00 20130101; B29B 17/02 20130101; B07B 1/20 20130101; B29K
2711/12 20130101; C08J 2475/04 20130101; B29L 2007/00 20130101;
C08L 75/04 20130101; B29K 2025/00 20130101; B29L 2031/744 20130101;
B29B 17/0412 20130101; B29B 2017/0224 20130101; B29K 2709/08
20130101; B29L 2009/005 20130101; C08J 11/06 20130101; B29K
2105/065 20130101; B29B 2017/0203 20130101; C08L 75/04 20130101;
C08L 2666/20 20130101 |
Class at
Publication: |
521/050 |
International
Class: |
C08J 9/00 20060101
C08J009/00 |
Claims
1. A device for collecting foam powder from a mill having a first
roll including a first cylindrical surface and a second roll
including a second cylindrical surface, the device comprising: a) a
first side wall having a first edge, wherein the first edge is
adapted for positioning proximal the first cylindrical surface and
substantially parallel to the first cylindrical surface, b) a
second side wall having a second edge, wherein the second edge is
adapted for positioning proximal the second cylindrical surface and
substantially parallel to the second cylindrical surface, c) a
bottom joining the first side wall and the second side wall, d) a
first end wall joining the bottom and the first and second side
walls, wherein the first end wall includes a first end wall edge
that is adapted for positioning proximal the first and second
cylindrical surfaces and substantially perpendicular to the first
cylindrical surface, e) a second end wall opposing the first end
wall and joining the bottom and the first and second side walls,
wherein the second end wall includes a second end wall edge that is
adapted for positioning proximal the first and second cylindrical
surfaces and substantially perpendicular to the first cylindrical
surface, f) a gaseous flow inlet; and g) a gaseous flow outlet.
2. The device of claim 1 additionally comprising at least one
scraper blade adapted for positioning proximal a first of the first
and second cylindrical surfaces and substantially parallel to the
first cylindrical surface.
3. The device of claim 1 additionally comprising an auger
positioned inside the chamber for discharging foam powder from the
chamber.
4. The device of claim 1 wherein the first and second side wall
edges include a material softer than the first and second
cylindrical surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. Ser.
No. 11/133,281, filed on May 20, 2005; which is a continuation
application of Ser. No. 10/698,436 filed on Nov. 3, 2003; which is
a divisional application of Ser. No. 09/748,307, filed on Dec. 21,
2000; which claims priority to provisional application No.
60/172,081 filed on Dec. 23, 1999. The disclosure of the prior
application is considered part of and is incorporated by reference
in the disclosure of this application.
FIELD OF THE INVENTION
[0002] 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
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] "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.
[0009] "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.sub.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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] None of the documents cited above disclose the inventive
processes and foam products described herein.
SUMMARY OF THE INVENTION
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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
[0027] FIG. 1 is a block diagram schematically illustrating the
generic polymeric foam powder process of this invention.
[0028] FIG. 2 is a flowchart schematically showing a fragmenting
and screening portion of the process illustrated in FIG. 1.
[0029] FIG. 3 shows a schematic view of a foam piece storage
container having a discharge mechanism of the present
invention.
[0030] FIG. 4 shows a schematic view of a foam powder conveying
system.
[0031] FIG. 5 shows a perspective view, with parts broken away, of
an open-face fan.
[0032] FIG. 6 is a schematic representation of a cyclone.
[0033] FIG. 7 is a flowchart schematically showing an alternative
fragmenting and screening portion of the process illustrated in
FIG. 1.
[0034] FIG. 8 is a flowchart schematically showing a comminution
and screening portion of the process illustrated in FIG. 1.
[0035] FIG. 9 is a flowchart schematically showing a technique for
controlling conveyor speed by a roll mill.
[0036] FIG. 10A shows an inventive differential speed roll mill
device.
[0037] FIG. 10B shows a controller suitable for controlling the
differential speed roll mill device of FIG. 10A.
[0038] FIG. 11 shows a schematic perspective view of a collection
chamber of the present invention utilizing the quench process.
[0039] FIG. 12 is a schematic view of the positioning of the
collection chamber illustrated in FIG. 11.
[0040] FIG. 13A shows a perspective, exploded view of the inventive
screening device.
[0041] FIG. 13B shows a perspective view of the a flange shown in
FIG. 13A.
[0042] FIGS. 14A and 14B schematically depict the airflow through
the screening device of FIG. 13A.
[0043] FIG. 14C shows an air controller on the screening device of
FIG. 13A.
[0044] FIG. 15 depicts the screen-tension adjustment mechanism for
the sifter screen of FIG. 13A.
[0045] FIG. 16 is a schematic representation of a comminution and
screening device as illustrated in FIG. 1.
[0046] FIG. 17 is a flowchart schematically the solvent-washing
feature of the process illustrated in FIG. 1.
[0047] FIG. 18 is a flowchart schematically showing the continuous
mixing sequence of the process illustrated in FIG. 1.
[0048] FIG. 19 is a flowchart schematically showing the batch
mixing sequence of the process illustrated in FIG. 1.
[0049] FIG. 20 is a flowchart schematically depicting a comminution
step of the process illustrated in FIG. 1.
[0050] FIG. 21 is a flowchart schematically showing another
processing sequence of the process illustrated in FIG. 1.
[0051] FIG. 22 is a graphical illustration of a foam powder size
distribution made according to the invention as shown in the
Examples.
[0052] FIG. 23 is a graphical illustration of a foam powder size
distribution made according to the invention as shown in the
Examples.
DESCRIPTION OF THE INVENTION
[0053] 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.
Overall Process
[0054] FIG. 1 shows a preferred variation of the inventive
procedure in which an integrated process is employed for
comminution of polymeric foams to prepare foam powder particles and
subsequently incorporating the foam powder in newly formed
polymeric foams. The various processing steps of this inventive
process may be combined to function cooperatively to form an
integrated process as is schematically illustrated in FIG. 1. FIG.
1 provides a summarized schematic illustration of an integrated
process 150 having processing procedures 200, 300, 400, and 500.
Each processing module includes one or more processing steps or
sequences. Processing module 200 includes processes for fragmenting
of articles containing polymeric foam, to prepare smaller foam
pieces. This module comprises a first-stage comminution, as is
described in more detail in connection with FIGS. 2 and 7. FIGS. 3,
4, 5, and 6 show configurations of equipment for conveying foam
from one stage to another in the inventive process. Processing
module 300 in FIG. 1 shows a second-stage comminution in which foam
powder particles are prepared from the foam pieces resulting from
the processes carried out in processing module 200. Module 400
depicted in FIG. 1, includes processes for preparing mixtures of
foam powder and one or more polymerizable liquids. Optionally,
mixtures of foam powder and polymerizable liquid may be comminuted
using the methods of processing module 400, thereby providing a
third-stage comminution of foam particles. Module 500 in FIG. 1
includes process steps for preparing solid polymeric foams by
adding various ingredients to a mixture of foam powder and
polymerizable liquid, and subsequently polymerizing the mixture to
form a new foam that incorporates the foam powders of the present
invention.
First-Stage Comminution
[0055] Processing module 200 (FIG. 1) includes processing sequence
210, shown in FIG. 2, and alternative processing sequence 250,
depicted in FIG. 7. These two processing sequences generally differ
in the types of polymeric foam products and foam articles that are
fragmented in the first-stage comminution. Returning to FIG. 2, a
first step 212 in processing sequence 210 includes fragmenting foam
products and articles containing uncontaminated foam or foam
articles that are contaminated with production contaminants only.
The expression "uncontaminated foam" as defined herein, includes
polymeric foam products or articles that are substantially free
from production contaminants and other contaminants such as metal,
wood, fiber, and other polymeric compounds. As mentioned above, the
expression "production contaminants" includes materials that are
typically present in the manufacturing of polymer foam, such as
paper, plastic-coated paper, and polymeric films or netting as well
as foam skins. Foam skins are layers of non-foam or very high
density foam that are formed during the foam polymerization
procedures. These plastic films are used to line the forms used to
make the "buns" or "loaves" discussed above. The plastics used are
typically polyolefins such as polyethylene or polypropylene,
although other polymers are suitable. Suitable methods for foam
fragmentation step 212 include size reduction using any of the
technologies that are well known to those of ordinary skill in the
art. Examples of size-reduction equipment suitable for fragmenting
foam in step 212 (FIG. 2) include comminution equipment types such
as roll crushers utilizing two rolls counter-rotating at different
speeds, impact mills utilizing for example hammer crushers,
shredders employing shredder teeth on a single roll or using
sawtooth and counter-rotating spacer assemblies, ring mills
employing hooked rings attached to a rotor spinning at a high
speed, and ring-roller mills utilizing rollers in conjunction with
grinding rings. Examples of preferred size reduction equipment for
step 212 include rotary grinders, hammer mills, and shear
shredders.
[0056] 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.
[0057] 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.
[0058] 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 (FIG. 2). Foam pieces
discharging from the fragmentation equipment of step 212 are
screened in step 214 resulting in a target size, such as foam
pieces no larger than about 10 cm, and oversize pieces including
foam pieces larger than the target size. Suitable equipment for
screening step 214 includes well known screening equipment using
revolving, shaking, vibrating, oscillating or reciprocating
screens. Oversize pieces are recycled to the fragmentation
equipment in step 216 of processing sequence 210 (FIG. 2).
Recycling step 216 includes the use of devices such as conveyor
belts, conveying screws, or pneumatic conveying, i.e. conveying in
a gaseous flow, to return these foam pieces to the fragmentation
equipment of step 214. Foam pieces within the target size range are
conveyed in step 218 to foam piece storing step 220, using such
conventional conveying techniques as conveying belts, conveying
screws, or pneumatic conveying. Typically, fragmentation 5
equipment suitable for the present technology has built-in
components for screening and recycling of oversize pieces (steps
212, 214, and 216).
[0059] 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 FIG. 3.
The inventive discharge method includes storing the foam pieces in
a storage container 230, having a bottom section comprising a
mechanically activated screen 232 employing for example vibrating,
oscillating, or shaking movement, and preferably having a screen
aperture, i.e. the size of the screen opening, exceeding the
largest diameter of the largest foam pieces, i.e. the maximum size
of the foam pieces, by at least about 2%. A flexible connection 234
can be provided between screen 232 and storage container 230 to
facilitate mechanical activation of the screen. The inventive
method additionally includes a conveying surface 236 moving
underneath the screen.
[0060] Optionally, the moving conveying surface has protrusions 238
(FIG. 3) thereon, which reach in close proximity to the screen
within a distance about equal to the dimension of the screen
aperture. These protrusions may be brackets or flexible or rigid
strips or bars mounted on the conveyer surface. Preferably, these
protrusions extend from about 0.3 cm to about 7.5 cm from the
conveying surface. The conveying surface may be inclined from the
direction, or plane, parallel to the screen by an angle of
0.degree. to 30.degree. to provide for a consistent discharge rate
from all parts of the storage container. We have found that the
screen provides support for the material, i.e., the foam pieces, in
the storage container and thereby reduces the weight of the
material on the conveying surface and allows the use of simpler,
more cost-effective, and less massive conveying equipment. The
combination of the screen and the conveying surface prevent
gravity-assisted flow of foam pieces from the storage facility when
the conveying surface and the screen are not activated.
[0061] 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 FIG. 4. A first fan
270 communicates with inlet 272 of cyclone 274, feeding foam pieces
or foam powder particles suspended in air into cyclone 274. A
second fan 276 communicates with cyclone outlet 278 to remove air
or other conveying gas from the cyclone through outlet 278. The
fans are usually designed and operated such that an optimum
downward pressure is realized in cyclone material outlet 280 to
eliminate problems with plugging of the cyclone unique to handling
foam pieces or foam powders. The downward pressure in the cyclone
material outlet 280 may also be adjusted by changing the pressure
in cyclone air outlet 278 with, for example, adjustable baffles,
filters, a baghouse, or other restrictions. Both fans preferably
use a so called "open-face" design.
[0062] FIG. 5 schematically illustrates an open-face fan 282. The
fan has a substantially cylindrical housing 284, a front cover 286
and a rear cover 288. Inside the housing 284 is a disk shaped plate
290 mounted such that a drive mechanism (not shown) rotates the
disk when in use. On the disk are mounted several paddle shaped
vanes such as vanes 294 and 296. There is a substantial clearance
between the vanes and the inside of front cover 286 resulting in an
open-face design. An inlet is provided at opening 298 of front
cover 286. An outlet 299 is provided at the outer perimeter of the
cylindrical chamber. When disk 290 is rotated, a centrifugal action
is provided for conveying air, or foam powder particles suspended
in air, from inlet 298 to outlet 299.
[0063] 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 FIG. 6,
that is suspended from a top portion 285 of a cyclone 287 and that
extends down and is attached to a cyclone material outlet 289
located at bottom 291 of the cyclone. Air flow inside the cyclone
causes flexible element 283 to flex and move around inside the
cyclone, continuously removing foam from the inside of cyclone
walls 287 and from cyclone material outlet 289. Suitable materials
for flexible element 283, include rope, plastic and rubber tubing
or hose, plastic chain and metal chain. Most highly preferred is a
rope comprised of an engineering polymer such as aromatic polyamide
polymers, e.g., Kevlar. Air enters the cyclone at inlet 293 and is
discharged through outlet 295.
[0064] The conveying devices and procedure shown in FIGS. 4-6 and
portions of them may be used in a variety of ways for conveying
both foam pieces and foam powder among equipment shown herein.
Alternative First Comminution Step
[0065] As shown in FIG. 7, processing sequence 250 of process
module 200 (FIG. 1) may be used on polymeric foam products and
articles that are contaminated with, for example, wood, fiber,
leather, ferrous and non-ferrous metals, plastics and glass, such
as might be found in chairs, car seats, and the like. As mentioned
above, we refer to this class of contaminants as "consumer
contaminants" or "post-consumer contaminants." The foam-containing
products and articles are fragmented in a fragmenting step 252,
using size reduction equipment that may be similar to the equipment
described in connection with foam fragmentation step 212 of
processing sequence 210 shown in FIG. 2. It will be understood that
the specific type of size reduction equipment in step 252 depends
on the type of contamination. For example, metal contamination
requires size-reduction equipment with a higher energy input and
higher wear resistance than equipment associated with fabric
contamination.
[0066] 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.
[0067] The foam pieces that are thus obtained may be screened and
recycled according to size in steps 258 and 260 (FIG. 7), which are
similar to steps 214 and 216 respectively of processing sequence
210 depicted in FIG. 2. Returning to FIG. 7, the target size
fraction of the foam pieces is conveyed in a step 262 and stored in
a step 264, wherein these steps are similar to steps 218 and 220
respectively of FIG. 2, including the inventive step of discharging
the foam pieces from the storage equipment employing a mechanically
activated screen described in connection with FIG. 3.
Milling Step Controller
[0068] As shown in processing sequence 300, illustrated in FIG. 8,
foam pieces including production contaminants are conveyed in step
310 to a milling or comminuting step 314, optionally removing
conveying gas as shown in step 312. Suitable conveying equipment
includes the equipment described in connection with FIGS. 4-6.
However, it is well known that it is difficult to dependably
control the feed rate of foam pieces due to their low bulk density
and tendency to bridge. According to the present invention, it has
now been discovered that the mill throughput can be optimized using
a conveying method wherein the rate of conveying is controlled by
the comminution rate. In one variation of this technique, the power
consumption of the mill is monitored during the comminution
process. An electrical feedback technique is then employed to
electrically couple the mill power consumption to the feed rate.
For example, if an excessive amount of foam pieces is conveyed on
the mill, increased mill power consumption typically results. The
signal resulting from the HIGHER power consumption can be fed to
the conveying equipment, causing the conveying equipment to reduce
the conveying rate of foam pieces to the mill. Similarly, when the
feed rate of foam pieces to the mill is too low, the mill typically
uses less power. The mill's reduced power signal can then be fed
back to the conveying equipment, causing it to increase the
conveying rate. The correlation between mill power consumption and
foam feed rate may be determined experimentally for different types
of foam. The novel mill feed control method is illustrated in FIG.
9, wherein the roll mill motor current draw signal 362 is fed to a
PID (proportional-integral-derivative) controller 364, which then
controls conveyor speed 366. PID controllers and the technology for
using PID controllers are well known to those of ordinary skill in
the art.
[0069] 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
[0070] Foam pieces resulting from the methods of processing module
200 are comminuted employing a comminution step 314, see FIG. 8, to
prepare a foam powder preferably having a particle size of about 2
mm or less, preferably less than about 0.25 mm, but likely larger
than about 0.001 mm, e.g., 0.005 mm, including size ranges such as
0.001 mm to 0.010 mm, 0.001 mm to 0.020 mm, 0.001 mm to 0.045 mm,
0.001 mm to 0.150 mm, 0.005 mm to 0.010 mm, 0.005 mm to 0.020 mm,
0.005 mm to 0.045 mm, 0.005 mm to 0.150 mm, and any sub-ranges of
these values. It will be understood that foam powder having a
particle size of 2 mm or less contains the broken parts of foam
bubbles or cells without any substantial volume fraction (e.g.,
less than about 7.5%, preferably less than about 5%, and most
preferably less than about 2.5% by volume) of complete cells or
bubbles. Preferably, a majority (or all) of the particles are of
such a size that, when viewed on a particle-by-particle basis, do
not have elongated sections left from the microscopic foam
structure jutting from a central junction. This comminution step is
a second-stage comminution in the inventive process. We have found
that polymeric foam that is contaminated with production
contaminants such as polymeric foam skins, paper, and plastic film
or netting may be effectively comminuted on a two-roll mill
employing a quenching technique for rapidly cooling the discharged
foam powder. The comminuted foam powder, in the noted particle
ranges, may contain as much as 75% (by weight) of polymeric foam
skins or smaller amounts, including the ranges of 20% to 60%, 20%
to 50%, 20% to 65% and any sub-range up to that 75%. It is an
advantage of this process that extremely large amounts of those
polymeric foam skins and other production contaminants may be
included and yet the small particle sizes of the foam powder
attained.
[0071] 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 comminuted foam particles having any
one of the production contaminants. 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
[0072] Foam powder is discharged from the mill in discharging step
316, depicted in FIG. 8. Comminution of polymeric foam on a mill
such as a two-roll mill causes the temperature of the foam to
increase as it passes through the grinding zone. For example,
comminuting foam can raise the foam temperature as high as
150.degree. C., which is above the softening temperature of
commonly used thermoplastics such as polyethylene, polypropylene,
polystyrene, and the like. Such temperature increases can result in
thermal degradation of the polymeric foam, particularly when the
foam is subjected to several passes through the mill. For example,
the softening temperature of high-density polyethylene is about
135.degree. C. The softening or melting of thermoplastic materials
during comminution results in reduced mill efficiency since those
materials will tend to adhere to the mill surface or agglomerate to
form hard flakes or lumps during comminution. In addition,
increased temperatures affect the comminution characteristics of
the foam. For example, at those temperatures, PUR foam and/or foam
powder will form a layer on the mill rolls. Although internally
cooled mill rolls provide some beneficial cooling, they generally
do not provide the desired level of cooling. We have found that if
we "quench" the foam powder product as it exits the roller
surfaces, the cooled foam powder does not agglomerate nor does it
stick to the rollers. Specifically, it is highly desirable to
direct the cooling medium directly at the nip between the two
rollers to achieve a maximum benefit of the procedure. Likely,
there is also a direct and/or indirect heat transfer effect on the
rolls themselves. By "quench" we mean that the difference in
temperature between the foam powder and the cooling medium is from
5.degree.-10.degree. up to 125.degree. C., preferably between
25.degree. C. and 125.degree. C., and most preferably between
50.degree. C. and 100.degree. C. Preferably, the cooling medium is
introduced at a temperature less than 115.degree. C. It is also
highly desirable that the cooling medium be introduced onto the
foam powder product as it exits the roller surfaces e.g., at the
nip between the rollers, in turbulent flow and further, the
resultant mixture of foam powder and cooling medium be in turbulent
flow. Preferably, the mass flow rate of the cooling medium has a
value that is at least 3% of the mass flow rate of the foam powder
product. For most of the powder produced by this process, this
value is also the minimum value suitable for dilute phase pneumatic
conveying. More preferably, the mass flow rate of the cooling
medium has a value that is at least 30% of the mass flow rate of
the foam powder product.
[0073] 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 m.sup.3/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.
[0074] 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.
[0075] 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 FIGS.
10A and 10B. FIG. 10A shows a pair of rollers: a faster, driven
roll 311 and a relatively slower roll 313 that is driven by the
fast roll 311. By "faster" and "slower" in this context, we refer
to the relative surface speeds of the rolls. There is a
differential speed where the rolls meet and shear the foam between
them. In this variation of the invention, the fastest roll 311 may
be driven by an electric motor or the like (not shown), while the
second roll 313 is indirectly driven by the first roll through the
friction between the directly driven roll and the material in the
nip between the two rolls.
[0076] The speed reduction on the slow roll 313 may be achieved by
mechanical braking in the depiction in FIG. 10A using brake shoes
315 in order to maintain the desired speed ratio between the two
rolls. Of course, the speed reduction may be obtained with the
generation of electrical or hydraulic power. We have found that the
differential in surface speed between the two rolls vastly improves
the efficiency of the comminution step. The ratio. of the
respective surface speeds may be between 10:1 and just above 1:1,
preferably between 10:1 and 3:1, more preferably between 8:1 and
3:1, and most preferably between 5:1 and 3:1. The peripheral speed
of the rolls is generally 0.1 to 10 m/s, preferably 0.1 to 4.5 m/s,
and most preferably 0.1 to 3.0 m/s.
[0077] FIG. 10B shows a schematic outline of a control scheme for
the FIG. 10A device in which torque output from the slow roll is
monitored by controller 314 and used to control torque feedback
from the slow roll 313 to the fast roll 311 in order to maintain a
desired differential in the roll speeds.
[0078] On to the quench feature of this inventive device.
[0079] An example of a quench feature is employed in the FIGS. 11
and 12. The quench is found in collection chamber 402. First side
wall 421 of the chamber 402 has an edge 422 that is positioned in
close proximity to cylindrical surface 424 of first roll 426 of a
two-roll mill having a second roll 428. Edge 422 is substantially
parallel to cylindrical surface 424. A chamber bottom 430 connects
side wall 421 with a second side wall (not shown) having an edge
(not shown) that is positioned in close proximity to cylindrical
surface 432 of second roll 428. A first end wall 434 connects the
two side walls. This end wall has an edge that is positioned in
close proximity to cylindrical surfaces 424 and 432. End wall 434
is substantially perpendicular to cylindrical surfaces 424 and 432.
A second end wall 438 similar to the first end wall 434 is
positioned opposite the first end wall. Preferably, the edges of
the side walls and the end walls are snugly fitted to the rolls to
avoid any substantial gaps between the rolls and the edges.
Preferably, the edges of the side walls 422 and end walls 436 are
provided with a rim made from a material that is softer than the
rolls, for example a polymeric material, in order to closely fit
the rolls without causing damage to the surface of the rolls.
[0080] 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.
[0081] As shown in FIG. 12, the rolls of a two-roll mill, such as
roll 426 are commonly mounted in side brackets 448 and 450 of the
mill. Chamber 402 is mounted (not shown) to the side brackets using
such mounting means as are well known to those of ordinary skill in
the art. In an alternative design (not shown) the chamber can
extend along the entire length of the rolls if side brackets 448
and 450 are adapted to provide space for access to inlet 444 and
outlet 446. Scraper bars such as scraper bar 440 are mounted to
side brackets 448 and 450. Alternatively, the scraper bars can be
mounted to chamber 402. Preferably, the scraper bars are mounted in
adjustable positions to provide an effective fit with the mill roll
surfaces. Typically, rolls 426 and 428 are provided with guides,
such as guides 452 and/454 (FIG. 12) to keep the foam away from the
ends of the rolls.
[0082] As noted in FIG. 8, the foam powder is conveyed from the
quenching step 318 in a conveying step 320. Pneumatic conveying
procedures and devices such as shown in connection with FIGS. 4-6
may be used to convey foam powder to a foam powder screening step
324. When pneumatic conveying is utilized, it is preferable to
separate the foam powder in a conveying gas removal step 322 (FIG.
8). Conventional cyclones may be used in step 322, but it is
preferable to use a cyclone such as described in connection with
FIG. 6.
[0083] The foam powder may be screened using any of the
conventional types of screening devices described in connection
with screening step 214 of processing sequence 210 shown in FIG.
2.
[0084] Returning to FIG. 8, oversize foam particles are returned to
comminution step 314 through a recirculation loop in step 326.
Typically, step 326 includes pneumatic conveying and the use of a
cyclone (not shown) to separate the recirculated foam from the
pneumatic air, using a conventional cyclone, or a cyclone such as
is described in connection with FIG. 6, in recirculating the
oversize foam particles to comminution step 314, shown in FIG. 8.
Also, it is advantageous to discharge oversize particles through an
optional novel purging step 328 when the oversize fraction contains
a significant quantity of materials that are generally either
post-consumer contaminants and/or contaminants that are difficult
to pulverize in comminution step 314. Purging of the recirculation
loop is accomplished through a device or component that is adapted
for removing material from the loop, such as a diverter valve (not
shown).
Sifter
[0085] In any event, foam powder screening step 324 (FIG. 8) is
preferably carried out in inventive screening device or sifter 374.
FIGS. 13A, 13B, 14A, 14B, 14C, and 15 show an inventive foam sifter
that reduces or eliminates many of the processing difficulties
associated with the conveying and handling of foam powder, those
difficulties including coatings on the processing equipment, the
blinding of screens, and bridging. As will be described in greater
detail below, inventive sifter 374 has several significant benefits
that derive from its mechanical design. In particular, the use of
the rotating beater bars in close proximity to the cylindrical
screen unit allows high efficiency sifting, the placement of the
screen close to the sifter housing in conjunction with the use of
vacuum promotes very high speed flow in a semi-circumferential flow
around the screen unit carrying the tenacious foam powder away form
the screen, the axial flow of air through the screen unit carries
the larger pieces of foam without bridging or binding, and the
design of the sifter screen permits adjustment on the fly.
[0086] FIG. 13A shows a perspective, exploded view of the inventive
sifter 374. The inventive device includes a foam powder inlet
section 376, and a screen housing 378 by a flange 382. A flange for
attachment of screening tube 393 is attached to flange 385.
Threaded rods 386 (perhaps three or more) are movably attached to
screen tensioning flange 385 via threaded holes 356. The threaded
rods 356 may have wrench flats or the like with shoulders 387 that
support springs 375 at the other end. The details of screen
tensioning flange 385 are shown in FIG. 13B. The springs 375 are
compressed between shoulders 387 and ring flange 392. Ring flange
392 is movably supported over flange 377 of foam powder inlet
section 376. The ring flange 392 is provided with a second flange
for attachment of screening tube 391 positioned opposite flange
393. The threaded rods 386 may be turned as the sifter operates. By
turning rods 386, the ring flange 392 moves axially along flange
377 and thus provides axial tension to screening tube 391. Springs
375 provide a passive mechanism for maintaining the tension on the
screening tube at an approximately constant level as the screening
tube 391 stretches or relaxes.
[0087] 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.
[0088] The area surrounding bearing 389 within tensioning flange
385 provides a foam powder discharge outlet 410. A foam powder
discharge collection cap 412 (FIG. 13A) is provided to receive the
coarse particles--that may comprise fine foam powder, coarse foam
powder, and foam pieces--which are discharged through foam powder
discharge outlet 410 and funnel them to coarse foam powder outlet
416. Cap 412 is mounted such that a gap 414, having an adjustable
width (shown below and discussed in more detail with respect to
FIG. 14B), is situated between flange 385 and the cap.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] FIGS. 14A, 14B, and 14C depict various aspects of the
operation of the inventive screening device. In FIG. 14A, a vacuum
or suction is applied to the outlet of foam powder discharge outlet
383. This suction, in turn, draws gas flow through the annular
space between screen 391 and screen housing 378. Screen 391 and
screen housing 378 are in close proximity, e.g., a spacing of 2
inches or less in many instances, and this proximity provides a
high speed gas flow through that annular space thereby carrying
away any foam particles or foam powder that has passed through the
screen 391. The average gas velocity around the semi-circular path
in the noted annular space is between 2,500 and 6,500 feet per
minute (fpm), preferably between 4,000 and 5,500 fpm, and most
preferably about 4,500 and 5,000 fpm. This gas flow is generally
considered to be somewhat isolated from the gas flow through the
center of the screening assembly 391.
[0093] FIG. 14C shows an optional variation, which enhances the
ability of the device to remain clog-free. We have found that by
"activating" or shaking the screen material, for example by a
vibrating or flexing the screen material of screening tube 391, the
screen remains generally free of the blinding problems commonly
associated with screening foam powder. A vibrating movement may be
obtained by subjecting tube 391 to a pulsed air flow resulting in a
screen vibration having a frequency preferably ranging from about
0.01 Hz to about 1000 Hz. Such a pulse flow may be caused by a
variety of devices. FIG. 14C shows an inventive way to cause such
pulsing. A freely rotating plate 353 is situated in slot 384. As
air is pulled past the plate, it rotates and momentarily limits gas
flow into the slot 384 as it closes the slot. As it continues to
rotate, it opens and allows gas flow. Rotation at high speed causes
flutter in gas rate and consequent oscillation of the screen 391.
Of course, it is also contemplated that such a rotating plate may
be placed in the sifter outlet (e.g., foam powder discharge outlet
383 or coarse foam powder outlet 416) or in the gas ducts leading
to (e.g., foam powder inlet section 376) or away from the sifter.
The rotating plate 353 may also be driven, for example with an
electric motor, at a frequency from about 0.01 Hz to about 1000
Hz.
[0094] FIG. 14B depicts the other major gas flow through and along
the axis of the screen assembly 391. In this instance, a vacuum or
suction is applied to the outlet 416 of discharge funnel 412. This
results in flow both though the interior of screen assembly 391 and
through the slot 414 provided at the edge of end funnel 412. This
"staging" of gas flow allows the larger foam pieces to progress
more slowly through the interior of screen assembly 391 towards the
discharge end whilst being beat upon by the beater bars. Yet as the
foam pieces leave the screen assembly 391, the added gas flow
entering, through slot 414, in combination with the decreased
cross-sectional area in discharge 416, forcefully carry the larger
foam pieces out of the unit 374. The staging of gas flow
substantially eliminates the possibility of bridging in the
inventive sifter 374.
[0095] Clearly, the size of the slots 414 shown in the FIG. 14B may
be adjusted by moving the discharge funnel 412 with relation to the
flange 385. Proper slot adjustments will, for instance, prevent the
foam powder from being "by-passed" into the discharge funnel 412.
In this manner, an optimum residence time of material within the
screen assembly can be obtained. Likewise, slots 384 may be made
adjustable to effect proper airflow around screen 391.
[0096] Another useful aspect of the invention is shown in FIG. 15.
As the inventive device is used, the screen material of screening
assembly 391 stretches and may begin to flap or to flutter. This
may cause early failure of the screen material. Too much slack in
the screen may allow interference with the beater bars with
generally catastrophic results. The operating tension of our sifter
screen 391 may easily be adjusted by use of the threaded adjusting
rod 386 shown in FIG. 15. The process need not be shut down for
this adjustment.
[0097] 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.
[0098] Foam particles in the target size range are discharged from
the screening equipment of step 324 (FIG. 8) and may be conveyed to
an optional storage step 330. Again, the foam powder is preferably
conveyed by the pneumatic conveying and separating devices shown in
FIGS. 4-6.
[0099] 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 FIG. 16.
Polymeric foam pieces containing production contaminants are
comminuted on a two-roll mill 401. The comminuted foam powder
typically includes fine particles that are within a predetermined
target particle size range and coarse particles that have a size
exceeding the target size range. The comminuted foam particles
containing production contaminants are discharged into a collection
chamber 402, as described in more detail in connection with FIG.
11. A gaseous cooling medium 404 is introduced into the comminuted
foam powder inside collection chamber 402. Chamber 402 communicates
with a sifter 408 by means of a conduit 406. Cooling medium 404
flows through conduit 406, conveying the comminuted foam powder
from chamber 402 to sifter 408, upon the creation of a pressure
differential between chamber 402 and sifter 408 such that the
pressure in the chamber is higher than the pressure in the inlet of
sifter 408. Such a pressure differential can, for example, be
created by employing a fan (not shown) in conduit 406 such that
gaseous cooling medium is caused to flow from chamber 402 to sifter
408. Suitable fans include fans commonly known as centrifugal fans,
which are typically used for moving large volumes of air or gas or
for conveying material suspended in a gas stream. Alternatively, of
course, an open-face fan such as described in connection with FIG.
5, may be utilized to create an effective pressure differential
between chamber 402 and sifter 408.
[0100] Sifter 408 (FIG. 16) is employed for sifting or screening
the comminuted foam powder by separately discharging fine particles
that are within a predetermined target particle size range 410, and
coarse particles 412. Production contaminants such as polymer foam
skin, polymer film, and paper contamination may be present in the
fine particles that have the desired particle size and/or in the
coarse particles. The coarse particles are recirculated through a
conduit 414, to mill 401 for additional comminution. The coarse
particles are conveyed through conduit 414 employing for example a
centrifugal or open-face fan (not shown) in conduit 414.
Optionally, a diverter valve 416 is positioned between sifter 408
and mill 401 for diverting (418) coarse particles, for example when
this coarse foam powder contains material that is not readily
comminuted in mill 401. Preferably, sifter 408 comprises inventive
sifter 374 as described above.
[0101] 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.
Solvent Extraction
[0102] Processing sequence 520, illustrated in FIG. 17, depicts a
portion of the inventive process in which foam powder is treated
with a solvent to remove oil and grease contamination. The foam
powder is preferably target size foam powder from screening step
324 (FIG. 8) or from storing step 330. Returning to FIG. 17, the
foam powder is conveyed to a solvent washing step 524 wherein the
foam powder is treated with one or more solvents, specifically
solvents that do not degrade PUR. Such solvents include for
example, liquid carbon dioxide, perchloroethylene
(CCl.sub.2CCl.sub.2), trichloroethanes, some alcohols, ketones such
as acetone, alkanes, and halogenated hydrocarbons such as methylene
chloride (CH.sub.2Cl.sub.2). Treatment includes agitation of foam
particles suspended in solvent. Following washing step 524, solvent
is removed for example by spin drying or spray drying in step 526.
If necessary, the washing and drying steps can be repeated until
substantially all oil and grease contamination is removed, after
which the dry foam powder is collected in a storing step 528.
Alternatively, a plurality of washing and drying steps can be used
in series with the solvent and foam powder traveling
counter-current to each other so that the cleanest solvent contacts
the cleanest foam powder. The solvent is recycled within the
washing step by, for example, distillation of the solvent from the
oil and grease contamination and return of the solvent to the
process and disposal of the separated contaminants.
[0103] 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 (FIG. 16) is
then used to provide an incomplete solvent removal resulting in
foam particles having a desired quantity of absorbed solvent. A
subsequent storing step such as step 528 is used to collect the
foam powder with absorbed solvent. During storage, the solvent
absorption on the foam particles equilibrates, resulting in a batch
of foam powder that is substantially uniform in solvent absorption
on the foam particles, even if not all foam powder increments that
are discharged in the storage facility have the same level of
solvent at the time when they are discharged for storage. This
inventive process may, for example, be utilized to eliminate heat
treatment of foam powder to remove solvent since it is not
necessary to remove all of the solvent from the foam powder if the
solvent is a blowing agent or is otherwise compatible with the new
foam.
Preparing Mixtures with Foam Powder
[0104] Processing module 400 (FIG. 1), includes processing sequence
530, shown in FIG. 18, and alternative processing sequence 540,
depicted in FIG. 19. Processing sequence 530 shows a continuous
process for preparing mixtures of foam powder and polymerizable
liquid; processing sequence 540 provides a batch process for
preparing these mixtures.
[0105] Returning to FIG. 18, foam powder is continuously fed in a
foam powder feeding step 532, at a predetermined controlled rate to
blending step 536, using for example a continuous weigh-feeder with
a conveying belt heaving load cells underneath the belt to detect
weight changes as material on the belt passes over the load cells.
These types of continuous weigh feeders are well known to those of
ordinary skill in the art. Polymerizable liquid is continuously fed
at a predetermined controlled rate in liquid feeding step 534 of
processing sequence 530. The liquid is fed at a controlled rate
using for example pumps such as metering pumps that transfer liquid
at a controlled rate. These pumps are well known to those of
ordinary skill in the art. The foam powder and liquid components
are fed to blending step 536 at rates that are predetermined in
order to obtain the desired foam powder-to-liquid ratio. The foam
powder and polymerizable liquid are continuously mixed in blending
step 536 using for example in-line mixers such as are well known to
those of ordinary skill in the art. The liquid blend is collected
in optional storage step 538. When processing sequence 530 is used
as part of a larger continuous process, the liquid blend may be
continuously added to storing step 538 from blending step 536 and
continuously removed from storage step 538 to subsequent processes,
for example to step 612 (FIG. 21).
[0106] 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 (FIG. 18).
[0107] 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.
[0108] Processing sequence 540, shown in FIG. 19, provides an
alternate process for preparing a mixture of foam powder and
polymerizable liquid, using batch preparation techniques. A
predetermined quantity of foam powder is added in a batch feeding
step 542, see FIG. 19, to a facility for conducting a batch
blending step 546. Examples of suitable blending facilities include
mixing containers or tanks equipped with one or more impeller or
paddle mixers. Foam powder feeding step 542 can for example be
executed by weighing a predetermined quantity of foam powder, or by
continuously adding foam powder at a controlled rate similar to
step 532 (FIG. 18) until the desired amount of foam powder has been
added to the blending facility. A predetermined quantity of
polymerizable liquid is added to the blending facility in batch
feeding step 544. A predetermined quantity of liquid can be added
by for example adding a predetermined weight or volume quantity of
liquid to blending step 546. Alternatively, a predetermined
quantity of liquid can be added through continuously feeding liquid
at a controlled rate similar to step 534 (FIG. 18) until the
desired quantity of polymerizable liquid has been added to blending
step 546, shown in FIG. 19. Upon completion of blending step 546, a
storing step 548 can be carried out in the blending facility.
Alternatively, a storing step 548 can be carried out in a separate
storage facility such as a storage tank or a drum. Entrapped air
bubbles can be removed from the liquid blend using any of the
technologies described in connection with processing sequence 530
(FIG. 18).
[0109] In an alternative method (not shown) foam powder is added
under vacuum to continuous blending step 536 (FIG. 18) or batch
blending step 546 (FIG. 19), thereby reducing the incorporation of
air during the blending step. In yet another, but preferred method,
foam powder is added to continuous blending step 536 under an
atmosphere of CO.sub.2 from which substantially all air is
continuously purged. Because CO.sub.2 is more soluble in the
polyhydroxyl compound than air, significantly less bubbles are
formed in the blend. This is advantageous because while the
presence of dissolved gas promotes good foam structure, the
presence of gas bubbles degrades the foam structure. Carbon dioxide
is a well-known, environmentally benign blowing agent for PUR
foam.
[0110] Returning to FIG. 1, the master process schematic shows a
mixing step 400 for mixing powder and a polymerizing liquid. FIG.
20, in turn, shows a variation of that mixing step. In particular,
an optional third-stage comminution is schematically depicted in
FIG. 20 perhaps from continuous blending or storing steps 536 and
538 (FIG. 18) or from batch blending or storing steps 546 and 548
(FIG. 19) to comminution step 582, depicted in FIG. 20. Preferably,
this comminution step is performed utilizing a mill adapted for
comminuting materials having a liquid or paste consistency. Such
mills include dispersion or colloid mills wherein the material is
subjected to fluid shear forces generated by one or more
mechanically activated surfaces. Examples include roller mills
employing two or more rolls counter-rotating at different speeds
and colloid mills wherein the liquid blend is comminuted between
converging disks. Use of this step may allow removal of the earlier
described generally dry roller mills. In any event, the
most-desired use of the procedure is to produce foam powder
particles of 100 microns, preferably 40 microns or smaller, and
most preferably, of 10 microns or smaller. The comminuted foam
powder, in the noted particle ranges may contain as much as 75% (by
weight) of polymeric foam skins or smaller amounts, including the
ranges of 20% to 60%, 20% to 50%, and any sub-range up to that 75%.
It is an advantage of this process that extremely large amounts of
those polymeric foam skins may be included and yet the small
particle sizes of the foam powder attained.
[0111] 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 FIGS. 17 and 18.
[0112] Processing module 500 (FIG. 1 and FIG. 21) provides methods
for polymerizing the blends containing foam powder emanating
perhaps from storage steps such as steps 538 (FIG. 18), 548 (FIG.
19) or 586 (FIG. 20) or a continuous mixing step to prepare
polymerized new foam that contains that foam powder. The blend of
foam powder and liquid is fed in a controlled manner in feeding
step 612 to a mixing step 616 using such techniques and devices as
are well known to those of ordinary skill in the art including
batch feeding and continuous feeding. Other polymerization and foam
forming ingredients are similarly added in a controlled feeding
step 614 to mixing step 616. It will be understood that step 614
may include several steps in order to add a variety of ingredients.
For example, if PUR foam is desired, step 612 may comprise the step
of feeding a blend of foam powder and active-hydrogen (e.g.,
polyhydroxyl or polyol) compounds. Step 614 may include the
controlled feeding of a polyol blend containing water, one or more
surfactants, catalysts, and blowing agents while a polyfunctional
isocyanate such as toluene diisocyanate is separately added in a
controlled manner to mixing step 616. Alternatively, each of the
various materials may be added separately at a point immediately
before the mix head that mixes all ingredients for forming the
foam.
[0113] The foam powder may also be added to one or more liquids of
processing step 614, shown in FIG. 21, in order to prepare liquid
blends in processing steps 612 and 614 that have similar
viscosities, resulting in improved mixing efficiency. The
ingredients may be batch- or continuous-mixed in mixing step 616.
Batch mixing is generally suitable when the ingredient mixture
requires elevated temperatures to polymerize, e.g., polyimide foam.
Continuous mixing is preferred when the ingredient mixture is
capable of initiating polymerization at ambient temperatures, e.g.,
PUR foam. The polymerizable mixture is discharged in a discharging
step 618 (FIG. 21) from mixing step 616 to a polymerization and new
foam formation step 620. Step 620 may take place in a mold or may
be continuous, depending on the type of polymeric foam and the
intended function of the foam.
[0114] As described in connection with FIGS. 18, 19, and 20,
blending of foam powder and polymerizable liquid, particularly if
done in the presence of air, may require a deaeration step to
remove foam and air bubbles. We have found that preparation of
blends of foam powder with polymerizable liquid under an atmosphere
of CO.sub.2 from which air was substantially purged produces blends
that require less degassing than blends that have not been prepared
in a CO.sub.2 environment.
[0115] 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
[0116] 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.
[0117] 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 trimmings. 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/m.sup.3. The hardness of this foam (as determined by
the 25% IFD test in method ASTM D3574) is typically about 25 to 200
N/323 cm.sup.2. Foams with higher density and hardness are also
possible; however, these have less commercial significance.
EXAMPLES
Example 1
[0118] 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 FIG. 11
with speeds of 27 and 80 rpm. The resulting material was scraped
together and quenched as it exited the rolls, and exposed to a
turbulent air flow at room temperature. The material was discharged
together with the air flow and conveyed to a sifter. The material
was screened in the sifter, resulting in a fine foam powder having
the particle-size distribution shown in Table 1. A coarse fraction
that was also obtained from the sifter was returned to the
counter-rotating rolls. The fine foam powder collected from the
sifter was subsequently used to make new flexible-slabstock
polyurethane foams with densities from 18 kg/m.sup.3 to 35
kg/m.sup.3 with powder content of up to 15% by weight of this
powder. TABLE-US-00001 TABLE 1 U.S. standard weight % sieve passing
the screen designation example 1 example 2 No. 80 100% 100% No. 120
100% 89% No. 200 84% 55% No. 325 49% 24%
Example 2
[0119] 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 FIG. 11 with speeds of 30 and 120 rpm. The resulting
material was scraped together and quenched as it exited the rolls,
and exposed to a turbulent air flow at room temperature. The
material was discharged together with the air flow and conveyed to
the inventive sifter as shown in FIG. 13A. The material was
screened in the sifter, resulting in a fine foam powder having the
particle-size distribution shown in Table 1. A coarse fraction that
was also obtained from the sifter was returned to the
counter-rotating rolls.
Example 3
[0120] A slurry sample was prepared by mixing 15 parts of the fine
polyurethane powder described in Example 1 with 100 parts of
VORANOLO.RTM. 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.degree. C.
[0121] The beneficial size reduction effects which are obtained by
high-shear mixing of polyurethane powder in a polyhydroxyl compound
are illustrated in FIGS. 22 and 23. After taking a small sample to
measure particle size before high shear mixing, the remaining batch
was subjected to 2.5 minutes of high shear mixing using a Silverson
L4R laboratory high shear mixer. The mixer generates fluid shear by
means of centrifugal action of a rotor in a high shear rotor/stator
workhead. Particle size analysis was performed using a
laser-diffraction technique with a Mastersizer 2000 from Malvern
Instruments, Southborough, Mass.
[0122] The results are shown in the graphs depicted in FIGS. 22 and
23, which show particle size in microns on the x-axis. FIG. 22
shows a cumulative distribution in volume fraction while FIG. 22
shows volume percent as a function of particle size in microns.
These graphs show a significant shift in foam particle size,
particularly at the high end of the size range. The content of high
end particles is less: for instance, before the grinding step, 5%
of the particles were larger than 600 microns; after the grinding,
there were no particles larger than 600 microns.
Example 4
[0123] Pieces of polyurethane foam with a size of approximately 1
cm were loaded into a bin. The bin had a 1 ft.sup.2 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
ft.sup.3/min. When the agitation was stopped, flow of the foam
chunks also stopped.
Example 5
[0124] 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.
Example 6
[0125] 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 CO.sub.2, had 16% entrained gas bubbles by
volume (presumably air).
* * * * *