U.S. patent application number 12/786206 was filed with the patent office on 2010-09-16 for extrusion of polyurethane composite materials.
This patent application is currently assigned to CENTURY-BOARD USA, LLC. Invention is credited to Wade H. Brown.
Application Number | 20100230852 12/786206 |
Document ID | / |
Family ID | 38372521 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100230852 |
Kind Code |
A1 |
Brown; Wade H. |
September 16, 2010 |
EXTRUSION OF POLYURETHANE COMPOSITE MATERIALS
Abstract
Methods of extruding polyurethane composite materials are
described. One method includes introducing at least one polyol and
inorganic filler to a first conveying section of the extruder,
transferring the at least one polyol and inorganic filler to a
first mixing section of an extruder, mixing the at least one polyol
and the inorganic filler in the first mixing section, transferring
the mixed at least one polyol and inorganic filler to a second
conveying section of the extruder, introducing a di- or
poly-isocyanate to the second conveying section, transferring the
mixed at least one polyol and inorganic filler and the di- or
poly-isocyanate to a second mixing section, mixing the mixed at
least one polyol and inorganic filler with the di- or
poly-isocyanate in the second mixing section of the extruder to
provide a composite mixture, and transferring the composite mixture
to an output end of the extruder. Other related methods are also
described.
Inventors: |
Brown; Wade H.;
(Mooresville, NC) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
CENTURY-BOARD USA, LLC
Mooresville
NC
|
Family ID: |
38372521 |
Appl. No.: |
12/786206 |
Filed: |
May 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11691446 |
Mar 26, 2007 |
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12786206 |
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60785726 |
Mar 24, 2006 |
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60785749 |
Mar 24, 2006 |
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Current U.S.
Class: |
264/211 ;
366/76.4 |
Current CPC
Class: |
B29C 48/55 20190201;
C08G 2101/00 20130101; B29K 2709/00 20130101; B29K 2105/06
20130101; B29K 2105/12 20130101; C08K 7/10 20130101; C08K 3/04
20130101; B29C 48/395 20190201; C08L 75/04 20130101; B29C 45/0001
20130101; B29K 2049/00 20130101; B29K 2105/0014 20130101; B29C
48/575 20190201; C08K 3/00 20130101; B29C 48/834 20190201; B29K
2105/0044 20130101; B29C 48/285 20190201; B29C 48/63 20190201; B29K
2075/00 20130101; C08G 18/7657 20130101; C08J 2201/03 20130101;
B29C 48/2886 20190201; B29C 48/405 20190201; B29C 48/022 20190201;
B29C 48/57 20190201; B29C 48/402 20190201; B29K 2105/0032 20130101;
B29C 48/67 20190201; C08G 18/4045 20130101; C08L 75/08 20130101;
C08G 2110/0083 20210101; B29C 48/29 20190201; C08K 7/14 20130101;
B29K 2105/16 20130101; B29K 2105/0005 20130101; C08J 5/10 20130101;
Y02W 30/91 20150501; B29C 48/54 20190201; B29K 2105/005 20130101;
C08G 18/4804 20130101; C08J 9/125 20130101; C04B 26/16 20130101;
C08K 3/013 20180101; B29C 48/56 20190201; C08G 18/0895 20130101;
C08J 2375/04 20130101; B29C 48/07 20190201; B29C 48/297 20190201;
C08G 18/36 20130101; C08G 18/7671 20130101; C04B 26/16 20130101;
C04B 14/22 20130101; C04B 38/02 20130101; C04B 26/16 20130101; C04B
18/08 20130101; C04B 38/02 20130101 |
Class at
Publication: |
264/211 ;
366/76.4 |
International
Class: |
B29C 47/38 20060101
B29C047/38 |
Claims
1. A method of forming a polymeric composite material in an
extruder, the method comprising: introducing at least one polyol, a
di- or poly-isocyanate, and inorganic filler to a first conveying
section of the extruder, the first conveying section comprising one
or more transport screws; transferring the at least one polyol, the
di- or poly-isocyanate, and the inorganic filler to a first mixing
section of an extruder; mixing the at least one polyol, the di- or
poly-isocyanate and the inorganic filler in the first mixing
section to producing a composite material, the first mixing section
comprising a reverse screw; and transferring the composite mixture
to an output end of the extruder.
2. The method of claim 1, wherein the first mixing section
comprises a lobal screw.
3. The method of claim 1, further comprising introducing fibrous
material in the first conveying section and mixing the fibrous
material with the at least one polyol, the di- or poly-isocyanate
and the inorganic filler in the first mixing section.
4. The method of claim 1, further comprising mixing a catalyst with
the at least one polyol, the di- or poly-isocyanate and the
inorganic filler.
5. The method of claim 2, wherein the catalyst is mixed prior to
the composite mixture exiting an output end of the extruder.
6. The method of claim 5, further comprising extruding the
composite mixture through a die.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of Ser. No. 11/691,446,
filed Mar. 26, 2007, which claims the priority benefit under 35
U.S.C. .sctn.119(e) of provisional applications 60/785,726, filed
Mar. 24, 2006 and 60/785,749, filed Mar. 24, 2006, all of which are
hereby incorporated by reference in their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field
[0003] The invention relates to foamed and nonfoamed polymeric
material, and more particularly polyurethane composite materials,
and methods for extruding the same.
[0004] 2. Description of the Related Technology
[0005] Polymeric composite materials that contain organic or
inorganic filler materials have become desirable for a variety of
uses because of their excellent mechanical properties, weathering
stability, and environmental friendliness.
[0006] These materials can be are relatively low density, due to
their foaming, or high density when unfoamed, but are extremely
strong, due to the reinforcing particles or fibers used throughout.
Their polymer content also gives them good toughness (i.e.,
resistance to brittle fracture), and good resistance to degradation
from weathering when they are exposed to the environment. This
combination of properties renders some polymeric composite
materials very desirable for use in building materials, such as
roofing materials, decorative or architectural products, outdoor
products, insulation panels, and the like.
SUMMARY OF THE INVENTION
[0007] Described herein are extrusion processes as related to
polymeric composite materials. More particularly, the extrusion
processes related to polyurethane composite materials. In some
embodiments, highly filled polyurethane composite materials are
extruded. Such materials may then be shaped and formed into solid
surface articles. Articles comprising the polyurethane composite
material as described herein are suitable for structure, building,
and outdoor applications.
[0008] In one embodiment, a method of forming a polymeric composite
material includes introducing at least one polyol and inorganic
filler to a first conveying section of the extruder, transferring
the at least one polyol and inorganic filler to a first mixing
section of an extruder, mixing the at least one polyol and the
inorganic filler in the first mixing section, transferring the
mixed at least one polyol and inorganic filler to a second
conveying section of the extruder, introducing a di- or
poly-isocyanate to the second conveying section, transferring the
mixed at least one polyol and inorganic filler and the di- or
poly-isocyanate to a second mixing section, mixing the mixed at
least one polyol and inorganic filler with the di- or
poly-isocyanate in the second mixing section of the extruder to
provide a composite mixture, and transferring the composite mixture
to an output end of the extruder.
[0009] In some embodiments, the composite mixture includes about 40
to about 85 weight percent of the inorganic filler. In some
embodiments, the composite mixture includes about 60 to about 85
weight percent of the inorganic filler. In some embodiments, the
composite mixture includes about 65 to about 80 weight percent of
the inorganic filler. The inorganic filler may include many
different types of filler. One preferred filler includes fly
ash.
[0010] In certain embodiments, the conveying sections and mixing
sections are defined in terms of the screw segments and screw
elements contained within the conveying or mixing section. In one
embodiment, the first conveying section includes one or more
transfer screws. In one embodiment, the first mixing section
includes a slotted screw. In another embodiment, the first mixing
section includes a lobal screw. In one embodiment, the first mixing
section includes a lobal screw and a slotted screw.
[0011] In some embodiments, the second conveying section is located
downstream of a first conveying section. In some embodiments, the
second conveying section is located downstream of a first mixing
section. In some embodiments, the section conveying section
includes one or more transfer screws.
[0012] In some embodiments, a second mixing section is located
downstream of a first mixing section. In some embodiments, a second
mixing section is located downstream of the second conveying
section. In certain embodiments, the second mixing section is
adjacent to the output end of the extruder. In certain embodiments,
the second mixing station includes a reverse screw. In certain
embodiments, the reverse screw includes a reverse slotted
screw.
[0013] In some embodiments, the method may further include adding
one or more components of the composite mixture in the first
conveying section of the extruder. Such additional components are
further described herein. In one embodiment, the one or more
components is selected from the group consisting of a catalyst, a
surfactant, and a blowing agent. In other embodiments, the one or
more components may include one or more of a cross linker, a chain
extender, and a coupling agent. In certain of these embodiments,
the method further includes blending the one or more components
with the at least one polyol prior to introduction to the first
conveying section.
[0014] In some embodiments, the method further includes mixing the
mixed at least one polyol and inorganic filler and the di- or
poly-isocyanate in a third mixing section subsequent to the second
conveying section and prior to the second mixing section. In some
embodiments, the third mixing section includes a reverse screw.
Certain embodiments, further include introducing fibrous material
in the third conveying section. In certain embodiments, the third
conveying section is located between the second mixing section and
the third mixing section.
[0015] As described herein, one or more fibrous materials may be
extruded with the polymeric composite material. In one embodiment,
the method further includes introducing fibrous material in the
second conveying section. In certain embodiments, the method
includes mixing the fibrous material with the mixed at least one
polyol and inorganic filler and the di- or poly-isocyanate in the
second mixing section.
[0016] In another embodiment, the method includes introducing at
least one polyol, a di- or poly-isocyanate, and inorganic filler to
a first conveying section of the extruder. In certain embodiments,
the first conveying section includes one or more transport screws.
The method further includes transferring the at least one polyol,
the di- or poly-isocyanate, and the inorganic filler to a first
mixing section of an extruder, mixing the at least one polyol, the
di- or poly-isocyanate and the inorganic filler in the first mixing
section to producing a composite material. In some embodiments, the
first mixing section includes a reverse screw. The method further
includes transferring the composite mixture to an output end of the
extruder. In certain embodiments, the first mixing section includes
a lobal screw.
[0017] In this methods described above, the method may further
include introducing fibrous material in the first conveying section
and mixing the fibrous material with the at least one polyol, the
di- or poly-isocyanate and the inorganic filler in the first mixing
section. In certain embodiments, the method includes mixing a
catalyst with the at least one polyol, the di- or poly-isocyanate
and the inorganic filler. According to some embodiments, the
catalyst is mixed prior to the composite mixture exiting an output
end of the extruder. In certain embodiments, the method includes
extruding the composite mixture through a die.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an illustration of an extruder including a screw
shaft with various screw elements.
[0019] FIG. 2 is a drawing of a kneading block element.
[0020] FIG. 3 is an view of lobal screw elements in a twin screw
extruder.
[0021] FIG. 4 is an illustration of one configuration of an
extruder containing multiple segments useful in the production of
polyurethane composite materials.
[0022] FIG. 5 is an illustration of one configuration of an
extruder containing conveying and mixing section useful in the
production of polyurethane composite materials.
[0023] FIG. 6 is an illustration of another configuration of an
extruder containing conveying and mixing sections useful in the
production of polyurethane composite materials.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] Thermosetting polymeric composite materials may be made
using an extruder. Such a process allows for thorough mixing of the
various components of the polymeric composite material in the
extruder. The screw and screw elements may be configured in various
ways within an extruder to provide a substantially homogeneous
mixture of the various components of the polymeric composite
material. In addition, friction and other forces may promote the
reaction of various monomers and other additives that create a
polymeric matrix in the polymeric composite material. Moreover, the
various components of a polymeric composite material may be added
in different orders and at different positions in an extruder.
Thus, extrusion of polymeric composite material is a desirable
method for providing a medium for reaction, controlling reaction
ingredients and conditions, and mixing the various components.
[0025] An extruder having one or more material inputs may be used
to form such polymeric composite materials. In accordance with
certain embodiments, a single screw extruder or a twin screw
extruder may be used. Each screw of the extruder is mounted on a
single shaft that transmits rotary motion to the screw. In
embodiments of a twin screw extruder, each screw may be counter
rotary to the other screw. The screw may comprise one or more screw
elements mounted on the rotating shaft. The screw may alternatively
be assembled from several separate screw elements, each of which
forms a portion of the screw operated within the extruder. Screw
elements may be rotatably disposed in an appropriate sequence of
the axial shaft to form multiple segments of the screw. Various
screw elements may include one or more of transport screw elements,
lobal screw elements, reverse screw elements, slotted screw
elements, and kneading block elements. Various screw elements are
described in U.S. Pat. Nos. 5,728,337, 6,136,246 and 6,908,573,
which are hereby incorporated by reference.
[0026] Referring to FIG. 1, an extruder body 12 contains a screw
body which includes a screw shaft 22 and a plurality of screw
elements 23. The extruder body 12 is outfitted with one or more
vents 17 which allow air to escape from composite materials and the
extruder body 12. The screw body also includes one or more feed
sections 19 where components of the polymeric composite are fed
into respective segments of the extruder body 12. The extruder body
also includes outlet 18. Outlet 18 may be equipped with a die.
Screw elements 23 include a transport screw elements 15, a kneading
blocks 16 and 40, a reverse transport screw element 45, a lobal
screw element 50, and a slotted screw element 55. While the various
screw segments may be connected to or engaged with the screw shaft
22 in any manner, spline fitting grooves may be mated to a spined
screw shaft.
[0027] In some embodiments, transport screw elements have a flight
that is helically wound around the screw. The flight of the
transport screw has a positive pitch and therefore transfers
materials in the extruder barrel from the feed end to the output
end. According to some embodiments, the flight of the transport
screw may be made faster or slower, depending on the pitch of the
threads of the transport screw element. In a transport screw, a
greater pitch (i.e., threads/per unit of length) will result in
slower transport of the material, while a lower pitch will result
in faster transport of the material. Many different varieties of
transport screw elements may be used. In some embodiments,
utilizing a twin screw extruder, each screw may contain transport
screw elements that are intermeshed. While transport screw elements
mix some composite material, the primary function is conveying
materials downstream in the extruder.
[0028] In some embodiments, the extruder may comprise one or more
reverse screw element 45. These are generally utilized to reverse
the flow of the composite materials toward the feed end of the
extruder. As such, a reverse screw element 45 blocks the flow of
components of the composite mixture, thus acting as a temporary
seal and promotes added blending of the components and dispersion
of fillers and other additives. In some embodiments, such
components of the composite mixture may pass the reverse screw
element after another shearing force or pressure allows the
components to pass the reverse screw element. In some embodiments,
the reverse screw element allows for substantial mixing of filler
and other polymer composite materials.
[0029] As shown in FIG. 2, a kneading block 25 is a screw element
that includes a plurality of double-tipped kneading discs having a
substantially oval cross section and arranged in the axial
direction of the screw shaft. Each kneading disc may be displaced
from one another. In twin screw extruders, kneading discs of the
first screw are kept staggered at about 90 degrees to the
corresponding kneading discs on the second screw. An alternative
embodiment of kneading blocks may include the configuration of
kneading block 40 as shown in FIG. 1. Kneading blocks typically
have from about 4 to about 6 blades per screw element. Kneading
blocks are typically used to provide high shear stress and high
mixing strengths, particularly when mixing solids with liquids (or
melted plastics). Kneading blocks are generally self-wiping.
[0030] Lobal screw elements are generally a longer screw element.
In some embodiments, a lobal screw element has 2 or 3 or more
faces. In some embodiments, the lobal screw may be polygonal. Lobal
screw elements do not comprise a plurality of discs like kneading
blocks. Instead, lobal screw elements are generally a single
structure. However, lobal screw elements may have one or more axial
twists. In some embodiments, the axial twist of a lobal screw
element is less than 180.degree.. In some embodiments, the axial
twist of a lobal screw element is less than 140.degree.. In some
embodiments, the axial twist of a lobal screw element is less than
90.degree.. In some embodiments, the axial twist of a lobal screw
element is less than 45.degree.. In some embodiments, the axial
twist of a lobal screw element is substantially 0.degree.. One
purpose of a lobal screw element is to squeeze various composite
material in a defined space. Such lobal screw elements cause very
high shear in the defined area. It has been discovered that lobal
screw elements may force liquids to mix intimately with one
another. In additionally embodiments, lobal screw element can
provide substantial wetting of inorganic materials such as fibers
and fillers by liquid components of the polymeric composite
material, such as melted resins or liquid monomers. Lobal screw
elements may be neutral or forward moving elements. Lobal screw
elements are typically self-wiping in a twin screw extruder
configuration as shown in FIG. 3.
[0031] Slotted screw elements 55 may include a plurality of blades
on all sides of the screw elements. In some embodiments, the blades
may be disposed in line with other blades, such as a transfer screw
element with spaces or slots between the helically wound flight.
However, there is no requirement for the blades to be uniform or to
have positive pitch. In some embodiments, a slotted screw blade
includes angled ends. In some embodiments, the slotted screws have
positive, negative, and neutral pitch (i.e., they may convey or
block the composite material according to the type and arrangement
of blades). However, some blades with angles ends may produce less
conveying effect than a screw such as a transfer screw. In some
embodiments, slotted screws are partially self-wiping. In some
embodiments, slotted screws are not self wiping in a twin screw
arrangement. In some embodiments, the slots of the slotted screw
element may be filled with one or more composite materials, such as
a hardened urethane. As a result, such slotted screw elements may
produces substantial amount of mixing of various components of the
mixture and also knead the mixture. In particular embodiments,
slotted screws may be placed toward the feed end of an extruder
which allows slots not to fill with polymeric resin, such as
hardened polyurethane. Example of slotted screw elements may be
found in U.S. Pat. No. 6,136,246.
[0032] Advantageously, these screw elements may be used to produce
a desired amount of blending of components of the polymeric
composite system. In certain embodiments, each screw element
defines a segment of the extruder. In some embodiments, the
segments may have substantially the same length. However, certain
segments may have longer lengths than other segments and segments
may also contain more than one screw element. In certain
embodiments, the extruder may have up to nine extruder segments.
However, the extruder may container more or less segments depending
on the desired composite material characteristics. In some
embodiments, the extruder includes 1, 2, 3, 4, 5, 6, 7, 8, or 9
segments.
[0033] Various segments of the extruder may be air or water cooled.
Often, exothermic reactions during the production of the polymeric
composite material may require sufficient cooling to prevent
runaway exotherms. Such temperatures and cooling may be controlled
by various means known to persons having ordinary skill in the
art.
[0034] One or more components of the polymeric composite material
may be introduced into one or more segments of the extruder through
hoppers, feed chutes, or side feeders. One or more components may
also be metered into the extruder through various means. Continuous
feeding of the respective components of the polymeric composite
material results in a continuous process of extruding the polymeric
composite material.
[0035] Depending on the exact arrangement of the screw elements,
the segments may further be classified into broader sections such
as conveying sections and mixing sections. For example, a first
composite component may be introduced in a first segment having a
first transport screw, and a second composite component may be
introduced in a second segment have a second transport screw. If
such first and second segments are adjacent to each other, then the
first and second segment may be classified as a conveying section.
However, classification as a conveying section does not preclude
mixing, even intimate mixing, of the various components of the
polymeric composite material.
[0036] Such composite components may then be further transferred
into other segments or sections. The components generally are
transferred by the screws from the feed end to the discharge end of
the extruder. In one embodiment, components are transferred into a
mixing section. A mixing section may include a kneading blocks or
reverse screws. Reverse screws have negative pitch. Thus, the
reverse screws may block the materials until sufficient shearing
forces the various components of the composite material through
this barrel segment. Generally, this results in substantial mixing
of the various components of the composite material.
[0037] It has been discovered that certain embodiments of extruders
are able to produce highly filled polyurethane composite materials.
Various components of the polymer composite material may include
one or more of the following: at least polyol, at least one monomer
or oligomeric di- or poly-isocyanates, an inorganic filler, fibrous
materials, at least one catalyst, surfactants, colorants, and other
various additive. Such components are further described herein.
[0038] Described herein are polymeric composite materials. In
particular embodiments, the polymeric composite material include
polyurethane composite materials. While the embodiments described
herein are specifically related to polyurethane composite
materials, the technology may also be applicable to many other
polymeric resins, particularly those related to highly filled
thermosetting polymers. Generally, a polyurethane is any polymer
consisting of a chain of organic units joined by urethane linkages.
Typically, a polyurethane may be formed by reaction of one or more
monomeric or oligomeric poly- or di-isocyanates (sometimes referred
to as "isocyanate") and at least one polyol, such as a polyester
polyol or a polyether polyol. These reactions may further be
controlled by various additives and reaction conditions. For
example, one or more surfactants may be used to control cell
structure and one or more catalysts may be used to control reaction
rates. Advantageously, the addition of certain polyol and
isocyanate monomers and certain additives (e.g., catalysts,
crosslinkers, surfactants, blowing agents), may produce a
polyurethane material that is suitable for commercial
applications.
[0039] As is well known to persons having ordinary skill in the
art, polyurethane materials may also container other polymeric
components by virtue of side reactions of the polyol or isocyanate
monomers. For example, a polyisocyanurate may be formed by the
reaction of optionally added water and isocyanate. In addition,
polyurea polymers may also be formed. In some embodiments, such
additional polymer resins may have an effect on the overall
characteristics of the polyurethane composite material.
[0040] It has further been found that some portion of the polymeric
component of polyurethanes may be replaced with one or more fillers
such as particulate material and fibrous materials. With the
addition of such fillers, the polyurethane composite materials may
still retain good chemical and mechanical properties. These
properties of the polyurethane composite material allows for its
use in building materials and other structural applications.
Advantageously, the polyurethane composite material may contain
large loadings of filler content without substantially sacrificing
the intrinsic structural, physical, and mechanical properties of
the polymer. Such building materials would have advantages over
composite materials made of less or no filler. For example, the
building materials may be produced at substantially decreased cost.
Furthermore, decreased complexity of the process chemistry may also
lead to decreased capital investment in process equipment.
[0041] In one embodiment, the composite materials have a matrix of
polymer networks and dispersed phases of particulate or fibrous
materials. The polymer matrix includes a polyurethane network
formed by the reaction of a poly- or di-isocyanate and one or more
polyols. The matrix is filled with a particulate phase, which can
be selected from one or more of a variety of components, such as
fly ash particles, axially oriented fibers, fabrics, chopped random
fibers, mineral fibers, ground waste glass, granite dust, slate
dust or other solid waste materials.
[0042] Such polyurethane composite materials may be formed with a
desired density, even when foamed, to provide structural stability
and strength. In addition, the polyurethane composite materials can
be easily tuned to modify its properties by, e.g., adding oriented
fibers to increase flexural stiffness, or by adding pigment or dyes
to hide the effects of scratches. Also, such polyurethane composite
materials may also be self-skinning, forming a tough, slightly
porous layer that covers and protects the more porous material
beneath. Such tough, continuous, highly adherent skin provides
excellent water and scratch resistance. In addition, as the skin is
forming, an ornamental pattern (e.g., a simulated wood grain) can
be impressed on it, increasing the commercial acceptability of
products made from the composite.
[0043] Described herein are certain improvements that may be used
in the production of polyurethane composite materials. Some
previously described polyurethane composite material systems are
included in U.S. patent application Ser. No. 10/764,012, filed Jan.
23, 2004, and entitled "FILLED POLYMER COMPOSITE AND SYNTHETIC
BUILDING MATERIAL COMPOSITIONS," now published as U.S Patent
Application Publication No. 2005-163969-A1, and U.S. patent
application Ser. No. 11/190,760, filed Jul. 27, 2005, and entitled
"COMPOSITE MATERIAL INCLUDING RIGID FOAM WITH INORGANIC FILLERS,"
now published as U.S Patent Application Publication No.
2007-0027227 A1, which are both hereby incorporated by reference in
their entireties. However, in now way, are such polyurethane
composite material systems intended to limit the scope of the
improvements described in the present application.
[0044] The various components and processes of preferred
polyurethane composite materials are further described herein:
Monomeric or Oligomeric Poly or Di-Isocyanates
[0045] As discussed above, one of the monomeric components used to
form a polyurethane polymer of the polyurethane composite material
is one or more monomeric or oligomeric poly or di-isocyanates. The
polyurethane is formed by reacting a poly- or di-isocyanate. In
some embodiments, an aromatic diisocyanate or polyisocyanate may be
used.
[0046] In certain embodiments methylene diphenyl diisocyanate (MDI)
is used. The MDI can be MDI monomer, MDI oligomer, or mixtures
thereof. The particular MDI used can be selected based on the
desired overall properties, such as the amount of foaming, strength
of bonding to the inorganic particulates, wetting of the inorganic
particulates in the reaction mixture, strength of the resulting
composite material, and stiffness (elastic modulus). Although
toluene diisocyanate can be used, MDI is generally preferable due
to its lower volatility and lower toxicity. Other factors that
influence the particular MDI or MDI mixture are viscosity (a low
viscosity is desirable from an ease of handling standpoint), cost,
volatility, reactivity, and content of 2,4 isomer. Color may be a
significant factor for some applications, but does not generally
affect selection of an MDI for preparing an article.
[0047] Light stability is also not a particular concern for
selecting MDI for use in the composite material. According to some
embodiments, the composite material allows the use of isocyanate
mixtures not generally regarded as suitable for outdoor use,
because of their limited light stability. When used in to form the
polyurethane composite material, such materials surprisingly
exhibit excellent light stability, with little or no yellowing or
chalking. Suitable MDI compositions include those having
viscosities ranging from about 25 to about 200 cp at 25.degree. C.
and NCO contents ranging from about 30% to about 35%. Generally,
isocyanates are used that provide at least 1 equivalent NCO group
to 1 equivalent OH group from the polyols, desirably with about 5%
to about 10% excess NCO groups. Useful polyisocyanates also may
include aromatic polyisocyanates. Suitable examples of aromatic
polyisocyanates include 4,4-diphenylmethane diisocyanate (methylene
diphenyl diisocyanate), 2,4- or 2,6-toluene diisocyanate, including
mixtures thereof, p-phenylene diisocyanate, tetramethylene and
hexamethylene diisocyanates, 4,4-dicyclohexylmethane diisocyanate,
isophorone diisocyanate, mixtures of 4,4-phenylmethane diisocyanate
and polymethylene polyphenylisocyanate. In addition, triisocyanates
such as, 4,4,4-triphenylmethane triisocyanate 1,2,4-benzene
triisocyanate; polymethylene polyphenyl polyisocyanate; and
methylene polyphenyl polyisocyanate, may be used. Isocyanates are
commercially available from Bayer USA, Inc. under the trademarks
MONDUR and DESMODUR. Suitable isocyanates include Bayer MRS-4,
Bayer MR Light, Dow PAPI 27, Bayer MR5, Bayer MRS-2, and Huntsman
Rubinate 9415.
[0048] In certain embodiments, the average functionality of the
isocyanate component is between about 1.5 to about 4. In other
embodiments, the average functionality of the isocyanate component
is about 3. In other embodiments, the average functionality of the
isocyanate component is less than about 3, including, about 1.8,
1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, and 2.9. In some
embodiments, the isocyanate has a functionality of about 2. Some of
these embodiments produce polyurethane composite materials with
higher mechanical strengths and lower costs than polyurethane
composite material comprising more than about 2.
[0049] As indicated above, the isocyanate used in the invention is
reacted with one or more polyols. In general, the ratio of
isocyanate to polyol (isocyanate index), based on equivalent
weights (OH groups for polyols and NCO groups for isocyanates) is
generally in the range of about 0.5:1 to about 1.5:1, more
particularly from about 0.8:1 to about 1.1:1, and in another
embodiment, from about 0.8:1 to about 1.2:1. Ratios in these ranges
provide good foaming and bonding to inorganic particulates, and
yields low water pickup, fiber bonding, heat distortion resistance,
and creep resistance properties. However, precise selection of the
desired ratio will be affected by the amount of water in the
system, including water added per se as a foaming agent, and water
introduced with other components as an "impurity."
[0050] In some embodiments, an isocyanate may be selected to
provide a reduced isocyanate index. It has been discovered that the
isocyanate index can be reduced without compromising the
polyurethane composite material's chemical or mechanical
properties. It is additionally advantageous according to some
embodiments to use an isocyanate with a reduced isocyanate index as
isocyanates are generally higher priced than polyols. Thus, a
polyurethane system formed by an isocyanate monomer with a reduced
isocyanate index may result in reduced cost of producing the total
system.
Polyols
[0051] According to some embodiments, the polyurethane polymer is a
reaction product of one or more polyols with an isocyanate. The one
or more polyols used may be single monomers, oligomers, or blends.
Mixtures of polyols can be used to influence or control the
properties of the resulting polymer network and composite material.
The properties, amounts, and number of polyols used may be varied
to produce a desired polyurethane composite material.
[0052] It is generally desirable to use polyols in liquid form, and
generally in the lowest viscosity liquid form available, as these
can be more easily mixed with the inorganic particulate material.
So-called "EO" tipped polyols can be used; however their use is
generally avoided where it is desired to avoid "frosting" of the
polymer material when exposed to water.
[0053] In some embodiments, the at least one polyol include a
polyester or polyether polyol. Polyether polyols are commercially
available from, for example, Bayer Corporation under the trademark
MULTRANOL. In general, desirable polyols include polyether polyols,
such as MULTRANOL (Bayer), including MULTRANOL 3400 or MULTRANOL
4035, ethylene glycol, polypropylene glycol, polyethylene glycol,
diethylene glycol, triethylene glycol, dipropylene glycol,
glycerol, 2-pentane diol, pentaerythritol adducts,
1trimethylolpropane adducts, trimethylolethane adducts,
ethylendiamine adducts, and diethylenetriamine adducts,
2-butyn-1,4-diol, neopentyl glycol, 1,2-propanediol,
pentaerythritol, mannitol, 1,6-hexanediol, 1,3-buytylene glycol,
hydrogenated bisphenol A, polytetramethyleneglycolethers,
polythioethers, and other di- and multi-functional polyethers and
polyester polyethers, and mixtures thereof. The polyols need not be
miscible, but should not cause compatibility problems in the
polymeric composite.
[0054] In some embodiments, plant-based polyols are used as at
least one polyol. These polyols are lower in cost, and not
dependent on the price and availability of petroleum. In some
embodiments, the plant-based polyols provide a polyurethane system
that is substantially identical to that provided by oil-based
polyols. In other embodiments, plant-based polyols can be used to
replace at least a portion of the oil-based polyols. By employing
plant-based polyols, the polyurethane composite material is more
environmentally safe and friendly. In addition, certain equipment
used to handle and dispose of oil-based polyols may be costly.
[0055] In some embodiments, the at least one polyol is a polyester
polyol that is substantially resistant to water soaking and
swelling. Thus, these polyols can be used in the formation of
polyurethane composite materials which, when cured, attracts less
water. In certain cases, the polyester polyols absorb less water
than polyether polyols. However, in some embodiments, polyester
polyols and polyether polyols can be mixed in the formation of
polyurethane composite material to provide better water
resistance.
[0056] Some embodiments of the polyurethane composite material
comprise at least one polycarbonate polyol. These embodiments
provide higher impact and/or chemical resistance, as compared to
polyurethane composite material made from polyester and/or
polyether polyols. However, combinations of polycarbonate polyols,
polyester polyols, and polyether polyols can be used in systems
with high inorganic fillers to provide the desired mechanical and
physical property of the polyurethane composite material. In some
embodiments, building products comprising the polyurethane
composite materials which employ at least one polyester polyol
demonstrate improved water resistance.
[0057] In some embodiments, at least some phenolic polyols are used
to make polyurethane composite materials which have improved flame
retardancy as compared to those polyurethane composite materials
that are not made from phenolic polyols. Such polyurethane
composite materials may also be fire and smoke resistance.
[0058] In other embodiments, the polyurethane composite materials
are made from at least one acrylic polyol. In some embodiments, the
polyurethane composite materials made from the at least one acrylic
polyol demonstrate improved weathering as compared to those that
are not made from at least one acrylic polyol. In other
embodiments, the polyurethane composite materials are made from at
least one acrylic polyol exhibit substantially no discoloration
when exposed to sunlight.
[0059] In one embodiment, a first polyol having a first hydroxyl
number and a second polyol having a second hydroxyl number less
than the first hydroxyl number may be used. Such combination of
polyols form a first polyurethane that is less rigid than a second
polyurethane that would be formed by the reaction of the first
polyol in the absence of the second polyol. In some embodiments,
the first polyol has a hydroxyl number ranging from about 250 to
about 500 mg KOH/g. In some embodiments, the first polyol has a
hydroxyl number ranging from about 300 to about 450 mg KOH/g. In
some embodiments, the first polyol has a hydroxyl number ranging
from about 320 to about 400 mg KOH/g. In some embodiments, the
first polyol has a hydroxyl number ranging from about 350 to about
500 mg KOH/g. In some embodiments, the first polyol has a hydroxyl
number ranging from about 370 to about 600 mg KOH/g. In some
embodiments, the second polyol has a hydroxyl number less than the
first polyol. In some embodiments, the second polyol has a hydroxyl
number ranging from about 20 to about 120 mg KOH/g. In some
embodiments, the second polyol has a hydroxyl number ranging from
about 20 to about 70 mg KOH/g. In some embodiments, the second
polyol has a hydroxyl number ranging from about 30 to about 60 mg
KOH/g. In some embodiments, the second polyol has a hydroxyl number
ranging from about 50 to about 75 mg KOH/g. In some embodiments,
the second polyol has a hydroxyl number ranging from about 40 to
about 60 mg KOH/g. In some embodiments, the second polyol has a
hydroxyl number ranging from about 30 to about 50 mg KOH/g.
[0060] For example, a first polyol such as Bayer's MULTRANOL 4500
may be used in combination with Bayer's ARCOL LG-56 and MULTRANOL
3900. In this case, the first polyol has a hydroxyl number ranging
from 365-395 mg KOH/g. For ARCOL LG-56, the second polyol has a
hydroxyl number ranging from 56.2 to 59.0 mg KOH/g. For MULTRANOL
3900 has a hydroxyl number ranging from 33.8 to 37.2 mg KOH/g.
However, these examples are not intended to be limiting. Any number
of polyol as described above may be selected for the hydroxyl
number in controlling the flexibility or rigidity of a polyurethane
product.
[0061] In one embodiment, mixture of polyols can be used to achieve
the desired mechanical strength and rigidity of the final
polyurethane composite material. In some embodiments, polyols with
OH functionality between about 2 to about 7 can be used. In other
embodiments, the average functionality of the polyols is between
about 4 to about 7. The polyurethane composite materials become
less expensive because the amount of isocyanate needed to react
with the polyols to substantially form the desired polyurethane
decreases. While this in some case may increase the rubberiness,
non-brittleness, or flexibility of the polyurethane composite
material, the correct balance of these functional polyols with OH
functionality, between about 4 to about 8, maintains the mechanical
properties of the polyurethane composite material, as compared to a
polyurethane composite material made from polyols with an average
functionality less than 4.
[0062] In some embodiments, the polyurethane composite material is
made by using higher functional polyols in place of polyols having
an average functionality of 2 or 3. In these embodiments, the
polyurethane composite material has more cross linking. Some
embodiments have higher impact strength, flexural strength,
flexural modulus, chemical resistance, and water resistance as
compared to the polyurethane composite material formed by polyols
having a functionality of about 2 to about 3.
[0063] In some embodiments, the polyurethane composite material is
made by using more than one polyol with different OH numbers to
give the same weighted average OH number. Such polyurethane
composite materials yield a more segmented polymer. By allowing
many polyols of different functionality and/or molecular weight to
be mixed together to make the needed OH number to balance the
number of isocyanate groups, the orderliness of the resulting
polymer chain is more segmented and less likely to align together.
In some embodiments, the polyurethane composite material comprises
three, four, five, or six types of polyols of different
functionality and/or molecular weight. For example, a polyurethane
system can be made from combination of multiple types of polyols,
wherein at least one first polyol has an average functionality of
about 2, wherein at least one second polyol has an average
functionality of about 4, and wherein at least one third polyol has
an average functionality of about 6. In one embodiment, the overall
number of hydroxyl groups may be adjusted with varying polyols. In
some embodiments, combinations of polyols with great number of
hydroxyl groups may be blended with smaller quantities of polyols
with less hydroxyl groups in order to produce a desired overall
number of hydroxyl groups, which will react with the
isocyanate.
[0064] In some embodiments, impact strength of the polyurethane
composite material is greater than polyurethane composite materials
comprising polyols of the same or substantially similar
functionality and/or molecular weight. Although the two
polyurethane compositions may comprise polyols with substantially
similar average functionality and/or molecular weight, the
polyurethane composition comprising polyols with substantially
different functionality may exhibit improved mechanical properties
such as impact strength. In some embodiments, polyurethane
composite materials comprising polyols of multiple functionalities
are more resistant to stress cracking.
[0065] Other embodiments of the polyurethane composite material are
made from at least one polyol with a molecular weight from about
2000 to about 8000. These polyurethane composite materials exhibit
an integral skin. In some embodiments, the skin is thicker. In
other embodiments, the skin is less porous and harder. In some
embodiments, the use of at least one polyol with a molecular weight
from about 2000 to about 8000 results in the migration of the at
least one polyol to migrate to the outer surface of the
polyurethane composite material, thus allowing more outer skin to
be formed.
[0066] In one embodiment, mixtures of two or more polyols may be
used. In some embodiments, each polyol of a multi-polyol
polyurethane system may be chosen for the various mechanical and
chemical properties that result in the polyurethane composite
produced as a result of using the polyol. For example, it is known
to persons having ordinary skill in the art that polyols are often
classified as rigid or flexible polyols based on various properties
of the individual polyol and the overall flexibility of a
polyurethane polymer produced from the respective polyols.
Typically, the rigidity or flexibility of the polyurethane formed
from any single polyol may be governed by one or more of the
hydroxyl number, functionality, and molecular weight of the polyol.
As such, one or more polyols with different characteristics may be
used to control the physical and mechanical characteristics of the
polyurethane composite material.
[0067] In one embodiment, the amount of rigid polyol is carefully
controlled in order to avoid making the composite too brittle. In
some embodiments, the weight ratio of rigid to flexible polyol
ranges from about 0.5 to about 20. In other embodiments, the ratio
of rigid to flexible polyol is about 1 to about 15. In other
embodiments, the ratio of rigid to flexible polyol is about 4 to
about 15. In other embodiments, the ratio of rigid to flexible
polyol is about 3 to about 10. In other embodiments, the ratio of
rigid to flexible polyol is about 6 to about 12.
[0068] If more than one polyol is used to form the polyurethane
composition, mixtures of polyols can be used. In certain
embodiments, the polyurethane is formed by reaction of a first
polyol and a second polyol. In some of these embodiments, the first
polyols has a functionality of at least three and a hydroxyl number
of about 250 to about 800, and more preferably about 300 to about
400. In some embodiments, the first polyol hydroxyl number is about
350 to about 410. In some of these embodiments, the molecular
weight of the first polyol ranges from about 200 to about 1000. In
other embodiments, the molecular weight of the first polyol ranges
from about 300 to about 600. In other embodiments, the molecular
weight of the first polyol ranges from about 400 to about 500.
Still, in some embodiments, the molecular weight of the first
polyol is about 440.
[0069] A second polyol can be used which produces a less rigid
polyurethane compared to a polyurethane produced if only the first
polyol is used. In some embodiments, the second polyol has a
functionality of about 3. In some embodiments, the functionality of
the second polyol is not greater than three. In these embodiments,
the second polyol can have a molecular weight of about 1000 to
about 6000. In other embodiments, the second polyol has a molecular
weight of about 2500 to about 5000. In some embodiments, the second
polyol has a molecular weight of about 3500 to about 5000. In some
embodiments, the molecular weight is about 4800. In other
embodiments, the molecular weight of the second polyol is about
3000. In some of these embodiments, the second polyol has a
hydroxyl number of about 25 to about 70, and more preferably about
50 to about 60.
Fillers
[0070] As discussed above, one or more filler materials may be
included in the polyurethane composite material. In some
embodiments, it is generally desirable to use particulate materials
with a broad particle size distribution, because this provides
better particulate packing, leading to increased density and
decreased resin level per unit weight of composite. Since the
inorganic particulate is typically some form of waste or scrap
material, this leads to decreased raw material cost as well. In
certain embodiments, particles having size distributions ranging
from about 0.0625 inches to below 325 mesh have been found to be
particularly suitable. In other embodiments, particles having size
distribution range from about 5 .mu.m to about 200 .mu.m, and in
another embodiment, from about 20 .mu.m to about 50 .mu.m.
[0071] Suitable inorganic particulates can include ground glass
particles, fly ash, bottom ash, sand, granite dust, slate dust, and
the like, as well as mixtures of these. Fly ash is desirable
because it is uniform in consistency, contains some carbon (which
can provide some desirable weathering properties to the product due
to the inclusion of fine carbon particles which are known to
provide weathering protection to plastics, and the effect of opaque
ash particles which block UV light, and contains some metallic
species, such as metal oxides, which are believed to provide
additional catalysis of the polymerization reactions. Ground glass
(such as window or bottle glass) absorbs less resin, decreasing the
cost of the composite.
[0072] In general, fly ash having very low bulk density (e.g., less
than about 40 lb/ft.sup.3) and/or high carbon contents (e.g.,
around 20 wt % or higher) are less suitable, since they are more
difficult to incorporate into the resin system, and may require
additional inorganic fillers that have much less carbon, such as
foundry sand, to be added. Fly ash produced by coal-fueled power
plants, including Houston Lighting and Power power plants, fly and
bottom ash from Southern California Edison plants (Navajo or
Mohave), fly ash from Scottish Power/Jim Bridger power plant in
Wyoming, and fly ash from Central Hudson Power plant have been
found to be suitable for use in the invention.
[0073] Some embodiments of the polyurethane composite materials
additionally comprise blends of various fillers. In some of these
embodiments, the polyurethane composite materials exhibit better
mechanical such as impact strength, flexural modulus, and flexural
strength. One advantage in using blends of such systems is higher
packing ability of blends of fillers. For example, a 1:1 mixture of
coal fly ash and bottom ash has also been found to be suitable as
the inorganic particulate composition.
[0074] Example in Table 1: The examples below were all mixed in a
thermoset aromatic polyurethane system made with Hehr 1468
polyether polyol (15% of the total weight of the non-ash portion),
water (0.2%), Air Products DC-197 (1.5%), Air Products 33LV amine
catalyst (0.06%), Witco Fomrez UL28 tin catalyst (0.02%), and Hehr
1426A isocyanate (15%). 1.5.times.3.5.times.24 inch boards were
made.
TABLE-US-00001 TABLE 1 Ash % by Weight of Total Flexural Flexural
Resin Density, strength, Modulus, Coal Ash Type System lbs/cu ft
psi Ksi Mohave bottom ash 65% 70 1911 421 Mohave bottom ash + 65%
74 2349 466 Mohave fly ash (50/50) Mohave bottom ash 75% 68 930 266
Mohave bottom ash + 75% 79 2407 644 Mohave fly ash (50/50) Navajo
bottom ash 65% 69 2092 525 Navajo bottom ash + Navajo 65% 74 2540
404 fly ash (50/50) Navajo bottom ash 75% 70 1223 377 Navajo bottom
ash + Navajo 75% 84 2662 691 fly ash (50/50)
[0075] Thus, embodiments of the polyurethane composite material
which comprise bottom and fly ash exhibit increased flexural
strength and flexural modules as compared to polyurethane composite
material comprising bottom ash alone. Some of these embodiments
have a density of about 65 lbs/ft.sup.3 to about 85 lbs/ft.sup.3,
including about 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, or 85
lbs/ft.sup.3.
[0076] In some of embodiments, the polyurethane composite material
comprising about 65% ash filler of which about 32.5 wt % was bottom
ash and about 32.5% was fly ash had a flexural strength of at least
about 2300 psi, more preferably at least about 2400 psi, and even
more preferably at least about 2500 psi. In some of embodiments,
the polyurethane composite material comprising about 75% ash filler
of which about 37.5 wt % was bottom ash and about 37.5% was fly ash
had a flexural strength of at least about 2400 psi, more preferably
at least about 2500 psi, and even more preferably at least about
2650 psi.
[0077] In some of embodiments, the polyurethane composite material
comprising about 65% ash filler of which about 32.5 wt % was bottom
ash and about 32.5% was fly ash had a flexural modulus of at least
about 400 Ksi, more preferably at least about 440 Ksi, and even
more preferably at least about 460 Ksi. In some of embodiments, the
polyurethane composite material comprising about 75% ash filler of
which about 37.5 wt % was bottom ash and about 37.5% was fly ash
had a flexural modulus of at least about 640 Ksi, more preferably
at least about 660 Ksi, and even more preferably at least about 690
Ksi.
[0078] In some embodiments, slate dust can be added to the
polyurethane composite material to provide UV protection to the
polyurethane composite material. Some of these embodiments
additionally comprise one or more of pigments, light stabilizers,
and combinations thereof. In some embodiments, polyurethane
composite materials comprising slate dust exhibit substantially
improved weathering. In some embodiments, the polyurethane
composite material comprises a dust. A dust may be selected from at
least one of slate dust, granite dust, marble dust, other
stone-based dusts, and combinations thereof. In some embodiments,
the polyurethane composite material comprises about 0.2 to about 70
wt % dust. In other embodiments, the polyurethane composite
materials comprise about 10 to about 50 wt % of dust. In other
embodiments, the polyurethane composite materials comprise about 20
to about 60 wt % of dust. In other embodiments, the polyurethane
composite materials comprise about 30 to about 55 wt % of dust. In
some embodiments, dust may be added to the composite material as
additional filler. In this embodiment, the filler that is not dust
may be present in the composite in amounts from about 10 to about
70 weight percent and the dust may be added in amounts of about 5
to about 35 weight percent.
[0079] The following is an example of a polyurethane composite
material that comprises dust. The example should be in no way
limiting, as other embodiments will be readily understood by a
person having ordinary skill in the art.
[0080] Example from Table 2: In a blend of Cook Composites 5180 MDI
(13.1% by weight), 5205 polyol (3.91%), Dow DER (1.98%), antimony
trioxide flame retardant (3.52%), with Air Products DC-197 silicone
surfactant (0.23%), benzoyl peroxide (0.55%), and chipped slate
(59.5%), with the added pigments, carbon black and slate dust, all
acting as UV inhibitors. The light exposure was to a high fusion
(UV light) chamber at AlliedSignal Aerospace. Usually a 10 minute
exposure in this chamber would deeply discolor this resin system
due to the yellowing of the MDI-based ingredients in the resin
system.
TABLE-US-00002 TABLE 2 Sample # (Numbers Coal Red Iron Oxide Green
Chromium Time for Slight Change are purposely Fly Slate Pigment,
Cardinal Oxide Pigment, Carbon Black, in Sheen or Slight not in
order) Ash Dust Color Co. Cardinal Color Co. Chroma-Tek Co.
Discoloration, minutes 1 16.7% -- 10 2 16.7% -- 0.58% 10 3 16.6% --
0.58% 10 4 16.7% -- 0.58% 10 5 -- 16.6% 20 7 -- 16.6% 0.58% 20 8 --
16.6% 0.58% 20 6 -- 16.6% 0.58% 20+ (Test Ended)
[0081] In the above test, clearly slate dust provided better light
stability than coal ash, and the combination of slate dust plus
carbon black provided the best UV resistance, and had not failed
yet in the 20 minute test (the only sample to not fail). The effect
of the slate dust was far more influential for UV stability then
the various pigments tested, including carbon black plus fly
ash.
[0082] In some embodiments, the polyurethane composite material
composition comprises about 20 to about 95 weight percent of
inorganic filler, which includes, for example, approximately 20,
25, 30, 35, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66,
68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, or 94 weight
percent of filler. These amounts may be based on the total of all
of the fillers, such as one or more of fly ash, dust, and fibrous
material. However, the filler values may also be representative of
only one type of filler, e.g, fly ash. In certain embodiments, the
polymeric composite material may contain the filler in an amount
within a range formed by the two of the foregoing approximate
weight percent. In other embodiments, the polyurethane composite
material comprises about 40 to about 85 weight percent of the
filler. In other embodiments, the polyurethane composite material
comprises about 55 to about 80 weight percent of the filler. In
other embodiments, the polyurethane composite material comprises
about 65 to about 85 weight percent of the filler. In other
embodiments, the polyurethane composite material comprises about 40
to about 60 weight percent of the filler. In other embodiments, the
polyurethane composite material comprises about 55 to about 70
weight percent of the filler. Here, the unit "weight percent"
refers to the relative weight of the filler component compared to
the total weight of the composite material.
Fibers
[0083] In some embodiments, reinforcing fibers can also be
introduced into the polyol mixture prior to introduction of the
isocyanate. In some embodiments, reinforcing fibers may be
introduced after the at least one polyol and the isocyanate are
mixed. These can include fibers per se, such as chopped fiberglass
(chopped before or during mixing process such as extrusion), or
fabrics or portions of fabrics, such as rovings or linear tows, or
combinations of these. Typically, the reinforcing fibers range from
about 0.125 in. to about 1 in, more particularly from about 0.25 in
to about 0.5 in. The reinforcing fibers give the material added
strength (flexural, tensile, and compressive), increase its
stiffness, and provide increased toughness (impact strength or
resistance to brittle fracture). Fabrics, rovings, or tows increase
flexural stiffness and creep resistance. The inclusion of the
particular polyurethane networks of the invention, together with
the optional surfactants, and the inorganic particulate sizes used
make the composite of the invention particularly and surprisingly
well suited for inclusion of reinforcing fibers in foamed material,
which normally would be expected to rupture or distort the foam
bubbles and decrease the strength of the composite system.
[0084] In addition to inclusion of reinforcing fibers into the
polyol mixture prior to polymerization, oriented axial fibers can
also be introduced into the composite after extrusion, as the
polymer exits the extruder and prior to any molding. The fibers
(e.g., glass strings) can desirably be wetted with a mixture of
polyol (typically a higher molecular weight, rigid polyol) and
isocyanate, but without catalyst or with a slow cure catalyst, or
with other rigid or thermosetting resins, such as epoxies. This
allows the wetted fiber to be incorporated into the composite
before the newly added materials can cure, and allows this curing
to be driven by the exotherm of the already curing polymer in the
bulk material.
[0085] Whether added before or after polymerization and/or other
mixing processing such as extrusion, the dispersed reinforcing
fibers may be bonded to the polymeric matrix phase, thereby
increasing the strength and stiffness of the resulting material.
This enables the material to be used as a structural synthetic
lumber, even at relatively low densities (e.g., about 20 to about
60 lb/ft.sup.3).
[0086] According to certain embodiments, many types of fibers may
be suitable for use in the polyurethane composite material. In some
embodiments, the polyurethane composite materials comprise at least
one of basalt, Wollastinite, other mineral fibers, or combinations
thereof. In some embodiments, these components may be used in place
of or in combination with glass fibers
[0087] Example from Table 3: In a mixture of Hehr 1468 polyether
polyol (500 grams), Hehr 1468 MDI (432 g), water (3 g), Air
Products 33LV amine catalyst (1 g), Mohave coal fly ash (800 g),
and the following reinforcing fibers, all made in
1.5.times.3.5.times.24 inch lumber samples:
TABLE-US-00003 TABLE 3 Flexural Flexural Fiber Strength, Modulus,
Added psi Ksi None -- 1239 68 1/4 inch long chopped 1% 1587 92
fiberglass 1/4 inch long chopped 2.5% 1436 91 fiberglass 1/4 inch
long chopped 5% 1887 125 fiberglass 1/4 inch long chopped 1% 2241
97 basalt fiber 1/4 inch long chopped 2.5% 2646 131 basalt fiber
1/4 inch long chopped 5% 3516 174 basalt fiber Fiberglass + basalt
2.5% 2732 135 (1.25% each)
[0088] In some embodiments, basalt fibers provide more flexural
strength, and flexural modulus to the highly-filled polyurethane
composite materials than fiberglass, and the combination of the two
fibers gives a synergistic effect on both measured properties.
[0089] In some of embodiments, the polyurethane composite material
comprising about 1.25% of chopped fiber glass and about 1.25% of
basalt had a flexural strength of at least about 2650 psi, more
preferably at least about 2700 psi, and even more preferably at
least about 2730 psi.
[0090] Axial fibers or fabrics can also be added to the
polyurethane composite material. These fiber and/or fabric
typically increase the rigidity of the polyurethane composite
material, and increase the mechanical strength. Using thicker
fibers, rovings, tows, fabrics or rebar in the axial or stressed
direction of the product can eliminate or reduce the tendency of
the plastic to creep with time or higher temperature. These
reinforcements also give higher initial tensile and flexural
strength, and higher flexural and tensile stiffness of the
polyurethane composite material. One advantage of using axial
fibers or fabrics is that the fibers or fabrics are oriented in a
direction that supports the polyurethane composite material. Unlike
axial fibers, randomly chopped fibers are less structurally
supportive.
[0091] In some embodiments, the axial fibers or fabrics may be
added while dry (no resin on them). In other embodiments, the
fibers or fabrics may be "wet" with resin when mixed with the
polyurethane composite material. In some embodiments, the axial
fibers or fabrics are added to the polyol and catalyst premix. In
other embodiments, the axial fibers or fabrics are added to the
isocyanate premix. Still, other embodiment may include adding the
axial fibers of fabric together with a slow or delayed reaction
polyol, catalyst, and isocyanate. Thus, the axial fibers can be
added with multiple components of the polyurethane composite
material.
[0092] In some embodiments, the axial fibers or fabrics may be
added to the polyurethane composite material under tension, as is
done with steel rebar in structural concrete. This provides
additional strength in the tension direction, and in bending, as
well as higher stiffness in the tension and bending directions.
[0093] Example in Table 4: Glass and basalt fibers were implanted
in a highly-filled coal ash-thermosetting polyurethane mixture
while still uncured, and the fibers laid lengthwise down the
urethane in a box mold, and only on the top of the board (on one
face). The fibers were laid in the urethane mixture about 1/8 inch
below the surface of the mix, but frequently the fibers moved
during the subsequent foaming and cure in the closed box mold, and
sometimes showed on the board surface.
[0094] The flexural properties were unaffected by this fiber
movement. The glass fibers from rovings were 0.755 g/ft, the basalt
rovings from Ahlstrom (Canada) were 0.193 g/ft. The boards were
1.5.times.3.5.times.24 inches. During flexural testing the boards
were tested so that the rovings were on the tensile side of the
boards (not the compression side). Some of the rovings were
pre-wetted with the same resin system as in the boards, but without
the coal ash filler. The resin system was: Bayer Multranol 4035
polyether polyol (16.6% by weight), Bayer Multranol 3900 polyether
polyol (5.5%), Air products DC-197 silicone surfactant (0.16%),
water (0.07%), Witco Fomrez UL-28 tin catalyst (0.03%), Air
Products 33LV amine catalyst (0.10%), Coal fly ash (49%), Bayer
MRS4 MDI isocyanate (20.4%).
TABLE-US-00004 TABLE 4 Number of Rovings Total % Board Inserted in
Board, Fiber Density, Flexural Flexural on 1 face, spread Wetted
with on Board lbs/cu Strength, Modulus, Fiber Type evenly on face
Resin? Weight ft psi Ksi None (Resin Alone) -- -- -- 45 1319 82
Glass 10 No 0.77% 32 2717 37 '': 10 Yes 1.43% 36 3533 77 '' 10 Yes,
but pre-cured 0.73% 58 4000 188 '' 20 Yes 2.72% 35 4356 84 Basalt
fiber 10 No 0.26% 41 1191 73 '' 40 No 0.79% 49 2465 96
[0095] By wetting the glass fibers with uncured resin or cured
resin, the boards are considerably stronger--even stronger than
basalt reinforced boards with the same weight of fiber. By wetting
the glass roving with polyurethane resin, the strength of the glass
roving exceeds that of the unwetted basalt fiber.
[0096] In some embodiments, polyurethane composite materials
comprising less than about 1.5 wt % of glass fiber rovings prewet
with resin had a flexural strength of at least about 3500 psi and
more preferably at least about 4000 psi. In embodiments wherein the
prewet glass fiber rovings were procured with the polyurethane
resin, the flexural strength was at least about 150 Ksi, and more
preferably at least about 180 Ksi.
Chain Extenders & Cross Linkers
[0097] In some embodiments of the polyurethane composite material,
low molecular weight reactants such as chain extenders or cross
linkers provide a more polar area in the polyurethane composite
material. These reactants allow the polyurethane system to more
readily bind the inorganic filler and/or inorganic or organic
fibers in the polyurethane composite material.
[0098] In some embodiments, the polyurethane composite material
comprises one or more selected from chain extenders, crosslinkers,
and combinations thereof. In some embodiments, the chain extenders
can be selected one or more from the group comprising ethylene
glycol, glycerin, 1,4-butane diol, trimethylolpropane, glycerol, or
sorbitol. In some embodiments, at least one cross linker may be
used to replace at least a portion of the at least one polyol in
the polyurethane composite material. In some cases, this results in
reduced costs of the overall product.
[0099] In some embodiments which comprise chain extenders, the
mechanical properties of the polyurethane composite material are
improved. In some embodiments, chain extenders are not blocked from
reacting with the isocyanate by the filler. This is due to the
molecular size of the chain extenders. In some embodiments, the
chain extenders result in better mechanical properties as compared
to polyurethane composite materials with high filler inorganic
loads, which do not use chain extenders. These mechanical
properties include flexural strength and modulus, impact strength,
surface hardness, and scratch resistance.
[0100] In other embodiments, polyurethane composite material
comprising chain extenders traps metals and metal oxides. This is
advantageous in highly filled polyurethane composite materials when
the filler is coal or other ashes, including fly ash and bottom
ash, which can contain hazardous heavy metals. In some embodiments,
the polyurethane composite material substantially prevents leaching
of heavy metals in the polyurethane composite material.
[0101] In some embodiments, a highly filled polymer composition
comprising chain extenders provides faster curing and less need for
post-curing of the polyurethane composite materials. In some
embodiments, the chain extenders provide better water resistance
for the polyurethane composite material. These chain extenders
include diamine chain extenders, such as MBOCA and DETDA. However,
other embodiments of the polyurethane composite material may
comprise glycol extenders.
Blowing Agents
[0102] Foaming agent may also be added to the reaction mixture if a
foamed product is desired. While these may include organic blowing
agents, such as halogenated hydrocarbons, hexanes, and other
materials that vaporize when heated by the polyol-isocyanate
reaction, it has been found that water is much less expensive, and
reacts with isocyanate to yield CO.sub.2, which is inert, safe, and
need not be scrubbed from the process. In addition, CO.sub.2
provides the type of polyurethane cells desirable in a foamed
product (i.e., mostly closed, but some open cells), is highly
compatible with the use of most inorganic particulate fillers,
particularly at high filler levels, and is compatible with the use
of reinforcing fibers.
[0103] If water is not added to the composition, some foaming may
still occur due to the presence of small quantities of water
(around 0.2 wt %, based on the total weight of the reaction
mixture) introduced with the other components as an "impurity."
Such water-based impurities may be removed by drying of the
components prior to blending. On the other hand, excessive foaming
resulting from the addition of too much water (either directly or
through the introduction of "wet" reactants or inorganic
particulate materials) can be controlled by addition of an
absorbent, such as UOP "T" powder.
[0104] The amount of water present in the system will have an
important effect on the density of the resulting composite
material. This amount generally ranges from about 0.10 wt % to
about 0.40 wt %, based on the weight of polyol added, for composite
densities ranging from about 20 lb/ft' to about 90 lb/ft.sup.3.
However, polyurethane composite material densities may be
controlled by varying one or more other components as well. In some
embodiments, the overall density of the polyurethane composite
material may range from about 30 lb/ft' to about 80 lb/ft.sup.3. In
some embodiments, the overall density of the polyurethane composite
material may range from about 40 lb/ft' to about 60
lb/ft.sup.3.
[0105] In some embodiments, the addition of excess blowing agent or
water above what is needed to complete the foam reaction adds
strength and stiffness to the polyurethane composite material, if
the material is restrained during the forming of the composite
material. Typically, excess blowing agent may be added to the
polyol premixture. Such excessive blowing agent may produce a
vigorously foaming reaction product. To contain such reaction
product, a forming device that contains the pressure or restrains
the materials from expanding may be used. Such forming devices are
further described herein. The restraint of the material or the
higher pressure created by a mold or restraining forming belts,
causes higher pressure within the material which modifies the foam
cell structure, thus allowing higher mechanical properties of the
resulting cured material.
[0106] According to certain embodiments, use of excess blowing
agent in formation of the polyurethane composite material may also
improves the water resistance of the polyurethane composite
material. In some embodiments, use of excessive blowing agent may
also increase the thickness and durability of the outer skin of the
self skinning polyurethane composite material.
Solvents
[0107] The addition of solvents to the reaction mixture may also
provide certain advantages. In some embodiments of the polyurethane
composite materials, solvents can be added to the polyol premix
prior to or during the formation of the polyurethane. While it is
described that solvents are added to the polyol premix, solvents
may also be added at other stages of mixing of various components
of the polyurethane composite material. In some embodiments, the
solvent may be added with any one or more components of the
reaction mixture which produces the polyurethane composite
material.
[0108] In some embodiments, addition of a solvent to a polyol
premix results in a polyurethane composite material that is more
scratch and mar resistance as compared to the same polyurethane
composition made without the solvent added to the polyol premix.
Additional properties that result in some embodiments include a
harder skin. In addition, solvents may cause a higher concentration
of resin material to be in the self skinning layer, as opposed to
the fillers and reinforcing fibers. In some materials, this
provides a polyurethane composite material having a higher
concentration of ultraviolet stabilizers, antioxidants, and other
additives are closer to the outside of the composite material. In
some embodiments, use of solvent produces a polyurethane composite
material with an increases skin thickness. In other embodiments,
the skin density may also be increased. Still, in other
embodiments, the addition of solvents may decrease the interior
density of the polyurethane composite material.
[0109] In some embodiments, the addition of solvent to the polyol
premix substantially improves the weathering of the polyurethane
composite material due to the higher density and thickness of the
outer skin, which can contain more concentrated antioxidants,
pigments, fillers and UV inhibitors. In other embodiments, the
addition of the solvent to the polyol premix substantially prevents
discoloration of the polyurethane composite material when a sample
of the material is exposed to sunlight or UV radiation. In other
embodiments, the addition of the solvent to the polyol premix
provides a polyurethane composite material (upon mixing of the rest
of the components) which has improved anti-static properties.
[0110] For example, the addition of about 2 to about 10 wt % of a
solvent selected from the group consisting of a hydrocarbon solvent
(pentane, hexane), carbon tetrachloride, trichloroethylene,
methylene chloride, chloroform, methyl chloroform,
perchloroethylene, or ethyl acetate to a polyol premix, the
resulting self-skinning polyurethane composite material has a
thicker skin as compared to polyurethane composite materials which
are not create by the addition of a solvent to the polyol premix.
As a result, the outer skin is much thicker, including greater than
about 100, 200, 500, and about 1500% thicker as compared to a
polyurethane made without adding solvent to the polyol premix. In
some embodiments, the polyurethane composite material made by the
addition of solvent to the polyol premix may have an increase outer
density skin, thus making the skin harder, where the skin is
greater than about 50, 75 and about 150% harder as compared to a
polyurethane made without adding the solvent to the polyol premix.
Furthermore, some embodiments of the polyurethane composite
material have an interior density that is less than between about
10 and about 50% as compared as compared to a polyurethane made
without adding the solvent to the polyol.
Additional Components
[0111] The polyurethane composite materials can contain one or more
compounds or polymers in addition to the foregoing components.
Additional components or additives may be added to provide
additional properties or characteristics to the composition or to
modify existing properties (such as mechanical strength or heat
deflection temperature) of the composition. For example, the
polyurethane composite material may further include a heat
stabilizer, an anti-oxidant, an ultraviolet absorbing agent, a
light stabilizer, a flame retardant, a lubricant, a pigment and/or
dye. One having ordinary skill in the art will appreciate that
various additives may be added to the polymer compositions
according to embodiments of the invention. Some of these additional
additives are further described herein.
UV Light Stabilizers, Antioxidants, Pigments
[0112] Ultraviolet light stabilizers, such as UV absorbers, can be
added to the polyurethane composite material prior to or during its
formation. Hindered amine type stabilizers, and opaque pigments
like carbon black powder, can greatly increase the light stability
of plastics and coatings. In some embodiments, phenolic
antioxidants are provided. These antioxidants provide increased UV
protection, as well as thermal oxidation protection.
[0113] In some embodiments, the polyurethane composite material
comprises one or more selected from the group consisting of light
stabilizers and antioxidants. In combination, the light stabilizers
and antioxidants provide a synergistic effect of reducing the
detrimental effects of UV light as compared to either component
used alone in the polyurethane composite material. According to
certain embodiments, the effect is non-additive.
[0114] For example, in aromatic thermosetting polyurethanes, using
0.5 wt % Tinuvin 328 light absorber alone provides some resistance
to UV, such as reduced yellowing, less chalking, and less
embrittlement. Adding Irganox 1010 antioxidant at 0.5 wt % greatly
improves the resistance to UV, and even using 0.2 wt % of each
provides better stability than either of the stabilizers at 0.5 wt
% alone.
[0115] Pigment or dye can be added to the polyol mixture or can be
added at other points in the process. The pigment is optional, but
can help make the composite material more commercially acceptable,
more distinctive, and help to hide any scratches that might form in
the surface of the material. Typical examples of pigments include
iron oxide, typically added in amounts ranging from about 2 wt % to
about 7 wt %, based on the total weight of the reaction
mixture.
Surfactants and Catalysts
[0116] One or more catalysts are generally added to control the
curing time of the polymer matrix (upon addition of the
isocyanate), and these may be selected from among those known to
initiate reaction between isocyanates and polyols, such as
amine-containing catalysts, such as DABCO and
tetramethylbutanediamine, tin-, mercury- and bismuth-containing
catalysts. To increase uniformity and rapidity of cure, it may be
desirable to add multiple catalysts, including a catalyst that
provides overall curing via gelation, and another that provides
rapid surface curing to form a skin and eliminate tackiness. For
example, a liquid mixture of 1 part tin-containing catalyst to 10
parts amine-containing catalyst can be added in an amount greater
than 0 wt % and below about 0.10 wt % (based on the total reaction
mixture) or less, depending on the length of curing time desired.
Too much catalyst can result in overcuring, which could cause
buildup of cured material on the processing equipment, or too stiff
a material which cannot be properly shaped, or scorching; in severe
cases, this can lead to unsaleable product or fire. Curing times
generally range from about 5 seconds to about 2 hours.
[0117] A surfactant may optionally be added to the polyol mixture
to function as a wetting agent and assist in mixing of the
inorganic particulate material. The surfactant also stabilizes and
controls the size of bubbles formed during foaming (if a foamed
product is desired) and passivates the surface of the inorganic
particulates, so that the polymeric matrix covers and bonds to a
higher surface area. Surfactants can be used in amounts below about
0.5 wt %, desirably about 0.3 wt %, based on the total weight of
the mixture. Excess amount of surfactant can lead to excess water
absorption, which can lead to freeze/thaw damage to the composite
material. Silicone surfactants have been found to be suitable for
use in the invention. Examples include DC-197 and DC-193
(silicone-based, Air Products), and other nonpolar and polar
(anionic and cationic) products.
Other Additives
[0118] In some embodiments, the filled polyurethane composite
material additionally comprises at least one coupling agent.
Coupling agents and other surface treatments such as viscosity
reducers or flow control agents can be added directly to the filler
or fiber, and incorporated prior to, during, and after the mixing
and reaction of the polyurethane composite material. In some
embodiments, the polyurethane composite materials comprise
pre-treated fillers and fibers.
[0119] In some embodiments, the coupling agents allow higher filler
loadings of an inorganic filler such as fly ash. In embodiments,
these ingredients may be used in small quantities. For example, the
polyurethane composite material may comprises about 0.01 wt % to
about 0.5 wt % of at least one coupling agent. In some of these
embodiments, the polyurethane composite materials exhibit greater
impact strength, as well as greater flexural modulus and strength,
as compared to those materials without at least one coupling agent.
Coupling agents reduce the viscosity of the resin/filler mixture.
In some embodiments, coupling agents increase the wetting of the
fibers and fillers by the resin components during the mixing the
components.
[0120] In other embodiments, coupling agents reduce the need for
colorants by improving the dispersion of the colorants, and the
break up of colorant clumps. Thus, the polyurethane composite
material which comprises coupling agents and a colorant may exhibit
substantially uniform coloration throughout the polyurethane
composite material.
[0121] Example in Table 5: The following flow control agents were
tested in a urethane polyol with a high loading of filler, such
that the combination would flow through a Zahn #5 cup viscometer.
The polyol was Bayer Multranol 4035 polyether used at 70 g, with 30
g of two different fillers--tested separately. The polyol+filler
were hand mixed and put into the Zahn Cup with the bottom port
closed with tape. When the Zahn cup was full, the tape was removed
and the time for the mixture to flow out of the Cup was measured.
All tests at 65.degree. F. (18.degree. C.). The agents were: Air
Products DABCO DC197 silicone-based surfactant, Kenrich
Petrochemicals Ken-React LICA 38, and Ken-React KR 55
organo-titanates, Shin-Etsu Chemical KBM-403 organo-silane.
[0122] These tests show that even 0.1% of the flow control agent on
the weight of the filler can markedly improve the flow of the
mixture. This flow improvement allows higher levels of filler to be
used in urethane mixtures, better wetting of the filler by the
polyol, and more thorough mixing of all the components. The DC-197
surfactant works well, but only at much higher concentrations.
TABLE-US-00005 TABLE 5 Time to Flow out of #5 Zahn % Flow Cup,
& Improvement Improver stop (Faster Weight, dripping, Flow)
Filler Type Flow Improver grams seconds Over Control Ground None
(Control) -- 60 -- waste bottle glass Ground KBM 403 0.14 50 15%
waste bottle glass Ground KBM 403 0.51 g + 1.34 53 18% waste bottle
DC-197 0.83 g glass Ground KBM 403 0.15 g + 0.75 56 7% waste bottle
DC-197 0.60 g glass Ground DC-197 0.67 50 13% waste bottle glass
Cinergy fly None (Control) -- 46 -- ash Cinergy fly KBM 403 0.21 38
17% ash Cinergy fly KR 55 0.06 41 11% ash Cinergy fly LICA 38 0.04
42 13% ash Cinergy fly KBM 403 0.03 40 16% ash
Ratios of the Components Used to Make the Polyurethane Composite
Material
[0123] Variations in the ratio of the at least one polyol to the
isocyanate have various changes on the overall polyurethane product
and the process for making the polyurethane composites with high
inorganic filler loads. High filler in such systems typically
inhibit or physically block the reaction or action of the various
polyurethane composite components, including the at least one
polyol, the di- or polyisocyanate, the surfactants, flow modifiers,
cell regulators and the catalysts. In addition, the heat that is
released during the course of the exothermic reaction in forming
the polyurethane composite is much higher in an unfilled
polyurethane system. A larger isocyanate index gives higher
temperature exotherms during the process of making the polyurethane
composite material. By adding, 5 to 20 wt % excess, and more
preferably 5 to 10 wt % excess, of the isocyanate to the otherwise
chemically balanced at least one polyol that may comprise chain
extenders with additional OH groups (thus, measuring the balance by
the overall OH numbers).
[0124] Higher temperature exotherms result in more cross linking of
the polyol and isocyanate, and/or a more complete reaction of the
hydroxyl groups and isocyanate groups. In some embodiments, a
higher isocyanate index also causes much higher cross link
densities. In other embodiments, the higher isocyanate index
provides a more "thermoset" type of polyurethane composite. In
other embodiments, the higher isocyanate index provides a
polyurethane with a more chemically resistant polyurethane
composite material when exposed to chemicals. In some cases, these
chemicals are solvents and water. In certain embodiments, the
higher isocyanate index provides a polyurethane composite system
with a higher heat distortion temperature. The heat distortion
temperature or its effects may be determined by elevated
temperature creep tests, standard ASTM heat distortion testing,
surface hardness variations with increased temperature, for
example, in an oven, and changes in mechanical properties at
increasing temperature.
[0125] Representative suitable compositional ranges for synthetic
lumber, in percent based on the total composite composition, are
provided below:
[0126] At least one polyol: about 6 to about 28 wt %
[0127] Surfactant: about 0.2 to about 0.5 wt %
[0128] Skin forming catalyst about 0.002 to about 0.01 wt %
[0129] Gelation catalyst about 0.02 to about 0.1 wt %
[0130] Water 0 to about 0.5 wt %
[0131] Chopped fiberglass 0 to about 10 wt %
[0132] Pigments 0 to about 6 wt %
[0133] Inorganic particulates about 60 to about 85 wt %
[0134] Isocyanate about 6 to about 20 wt %
[0135] Axial tows 0 to about 6 wt %.
[0136] Additional components described herein can be added in
various amounts. Such amount may be determined by persons having
ordinary skill in the art.
Mixing and Reaction of the Components of the Polyurethane Composite
Material
[0137] The polyurethane composite material can be prepared by
mixing the various components described above including the
isocyanate, the polyol, the catalyst, the inorganic filler, and
various other additives. In some embodiments, one or more other
additives may be mixed together with the components of the
polyurethane composition. One or more component resins can be
heated to melt prior to the mixing or the composition may be heated
during the mixing. However, the mixing can occur when each
components is in a solid, liquid, or dissolved state, or mixtures
thereof. In one embodiment, the above components are mixed together
all at once. Alternatively, one or more components are added
individually. Formulating and mixing the components may be made by
any method known to those persons having ordinary skill in the art,
or those methods that may be later discovered. The mixing may occur
in a pre-mixing state in a device such as a ribbon blender,
followed by further mixing in a Henschel mixer, Banbury mixer, a
single screw extruder, a twin screw extruder, a multi screw
extruder, or a cokneader.
[0138] In some preferred embodiments, the polyurethane composite
material can be prepared by mixing the polyols together (if
multiple polyols are used), and then mixing them with various
additives, such as catalysts, surfactants, and foaming agent, and
then adding the inorganic particulate phase, then any reinforcing
fiber, and finally the isocyanate. While mixing of some of the
components can occur prior to extrusion, all of the components may
alternatively be mixed in a mixer such as an extruder.
[0139] In one embodiment, it has been found that this order of
blending results in the manufacture of polyurethane composite
materials suitable for building material applications. Thus, it has
been discovered that the order of mixing, as well as other reaction
conditions may impact the appearance and properties of the
resulting polyurethane composite material, and thus its commercial
acceptability.
[0140] One particular embodiment relates to a method of producing a
polymer matrix composite, by (1) mixing a first polyol and a second
polyol with a catalyst, optional water, and optional surfactant;
(2) optionally introducing reinforcing fibrous materials into the
mixture; (3) introducing inorganic filler into the mixture; (4)
introducing poly- or di-isocyanate into the mixture; and (5)
allowing the exothermic reaction to proceed without forced cooling
except to control runaway exotherms.
[0141] The process for producing the composite material may be
operated in a batch, semibatch, or continuous manner. Mixing may be
conducted using conventional mixers, such as Banbury type mixers,
stirred tanks, and the like, or may be conducted in an extruder,
such as a twin screw, co-rotating extruder. When an extruder is
used, additional heating is generally not necessary, especially if
liquid polyols are used. In addition, forced cooling is not
generally required, except for minimal cooling to control excessive
or runaway exotherms.
[0142] For example, a multi-zone extruder can be used, with polyols
and additives introduced into the first zone, inorganic
particulates introduced in the second zone, and chopped fibers,
isocyanate, and pigments introduced in the fifth zone. A twin
screw, co-rotating, extruder (e.g. 100 mm diameter, although the
diameter can be varied substantially) can be used, with only water
cooling (to maintain substantially near room temperature), and
without extruder vacuum (except for ash dust). Liquid materials can
be pumped into the extruder, while solids can be added by suitable
hopper/screw feeder arrangements. Internal pressure build up in
such an exemplary arrangement is not significant.
[0143] Although gelation occurs essentially immediately, complete
curing can take as long as 48 hours, and it is therefore desirable
to wait at least that long before assessing the mechanical
properties of the composite, in order to allow both the composition
and the properties to stabilize.
Extrusion
[0144] As discussed above, particular methods related to extruding
polyurethane composite materials. One particular method includes
extruding the polyurethane composite materials as described herein
through an extruder having various segments and multiple screw
elements
[0145] Referring to FIG. 4, one example of an extruder suitable for
forming polyurethane composite materials may include up to nine
barrel segments. As shown, each barrel segment includes at least
one screw element. In addition, some or all of the barrel segments
have a material input port.
[0146] In a first segment of the extruder, the at least one polyol
may be introduced to the extruder. In some embodiments, the at
least one polyol may include a blend of one or more polyols.
Additionally, the at least one polyol may be blended with one or
more of the catalyst, surfactants, blowing agents and other
components described herein. In some embodiment, each components
may be added individually or together. In some embodiments, the
components are preblended prior to introduction to the extruder. As
shown in FIG. 4, a first segment of the extruder includes a
transport screw. As the transport screw is driven, the at least one
polyol and optional other components are transported by the screw
toward the output end of the extruder
[0147] In a second segment of the extruder, inorganic filler
material such as ash may be introduced to the extruder. The
inorganic filler material is blended with the components from the
first segment. As shown in FIG. 4, a second segment of the extruder
includes a transport screw. The transport screw may further
transfer the components from the first and second segments of the
extruder toward the output end of the extruder. As the first and
second segment include a transport screw, the first and second
segment may be classified as a first conveying section.
[0148] Components inputted in a first or second segment may be
transferred to a third segment of the extruder by the screw. In a
third segment of the extruder, previously inputted components may
be mixed further by slotted screws. A third segment may also
include lobal screws. In some embodiments, the mixing provides a
substantially uniform mixture of one or more of least one polyol,
at least one catalyst, a surfactant, an optional blowing agent,
pigment, and filler. These components experience more shearing
forces created by the slotted screw. The previous introduced
components may then be further transferred toward the output end of
the extruder. In some embodiments, the components are transferred
to a fourth segment of the extruder. As shown in FIG. 4, a fourth
segment may contain one or more of lobal and slow transport screws.
As the third and fourth segments may contain mixing elements, such
segments may be classified as a first mixing section. This screw
provides additional mixing to provide a more homogenous mixture of
the components. This screw also may provide good wetting of the
fillers and fibers. It has been discovered that lobal screws
provide a more homogeneous mixture of the previously introduced
components.
[0149] In some embodiments, the isocyanate components may be
introduced subsequent to the polyol component. As shown in FIG. 4,
the isocyanate component (monomeric or oligomeric di- or
polyioscyanate) is introduced in a subsequent segment of extruder
related to the segment in which the at least one polyol was
introduced. More specifically, the isocyanate component is
introduced in a fifth segment of the extruder. In some embodiments,
a reaction may begin to occur between the at least one polyol and
the at least one isocyanate. However, a delayed action catalyst may
used to substantially prevent overreaction of the components until
the composite material has exited the extruder. As the reaction
between the at least one polyol and the at least one isocyanate is
exothermic, cooling may be required. Cooling may also be required
in subsequent barrel segments. In previous barrel segments, cooling
is generally not required as no reaction has occurred. However,
cooling may be provided to previous barrel segments according to
some embodiments.
[0150] As shown in FIG. 4, the fifth segment may contain a screw
element such as a transport screw element. The transport screw may
provide mixing of the isocyanate and previously added components
including at least one polyol and the inorganic filler. To allow
substantially thorough mixing of these components, one or more
mixing screw elements may be used. The transport screw of the fifth
segment may transfer the at least one polyol, the inorganic filler,
and the isocyanate (and optional other additives) to a subsequent
segment. Such subsequent segment may be all or a portion of a
second mixing section. In some embodiments, these components are
transferred to a sixth segment as shown in FIG. 4.
[0151] In a sixth barrel segment or in the second mixing section, a
reverse screw provides a substantial amount of mixing to the
previous added components of the composite mixture. In some
embodiments, substantial shearing is provided to the composite
mixture. As a reverse screw has negative pitch, the components of
the composite material may be block from being transferred through
such a segment until sufficient shearing forces and pressure allow
the mixture to pass through this segment. In some embodiments, the
reverse screw is configured to block the mixture back to a
subsequent segment or section. For example, the entire mixture may
be blocked to one or more of the first segment, second segment,
third segment, fourth segment, or fifth segment. In another
embodiment, the components of the mixture are blocked to one or
more of the first conveying section, second conveying section, or
the first mixing section. Such shearing together with the
exothermic reaction of the polyol and the isocyanate may require
cooling in the segment or section.
[0152] In an alternative embodiment, a sixth segment may contain a
transport screw and the previously added components may be further
transferred toward the output end of the extruder. As shown in FIG.
4, substantial mixing by a reverse screw may occur in a subsequent
segment (e.g., an eighth or ninth segment) subsequent to
introduction of one or more other components such as fibrous
materials.
[0153] Vents may be disposed on either side of the second mixing
section. As large amounts of mixing may release entrained air in
the one or more components of the polyurethane composite mixture,
such air must be released. Additionally, gas produced by the
blowing agent may be required to be released. In some embodiments,
a vacuum may be used to remove the entrained air and/or gas from
the blowing agent. In some embodiments, the removed air or gas
results in the formation of a more dense and uniform polyurethane
composite material.
[0154] In optional embodiments, fiber rovings may be added to the
composite mixture in a subsequent segment. This segment may be
found in a third conveying section. As shown in FIG. 4, fibrous
material may be introduced in a seventh segment of the extruder.
Such a segment may also contain a transport screw. In particular
embodiments, the transport screw may be a fast transport screw. In
some embodiments, the fast transport screw has fewer screw threads
per unit of length as compared to a slow transport screw. The
transport screw of the segment may introduce, chop up, and mix the
fiber rovings.
[0155] In subsequent segments, the mixture may be further mixed and
transported toward the output end of the extruder. Such subsequent
segments may constitute a second or third mixing section, depending
on the embodiment as discussed above. For example, in an eighth
segment, lobal screws may provide further mixing to the composite
mixture. In addition, a reverse screw may be provided in this or
subsequent segments to provide substantial mixing and/or shearing
of the components of the composite mixture.
[0156] As mentioned above a mixing section adjacent to the output
end of the extruder may include one or more reverse screws and
lobal screws. In some embodiments, a reverse screw is in the last
segment of the extruder. In some embodiments, the reverse screw is
a reverse slotted screw. As enough shearing forces and/or pressure
transfer the mixture past the reverse screw, the mixture is
extruded through a die.
[0157] In some embodiments, the extruder has a L/D of about 10 to
about 40. In some embodiments, the extruder has a L/D of about 10
to about 15. In some embodiments, the extruder has a L/D of about
20 to about 40. In some embodiments, the extruder has a L/D that is
greater than about 24. In some embodiments, the extruder may
operate from between about 200 to about 2000 rpm.
[0158] FIG. 5 represents one configuration of an extruder for the
introduction of the components materials as described above. This
extruder includes a first conveying section C.sub.1, a first mixing
section M.sub.1, a second conveying section C.sub.2, and a second
mixing section M.sub.2. A feed end is shown on the right and an
output end on the left.
[0159] FIG. 6 represents one configuration of an extruder for the
introduction of the components materials as described above. This
extruder includes a first conveying section C.sub.1 and a first
mixing section M.sub.1. A feed end is shown on the right and an
output end on the left.
[0160] In accordance with some embodiments, foaming of the
polyurethane composite materials occurs after the die. In some
embodiments, some foaming and reaction of the composite mixture may
occur prior to or during extrusion.
[0161] Other alternatives may be used when providing the mixed
polyurethane composite material. For example the extruder may have
more than or less than nine barrel segments. In some embodiments,
certain types of screws can be replaced by a different type of
screw. These variations should be apparent to a person having
ordinary skill in the art.
Forming
[0162] In some embodiments, the process of forming the highly
filled polyurethane composite material comprises providing the
components of the polyurethane composite material, mixing the
components together, extruding the components through a die, adding
any other additional components after the extrusion, and forming a
shaped article of the polyurethane composite material. As the
polyurethane composite material exits the die, the composite
material may be placed in a mold for post-extrusion curing and
shaping. In one embodiment, the composite material is allowed to
cure in a box or bucket.
[0163] In one embodiment the formation of the shaped articles
comprises injecting the extruded polyurethane composite material in
a mold cavity and curing the shaped article. However, some
embodiments require that the extruded polyurethane composite
material be placed in a mold cavity secured on all sides, and
exerting pressure on the polyurethane composite material. In some
of these embodiments, the polyurethane composite material will be
foaming or will already be foamed. However, it is preferred that
the material is placed under the pressure of the mold cavity prior
to or at least during at least some foaming of the polyurethane
composite material.
[0164] A shaped article can be made using the polyurethane
composite materials according to the foregoing embodiments. In some
embodiments, this article is molded into various shapes. In some
embodiments, the polyurethane composite material is extruded, and
then injected into a continuous production system. Suitable systems
for forming the composite materials of some embodiments are
described in U.S. patent application Ser. No. 10/764,013 filed Jan.
23, 2004 and entitled "CONTINUOUS FORMING SYSTEM UTILIZING UP TO
SIX ENDLESS BELTS," now published as U.S. Patent Application
Publication No. 2005-0161855-A1, and U.S. patent application Ser.
No. 11/165,071, filed Jun. 23, 2005, entitled "CONTINUOUS FORMING
APPARATUS FOR THREE-DIMENSIONAL FOAMED PRODUCTS," now published as
U.S. Patent Application Publication No. 2005-0287238-A1, both of
which are hereby incorporated by reference in their entireties.
[0165] The polyurethane composite material of certain embodiments
may exert certain pressures on the walls of any mold, such as that
found in the forming devices as described above. While the amount
of pressure may vary according to the amount of foaming and gas
production, it is preferred that such forming devices may exert or
hold pressures by the mold cavity ranging from about 35 to about 75
psi. In some embodiments, the pressure is from about 45 to about 65
psi. In some embodiments, the pressure is about 50 psi. However,
mold pressures in any embodiment of a method of making the
polyurethane composite material can be higher than or less than the
specified values. The exact pressure required in the formation of
the desired shaped article depends on the density, color, size,
shape, physical properties, and the mechanical properties of the
article comprising the polyurethane composite material.
[0166] When foaming polyurethane is formed by belts into a product
shape, the pressure that the belts exert on the foamed part is
related to the resulting mechanical properties. For example, as the
pressure of the foaming increases and the belt system can hold this
pressure without the belts separating, then the product may have
higher flexural strength, then if the belts allowed leaking, or
pressure drop. In some embodiments, pressures about 50 to about 75
psi have been used to obtain high mechanical properties in the
polyurethane composite material. In one example, an increase in the
flexural strength of 50 psi results from the higher pressure in the
belts, versus using a lower pressure.
[0167] In some embodiments, a shaped article comprising the
polyurethane composite material as described herein is roofing
material such as roof tile shingles, etc., siding material, carpet
backing, synthetic lumber, building panels, scaffolding, cast
molded products, decking materials, fencing materials, marine
lumber, doors, door parts, moldings, sills, stone, masonry, brick
products, post, signs, guard rails, retaining walls, park benches,
tables, slats and railroad ties.
[0168] Other shaped articles may comprise a portion of which
comprises the polyurethane composite material. In some embodiments,
the polyurethane composite material is coated or molded on one side
of an article. For example, the polyurethane composite material may
be coated or molded onto one side of a flat or S-shaped clay roof
tile, which has been cut thinner than normal, and laid on a
conveyor belt, followed by extrusion of the polyurethane composite
material onto at least a portion of the tile. Such portion may be
shaped by a mold which is adapted to shape the polyurethane
composite material deposited on the tile. For example, the forming
unit may operate with two mold belts which are adapted to shape the
polyurethane composite material on one side of the portion. In some
embodiments, the composite material may provide backing to an
article. In one embodiment, the composite material may be foamed
sufficient to provide insulation to an article.
[0169] In some embodiments, the polyurethane composite material can
reinforce an article. For example, by placing a coating or molding
of the polyurethane composite material on a roof tile, the impact
strength of the roof tile is increased. Thus one embodiment
comprises a method of substantially reducing the fracture of an
article by depositing the polyurethane composite on a solid surface
article, shaping the composite on the solid surface article by
methods described herein, and curing the composite on the solid
surface article. Such method may produce a one or more of a
reinforced, backed, or insulated article. Such article may also
have increased physical and mechanical properties. Additionally, a
reinforcing layer may be used to prevent water weeping, and
increases the overall thickness of a solid surface article.
[0170] In some embodiments, the polyurethane composite material can
bond directly to an article solid surface article such as a tile.
Alternatively, an adhesive can be applied to the solid surface
article and a shaped polyurethane composite article can be attached
thereto. A solid surface article such as a tile may include at
least one or more of cement, slate, granite, marble, and
combinations thereof; and the polyurethane composite material as
described in embodiments herein. Such tiles may be used as roofing
or siding tiles.
[0171] In some embodiments, the composite material may be used as
reinforcement of composite structural members including building
materials such as doors, windows, furniture and cabinets and for
well and concrete repair. In some embodiments, the composite
material may be used to fill any unintended gaps, particularly to
increase the strength of solid surface articles and/or structural
components. Structural components may formed from a variety of
materials such as wood, plastic, concrete and others, whereas the
defect to be repaired or reinforced can appear as cuts, gaps, deep
holes, cracks.
Optional Additional Mixing Process
[0172] One of the most difficult problems in forming polyurethane
composite materials which have large amounts of filler is getting
intimate mixing--blending the polyols and the isocyanate. In some
embodiments, an ultrasound device may be used to cause better
mixing of the various components of the polyurethane composite
material. In these embodiments, the ultrasound mixing may also
result in the enhanced mixing and/or wetting of the components. In
some embodiments, the enhanced mixing and/or wetting allows a high
concentration of filler, such as coal ash to be mixed with the
polyurethane matrix, including about 40, 50, 60, 70, 80, and about
85 wt % of the inorganic filler.
[0173] In some embodiments, the ultrasound device produces an
ultrasound of a certain frequency. In some embodiments, the
frequency of the ultrasound device is varied during the mixing
and/or extrusion process. In some embodiments, the components are
mixed in a continuous mixer, such as an extruder, equipped with an
ultrasound device. In some embodiments, an ultrasound device is
attached to or is adjacent to the extruder and/or mixer. In other
embodiments, an ultrasound device is attached to the die of the
extruder. In other embodiments, the ultrasound device is placed in
a port of the mixer. In further embodiments, an ultrasound device
provides vibrations at the location where the isocyanate and polyol
meet as the screw delivers the polyol to the isocyanate.
[0174] In addition, an ultrasound device may provide better mixing
for the other components, such as blowing agents, surfactants,
catalysts. In embodiments where additional components are added to
the polyol prior to mixing the polyol with the isocyanate, the
additional components are also exposed to ultrasound vibration. In
some embodiments, an ash selected from fly ash, bottom ash, or
combinations thereof, is mixed using an ultrasound device. In some
embodiments, ultrasound vibrations breaks up filler and fiber
bundles to allow more thorough wetting of these components to
provide a polyurethane composite material with better mechanical
properties, such as flexural modulus and flexural strength, as
compared to polyurethane composite materials which are created
without the use of ultrasound vibration. The wetting of fibers and
fillers could also be increased by the use of ultrasound at or near
the die of the extruder, thus forcing resin to coat the fibers and
fillers better, and even breaking up fiber bundles and filler
lumps. The sound frequency and intensity would be adjusted to give
the best mixing, and what frequency is best for the urethane raw
materials, may not be best for the filler and fibers.
[0175] Unless otherwise noted, all percentages and parts are by
weight.
[0176] The skilled artisan will recognize the interchangeability of
various features from different embodiments. Similarly, the various
features and steps discussed above, as well as other known
equivalents for each such feature or step, can be mixed and matched
by one of ordinary skill in this art to perform compositions or
methods in accordance with principles described herein. Although
the invention has been disclosed in the context of certain
embodiments and examples, it will be understood by those skilled in
the art that the invention extends beyond the specifically
disclosed embodiments to other alternative embodiments and/or uses
and obvious modifications and equivalents thereof. Accordingly, the
invention is not intended to be limited by the specific disclosures
of embodiments herein. Rather, the scope of the present invention
is to be interpreted with reference to the claims that follow.
* * * * *