U.S. patent application number 10/385055 was filed with the patent office on 2004-09-16 for reinforced foam articles.
This patent application is currently assigned to INNOVATIVE CONSTRUCTION TECHNOLOGIES, INC.. Invention is credited to Tremelling, Tim.
Application Number | 20040177579 10/385055 |
Document ID | / |
Family ID | 32961423 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040177579 |
Kind Code |
A1 |
Tremelling, Tim |
September 16, 2004 |
Reinforced foam articles
Abstract
Reinforcement for foamed articles is provided utilizing a matrix
of fiber elements disposed within the interior or core of the
article. The fiber elements are injected along with dry flowable
formable beads into a mold cavity. Upon heating of the mold
interior and subsequent wetting/expanding/fusing phase, the fiber
elements become joined to the expanding beads to provide enhanced
strength of the resulting molded article.
Inventors: |
Tremelling, Tim; (Rigby,
ID) |
Correspondence
Address: |
FITCH EVEN TABIN AND FLANNERY
120 SOUTH LA SALLE STREET
SUITE 1600
CHICAGO
IL
60603-3406
US
|
Assignee: |
INNOVATIVE CONSTRUCTION
TECHNOLOGIES, INC.
|
Family ID: |
32961423 |
Appl. No.: |
10/385055 |
Filed: |
March 10, 2003 |
Current U.S.
Class: |
52/426 ;
52/565 |
Current CPC
Class: |
E04B 2002/0206 20130101;
E04B 2002/0226 20130101; E04B 2/8641 20130101; E04C 1/40 20130101;
E04C 5/073 20130101; E04B 2/8617 20130101; E04C 3/34 20130101 |
Class at
Publication: |
052/426 ;
052/565 |
International
Class: |
E04B 002/00; E04C
003/30 |
Claims
What is claimed is:
1. A method of producing a reinforced foamed article comprising the
steps of: providing dry expandable flowable foam beads; providing a
plurality of fiber elements; providing a mold cavity; flowing the
foam beads into the mold cavity along with discrete fiber elements;
and heating the foam beads and fiber elements within the mold
cavity while allowing the foam beads to heat, expand, and fuse with
one another and with the reinforcing fiber elements to form a
three-dimensional foam matrix with internal reinforcing fiber
elements interspersed therein.
2. The method of claim 1 further comprising the step of forming a
chemical attachment between the fiber elements and the foam
beads.
3. The method according to claim 2 further comprising the step of
coating the fiber elements with a sizing material to enhance said
chemical attachment.
4. The method according to claim 1 wherein the step of providing
internal reinforcing fiber members comprises a step of providing
internal reinforcing fiber members having an aspect ratio ranging
between 0.001 and 0.00001.
5. The method according to claim 1 wherein the fiber elements
comprise fiberglass strands.
6. The method according to claim 5 wherein said foam beads are
comprised of one of said styrene and said polystyrene.
7. The method of claim 1 further comprising the step of mixing said
fiber elements and said foam beads together, prior to introduction
into the mold cavity.
8. The method of claim 1 further comprising the step of mixing said
fiber elements and said foam beads at the time of introduction into
the mold cavity.
9. The method of claim 1 further comprising the step of mixing said
fiber elements and said foam beads together, prior to introduction
into the mold cavity the step of providing said fiber elements
includes dimensioning said fiber elements to a length ranging
between 2 and 3 inches.
10. The method of claim 1 wherein the reinforced foam article is to
be subjected to an applied force extending in a preselected
direction, said method further comprising the step of orienting at
least a majority of said fiber elements in a direction generally
perpendicular to said preselected direction.
11. The method of claim 10 wherein at least 60% of said fiber
elements are oriented in a direction generally perpendicular to
said preselected direction.
12. The method of claim 1 wherein the foam beads are comprised of
polystyrene and said fiber elements are comprised of
fiberglass.
13. The method of claim 12 wherein the foam beads have a size
dimension of 0.40 to 1.10 mm.
14. The method of claim 12 wherein the foam beads have a size
dimension of 0.40 and 1.10.
15. The method of claim 12 wherein 50% of the foam beads have a
size dimension of 0.40 mm and 50% of the foam beads have a size
dimension of 1.10 mm.
16. In a freestanding form module for receiving flowable materials
to make a wall which includes the form module, the flowable
materials exerting a force in a selected direction, the form module
comprising at least two spaced-apart form members having opposed
interior form surfaces, each form member including a wall portion
and a rib portion extending from the wall portion toward another
one of said form members; and at least one monolithic molded
plastic tie member having opposed ends with a web member between
the ends extending along a web axis, a bearing member at each end
of the tie member, extending generally transverse to the web axis
and embedded in the wall portion of a respective form member with
the form member formed around so as to captively enclose the
bearing member and each end of the tie member having a stabilizing
member extending generally transverse to the web axis, spaced from
the bearing member and embedded in the rib portion of a respective
form member adjacent the interior form surface thereof with the
form member formed around so as to captively enclose the
stabilizing member; the improvement in said form members
comprising: a reinforced foamed article including a
three-dimensional foam matrix core of expanded dry flowable foam
beads; a plurality of discrete spaced-apart internal reinforcing
fiber elements interspersed in the foam matrix and attached to the
expanded beads of the foam matrix; a sizing between at least some
of the foam beads and the fiber elements; and at least a majority
of said fiber elements oriented in said foam matrix in a direction
generally perpendicular to said preselected direction.
17. The improvement of claim 16 wherein at least 60% of said fiber
elements are oriented in a direction generally perpendicular to
said preselected direction.
18. The improvement of claim 16 wherein the foam beads are
comprised of polystyrene and said fiber elements are comprised of
fiberglass.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention pertains to reinforced foam articles
and in particular to articles made with dry expandable flowable
foam beads.
[0003] 2. Description of the Related Art
[0004] Ongoing efforts have been made to develop three-dimensional
foam members for use in structural, i.e., load-bearing,
applications. In the aircraft industry, for example, laminate
structures have been proposed which include foam matrices formed
from a so-called wet foaming process in which a liquid resin is
flowed in place along with an expanding gas component or other
blowing agent which reduces the density of the liquid resin to a
desired level. The blowing agent may be incorporated in the liquid
resin composition or may be introduced as the liquid resin
composition is injected into the mold. The blowing agent may be
liberated from solid or liquid components added to the liquid resin
composition during mixing, or may comprise a gas, such as nitrogen
or carbon dioxide, which is injected directly into the liquid resin
composition.
[0005] One advantage of wet foaming processes is that the resin,
being provided in a liquid form, has a prolonged wetting time in a
liquid phase, and internal reinforcing components disposed within
the core of the foamed articles are subjected to the expanding
liquid resin over an extended time. This promotes intimate contact
between the resin and the surfaces of the internal reinforcing
members. During this time, the liquid resin conforms or flows
around and wets the outer surfaces of exposed internal reinforcing
members. In addition to such conformance aspects, the liquid resin
may be allowed to form chemical attachments with surface features
of the internal reinforcing members.
[0006] Often, the internal reinforcing members are treated with a
sizing or other external coatings which enhance and cause chemical
bonds with the foaming liquid resin. As the prolonged wetting phase
draws to an end, chemical interaction between the expanded resin
and the outer surfaces of the internal reinforcing members is
substantially completed achieving most, if not all of the resulting
pull out strength present within the core of the resulting foamed
article.
[0007] One example of a wet foaming process is given in U.S. Pat.
No. 4,073,840 where discrete reinforcing fiber filaments are
homogeneously dispersed in a liquid foamable resin composition
prior to foaming of the composition, to form a fiber slurry. The
fibers are typically provided in a bundle form and upon mixing in
the foamable resin, the fiber bundles are separated and are wetted
with the resin to form a wet foamable resin composition which is
then fed into a mold apparatus where the foamable resin composition
is caused to foam to achieve its final density. Thermoset resin
compositions such as foamable polyurethane resin compositions are
preferred. As may be required for a particular process, catalysts,
surfactants, foam stabilizers and curing agents are added to the
foamable resin composition during mixing, prior to injection in the
mold.
[0008] Despite advances in the art of producing foamed articles,
further refinements are sought to allow the use of different
foaming processes to produce foam articles having a self-supporting
reinforced core, whose reinforcing properties are continuous
throughout the body of the foamed article.
SUMMARY OF THE INVENTION
[0009] A wide variety of structural foamed articles are produced
today using so-called dry bead processes. Examples of such articles
are found in commonly assigned U.S. Pat. Nos. 5,701,710 and
5,809,728. The self-supporting concrete form modules provided by
these patents have met with widespread commercial acceptance. The
modules incorporate internal, plastic tie structures having bearing
surfaces embedded within the opposed walls of the resulting
concrete form modules. While the concrete form modules produced
according to these patents may employ liquid resin compositions, it
has been found commercially advantageous to form such modules using
commercially available dry expandable flowable foam beads.
[0010] Typically, the dry beads are blown into a mold cavity.
Initially, the dry beads are freely movable to form a free-flowing
packing arrangement within the mold cavity. The dry beads are then
heated while under packing pressure and are allowed to expand
within the mold cavity to achieve a desired target density value.
During the heating and expansion phase, the outer surfaces of the
dry beads are very briefly liquified to allow chemical and thermal
bonding with adjacent beads so as to form a familiar
three-dimensional unitary foam matrix. The wetting time of the dry
beads is very brief compared to that of liquid resin compositions
which are expanded using blowing agents. The wetting times of dry
beads are typically on the order of 45 to 60 seconds, a small
fraction of the wetting times of liquid resin compositions. As a
result, if significant pull out strength is to be attained with
reinforcing members disposed within the foam matrix, attachments
must be initiated and completed very quickly, as the expanding
beads are wrapped about or otherwise conform to the outer surfaces
of the internal reinforcing members.
[0011] According to one aspect of the present invention,
substantial attachment forces between the dry, expandable, flowable
beads are achieved using conventional molding processes which do
not require extended wetting times. In many instances, it would be
difficult, if not impossible, to substantially extend the very
brief wetting phase of the dry expandable flowable foam beads if
manufacturing advantages of conventional dry foam molding
techniques are to be maintained.
[0012] In other aspects of the present invention, foamed articles
having improved burst strength and other high performance qualities
are produced using dry, expandable, flowable foam beads which form
little, or no chemical attachment to internal reinforcing members.
Improved internal support is provided by internal reinforcing
members without appreciable pull out strength between the outer
surfaces of the internal reinforcing members and the foam matrix
within which the internal reinforcing members are embedded. For
example, when foamed articles, such as concrete forms, are
manufactured according to the present invention, two or
three-dimensional arrays of internal reinforcing members greatly
increase the burst strength of the form modules when subjected to
hydrostatic loadings of wet poured concrete.
[0013] While the present invention has found immediate acceptance
in the field of self-supporting concrete form modules, virtually
any useful structural foamed article will benefit from the present
invention to achieve reinforcement without substantial additional
costs to provide molded structural articles of commercial
significance. Because existing dry bead foaming processes can be
carried out according to the present invention without substantial
modification, reinforcement of existing foamed articles can be
enjoyed without requiring the manufacturer to incur prolonged
development times, and improved reinforced foamed articles can be
quickly brought to the marketplace.
[0014] It is an object of the present invention to provide foamed
articles utilizing dry expandable flowable foam beads.
[0015] Another object of the present invention is to provide
substantial internal reinforcement for such foamed articles.
[0016] A further object of the present invention is to provide
molding techniques for such foamed articles which can be quickly
carried out using inexpensive techniques.
[0017] A further object of the present invention is to provide
foamed articles having improved internal reinforcement without
requiring substantial pull out strength to be formed between
internal reinforcing members and the foam matrix formed by dry
expandable flowable foam beads.
[0018] Yet another object of the present invention is to provide
foamed articles of the type described above utilizing internal
reinforcing members of the elongated fiber type as individual fiber
members.
[0019] These and other objects according to principles of the
present invention are provided in a method of producing a
reinforced foamed article comprising the steps of providing dry
expandable flowable foam beads, a plurality of fiber elements and a
mold cavity. Flowing the foam beads into the mold cavity along with
discrete fiber elements. Heating the foam beads and fiber elements
within the mold cavity while allowing the foam beads to expand and
fuse with one another and with the reinforcing fiber elements to
form a three-dimensional foam matrix with internal reinforcing
fiber elements interspersed therein.
[0020] Other aspects of the present invention, and attendant
advantages are provided in a freestanding form module for receiving
flowable materials to make a wall which includes the form module,
the flowable materials exerting a force in a selected direction,
the form module comprising at least two spaced-apart form members
having opposed interior form surfaces, each form member including a
wall portion and a rib portion extending from the wall portion
toward another one of said form members. At least one monolithic
molded plastic tie member has opposed ends with a web member
between the ends that extends along a web axis. The tie member also
has a bearing member at each end of the tie member, extending
generally transverse to the web axis and embedded in the wall
portion of a respective form member with the form member formed
around so as to captively enclose the bearing member. Each end of
the tie member has a stabilizing member extending generally
transverse to the web axis, spaced from the bearing member and
embedded in the rib portion of a respective form member adjacent
the interior form surface thereof with the form member formed
around so as to captively enclose the stabilizing member. The
improvement in said form members comprises a reinforced foamed
article including a three-dimensional foam matrix core of expanded
dry flowable foam beads. A plurality of discrete spaced-apart
internal reinforcing fiber elements are interspersed in the foam
matrix and are attached to the expanded beads of the foam matrix. A
sizing is provided between at least some of the foam beads and the
fiber elements; and a majority of said fiber elements are oriented
in said foam matrix in a direction generally perpendicular to said
preselected direction.
[0021] Aspects of the present invention are described with regard
to a particular example of a commercially significant concrete form
module. The present invention is however not so limited and can be
employed with virtually any decorative or structural member made
from dry expandable foamable beads. Further, the reinforcement
matrix afforded by the present invention may be used with or
without other reinforcing systems, such as the plastic ties of the
preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a perspective view of a concrete form module
according to principles of the present invention;
[0023] FIG. 2 is cross-sectional view taken along the line 2-2 of
FIG. 5;
[0024] FIG. 3 is a first end view of the module of FIG. 1;
[0025] FIG. 4 is a second end view of the module of FIG. 1;
[0026] FIG. 5 is a cross-sectional view taken along the line 5-5 of
FIG. 2;
[0027] FIG. 6 is a cross-sectional view similar to that of FIG. 5
but showing an alternative embodiment according to principles of
the present invention;
[0028] FIG. 7 is a perspective view of a tie member; and
[0029] FIG. 8 is an exploded perspective view of an alternative tie
member.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Turning now to the drawings, FIG. 1 is a perspective view of
a self-supporting foam module for use as a concrete form. Module 10
preferably includes alternating tongue and groove interlocking
edges that allow multiple modules to be interlocked in a
two-dimensional array to form a continuous wall. As can be seen in
FIGS. 1 and 5, module 10 includes a serial succession of
substantially cylindrical cavities or cells 12 which receive a
flowable casting material, such as concrete, and which distribute
the concrete throughout the module during a pour, when concrete is
typically introduced into the top of a wall formed by multiple
modules 10. During initial stages of the pour, the preferred
casting material, i.e., concrete or the like cementious product
exhibits fluidic behavior, producing hydrostatic pressure that acts
laterally, in a horizontal direction as indicated by arrow 14 in
FIG. 1 pressing against the inner surfaces 16 of opposed, discrete
wall members 20.
[0031] Hydrostatic forces of the poured concrete act from within
the module 10 in a direction which causes internal bursting
pressure, tending to force the walls 20 apart from one another.
This direction of applied force extends along a Z-axis, as
indicated by arrow 14 in FIG. 1. Referring to FIG. 1, the outer
surface 24 of wall 20 extends in a plane, along a vertical Y-axis
(arrow 21) and a horizontal X-axis (arrow 23). As shown in FIG. 1,
an internal reinforcing matrix 30 has filamentous or fiber elements
32 extending in directions generally parallel to the X-Y plane of
outer surface 24. That is, in the preferred embodiments illustrated
in FIGS. 1-6, the fibers 32 are oriented in directions generally
perpendicular to the Z-axis direction of applied bursting force
indicated by arrow 14 in FIG. 1. Expressed in different terms, the
fibers extend in the directions of tension set up in wall 20 by the
lateral or horizontal Z-axis bursting forces of fluid concrete
poured in cavities 12 of module 10.
[0032] The internal bursting force caused by hydrostatic pressure
of the poured concrete eventually dissipates as the concrete sets,
becoming less fluid and eventually hardening into a solid form. It
is generally preferred when pouring a wall that the concrete is
poured at a relatively slow rate, allowing the bottommost portion
of the concrete within the wall to begin to set, preventing a head
pressure or internal bursting pressure acting over the full height
of the wall. In practice, the rate of set of the poured concrete
must be carefully monitored, taking into account the weight and
temperature of the concrete mix, the rate of placement of the
concrete use of admixtures in the concrete being poured and the
effect of vibration or other methods of consolidating the poured
concrete material.
[0033] The walls 20 of module 10 are preferably molded using foam
material characterized as dry expandable flowable beads, as are
known in the art, as distinguished from wet foaming systems in
which a liquid resin is expanded by a blowing agent. In the dry
bead technology of the present invention, the beads are dry and
flowable when introduced into a mold. After a sufficient quantity
of dry beads are packed into the internal cavity of a mold, the
beads are heated in situ within the mold cavity. The beads respond
to heating by expanding within the mold cavity, exerting pressure
on neighboring beads. The beads throughout the mold cavity undergo
substantially simultaneous expansion upon introduction of heat.
During the expansion, the outer surfaces of the beads are softened
or liquified with adjacent beads becoming fused together under
pressure of the bead expansion. The so-called wetting phase of the
dry beads, which coincides with their expansion phase, takes place
over a relatively short time, on the order of 45 to 60 seconds for
polystyrene beads of 0.40 to 1.10 mm size, as compared to liquid
resin processes having typical wetting, foaming, and expansion
phases of 100-1000 seconds.
[0034] As mentioned above, the present invention is directed to the
use of dry expandable flowable beads, in conjunction with
conventional molding methods and apparatus. As emphasized above,
the critical interaction period (i.e., the wetting/expanding/fusing
phase) for the dry expandable flowable beads is considerably
shorter than the critical interaction period for other molding
techniques, such as those employing liquid resin compositions. Due
to the substantial differences between these two disciplines (dry
expandable flowable beads and liquid resin compositions) the
techniques and apparatus associated with liquid resin molding
compositions are not applicable to the use of dry expandable
flowable beads in a conventional molding application. It is
understood that the critical interaction period for both
disciplines involve both polymer surface melt interactions on the
one hand and true chemical bonding and cross linking on the other
hand. However, it is important to realize that these two factors
are not equally important to the two disciplines. With the molding
discipline employing dry expandable flowable beads, polymer surface
melt interactions which lead to good melt adhesion is the
predominate factor promoted, while other factors such as true
chemical bonding between the beads and other components of the mold
composition are of far less importance. The successful molding
compositions using dry expandable flowable beads focus on polymer
surface melt interactions leading to good melt adhesion and this
would not be compromised in an effort to promote true chemical
bonding which is relatively unimportant to the success of the mold
process. On the other hand, the molding of liquid resin
compositions relies predominately on true chemical bonding, such as
covalent bonding and cross linking. While polymer surface melt
interactions may be present in the molding of liquid resin
compositions, this factor is relatively unimportant and is not
generally promoted at the risk of sacrificing the true chemical
bonding which is of predominate importance for the molding of
liquid resin compositions.
[0035] The present invention may be carried out utilizing virtually
any dry beads of the expandable and flowable type available today.
As will be seen herein, the present invention may be employed to
produce foam articles both decorative and structural of virtually
any shape and size desired. The present invention has however found
immediate commercial application in producing foam concrete forms
of the type described in commonly assigned U.S. Pat. Nos. 5,701,710
and 5,809,728 the disclosures of which are incorporated as if fully
set forth herein. The foam concrete form modules illustrated in the
figures herein are preferably made of dry flowable expandable beads
of styrene and polystyrene of sizes ranging between 0.40 and 1.60
mm, commercially available from Huntsman as Product No. 7454.
Examples of other dry beads suitable for use with this embodiment
of the present invention include: Huntsman--Grade 40 & 54
(i.e., 7454, 7440) available from Huntsman Chemical Corporation, a
Utah corporation; BASF Series BF or BFL (i.e., BF 422) available
from BASF Corporation of Mount Olive, N.J.; Samsung Series SF
(i.e., SF 301) available from Samsung Cheil Industries of Seoul,
South Korea; and Nova M Grade (i.e., M77b or 35 mb) available from
Nova Chemicals Corporation of Pittsburgh, Pa. The module walls 20
have height and width dimensions (extending in the X and Y
directions) of 12" and 48", respectively. Walls 20 have a thickness
ranging between 2-1/2" and 4" with minimum and maximum dimensions
occurring in the pattern shown in FIG. 5.
[0036] As can be seen in FIG. 5, the internal wall surfaces 16 are
irregular, i.e., non-planar, while the outer surfaces 24 of the
walls have a generally flat, planar appearance as can be seen for
example in FIG. 1. Referring to FIGS. 1 and 5, the opposed walls 20
are joined together at a fixed spacing by tie members 40 preferably
made of a non-metallic molded plastic material such as an ABS
compound commercially available from Dow Chemical Company under the
trade designation Magnum 9555. The plastic ties 40 are constructed
according to commonly assigned U.S. Pat. No. 5,701,710. An
individual tie 40 is shown in FIG. 10 having major bearing plates
42, 44 lying adjacent outer surfaces 24 of walls 20 and minor
bearing plates 80, 82 lying adjacent the inner surfaces 16 of walls
20. Referring to FIG. 6, plastic ties 40 further include cross
members 46, 48 and 50 which extend between the major bearing
plates.
[0037] Referring to FIGS. 1 and 8, modules 10 may also be
constructed using multi-component tie members shown in FIG. 8
including a central component 160 located between a pair of outer
components 134. The central component 160 is slidingly engaged with
outer components 134 being received in grooves 148 formed in inner
wall members 144. Inner wall members 144 include inner bearing
surfaces 146 which face toward an interconnecting webbing 150 and
outer, major bearing plate portions 142. Whether constructed in the
unitary fashion as shown in FIG. 7 or in an interlocking
multi-component fashion as illustrated in FIG. 8, the plastic tie
members of a module have bearing surfaces embedded within the foam
matrix of the walls 20 so as to form a unified load-bearing system
therewith. In particular, the plastic tie members reinforce the
foam matrix walls 20 with regard to internal bursting pressures
extending in the Z-direction indicated by arrow 14 of FIG. 1.
[0038] Despite the immediate commercial acceptance of concrete form
modules constructed according to commonly assigned U.S. Pat. Nos.
5,701,710 and 5,809,728 further advances were sought with regard to
strengthening. In particular, reinforcement was desired to provide
added resistance to the internal bursting pressure operating in the
Z-direction indicated by arrow 14 in FIG. 1 and, optionally, to
reduce foam density. As can be seen in FIG. 5, the plastic ties 40
provide a series of spaced apart reinforcements disposed between
the cavities 12 which, due to their generally concave shape give
rise to points of minimal wall thickness. It was desired to add
reinforcement, particularly reinforcement against bursting
pressures at the points of minimal wall thickness, in the form of
an internal reinforcing matrix 30.
[0039] The reinforcing matrix 30 is comprised of individual fiber
elements 32 which lie in an X-Y plane, i.e., parallel to the outer
flat surfaces 24 of walls 20 (see FIG. 1). The fiber elements 32
are dispersed throughout the interior or core of walls 20, and form
a unified structure in combination with the expanded dry flowable
beads comprising the molded walls 20. The reinforcing matrix 30
preferably comprises a plurality of fiber elements disposed
throughout the body or core of walls 20. The fiber elements are
preferably homogeneously spaced throughout the core or interior of
walls 20 but may also be irregularly dispersed throughout the wall
core as will be explained, for example, in the alternative
embodiment shown in FIG. 6. As will be seen herein, FIG. 6 shows an
alternative embodiment where the reinforcing matrix 30 of fiber
elements 32 are localized along the outer surfaces 24 of walls
20.
[0040] The fibers 32 may be formed of natural or synthetic
materials such as flax, straw or wool, glass, processed cellulose,
processed wool, synthetic polymers and fiberglass. As will be
explained herein, it is preferred that the fiber elements are
elongated so as to have a desired aspect ratio, defined herein as
the ratio of the fiber cross-section (i.e., diameter) dimension to
the fiber length dimension.
[0041] Preferably, fibers employed in carrying out the present
invention to form an internal integrated reinforcing matrix have
several important characteristics or properties which provide
optimal reinforcing enhancement to a (usually unreinforced) matrix
of dry flowable expandable beads which are molded in a commercially
advantageous known manner. The properties of the fiber elements
are, in certain aspects, related to the type of beads employed. For
example, the fiber elements must be chemically compatible with the
beads used, and must be compatible with the particular
wetting/expanding/fusing phase of the beads. The present invention
contemplates the use of dry flowable expandable beads of virtually
any composition and size. Examples of bead materials include
polystyrene, polypropylene and polyethylene bead sizes ranging
between 0.1 mm and 10 mm.
[0042] Typically, the dry flowable expandable beads contemplated by
the present invention undergo molding by injection into a mold
cavity with subsequent loading of the mold cavity with a
substantial quantity of beads, and subsequent exposure of the beads
to an external heat source which causes the outer surfaces of the
beads to become wetted while the beads expand to achieve a desired
target foam density. This critical period in the formation of the
molded structure is referred to herein as the
wetting/expansion/fusing phase in which the previously dry flowable
beads are expanded and joined or fused together to achieve an
integral solidified mass of selected (final) foam density.
According to one aspect of the present invention, the
three-dimensional reinforcing matrix of discrete, spaced apart
fiber elements is dispersed throughout the interior of the mold
cavity and accordingly is dispersed throughout the dry flowable
expandable beads at the onset of the wetting/expanding/fusin- g
phase of the molding operation.
[0043] It has been found important that certain identifying
characteristics of the fiber elements is needed to achieve a
desired strength enhancement compared to similar molded articles
comprised of unreinforced dry flowable expandable beads. These
desirable characteristics are believed helpful in obtaining a
desired engagement between the outer surfaces of the fiber elements
and the outer surfaces of the beads as they undergo the
wetting/expanding/fusing phase of the molding operation. These
characteristics will, to some extent, depend upon the bead material
and bead size chosen for the particular molded article.
[0044] As will be seen herein, identifying characteristics of the
reinforced molded article include: compatible chemical compositions
of dry beads and fiber elements; that the dry beads are of the
flowable, expandable type, sometimes referred to as self-expanding;
an aspect ratio of the fiber elements ranging between 0.01 and
0.00001; sizing or the like surface treatment on the fiber elements
to promote enhanced chemical attachment to the expanding beads; the
fiber elements arranged as discrete, spaced apart fibers,
preferably located throughout the core or interior of the molded
article; a proportion of fiber elements to foam beads of
approximately 1% to 15% by mass; and an orientation of at least 20%
of the fiber elements within the foam core in a direction parallel
to the direction of, tension and perpendicular to the direction of
stress imparted to the molded article.
[0045] The fiber elements making up the reinforcing matrix may be
of any size desired but are preferably sized in relation to the
size of the dry expandable flowable foam beads with which they are
to be attached. As mentioned, the dry foam beads are freely
flowable when introduced into the mold cavity and only upon later
application of heat are the beads, particularly the outer surfaces
of the beads, softened during the wetting/expanding/fusing phase.
During this phase, substantial inter-bead pressures are developed,
sufficient to cause individual beads to wrap around or otherwise
conform to the outer surfaces of the fiber elements, and fuse with
one another.
[0046] If desired, the outer surfaces of fiber elements making up
the reinforcing matrix may be coated with an appropriate sizing as
is known in the art to augment attaching forces between the
polymeric foam beads and the fiber elements. Typically, an
appropriate sizing will introduce surface structures on the fiber
elements which allow the foam beads an easier purchase or
interlocking grasp. It has been found important to assure that the
outer surfaces of the beads are adequately secured to the outer
surfaces of the adjacent beads at that point in time upon
completion of the wetting/expanding/fusing phase, when the molded
article begins a final curing phase, as is known in the art.
[0047] The present invention recognizes that certain fiber elements
may have external surface characteristics, typically seen as rough,
burred or fibrous under microscopic examination, which provide an
adequate securement site for the wetting/expanding/fusing beads as
the dry beads are heated to soften and expand. However, many
commercially important fiber elements may not have the intricate
surface structures needed to achieve desired bond strength with the
wetted/expanding beads. The present invention therefore
contemplates the use of conventional treatments to enhance the
surface characteristics of the fiber elements. Such surface
enhancing treatments may be referred to with a variety of terms,
the most common of which is sizing.
[0048] As mentioned above, for the concrete form module constructed
according to principles of the present invention dry flowable
expandable beads of polystyrene and fiber elements of fiberglass or
propylene are preferred. As is known, fiberglass fibers can be
constructed with a variety of different shapes and surface
textures. In general, regardless of the surface characteristics of
the fiberglass fibers, it is preferred that the fiber surfaces be
treated with silane sizing or coupling agents according to known
techniques.
[0049] The absolute size and aspect ratio of the fiberglass fibers
have been found to be important characteristics of the fiber
elements, in order to achieve the desired bonding strength in the
dry bead--foam matrix. The desired aspect ratio for concrete forms
according to principles of the present invention range between
0.001 and 0.00001. The absolute length of the fiberglass fibers
preferably ranges between 1 and 3 inches.
[0050] Among other important characteristics according to
principles of the present invention, the fibers are dispersed
within the mold cavity so as to take a final position within the
core or interior of the molded article. It has been found important
to ensure that the fiber elements are injected so as to take
discrete positions within the three-dimensional structure of the
molded article, without substantial clumping or bundling of fiber
elements.
[0051] As a further important aspect it has been found desirable to
limit the proportion of fiber elements to foam matrix, preferably
on a mass basis. For concrete form modules according to principles
of the present invention, a proportion of fiber elements to foam
matrix by mass is preferably 1% and 15%, although ranges between 1%
and 20% have been found to be acceptable in certain
applications.
[0052] A further characteristic found desirable to obtain the
desired increase in strength of the molded article, is the
orientation of a sufficient number of fiber elements in the core of
the molded article, with respect to the direction of applied force
for applied stress. As mentioned above with respect to FIG. 1, for
concrete form modules constructed according to principles of the
present invention, the Z-axis indicated by arrow 14 indicates the
direction of force or stress applied to the molded article. This
results in a tension imparted to the foam matrix in the X and
Y-direction (see arrows 23 and 21 of FIG. 1) and in directions
lying within the X-Y plane. As an important characteristic of the
fiber elements, it is desirable that most of the fiber elements
extend along the direction of tension, generally perpendicular to
the direction of applied load. Accordingly, as has been mentioned,
the fiber elements comprising fiber matrix 30 generally lie in the
X-Y plane and in planes parallel thereto. The fiber elements can be
oriented randomly, i.e., at any angle within the X-Y plane and
parallel planes. If desired, the fiber elements can be oriented in
generally rectilinear arrays, or can be oriented in a common
direction in the X-Y plane and parallel planes.
[0053] Although not preferred, a small percentage, preferably less
than 5% of the fibers can lie in directions having substantial
direction components generally parallel to the direction of applied
force (see arrow 14 in FIG. 1). If an excessive number of fibers
are allowed to become oriented in the direction of applied force,
the strength of the foamed article will be reduced, despite the
presence of reinforcing elements within the foam matrix. When
excessive forces are applied to the molded article, those fiber
elements oriented generally in the direction of applied force
create crack propagation pathways if the force-oriented fiber
elements are arranged in sufficient density to form a continuous or
near-continuous path or tunnel extending throughout the foam matrix
mass. It is generally desirable to limit the force-directed fiber
elements to a relatively low percentage ranging between 0 and 5% of
the total number of fiber elements in the molded article. Further,
it is desirable to ensure that the force-directed fiber elements
are sufficiently spaced one from another and are sufficiently
misaligned with one another in the three-dimension foamed article
so as to avoid forming a continuous pathway along which failure of
the molded article might occur.
[0054] Several examples of concrete form modules were prepared
according to principles of the present invention, and
characteristic data for these samples will now be reviewed. In a
first test sample a concrete form module constructed according to
commonly assigned U.S. Pat. No. 5,701,710 was prepared. Dry
flowable expandable beads of commercially available types 7454 and
7440 from Huntsman Chemical Corp. and having a 2.0 PCF density were
employed. Molding was performed on a Hirsch 1400 press with 200-210
second cycle time. Heating to attain the desired
wetting/expanding/fusing phase with attendant fusion of the beads
was accomplished using steam injected throughout the mold at a
temperature of 240-280.degree. F. and 40-60 psi (1 to 1.5 Bar). The
temperature was substantially constant throughout the mold interior
and this temperature was also observed on the exterior mold
surfaces. Although it is possible to pre-mix the fibers and dry
foam beads prior to mold injection, a test sample was prepared by
simultaneously injecting dry beads and fibers from different
sources, with mixing occurring upon entry into the mold cavity.
While either pressure or vacuum feed could be employed in the
molding operation, the sample was prepared using vacuum feed. The
fiber elements selected were of fiberglass material commercially
available as product 495 roving reinforcement from Owens Corning,
One Owens Corning Parkway, Toledo, Ohio. The fiber elements were
mixed at ratios of 5%, 10% and 15% with respect to the mass of the
dry beads. The fiber elements had overall lengths ranging between
1.5 inches and 2.0 inches and had an aspect ratio of approximately
0.001. The mold press was provided with a number of different
injection points and the direction of entry into the mold cavity at
each injection site was controlled, along with vacuum pressures to
ensure that the majority of the fiber elements, at least as great
as 30% were oriented in the X-Y plane and in planes generally
parallel thereto, that is, generally perpendicular to the Z-axis of
force to be applied to the molded article. Injection into the mold
cavity was controlled as to avoid clumping or bundling of the fiber
elements. Those fiber elements which were found to lie generally in
the direction of applied force were sufficiently spaced apart and
misaligned one with respect to the other so as to prevent forming a
tunnel or pathway throughout the mass of the molded article.
[0055] In a second sample, a concrete form module constructed
according to commonly assigned U.S. Pat. No. 5,701,710 was
prepared. Dry flowable expandable beads of type 7454 and 7440
commercially available from Huntsman supplier and having a 2.0 PCF
density were employed. Molding was performed on a Hirsch 1400 press
with 200-210 second cycle time. Heating to attain the desired
wetting/expanding/fusing phase with attendant fusion of the beads
was accomplished using steam injected throughout the mold at a
temperature of 240-280.degree. F. and 40-60 psi. The temperature
was substantially constant throughout the mold interior and this
temperature was also observed on the exterior mold surfaces. In
this example, the fibers and dry foam beads were pre-mixed prior to
mold injection. While either pressure or vacuum feed could be
employed in the molding operation, the sample was prepared using
vacuum feed. The fiber elements selected were of fiberglass roving
reinforcement, product description 495 from Owens Corning. The
fiber elements were mixed at a ratios of 5%, 10% and 15% with
respect to the mass of the dry beads. The fiber elements had
overall lengths ranging between 1.5 inches and 2 inches. The mold
press was provided with a number of different injection points and
the direction of entry into the mold cavity at each injection site
was controlled, along with vacuum pressures to ensure that the
majority of the fiber elements, were oriented in the X-Y plane and
in planes generally parallel thereto, that is, generally
perpendicular to the Z-axis of force to be applied to the molded
article. Injection into the mold cavity was controlled as to avoid
clumping or bundling of the fiber elements. Those fiber elements
which were found to lie generally in the direction of applied force
were sufficiently spaced apart and misaligned one with respect to
the other so as to prevent forming a tunnel or pathway throughout
the mass of the molded article.
[0056] In addition to the concrete form modules described above,
other types of foam articles can be reinforced according to
principles of the present invention. The concrete form articles
described above have internal cavities which are loaded with fluid
concrete or other relatively heavy fluid material, considerably
heavier than the foamed concrete article. Generally horizontal or
lateral bursting forces are applied to the interior walls of the
concrete form by the fluid concrete. Reinforcement according to
principles of the present invention is added to the foamed concrete
article to resist the applied forces, as described above. Other
types of commercially important articles which can benefit from the
present invention include multi-ply laminate construction having a
core layer of foamed material. Loadings applied to the structure
are typically oriented in directions perpendicular to the major
faces of the board construction. Fiber elements can be added to the
foam matrix according to principles of the present invention, to
provide added reinforcement. Given the direction of anticipated
loadings perpendicular to the major faces of the laminate
construction, the fiber elements would be arranged so as to lie in
planes generally parallel to the laminated major faces. Other types
of foamed articles which benefit from the present invention include
packaging materials and vessels which withstand an outer applied
loading. Further examples of articles to benefit from the present
invention include elongated load bearing members either straight or
arched in configuration. Virtually any foamed article subjected to
a loading due to gravitational or other forces will benefit from
the present invention, it being realized that the several important
characteristics of reinforcing matrices can be readily determined
upon selection of the desired materials for the dry beads and fiber
elements, utilizing known principles for the materials selected.
Further, the reinforcement matrix afforded by the present invention
may be used with or without other reinforcing systems, such as the
plastic ties of the preferred embodiment.
[0057] Referring to FIG. 7, a generalized foam matrix structure is
indicated at 200. The assumed direction of force to be resisted is
indicated by arrow 208 and a fiber reinforcement 30 according to
principles of the present invention is embedded within the foam
matrix core of structure 200 either with or without benefit of
chemical sizing for mechanical structural features to promote
adhesion of the foam beads to the fiber elements. The fiber
elements comprising the matrix 30 are illustrated in FIG. 200 as
extending generally in a common direction, oriented perpendicular
to the direction of applied force indicated by arrow 208. If
desired, the fiber elements comprising matrix 30 can be oriented in
a rectilinear directions and planes perpendicular to the direction
208 or may be randomly oriented along planes perpendicular to the
direction of arrow 208.
[0058] The drawings and the foregoing descriptions are not intended
to represent the only forms of the invention in regard to the
details of its construction and manner of operation. Changes in
form and in the proportion of parts, as well as the substitution of
equivalents, are contemplated as circumstances may suggest or
render expedient; and although specific terms have been employed,
they are intended in a generic and descriptive sense only and not
for the purposes of limitation, the scope of the invention being
delineated by the following claims.
* * * * *