US20040177579A1

US20040177579A1 - Reinforced foam articles

Info

Publication number: US20040177579A1
Application number: US10/385,055
Authority: US
Inventors: Tim Tremelling
Original assignee: Innovative Construction Tech Corp
Current assignee: INNOVATIVE CONSTRUCTION TECHNOLOGIES Inc; Innovative Construction Tech Corp
Priority date: 2003-03-10
Filing date: 2003-03-10
Publication date: 2004-09-16

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.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to reinforced foam articles and in particular to articles made with dry expandable flowable foam beads.

2. Description of the Related Art

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

It is an object of the present invention to provide foamed articles utilizing dry expandable flowable foam beads.

Another object of the present invention is to provide substantial internal reinforcement for such foamed articles.

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.

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.

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.

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.

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.

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

FIG. 1 is a perspective view of a concrete form module according to principles of the present invention; [0022]
FIG. 2 is cross-sectional view taken along the line [0023] 2-2 of FIG. 5;
FIG. 3 is a first end view of the module of FIG. 1; [0024]
FIG. 4 is a second end view of the module of FIG. 1; [0025]
FIG. 5 is a cross-sectional view taken along the line [0026] 5-5 of FIG. 2;
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; [0027]
FIG. 7 is a perspective view of a tie member; and [0028]
FIG. 8 is an exploded perspective view of an alternative tie member.[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, FIG. 1 is a perspective view of a self-supporting foam module for use as a concrete form. [0030] 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.
Hydrostatic forces of the poured concrete act from within the [0031] 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.
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. [0032]
The [0033] 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.
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. [0034]
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—[0035] 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 2-½″ and 4″ with minimum and maximum dimensions occurring in the pattern shown in FIG. 5.
As can be seen in FIG. 5, the internal wall surfaces [0036] 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.
Referring to FIGS. 1 and 8, [0037] 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.
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 [0038] 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.
The reinforcing [0039] 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.
The [0040] 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.
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. [0041]
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/fusing phase of the molding operation. [0042]
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. [0043]
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. [0044]
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. [0045]
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. [0046]
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. [0047]
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. [0048]
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. [0049]
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. [0050]
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. [0051]
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 [0052] 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.
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 [0053] 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.
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° 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. [0054]
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° 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. [0055]
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. [0056]
Referring to FIG. 7, a generalized foam matrix structure is indicated at [0057] 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.
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. [0058]

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.