WO2009152616A1

WO2009152616A1 - A system and process for producing expanded polystyrene (eps) beads coated with a coating composition and a composition used therefor

Info

Publication number: WO2009152616A1
Application number: PCT/CA2009/000850
Authority: WO
Inventors: Michael Peter Buriak
Original assignee: Vidabode Group Inc.
Priority date: 2008-06-20
Filing date: 2009-06-19
Publication date: 2009-12-23
Also published as: CA2635516A1; WO2009152617A1; CA2669703A1; CA2669707A1

Abstract

A system and process for making Expanded Polystyrene (EPS) beads coated with a coating composition and a concrete mixture containing the coated EPS beads are provided. The coating composition removes a restrictive gas layer on EPS beads by adhering to the beads and having a suitable porosity to allow the gas to dissipate, and thus enables a strong attraction and permanent adherence of a material, having cementitious properties, such as, for example concrete, to the EPS beads. The adherence of the material to EPS beads creates a mixture that can be pre-cast into building blocks or panels significantly lighter and sturdier structurally than existing methods allow for. The beads are specifically made to correct size and density for the process in pre-expanders, comprising fluid bed dryers, and then treated through the spray application of the coating composition.

Description

A SYSTEM AND PROCESS FOR PRODUCING EXPANDED POLYSTYRENE (EPS) BEADS COATED WITH A COATING COMPOSITION AND A COMPOSITION USED

THEREFOR

FIELD OF THE INVENTION

The invention relates to expanded polystyrene particles. In particular, the invention relates to pre-expanded polystyrene particles having a coating layer produced by coating the surface of the pre-expanded polystyrene particles with a functional coating composition.

BACKGROUND OF THE INVENTION

Expanded polystyrene is a polymer resin obtained by heating and curing the polystyrene resin to generate foams. Expanded polystyrene is white in color, light in weight, and has superior water resistance, thermal insulation, sound absorption and buffering properties. Due to these advantages, expanded polystyrene has wide industrial applicability.

A particular application of the expanded polystyrene is construction, in particular, as an additive for a building material. The introduction of granules or beads, for example of polystyrene, into concrete or plaster presents difficulties, however, in obtaining adequate binding adherence between the concrete and the granules. It is a known problem of building materials of this type that the granules are easily broken away from the concrete or plaster, with the result that the material tends to disintegrate as the granules break away. Previous issues in developing such a mixture were based primarily on the inability of concrete to adhere to EPS beads, and thus the inability of the mixture to blend evenly and produce an evenly distributed mixture that could be extruded or cast to form structurally sound, solid construction panels. This was because expanded polystyrene emits a miniscule amount of pentane gas for long periods of time, covering the bead with a molecular layer of gas which acts as a release agent, preventing concrete from properly adhering to beads. This lack of adherence resulted in poorly mixed lightweight concrete, which was characterized by, inter alia, bead clumping, bead floating, and non-consistent consolidation of mix as well as structural weakness and failure, in previous EPS and concrete mixtures.

Additional problems associated with prior concrete construction are: tests, studies and time, have shown that water causes shrinkage and cracks in concrete.

Expanded polystyrene beads coated with a functional layer and manufacturing processes thereof are known in the art.

For instance, U.S. Patent No. 3,257,338 issued June 21 , 1966 to Sefton relates to lightweight construction material, particularly to lightweight concrete. Sefton describes a concrete mix comprising cement, primary aggregate and/or filler, expanded, expandable polystyrene, and a homogenizing agent. The expanded polystyrene are made from particles of expandable styrene polymer and are preferably, but not limited to, spherical beads.

U.S. Patent No. 3,764.357 issued October 9, 1973, to Bowles et al., discloses a method of preparation of lightweight concrete and plaster comprising the steps of : wetting the surfaces of lightweight aggregate particles, such as, for example, polystyrene beads with an aqueous medium; admixing the wet aggregate particles with dry finely divided cementitious material to form a coating thereon; and, thereafter, adding additional aqueous medium in an amount to produce a coherent formable uncured concrete or plaster.

U.S. Patent No. 4,011.355 issued March 8. 1977 to Mandish et al., discloses a coated, lightweight aggregate, in particular expanded polymer beads, such as, expanded polystyrene beads, for mixing with cement, sand and water for producing a lightweight construction material is provided in which expanded polystyrene beads are coated with a mixture formed of dehydrated lime and hydrated alumina with water in an amount to impart a suitable consistency and a wetting agent. A method of making the mixture and coating the beads is also provided.

U.S. Patent No. 4.398,958 issued August 16. 1983 to Hodson et al., discloses a method of making lightweight concrete incorporating expanded polystyrene beads comprising, first, coating the expanded beads with an aqueous surfactant solution, which preferably contains a substantive cationic surfactant, e.g. a substituted or ethoxylated quaternary ammonium compound containing a C₁₀ to C₁₈ alkyl substituent or an ethoxylated primary or secondary amine having a C₁₀ to C₁₈ alkyl substituent, and a non- ionic surfactant such as an ethoxylated primary or secondary alcohol or a nonylphenol- ethylene oxide condensate. The wet beads are coated with dry cement and then mixed with a further supply of cement, water and sand or aggregate to complete the concrete mix.

U.S. Patent No. 4.385.156 issued May 24, 1983 to Ingram et al., discloses a process for producing styrenic polymer expandable beads that are useful in forming heat- resistant foamed articles comprising forming an aqueous suspension of initial styrenic polymer beads and adding thereto a portion of a comonomer solution of styrenic monomer and methacrylic acid, which solution also contains a polymerization regulator, forming an emulsion of catalyst, monomer solution and polyvinyl alcohol suspending agent, adding portions of the emulsion to the suspension and then adding the remainder of the comonomer solution to the suspension, and the suspension with added monomers is heated to copolymerize the styrenic monomer and methacrylic acid about the initial beads and form a coating about the beads.

U.S. Patent No. 4,433.029 issued February 21. 1984 to Senda et al., discloses expandable thermoplastic polymer beads and method of producing same, wherein a core of a polymer of one or more vinyl monomers is substantially surrounded by a layer of a polyolefin comprising one or more vinyl monomers, with a foaming agent contained in at least the core.

U.S. Patent No. 7,128,973 issued October 31 , 2006 to Park discloses expanded polystyrene particles having a polyvinyl acetate resin-based functional skin layer, and a process thereof are provided. The particle includes an inner expanded polystyrene layer; and a functional skin layer.

U.S. Patent No. 7.255.738 issued August 14, 2007 to Semmens describes a lightweight cementitious composite material includes expanded synthetic polymer particulate having a particle size of between 0.0625 and 0.5 inches. A dispersant coating on said particulate suppresses electrostatic attraction between particulate particles. A matrix surrounds the particulate and is present from 0.25 to 1 pound per gallon of dispersant coated particulate.

The invention was made in recognition of the need for a more efficient system and process for producing expanded polystyrene (EPS) beads coated with a coating composition and a concrete mixture containing the coated EPS beads. SUMMARY OF THE INVENTION

An object of the present invention is, thus, to provide a system and process for producing expanded polystyrene (EPS) beads coated with a coating composition, a coating composition used therefore, and a concrete mixture containing the coated EPS.

In accordance with an aspect of the present invention, there is provided a method for applying a coating composition to pre-expanded EPS beads for eliminating a restrictive gas layer on the surface of the EPS beads, the method comprising the steps of: pre- expanding particulate EPS raw material to form EPS beads; passing the EPS beads through a fluidized bed dryer; blowing the EPS beads through an EPS coating system, whereby the EPS beads are coated with a functional composition by means of spraying the composition over the EPS beads; and forcing the coated EPS beads through a rotating sieve for ensuring that beads of a predetermined size are transferred to an EPS beads storage means.

In accordance with another aspect of the present invention, there is provided a system having a reservoir, a coating chamber, the reservoir and the coating chamber being interconnected through a piping circuit, which delivers a pressurized fluid composition from the reservoir to the coating chamber, the coating chamber having an EPS beads inlet and an outlet duct, the EPS beads outlet duct being provided with a sieve, an air chamber, the air chamber being in communication with the coating chamber, a spraying assembly for delivering a fluid composition from the piping circuit into the coating chamber, a blower for providing forced air into the air chamber and an air diffuser plate, the air diffuser plate being positioned between the coating chamber and the air chamber so that forced air is introduced from the air chamber into the coating chamber through the air diffuser plate. In accordance with still another aspect of the present invention, there is provided a functional composition (VBC) for coating EPS beads. The functional composition for coating EPS particles used to produce a lightweight concrete material includes thalocyanine, polyvinyl acetate and polyvinyl alcohol. The composition can further include at least one additive. In accordance with another embodiment the functional composition for coating EPS particles used to produce a lightweight concrete material includes, in parts by volume, 1 part polyvinyl acetate, 1 part methyl hydrate, about 3 parts water, and 0.05 parts methyl blue.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will now be described, by way of example, in conjunction with the following drawing, in which:

Fig. 1 shows a system for coating EPS beads with the coating composition (VBC) in accordance with an embodiment of the present invention; and

Fig.2 shows a schema of the coating procedure in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable a person skilled in the art or science to which the present invention pertains to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art or science, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments disclosed, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Referring to Fig. 1 shown is the system for coating EPS beads with the coating composition (VBC) in accordance with a preferred embodiment of the present invention. The coating composition (12), in the form of a solution, is drawn from a reservoir (1) by a supply pipe (2) through a filter/strainer (3). A check valve (4) is pulled open by pump (5) suction. If the pump (5) is shut down, the check valve (4) closes to prevent loss of prime. The pump (5) pressurizes the coating fluid for delivery through the piping circuit. Should outlet flow become restricted as sensed by a pressure sensor (8), a pressure activated bypass (6) diverts flow back to the reservoir. Pressure can be monitored, for example, by a pressure gauge (9). A supply manifold (10) which houses a plurality of nozzles (11) is provided to deliver the spray coating (12) in a coating chamber (24).

The system further includes a blower (13), which provides forced air (14) in the air chamber (15) to pass through an air diffuser plate (16). The inlet from the expander (17) and inlet duct (18) bring in the uncoated EPS beads. The coating composition (12) is sprayed on and the coated EPS beads (21) are forced through a rotating sieve (22) to ensure a maximum size specification is met prior to exiting at the outlet to a storage silo (23).

In a preferred embodiment, a pump pushes the coating mixture through a hose under pressure. The spray/mist comes out of a nozzle installed at the end of the hose. Nozzle can be placed inside the conveyor pipe that carries newly expanded beads to silos. For example, a quantity of about 10 Gallons (38 liters) of mixture (Water and coating chemical) can be used per 40 m³ of loose beads. The coating breaks the pentane membrane from the surface of the bead; coating is porous and lets the excessive pentane to come out later on. It is, thus, desirable to coat the EPS beads, since it has been observed that cement makes a good bond with the coating and even to the Styrofoam in the absence of the pentane membrane on the surface.

A purpose of the coating composition of the present invention is to enable concrete to adhere to EPS beads in a concrete and EPS mixture, and the purpose of said lightweight concrete mixture being to enable the creation of a uniquely strong and sturdy lightweight concrete that is used to manufacture pre-cast concrete blocks, panels, or concrete elements used to construct cost-effective homes that are energy-efficient, and withstand wind, fire, flood and earthquake to meet the variable structural challenges of a changing world climate.

The structural light-weight concrete formula is, thus, desirable to allow for the creation of pre-cast structural concrete wall and roof panels that can be transported to construction sites and set into position creating a simplified, light-weight cost-effective concrete structure that will withstand any climate and weather damage.

Said light-weight concrete mixture can be molded into wall and roof forms which are then conveyed into a specifically designed curing facility, where it will cure sufficiently to be removed from the curing area and transported or stored, e.g., in less than approximately 24 hours. The pre-cast wall and roof panels can be transported to building sites in sequence, and set into position on a prepared certified engineered foundation, and fastened together utilizing either a two-part adhesive or any number of connection systems including, e.g., mechanical or welded options, as known to a person skilled in the art; said methods result in a three-dimensional structure that is fire, wind, water/flood, earthquake/seismic, mold/mildew, and pest resistant, suitable for all geographic regions and climates.

Examples of concrete mixtures (Vidacrete™) of the present invention are provided hereinbelow: Example 1 - Table 1

Example 2 - Table 2

As explained above, the EPS beads are coated with the coating composition (12) of the present invention, which is designed to eliminate a restrictive gas layer on EPS beads, that otherwise prevents concrete from adhering to EPS beads properly, and to maintain the contiguous nature of the mix.

The coating composition (12) adheres to the beads, and has a porosity allowing the gas to dissipate, thus enabling a strong attraction and permanent adherence of the concrete to the EPS beads, with said adherence of concrete to EPS beads creating a mixture that can be pre-cast into panels significantly lighter and sturdier structurally than existing methods allow for. The coating is, thus, desirable to create decreased weight and sturdiness in an EPS and concrete mixture, where previous EPS concrete mixtures failed.

In accordance with a preferred embodiment of the invention, the elements of the coating composition (12) are as follows: Thalocyanine (1 part per 100) and Polyvinyl acetate (free radical vinyl polymerization of the monomer vinyl acetate) and Polyvinyl alcohol and various additives, known to a person skilled in the art, to improve flow and surface wetting. This treatment encourages adhesion of the cementitious portion of the Vidacrete™ mix to the bead resulting in increased strength of the overall composite.

free radical vinyl polymerization

CH₂=CH - H-CH₂-CH-^

I I

O O

C=O C=O

CH₃ CH₃ vinyl acetate poly (vinyl acetate)

In accordance with another preferred embodiment, the elements of the coating composition (12) are as follows (in parts by volume): 1 part PVA (polyvinyl acetate), 1 part methyl hydrate, about 3 parts water, 0.05 parts methyl blue. The volume of water can vary depending on sprayer requirements and air pressure.

The coating composition is mixed with water at a ratio coating composition:water of about 1:3.

In a first step, the beads are specifically made to the correct size and density for the process, within the manufacturing plant, as known to a person skilled in art, for the purpose of creating the Expanded Polystyrene (EPS) material that is used at this stage in the process. The uncoated beads can have a density of between 22 to 25 kg/m³ with the loose bulk density being between 16 to 18 kg/m³. For example, pre-expanders which come equipped with "fluid bed dryers" for the finishing of the EPS beads once they have been expanded to the proper size from their original resin state may be used. Once the EPS beads have been treated through the spray application of the coating composition, they can be transported to the EPS bead air conveyor to silos with measured portions of the beads being moved to the mixer by an air conveyor system and placed in pre-measured bins. The beads in the EPS bins are emptied into the automated concrete batch mixers at the correct time, as one skilled in the art would know. Sequencing of time and conveyance of EPS and all other materials can be handled by a computer automation system which is known and normally used by those skilled in the art pertaining to the present invention or can be performed manually.

Fig. 2 shows a schema of the coating procedure according to an aspect of the present invention. Referring to Fig 2, compressed air is taken from compressor (101) to operate the pump. The air line has a couple of valves and pressure regulators to turn the pump on/off (102, 103). Air Exit (104) works as a sink to operate the pump (105). A premixed coating solution in a reservoir/pail is sucked in (106) by the pump and pushed into the flexible supply pipe which has a nozzle at the end (108). A control valve is provided close to the nozzle to shut off the coating solution for short periods of time for installing or positioning the nozzle (107). Beads pushed/sucked in from the EPS expander or Silo (109) gets coated with a mist of coating solution. They are then blown into the silo (110) for storage and future use in preparation of Vidacrete mix.

The advantage of having expanded polystyrene beads in the concrete mixture of the present invention, is readily apparent to a person skilled in the art, and is fourfold:

1 ) It creates a lighter concrete mixture, more useable in light construction such as homes and some commercial buildings. The concrete mixture of the present invention weighs about 95 (-+) pounds per cubic foot as compared to regular concrete which weighs 150 pounds per cubic foot; 2) The coating treatment causes the concrete to be attracted to the beads. This adds greatly to the strength of the panels;

3) The concrete mixture of the present invention is fire resistant with the burn characteristics of asbestos cement; this means that it does not contribute to or assist combustion in any way nor is there any form of "off-gassing"; and

4) The coating process allows finished panels to have microscopic air pockets that reduce the advent of cracking orspalling (flaking of surface layers of the concrete) in very cold temperatures.

In accordance with an embodiment of the present invention, the EPS bead, as component of concrete mixture, may be of a consistent size of approximately 3/16 inch in diameter. The sand, as a component of cementitious mixture, can be washed, coarse "broken" granule concrete sand. It may be preferable, to have non-reactive sand consisting of broken granite, however, although preferable, it is to be understood that the availability of the sand with all of these characteristics is limited and any sand or the like known to a person skilled in the art may be used in accordance with the invention.

In a preferred embodiment, in winter conditions, the sand may be heated during the manufacture of the mixture.

In one mixing sequence, in accordance with an embodiment of the invention, it may be desirable that the sand, cement and water be placed in the mixer first, and after several rotations, the additives and fibers are added (specific by weight and volume), and the mixer further rotated. Once it is clear to a person skilled in the art that the contents are thoroughly mixed, the EPS beads are added and the mixer runs for a short time (for example, 10-15 seconds) in order to draw the EPS beads completely into the mix. However, after the step of adding the EPS beads to the mixture the mixer may run for any period of time necessary for the beads to become homogenously distributed into the mixture. However, the entire mixing process may not exceed approximately 90 seconds.

Any mixer known in the art, which is suitable to the present invention, can be used. However, preferably, the mixer can be a twin shaft mixer; with mixing paddles designed to draw the EPS beads down into the mixture, and if said paddles are not designed to specifications, the EPS beads may float on top of the mix without properly becoming a part of the mass mixture, and will wear down through the abrasive action of the aggregate in the mix.

The fiber additive can be a polypropylene material.

The elements of the coating composition are preferably maintained in a temperature that is above freezing. The beads are sprayed with the coating composition and dried in a storage silo and transported to holding silos to await introduction into the cementitious mixture.

As stated above, the coating composition and process for applying the coating composition to EPS beads enable the concrete in the cementitious mixture to adhere to EPS beads.

In accordance with an embodiment of the invention a Fluid Bed Dryer (FBD) may be used in order to obtain maximum efficiency in the production of EPS beads. The purpose of the FBD is to prepare the beads for other uses such as block consolidation or molding into packing materials, etc.

The FBD consists of an open topped container with a screened cover. The size varies according to the assigned production of the EPS pre-expander attached thereto. (The expander is referred to as a pre-expander because in normal usage, the beads are introduced into molds, etc. where the expansion is furthered by another injection of steam in a partial vacuum atmosphere). In a preferred embodiment, the size of the FBD in the Vida Production System™ is approximately 5.5 meters long, 1.4 meters wide and 1 meter deep. The bottom of the FBD consists of a perforated aluminum plate. A high-speed fan provides the necessary air pressure to provide a constant strong airflow through the perforations.

The expanded EPS beads are introduced from the pre-expander into the FBD where the airflow agitates the beads and suspends in the air in a tumbling motion so as to dry the condensed water from the steam in the pre-expander.

The tumbling beads are moved to the end away from the expander. They pour over an interior bulkhead into an agitator that propels them through a specifically sized screen into a high-speed airflow, which carries them into the mesh silos where they dry further before being mixed in Vidacrete™ according to a specific formula.

As the beads are carried out of the FBD, they are coated with the Vida Bead Coating (VBC) by means of airless spray nozzles mounted at the top of the FBD approximately 60 degrees upstream of the interior bulkhead. The spray nozzles may be specifically sized according to the viscosity of the VBC and to the pressure to provide the a maximum coverage of the passing beads.

The airless pump is a modification of the airless paint systems widely used. The use of the FBD for such coatings is widely used in the industry. Most commonly, the beads may be coated with a light oil, as known to a person skilled in the art, in some molding procedures. INDUSTRIAL APPLICABILITY

The concrete as obtained by the process described above can exhibit "wood" characteristics when driving nails or inserting screws. It is thus desirable to obtain a material where there is no need for pilot holes or anchoring required adhering items to panels of concrete obtained as described above; there is reduced cracking or spalling of the surface. The concrete as obtained above also can require less effort to make modifications than regular concrete. Additionally, windows and doors may easily be cut with a simple abrasive saw.

The resulting concrete mixture can be a cost-effective structural lightweight concrete that can address the desire for a material which is fire, wind, water/flood, earthquake/seismic, mold/mildew, and pest resistant, suitable for all geographic regions and climates, and the weight of which (96 pcf) is approximately 64% of the weight of regular concrete (150 pcf).

LIST OF REFERENCE NUMERALS:

1 Reservoir

Supply pipe

3 Filter/strainer

Check valve

Pump

Pressure activated bypass

Return pipe

Pressure sensor

Pressure gauge 0 Supply manifold 1 Spray nozzle 2 Spray coating 3 Blower 4 Forced air 5 Air chamber 6 Air diffuser plate 7 Inlet from expander 8 Inlet duct 9 Uncoated EPS beads 0 Outlet duct 1 Coated EPS beads 2 Rotating sieve 3 Outlet to storage silo 4 Coating chamber

Claims

What is claimed is:

1. A method for applying a coating composition to pre-expanded EPS beads for eliminating a restrictive gas layer on the surface of the EPS beads, the method comprising the steps of: a. pre-expanding particulate EPS raw material to form EPS beads; b. passing the EPS beads through a fluid bed dryer; c. blowing the EPS beads through an EPS coating system, whereby the EPS beads are coated with a functional composition by means of spraying the composition over the EPS beads; and d. forcing the coated EPS beads through a rotating sieve for ensuring that beads of a predetermined size are transferred to an EPS beads storage means and for reduced clumping.

2. The method according to claim 1 , wherein the functional composition comprises thalocyanine, polyvinyl acetate and polyvinyl alcohol.

3. The method according to claim 2, wherein the functional composition further comprises at least one additive.

4. The method according to claim 1 , wherein the functional composition comprises in parts by volume: 1 part polyvinyl acetate, 1 part methyl hydrate, about 3 parts water, and 0.05 parts methyl blue.

5. The method according to claim 1 wherein the density of the particulate EPS raw material is from 22 to 25 kg/m³ and the loose bulk density is from 16 to 18 kg/m³.

6. An EPS coating system comprising a reservoir, a coating chamber, the reservoir and the coating chamber being interconnected through a piping circuit, which delivers a pressurized fluid composition from the reservoir to the coating chamber, the coating chamber having an EPS beads inlet and an outlet duct, the EPS beads outlet duct being provided with a sieve, an air chamber, the air chamber being in communication with the coating chamber, a spraying assembly for delivering a fluid composition from the piping circuit into the coating chamber, a blower for providing forced air into the air chamber and an air diffuser plate, the air diffuser plate being positioned between the coating chamber and the air chamber so that forced air is introduced from the air chamber into the coating chamber through the air diffuser plate.

7. The EPS coating system according to claim 6, wherein the spraying assembly comprises at least one nozzle.

8. The EPS coating system according to claim 6, further comprising a pressure sensor for monitoring the pressure in the coating chamber and for directing the pressurized fluid composition back to the reservoir through a pressure activated by-pass when the pressure is greater than or equal to a predetermined threshold.

9. A functional composition for coating EPS particles used to produce a lightweight concrete material, the composition comprising thalocyanine, polyvinyl acetate and polyvinyl alcohol.

10. The composition according to claim 9 further comprising at least one additive.

11. A functional composition for coating EPS particles used to produce a lightweight concrete material, the composition comprising in parts by volume: 1 part polyvinyl acetate, 1 part methyl hydrate, about 3 parts water, and 0.05 parts methyl blue.