Lightweight Polymer Concrete Composition

Abstract

A lightweight foamed polymer concrete admixture for use in fabricating building components, the polymer concrete comprising a mixture of a polyol, an isocyanate, an aggregate, and water, wherein once mixed, the mixture releases carbon dioxide gas creating a foamed mixture that may be shaped to form a building component such as, but not limited to, lap siding, shake siding, trim boards, stone and stucco sheeting.

Description

RELATED APPLICATION

This application claims the benefit of priority to U.S. Provisional Application No. 61/805,551 filed on Mar. 26, 2013.

TECHNICAL FIELD

This invention relates generally to the formation of decorative and structural building components made from a polymeric concrete admixture.

SUMMARY

Consumers are increasingly demanding that exterior building components such as lap siding, roof shakes, siding shakes, bricks, paving stones, stucco sheeting and lap siding provide a high quality appearance and yet are also extremely durable. These components are built to exacting specifications and constructed of materials that are capable of withstanding the bleaching effects of high intensity sunlight, daytime surface temperatures in excess of 250° F., repeated exposure to strong winds, hail impact, sub-zero temperatures and the typical insults building materials are exposed to throughout the United States including impacts from errant baseballs, hockey pucks, soccer balls, abrasive tree limbs and the like. In other words, the typical building component must now be nearly indestructible in order to maintain customer loyalty.

The building products must be hard, yet ductile and not brittle, to withstand high energy impacts and also impacts from tools, such as hammers, during installation. The building materials must have high tensile and compressive strengths to avoid undesirable deformation under loads or fracture when nails or screws are driven through the product. In addition, the building components must have low thermal expansion to avoid buckling when temperatures vary during a short time period such as at sunset in desert settings. The building components must be capable of retarding fires, have low moisture absorption and preferably adds R-value to provide insulating qualities thereby lowering energy costs for the consumer.

Making these building components capable of withstanding high energy impacts, temperature extremes and wind loading is a challenging task that requires considerable expertise with material properties. Further complicating the task of fabricating these building components is the challenge of producing components that are lightweight so that the individual installing the building component (e.g., siding) is not injured while attempting to move, for example a heavy panel, or prematurely experiences muscle fatigue from repeated movement of smaller yet heavy components such as siding shakes.

In order to integrate the many desirable characteristics referenced above the disclosed technology utilizes a polymer concrete admixture that invokes a polymerization reaction with water to intentionally cause the release of carbon dioxide gas. The release of the carbon dioxide gas foams the admixture by introducing the gas bubbles into the polymer concrete mixture. This foaming activity causes entrainment of the gas within the admixture thereby causing a set volume of the material with entrained carbon dioxide gas to weigh less, per unit of volume, than the admixture without the entrained carbon dioxide gas. The material with the entrained carbon dioxide gas weighs roughly one-half of what the non-entrained gas mixture weighs by a set volume of the material. When the gas entrained polymer concrete is molded into the desired product it maintains excellent structural strength, fire retardance, a low thermal expansion coefficient and many other desirable characteristics and also weighs substantially less than a product that did not undergo the foaming process.

For the foregoing reasons, there is a need for a polymer concrete admixture that can be shaped to form exterior weatherable building products.

For the foregoing reasons, there is a need for a polymer concrete admixture that has a low specific gravity in order that finished products are of the lightest weight possible without sacrificing other desirable performance characteristics.

For the foregoing reasons, there is a need for a polymer concrete admixture that has low moisture absorption.

For the foregoing reasons, there is a need for a polymer concrete admixture that has a low coefficient of thermal expansion.

For the foregoing reasons, there is a need for a polymer concrete admixture that is fire retardant.

For the foregoing reasons, there is a need for a polymer concrete admixture that adds R-value thereby enhancing the energy efficiency of the structure to which the building product is applied.

SUMMARY

The disclosed technology is directed to a multiplicity of building products that satisfies the requirements of high strength, high impact resistance, a low coefficient of thermal expansion, adds R-value, low moisture absorption, is fully resistant to wood rot, decay and insects among other important characteristics by using a light weight foamed polymer concrete that is molded into the desired shape. The polymer concrete that is employed is comprised of a mixture of a polyol, an isocyanate, an aggregate and water, wherein once mixed, the admixture is shaped to form the desired building component.

Exemplary building products that are produced using the disclosed technology include, but are not limited to lap siding, shake siding panels, shake roofing, paving stones and decking materials as well as exterior stucco sheeting and trim boards. Once the above referenced materials are combined and thoroughly aggregated the admixture is molded, extruded or pultruded to form the desired shape. Because of the release of carbon dioxide gas the admixture upon the addition of water begins to release carbon dioxide and form a foamed product. The foamed product has a density of approximately one-half that of the same admixture that does not have water introduced into the mixture.

The low density of the fully cured foamed product is a central attribute of this composition and system for production of building products. With building product densities ranging from 0.7 to 1.5 g/cm³ the product produced from the disclosed implementation is lightweight in comparison to standard concrete. Industrial concrete typically has a density of about 2.4 g/cm³ and therefore a paving stone produced from the disclosed composition may weigh only one-third that produced from standard industrial concrete. Weight savings of this magnitude will quickly translate into savings in shipping costs as well as fewer workplace soft tissue and joint injuries due to excessive weight being borne by the installer when moving the building products.

Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the method for admixing the polymer concrete composition;

FIG. 2 is a perspective view of an embodiment of lap siding fabricated from the polymer concrete composition;

FIG. 3 is a perspective view of an embodiment of roof shakes fabricated from the polymer concrete composition;

FIG. 4 is a perspective view of an embodiment of siding shakes fabricated from the polymer concrete composition;

FIG. 5 is a perspective view of an embodiment of siding stones fabricated from the polymer concrete composition;

FIG. 6 is a perspective view of an embodiment of paving stones fabricated from the polymer concrete composition, and

FIG. 7 is a perspective view of an embodiment of stucco siding fabricated from the polymer concrete composition.

DETAILED DESCRIPTION

The invention may be more fully appreciated by reference to the following detailed description, including the following glossary of terms and the example.

The terms “including”, “containing” and “comprising” are used herein in their open, non-limiting sense.

“Admixture” means the ingredients in the polymer concrete that are added to the mix immediately before or during mixing.

“Cure” means the process of toughening or hardening of a polymer material by cross-linking of polymer chains, brought about by chemical additives, ultraviolet radiation or heat.

“Polymer concrete” means the group of concretes that use polymers to replace cement as a binder.

The following detailed description is directed to a method of producing building materials from a polymer concrete mixture that possess highly desirable physical characteristics and that can be shaped into a wide variety of products for consumer use. Building materials such as siding, shakes, and trim boards must possess a wide range of physical characteristics that facilitate their continued use in the construction industry. Specifically, the building materials must have high tensile and compressive strengths yet be sufficiently ductile to avoid brittle facture particularly at low temperatures, they must be flame retardant, have a low coefficient of thermal expansion and contributes R-value to reduce the transfer of heat. Moreover, the material selected for the building products must be easily and quickly formed into the desired shape and finally must be lightweight to reduce shipping costs and to enhance the ease of installation.

In the following detailed description, references are made to the accompanying drawings that form a part hereof, and that show by way of illustration specific embodiments or examples. Referring now to the drawings, in which like numerals represent like elements through the several figures, the process of producing building materials from a polymer concrete mixture will be described.

FIG. 1 shows a flow diagram depicting the sequence of the aggregation of a series of materials to form the polymer concrete admixture 10. Block 1 depicts the selection of polymeric polyol 20 which is an alcohol containing multiple hydroxyl groups. The selected polymeric polyol may be either derived from vegetable sources, such as corn, or the polyol may be petroleum based. The preferred embodiment utilizes a vegetable based polyol for use in the polymer concrete admixture. The polyol 20 will preferably comprise in the range of 10 to 15% of the mass of the total mixture.

Block 2 of FIG. 1 reveals the selection of an isocyanate 30. The preferred isocyante is the aromatic isocyanate diphenylmethane diisocyanate, commonly referred to as MDI. Alternatively, the aromatic isocyanate toluene diisocyanate, commonly referred to as TDI, may be used. The isocyanate will preferably comprise in the range of 5 to 15% of the total mixture.

A third component for inclusion in the mixture, as seen in block 3, is an aggregate 40. The preferred aggregate is sand with an average particle size in the range of about 10 to 1,000 microns. Alternatives such as quartz silica, calcium carbonate or talc and other minerals may also be utilized in place of the sand. The aggregate 40 will serve as the backbone of the admixture and serve to provide structural rigidity to the composition when cured and also enhance the composition's weatherability, fire retardance, low thermal expansion characteristics and high R-value. The aggregate preferably comprises between about 50% to 90% of the mass of the total mixture. The aggregate further preferably comprises about 80% of the mass of the admixture.

The fourth component of the composition, as seen in block 4, is water 50. Water will comprise a very small percentage of the overall mass of the admixture but generally no less than 0.1% of the total mass of the mixture. Any water that does not react with the available isocyanate 30 is flashed off later in the molding process. The isocyanate 30 reacts in the presence of water 50 to form a urea linkage and carbon dioxide gas 60. The carbon dioxide gas forms throughout the admixture and creates tiny entrained bubbles of gas in the mixture.

The fifth component that may be added to the admixture, as seen in block 5, is a catalyst 70. At least two forms of catalyst may be used to alter the rate of the reaction of the constituents of the admixture. These two forms of catalyst are an amine compound catalyst and a metal compound catalyst. The catalyst does not serve to alter the characteristics of the admixture when fully cured, it does, however, serve to change the rate at which the mixture cures and is ready for release from the mold into which it is placed for shaping into a finished product.

The sixth component that may be added to the admixture is fiber. The introduction of fiber serves to increase the flexural and strength modulus as well as abrasion and impact resistance, to reduce the incidence of crack propagation. The preferred forms of fiber added to the admixture are chopped glass about one-quarter inch in length, milled glass, preferably one-sixteenth inch in length, cellulosic fibers principally cotton fibers, preferably about 4 mm in length. Fiber is preferably added in the amount ranging from 1 to 5% by weight of the total admixture. A range of fiber mass from 2 to 3% is further preferable.

To produce the desired mixture 10 the isocyanate 30 is blended with the polymeric polyol 20. The preferred ratio for blending this portion of the admixture is one part isocyanate 30 to one part alcohol content in the polymeric polyol 20. Consequently, more polymeric polyol 20, by mass, is added to the mixture as compared to isocyanate 30. Once these materials 20, 30 are blended the composition begins react. At this time the aggregate 40, preferably sand with a mean diameter in the range of from 10 to 1,000 microns, is added to the mixture. The aggregate 40 comprises preferably in the range of 50% to 90% by total mass with a further preference for the aggregate to provide roughly 80% of the total mass of the polymer concrete admixture.

As discussed above, the isocyanate 30 reacts with water to form carbon dioxide gas. Many times the aggregate, unless thoroughly dried will contain sufficient moisture (water 50) for reaction with the isocyanate 30. If a greater release of carbon dioxide gas for entrainment within the admixture is desired, additional water is added. Excess water; however, will flash-off during the molding process. As previously discussed, the mass of water added to the admixture is preferably in excess of 0.10% but less than 2%.

Once the admixture containing the polymeric polyol 20, the isocyanate 30, the aggregate 40 and the water 50 is thoroughly blended so that the material is essentially homogenous throughout the admixture 10 is placed into a closed mold 80 of the shape desired for the building product.

Alternatively, double-belt presses with circulating belts make it possible to implement continuous production processes (not shown). Continuous production methods can increase production capacity while achieving lower energy consumption. Pressing, heating and cooling the mixture, to produce for example siding panels, is achieved in a single production step. Siding panels can be manufactured with increased precision within tight tolerances for specified density.

The admixture 10 will continue to expand due to the entrainment of the carbon dioxide gas 60 to fill the volume of the closed mold 80.

In an exemplary scenario that is not intended to limit the range of alternatives available in the curing and demolding process, the admixture is then cured in the mold for approximately 2 hours at 100° C. and then demolded. Upon demolding, the product is post cured for approximately 16 hours at 70° C. Products that are not fully cured at elevated temperatures for the requisite period of time will suffer from deficiencies in the desired physical properties including reduced tensile strength, glass transition temperature and flexural strength and modulus. The increased temperature in the mold serves as a catalyst to accelerate the polyurethane linkage.

To further enhance the aesthetic appeal of the finished products coloration can be accomplished with the addition of pigments to the admixture during the mixing process. To further enhance the durability and weatherability of the finished materials certain building products produced from the disclosed composition, such as lap siding and shakes, may also include a protective fully encompassing cap that is preferably comprised of polyvinyl chloride (PVC) or acrylonitrile styrene acrylate (ASA). The cap is preferably in the range of 3 to 5 mils in thickness when applied using methods that are well known to those skilled in the manufacture of capped composite building materials. Paint and films comprised of acrylic preferably about 0.001 inches in thickness are also options available to protect the finished product.

As seen in FIGS. 2-7, a wide range of products 90 (lap siding), 100 (roof shakes), 110 (shake siding), 120 (brick), 130 (stone pavers) and 140 (stucco) can be produced from the polymer concrete admixture 10.

EXAMPLE

The invention is described in greater detail below by means of an exemplary embodiment, the physical property determination methods described herein are being used for the corresponding parameter in the implementation unless otherwise indicated.

Materials:

For the production of test specimens, the polyol BiOH X-210® produced by Cargill with an OH of 225, an acid value of 11.4 and an equivalent weight of 249 is used. The mass percentage of the polyol was 12.3% of the total mixture.

Isocyanate Rubinate® M from Huntsmen Chemical with an NCO % of 31.2 a function number (FN) of 2.7 and an equivalent weight (EW) of 135 is used. The mass percentage of the isocyanate is 9.0% of the total mixture.

The aggregate Sea Sand from Fisher Scientific comprised of quartz silica with a density of 2.65 g/cm³ and an average particle size of 300 microns is used. The mass percentage of the aggregate is 78.2% of the total mixture.

Distilled water equivalent to 0.50% of the overall mass is utilized.

Compounding:

Compounding of the above referenced additives is carried out in a six quart stand mixer manufactured by Kitchenaid®.

Test Specimens:

The compounded material is withdrawn from the stand mixer and placed into a mold for producing plank siding. The dimensions of the mold are 24″×8″× 5/16.″ The samples are cured for 16 hours at 120° C.

Measurement of Physical Parameters:

The specimens are tested to determine physical parameters, many of which are standard test protocols defined by American Society for Testing and Materials (ASTM International). The specific testing protocols are set forth below in Table 1.

TABLE 1
Physical Parameter ASTM or other Test Method Identifier
Tensile Strength   ASTM D638
Tensile Elongation ASTM D638
Tensile Modulus    ASTM D638
Density            ASTM D1622
Flexural Strength  ASTM C293
Flexural Modulus   ASTM C293
Gardner Impact     Falling Dart Impact
Glass Transition   Dynamic Mechanical Analysis (DMA)
Temperature—Tg
Coefficient of     Thermal Mechanical Analysis (TMA)
Expansion—COE

Example 1

The results of the physical parameter measurements are given in Table 2.

	TABLE 2
	PROPERTY	UNITS	VALUE
	Tensile Strength	Mpa	9.0-37.0
	Tensile Elongation	%	0.8-1.7
	Tensile Modulus	Mpa	2810-4650
	Density	g/cm3	0.9-1.13
	Flexural Strength	Mpa	6.0-9.0
	Flexural Modulus	Mpa	380-560
	Gardner Impact	Kg*cm	25-50
	Tg (glass transition	° C.	80-146
	temperature)
	COE (coefficient of	μm/m ° C. @ 25° C.	10.2-40.6
	thermal expansion)

While the preferred form of the present invention has been shown and described above, it should be apparent to those skilled in the art that the subject invention is not limited by the figures and that the scope of the invention includes modifications, variations and equivalents which fall within the scope of the attached claims. Moreover, it should be understood that the individual components of the invention include equivalent embodiments without departing from the spirit of this invention.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Not all steps listed in the various figures need be carried out in the specific order described.

Claims

1. A method for fabricating a building product from a curable polymer concrete composition comprising;

(a) admixing: (1) a polyol, (2) an isocyanate, (3) an aggregate; and (4) water, wherein the water and isocyanate react to provide crosslinking and evolve carbon dioxide gas resulting in a foamed admixture;

(b) placing the admixture in a mold defining the contours of the building product wherein the evolving carbon dioxide gas is entrained in the admixture causing the volume of the admixture to increase;

(c) curing the admixture in the mold; and

(d) removing from the mold the defined building product with a specific gravity in the range of about 0.7 to 1.5.

2. The method of claim 1, wherein the polyol is either a vegetable oil based polyol or a petroleum based polyol.

3. The method of claim 1, wherein the mold is either a closed mold or a continuous belt mold.

4. The method of claim 1, wherein when placed in the mold the volume of the admixture increases in the range of about 50 to 300 percent.

5. The method of claim 1, wherein the polyol comprises in the range of 5 to 15 percent of the total mass of the admixture.

6. The method of claim 1, wherein the isocyanate is in the range of 5 to 15 percent of the total mass of the admixture.

7. The method of claim 1, wherein a surfactant is admixed with the polyol, iscocyanate, aggregate and water to form the admixture.

8. The method of claim 1, wherein the aggregate is a mineral composition with an average particle size distribution range from about 10 to 1,000 microns.

9. The method of claim 8, wherein the mineral composition is an inorganic mineral.

10. The method of claim 1, wherein the aggregate comprises in the range of from about 50 to 95 percent of the mass of the admixture.

11. The method of claim 10, wherein the aggregate preferably comprises 80 percent of the mass of the admixture.

12. The method of claim 1, wherein the water comprises at least 0.1 percent of the mass of the admixture.

13. The method of claim 1, wherein the components shaped from the admixture are selected from the group consisting of roof shakes, siding shakes, bricks, paving stones, stucco sheeting, lap siding, fascia, trim, decking products and flooring.

14. The method of claim 1, wherein the tensile modulus of the cured admixture is in the range of from about 2810-4650 Mpa.

15. The method of claim 1, wherein the flexural strength of the cured admixture is in the range of from about 380-560 Mpa.

16. The method of claim 1, wherein the density of the cured admixture is in the range of about 0.7 to 1.5 g/cm3.

17. The method of claim 1, wherein the coefficient of thermal expansion of the concrete polymer mixture when fully cured is in the range of from about 10.2 μm/m° C. to 40.6 μm/m° C.

18. The method of claim 1, wherein the isocyante is preferably the aromatic isocyanate diphenylmethane diisocyanate.

19. The method of claim 1, wherein a catalyst is used to accelerate the curing time of the admixture.

20. A system for producing a polymer concrete for use in fabricating building products, the system comprising:

(a) a polyol, an isocyanate, an aggregate; and water, that are mixed together wherein the water and isocyanate react to provide crosslinking and evolve carbon dioxide gas resulting in a foamed admixture;

(b) a set volume of the foamed admixture is placed into a closed mold to expand because of the evolving carbon dioxide gas, the admixture completely filling the void within the mold;

(c) the admixture cured within the mold at a variable temperature in the range of 60 to 120° C. and for approximately 2 hours; and

(d) the building product is removed from the closed mold and cured again for a period of approximately 16 hours at 70° C., wherein the density of the cured building product is in the range of from 0.7 to 1.5 g/cm3.

21. The system of claim 20, wherein the polymer composition may be decorated prior to removal from the mold.

22. The system of claim 21, wherein the polymer composition may be painted to reveal decorative weathering.

23. The system of claim 20, wherein a mesh is integrated within the admixture at the time of placement of the admixture into the mold.

24. A polymer concrete composition useful for fabricating lightweight building products, the polymer concrete composition comprising;

(a) aggregate in an amount in the range from about 50 to 90% by weight of the polymer concrete composition;

(b) polyol in an amount in the range from about 10 to 20% by weight of the polymer concrete composition;

(c) isocyanate in an amount in the range from about 5 to 15% by weight of the polymer concrete composition; and

(d) water in an amount of at least 0.1% by weight of the polymer concrete composition, wherein the sum of the components (a) through (d) add up to 100 weight % and after the product is cured in a continuous belt mold the polymer concrete exhibits a density of from about 0.7 to 1.5 g/cm3 and a flexural strength of from about 0.6 to 1.0 Mpa.

25. The polymer concrete composition of claim 24, wherein fibers are added to the admixture in the range of about 1 to 5%.

26. The polymer concrete composition of claim 25, wherein chopped glass fibers preferably about one-quarter inch in length are added to the admixture.

27. The polymer concrete composition of claim 25, wherein milled glass fibers preferably about one-sixteenth inch in length are added to the admixture.

28. The polymer concrete composition of claim 25, wherein cellulose fibers are added to the admixture.

29. The polymer concrete composition of claim 25, wherein cotton fibers preferably about 4 mm in length are added to the admixture.

30. The polymer concrete composition of claim 24, wherein the cured building product is covered with a cap comprised of polyvinyl chloride in a thickness ranging from about 0.003 to 0.005 inches.

31. The polymer concrete composition of claim 24, wherein the cured building product is covered with a cap comprised of acrylonitrile styrene acrylate in a thickness ranging from about 0.003 to 0.005 inches.

32. The polymer concrete composition of claim 24, wherein the composition is cured in a mold for 2 hours at 100° C. and then demolded and cured for at least 2 hours at a temperature between 60 and 120 ° C.