Patent Grant
11001700
In order to provide more environmentally-responsible products, manufacturers are exploring alternative approaches to reduce the amount of polymer used to produce various polymer-based products. One such approach involves substituting a portion of the polymer content with a plant-based or “bio-based” filler such as wood flour, starch, or distilled grain. However, plant-based fillers absorb water and swell in a moist or humid environment and degrade at the high temperatures used during processing. This leads to poor product performance and undesirable characteristics.
Eggshell powder is an alternative to the standard plant-based materials. However, attempts to use eggshell powder as a filler in polymer composites has been problematic. First, the inner membrane associated with the eggshell, if left in association with the eggshell during the manufacturing process, produces a foul odor which can carry over into the ultimate product. The traditional methods used to remove the inner membrane from the eggshell involve the use of high-temperatures and/or harsh chemical treatments. This approach not only increases manufacturing costs, but also compromises the native lipid-protein surface structure of the eggshell. As a result, the interface between the eggshell powder and polymer is weakened resulting in sub-optimal product performance.
Therefore, a bio-based or environmentally-responsible filler material is needed for use in manufacturing polymer composites that maintain comparable or improved physical properties without undesirable characteristics and sub-optimal performance ratings.
The processes and compositions described herein relate to an eggshell powder that possesses improved characteristics for use in polymer composites. To this end, the present invention solves the problems associated with the use of eggshell material as a bio-based filler by providing a process in which the inner membrane is removed from the eggshell without the use of high temperatures or harsh chemical treatments. As a result, the eggshell material retains its native lipid-protein structure thereby permitting a strong interaction with an associated polymer.
A process for producing an eggshell powder is provided. The process involves exposing the eggshell to air flow at a speed sufficient to pulverize the eggshell thereby rendering a bulk pulverized material comprising an eggshell component and a separated inner membrane component. The separated eggshell component is then isolated from the inner membrane component by applying the bulk pulverized material to a first screen comprising a mesh size sufficient to retain the separated inner membrane component on the surface of the first screen while permitting passage of the eggshell component through the first screen. At this point, the collected eggshell component can either be applied to a second screen comprising a mesh size smaller than that of the first screen or re-exposed to the air flow at the same or an increased speed to further pulverize the material and then applied to the second screen. The pulverization step can be repeated additional times at the same or increased air flow speeds until the eggshell component is reduced to the desired particle size.
Additionally, an eggshell powder composition is provided. The eggshell powder composition is substantially free of the inner membrane and retains the lipid-protein structure present in the native eggshell material used to form the powder.
A polymer composite composition is also provided. The composite composition comprises a first component and a second component. The first component comprises a biobased filler consisting of eggshell powder that is void of the inner membrane and possesses the lipid-protein structure of the eggshell material used to form the powder. The second component comprises a polymer. In one aspect, the polymer is a thermoplastic polymer such as, but not limited to, polyolefin (e.g., polyethylene (PE)), polyesters (e.g., polyethylene terephthalate (PET)), polyamide (e.g., nylon), styrenic polymers (e.g., polystyrene), bio-degradable polymers (e.g., polylactic acid (PLA)), and engineering resins (e.g., polycarbonate). In another aspect, the polymer is a thermoset polymer such as, but not limited to, crosslink polymers (e.g., vulcanized rubber), melamine resin, epoxy resin, crosslink polyesters, and polyurethane. In yet another aspect, the composite composition further comprises a third component. The third component comprises one more additives such as, but not limited to, antioxidants, fiberglass fillers, color pigments (e.g., carbon black), and fragrances (e.g., citronella).
The present application claims priority to U.S. provisional application No. 61/560,973 of the same title which is incorporated by reference in its entirety herein.
In one aspect, a process for producing an eggshell powder is provided. The process involves removal of the inner membrane from the eggshell prior to pulverization through a process that does not rely on a liquid carrier or high temperatures, but rather on air flow at low temperatures. Thus, in a preferred embodiment, the entire process of producing eggshell powder described herein can be performed without heating the eggshell material. As a result, an eggshell powder is yielded that retains the lipid/protein structure of the original eggshell surface from which the powder is derived, and is also substantially free of the eggshell inner membrane material.
In some applications, it may be desirable to sterilize the eggshell prior to processing. The sterilization step can be performed by a number of different methods which are generally known to those skilled in the art. For example, the eggshell can be exposed to a moist heat treatment of a temperature sufficient to eliminate various pathogens and microorganisms. Moist heat treatments include, but are not limited to passing steam infused water through a quantity of shells or simply steam treating the eggshells. Other potential methodologies include exposing the eggshells to UV light, high energy radiation, chemical treatment or reducing the available water (AW).
Following the optional sterilization step, one or more pulverization steps are performed to crush the eggshell to a desired particle size and to remove the inner membrane from the eggshell. Pulverization is preferably performed using high speed air flow at low temperatures. The determination of air speed will largely be dependent on the type of apparatus used, but regardless, should be sufficient to cause separation of the eggshell component from the inner membrane component. Example 1 provides an initial pulverization using an air speed of 3,500 rpm in a pulverdryer which provides a good basis to determine the air speed required to obtain the same result in related air flow equipment. The pulverization step can be performed using a vortex dryer, cyclone wind tunnel or any other apparatus that provides sufficient air speed to crush the eggshell and separate it from the inner membrane. The initial pulverization step should be sufficient to separate the eggshell from the inner membrane. Thus, any additional pulverization steps can be employed to further dry and reduce the particle size of the eggshell component. If a reduced particle size is desired, the air speed can be increased from about 3,500 rpm to about 10,000 rpm and any range therebetween.
The initial pulverization step results in the production of a bulk pulverized material consisting of an eggshell component and inner membrane component. The next step is then to isolate the eggshell component from bulk pulverized material so that the resulting eggshell powder does not contain any of the inner membrane component. This can be performed by applying the bulk material to a mesh screen of a size sufficient to permit the eggshell component to pass through the screen while retaining the inner membrane component on the surface of the screen. For example, the bulk material can be applied to an ASTM 20 mesh screen. However, any number of approaches could be used by a skilled artisan to achieve the same ends as long as the eggshell component can be collected free from the inner membrane component.
The pulverization step can then be repeated for the entire eggshell component or only with respect to the large eggshell component particles (approximately greater that 100 μm) until a desired particle size is reached. The large eggshell component particles can be separated from the remaining eggshell component by using appropriately sized mesh screens. The subsequent pulverizing steps can be performed under the same conditions as the initial step or with higher air speeds for the same or longer time periods. If a specific particle size is desired, the pulverized eggshell component can be sifted through a screen having a particle size specific for the intended use of the eggshell powder. For example, an ASTM 270 mesh screen having a particle size of 53 μm.
The present process yields an improved eggshell powder that retains the lipid-protein structure of the original eggshell from which it is derived and is substantially free of eggshell inner membrane material. Thus, in another aspect of the present invention, an eggshell powder composition is provided. The eggshell powder composition possesses an ash content of about 90-95% and a moisture content from about 0.2% to about 5%, but is generally less than 1%. Of the ash content, approximately 33-36% is calcium in addition to less than 1% of each of magnesium, phosphorus, potassium, and sodium. The calcium content consists substantially of calcium oxide and other metal oxides rather than calcium carbonate. The fat content of the eggshell powder can be in the range of about 0.01% to about 3%, but is generally less than 1%. The protein content is generally less than 5% and more specifically, from about 0.2% to about 3%.
Furthermore, the present eggshell powder retains the original lipid/protein structure of the native eggshell surface from which the powder is derived. As a result, the present eggshell powder possesses hydrophobic properties.
The hydrophobic, lipid/protein structure of the present eggshell powder is more similar to polymer structure than traditional minced calcium carbonate thereby providing an improved interaction with the polymer matrix. As a result, the use of the present eggshell powder in a polymer composite provides improved mechanical properties such as impact resistance and tensile strength as compared to polymer alone, which is demonstrated in Example 5 herein below.
The particle size of the present eggshell powder is, for example, generally less than 100 μm and can be from about 10 μm to about 100 μm. Depending on the intended use of the powder, the particle size is more preferably from about 20 μm to 50 μm. Particle size can be controlled by, for example, using screen filters with the desired mesh sizes and by repeating the pulverization step as described above. For example, the particle size yielded by using an ASTM 150 mesh screen is generally less than 104 μm whereas the particle size yielded by an ASTM 325 mesh screen is generally less than 44 μm.
Although the eggshell powder composition described herein is isolated from chicken eggs, it should be understood that other types of eggshells can be used to yield a similar powder such as, but not limited to, shells from turkey eggs, duck eggs, and other bird eggs.
In another aspect of the current invention, a polymer composite composition is provided. The composite composition comprises a first component consisting of a bio-based material, a second component consisting of a polymer, and in some instances a third component such as an additive or additional filler material. For example, the first component comprises eggshell powder that is substantially free of eggshell inner membrane and retains the original lipid-protein surface structure of the eggshell from which the powder was derived. The particle size of the eggshell powder can be any size desired and most effective for the particular polymer used in the composite. For example, the powder particle size can be from about 10 μm to about 100 μm and more specifically, from about 20 μm to 50 μm.
The second component comprises a polymer. In some instances, the polymer is a thermoplastic polymer such as, but not limited to polyolefin (e.g., polyethylene, ethylene vinyl acetate, ethylene methyl acrylate, polypropylene, polybutylene, polymethyl pentene), styrenic polymers (e.g., general purpose polystyrene, impact modified polystyrene, acrylonitrile butadiene styrene, butadiene styrene copolymer, styrene maleic anhydride copolymer, polystyrene methyl methacrylate copolymer), polyesters (e.g., polyethylene phthalate, polybutylene phthalate, polylactic acid), bio-degradable polymers (e.g., polylactic acid, polycaprolactone, polyvinyl alcohol, polyglycolic acid, polyalkene succinate, aliphatic-aromatic copolyesters, polyanhydrides, and polyhydroxyalkanoate), polyamides (e.g., nylons), and engineering resins (e.g., acetyls, allyl resins, cellulosic resins, chlorinated polyethylene, fluoropolymers, fluorocarbon polymers, liquid crystal polymers, phenolic resins, polyaryl sulfone, polyal lowers, polyamide, polyacrylate, polyethersulfone, polymethyl methacrylate, polyphenyl sulfone, polyphenylene ether, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyurethane, polyvinyl chloride and polycarbonate). In other instances, the polymer is a thermoset polymer such as, but not limited to crosslink polymers (e,g., vulcanized rubber), melamine resin, vinyl ester, epoxy resin, crosslink polyesters, phenolics, melamine resins, and polyurethane.
Additionally, the composite composition can further comprise a third component in some instances. The third component can comprise one or more additives such as, but not limited to, heat stabilizers, antioxidants, UV/light stabilizers, antistatic agents, antifogging agents, lubricants, processing aids, anti-blocking agents, slipping agents, mold-releasing agents, flame-retardant agents, chemical-blowing agents, crosslink agents, nucleating agents, antimicrobial agents, coupling agents, gas scavengers, acid and base scavengers, water scavengers, odor controlling agents, and food flavoring agents.
Alternatively, the third component can include a filler material such as, but not limited to calcium carbonate, dolomite, magnesium carbonate, calcium sulfate, barium sulfate, silica, carbon black, talc, mica, kaolin, clay, graphite, wollastonite, whiskers, glass fiber, carbon fiber, conductive filler, nano-filler, organic filler (including wood flour, cellulose fiber and distilled drained grain), and colorant (including pigment, dye, and fluorescent whitening agent).
The percentage of eggshell powder in the composite ranges from 1% to 90% by weight, from about 30% to 50% by weight, and in many applications is at least 25% by weight. A product made from a composite composition comprising 25% biobased material is suitable to label as “biobased” under USDA regulations. Moreover, the percentage of eggshell powder in the composite is a function of the type of polymer structure desired. The eggshell/polymer composites can be molded into a variety of commercial plastic products including, but not limited to chips, boxes, trays, barrels, golf tees, and disposable bins.
The eggshell powder described herein is integrated with the associated polymer by extrusion; a process in which polymeric resins, eggshell powder, and optionally, other ingredients such as additives and pigments are fed into an extruder barrel with one or more rotating screws. The screw forces the mixture forward in the extruder barrel which is heated to a melting temperature of the particular polymer, and then forces the molten mixture (composite) out of the extruder. The extruded composite is generally then cut into pellet form and subjected to further manufacturing processes such as injection molding, blow molding, extrusion and thermoforming.
In composites comprising thermoset polymers, the present eggshell powder is integrated with the thermoset polymers by first adding monomers to the powder, cross-linking agent and/or other fillers such as fiberglass or color pigment into a cavity of the mold. Pressure is then applied to force the mixture to the cavity voids. The mixture is then annealed at a temperature above the curing temperature to allow the monomer to cure.
Therefore, in one embodiment, the process for producing a composite of eggshell powder and a polymer is provided. The process includes following steps:
The temperature profiles to be used in the extrusion and molding process for various polymers are set forth in Table 1. In instances in which polylactic acid, nylon 6, and nylon 66 are used as the polymer, an initial masterbatch is mixed and extruded under the appropriate conditions followed by a second mixing step in which the masterbatch is mixed with the virgin polymer prior to the injection molding process.
The following examples describe specific eggshell powder compositions and a process of producing such as well as polymer composite compositions formed using the processes described herein. The following examples are solely for purposes of illustrating certain aspects of the invention and not for the purpose of limitation.
In this example, a vortex dryer or pulverdryer was used to crush the eggshell material obtained from a group of white eggs and brown eggs and separate the eggshell material from the inner membrane material. In this instance, the initial pulverization was performed at the following conditions: (1) air speed—3,500 rpm; (2) feeding time—10 seconds; (3) cycling time—0 seconds; (4) discharging time—10 seconds; (5) feed rate—8 kg/time; and (6) temperature—room temperature. This resulted in the production of a bulk pulverized material consisting of an eggshell component and an inner membrane component. The bulk pulverized material was then applied to an ATSM 20 mesh screen to separate the inner membrane component, which was retained on the screen, from the eggshell component, which passed through the mesh. The inner membrane component and eggshell component were each collected and the moisture content analyzed. The inner membrane component possessed a moisture content of approximately 36.4% whereas the eggshell component had a moisture content of 5.85%.
The pulverization procedure was then repeated to further dry and decrease the particle size of the eggshell component. Pulverization was performed under the following conditions: (1) air speed—5,700 rpm; (2) feeding time—10 seconds; (3) cycling time—15 seconds; (4) discharging time—10 seconds; (5) feed rate—16 kg/time; (6) baghouse—60%; and (7) temperature—room temperature. The eggshell component was collected and moisture determined to be 1.1%.
The eggshell component from the second pulverization run included some larger particle sizes so the pulverization was repeated for a third time. The third pulverization was performed under the following conditions: (1) air speed—10,000 rpm; (2) feeding time—10 seconds; (3) cycling time—20 seconds; (4) discharging time—10 seconds; (5) feed rate—16 kg/time; (6) baghouse—60%; and (7) temperature—room temperature. The eggshell component (powder) was collected and analyzed for content. The content analysis for each of the brown eggs and white eggs are provided in Table 2 below.
Tables 3A and 3B below provide composite composition ratios (Table 3A) and manufacturing conditions (Table 3B) to produce a number of specific polymer composite plaques using the present eggshell powder composition and methods. As used in the tables below, “N/A” denotes that for the specific composite, this step was not performed in this particular example and should not be interpreted to mean that this step cannot be used with the particular composite. Specifically, composites 5 and 6 just proceeded through the extrusion process and in this particular example, did not undergo further manufacturing steps. Extrusion was performed by a twin screw extruder (Amco) for composites 1-4 and single screw extruder for composites 5-6.
This example demonstrates that the use of eggshell powder to form a polymer composite plaque with nylon 66 results in improved properties as compared to a plaque formed of nylon 66 alone. The eggshell polymer composite plaque was produced according to the following procedure:
The plaque comprising nylon 66 and 30% eggshell powder was then tested for flexural modulus, tensile strength, and heat deflection at 0.45 MPa and 1.8 MPa. The results are shown in Table 4 below. Table 4 also includes the heat deflection and flexural modulus data of virgin nylon 66 (based on data provided by the manufacturer, BASF). As provided in Table 4, the plaque formed of the nylon 66/eggshell composite displays better properties than virgin nylon 66. Specifically, the composite of nylon 66 and eggshell powder presents higher flexural modulus (3270 Mpa) than nylon 66 itself (2920 Mpa). In other words, the composite of nylon 66 and eggshell powder is stiffer than virgin nylon 66. Furthermore, the composite of nylon 66 and eggshell powder exhibits higher heat deflection temperature at 1.80 MPa (78.3° C.) than nylon 66 (74° C.). This data implies that the composite of nylon and eggshell powder is more deform resistant and has a higher heat resistant capacity than virgin nylon 66. These properties are very important in, for example, automotive applications where resistance to heat is crucial. Therefore, the composite of nylon 66 and eggshell powder may provide improved performance in automotive applications where virgin nylon 66 is traditionally used as it is stiffer and more heat resistant.
Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2012/065639 | 11/16/2012 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
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| WO2013/075003 | 5/23/2013 | WO | A |
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| Number | Date | Country | |
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