Patent Application
20120267368
1. Field of the Invention
The present application generally relates to polymer compositions particularly suited for disposable lids and the like. Particularly, the present application relates to a disposable lid comprising a thermoformed sheet having a polymer composite of polyolefin and at least one mineral filler.
2. Description of Related Art
Hot beverages, such as freshly brewed coffee for people on the go, are usually served in heavy paper cups with disposable lids. Coffee is typically brewed at 90-96° C., held at 82-88° C. and served at 70-80° C. A coffee cup lid preferably has a mechanical strength to withstand the force required to push the lid onto the cup and to maintain the dimensional stability at the temperature of the coffee. The mechanical strength of a material within a range of temperatures can be correlated to the material's heat deflection temperature (“HDT”) or deflection temperature under load (“DTUL”). Current lidding material for hot beverage cups is primarily made of high impact polystyrene (“HIPS”), which has an ease of processing and a good balance between rigidity and toughness due to its amorphous structure. However, high impact polystyrene resin can be susceptible to chemical attack and solvent crazing. In addition, the presence of residual styrene monomer in the resin can cause an unpleasant odor. Furthermore, high impact polystyrene resin, amongst all the commodity resins, has a comparatively high carbon footprint. Therefore, there remains an opportunity for an improved disposable lid.
The purpose and advantages of the present application will be set forth in and apparent from the description that follows, as well as will be learned by practice of the application. Additional advantages of the application will be realized and attained by the apparatus particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the application, as embodied and broadly described, the application includes a disposable lid comprising a thermoformed sheet in the shape of a lid for a hot beverage container. The sheet comprises a polymer composite of a polyolefin and at least one mineral filler. The sheet has a thickness less than about 0.035 inches and a heat deflection temperature at least comparable to that of high impact polystyrene.
In accordance with one aspect, the heat deflection temperature can be at least about that of high impact polystyrene. Particularly, the heat deflection temperature according to ASTM D648-06 Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position (2006) can be at least about 87° C.
As embodied herein, the mineral filler can include a high aspect ratio mineral filler, for example, selected from the group consisting of talc, mica, wollastonite, or combinations thereof. For example, the polymer composite can comprise at least about 10% by weight of the high aspect ratio mineral filler. Additionally or alternatively, the mineral filler can include a low aspect ratio mineral filler, such as calcium carbonate. For example, the polymer composite can comprise at least about 20% by weight of the low aspect ratio mineral filler. The polyolefin can be selected from the group consisting of polypropylene homopolymer, polypropylene impact copolymer, ethylene-propylene random copolymer, high density polyethylene, or combinations thereof.
In one embodiment, the polyolefin includes polypropylene, the mineral filler includes a high aspect ratio mineral filler, and the polymer composite comprises at least about 10% by weight of the mineral filler. In another embodiment, the polyolefin includes polypropylene, the mineral filler includes a low aspect ratio mineral filler, and the polymer composite comprises at least about 20% by weight of the mineral filler. In yet another embodiment, the polyolefin includes high density polyethylene, the mineral filler includes a high aspect ratio mineral filler, and the polymer composite comprises at least about 20% by weight of the mineral filler. In yet another embodiment, the polyolefin includes high density polyethylene, the mineral filler includes a low aspect ratio mineral filler, and the polymer composite comprises at least about 40% by weight of the mineral filler.
In accordance with another aspect, the polyolefin can include polypropylene, the mineral filler can include a high aspect ratio mineral filler, and the polymer composite can have a shrinkage comparable to that of high impact polystyrene. For example, the polymer composite can have a shrinkage of about 0.5% to about 1.0% when measured according to the ASTM D955 standard (1996). In this manner, the polymer composite comprises about 20% to about 40% by weight of the mineral filler.
In accordance with another aspect, the polyolefin can include polyethylene, the mineral filler can include a high aspect ratio mineral filler, and the polymer composite can have a shrinkage comparable to that of polypropylene. As such, the polymer composite can have a shrinkage of about 1.25% to about 1.75% when measured according to the ASTM D955 standard (1996). In this embodiment, the polymer composite comprises about 30% to about 50% by weight of the mineral filler.
In accordance with one aspect of the disclosed subject matter, the polymer composite consists essentially of the polyolefin and the at least one mineral filler. However, the polymer composite can further comprise additives selected from the group consisting of colorants, processing aids, and combinations thereof.
As embodied herein, the hot beverage container can be a coffee cup, although a lid for other suitable containers is contemplated.
In accordance with another aspect, the polymer composite can have a carbon footprint lower than high impact polystyrene. For example, the polymer composite can have a greenhouse gas emission lower than high impact polystyrene.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the application claimed.
The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the apparatus of the application. Together with the written description, the drawings serve to explain the principles of the application.
Reference will now be made in detail to the present preferred embodiments of the application, examples of which are illustrated in the accompanying drawings. The disposable lids presented herein generally are intended for use with cups or other containers for holding high temperature beverages, such as coffee. Although reference will be made herein to lids for hot beverage cups, other similar or suitable uses are contemplated.
Typically, polyolefins have a heat deflection temperature lower than high impact polystyrene (“HIPS”) and thus are not suitable for use alone (i.e., neat) as a lidding material for hot beverage cups. However, in accordance with the disclosed subject matter, the heat deflection temperature of the polyolefin can be improved by adding at least one mineral filler to form a polymer composite. The resulting polymer composite can have a heat deflection temperature at least about that of high impact polystyrene and thus be suitable for use as a lidding material for hot beverage cups or the like.
Disposable lids in accordance with the disclosed subject matter include a thermoformed sheet in the shape of a lid for a hot beverage container. The sheet comprises a polymer composite of a polyolefin and at least one mineral filler. The sheet has a thickness less than about 0.035 inches and a heat deflection temperature at least comparable to that of high impact polystyrene.
In one embodiment, the mineral filler can include any suitable mineral filler for increasing the heat deflection temperature of the polyolefin. For example but without limitation, the mineral filler can include a high aspect ratio filler, a low aspect ratio filler, or a blend of both. The term “aspect ratio” of a particle is defined herein for purpose of understanding as a ratio of a largest dimension of the particle divided by a smallest dimension of the particle. The aspect ratios are determined by scanning under an electron microscope (2,000 times magnified) and visually viewing the outside surfaces of the particles to determine the lengths and thicknesses of the particles.
A high aspect ratio filler is defined herein as a filler having an aspect ratio of at least about 5:1. The high aspect ratio fillers of the present disclosed subject matter generally have an aspect of from about 5:1 to about 40:1, and preferably from about 10:1 to about 20:1. The high aspect filler can include talc, mica, wollastonite, or combinations thereof. Commercially available talc materials include, but are not limited to, JETFIL® 575, available from Luzenac America of Englewood, Colo. Commercially available mica materials include SUZOREX® 325-PP, available from Zemex Industrial Minerals, Inc. Commercially available wollastonite includes, but is not limited to, the NYGLOS® series of wollastonite, available from NYCO Minerals Inc. of Calgary, Alberta, Canada.
A low aspect ratio filler of the disclosed subject matter generally has an aspect ratio of from 1:1 to about 3:1, preferably from 1:1 to about 2:1. The low aspect ratio filler can include calcium carbonate, barium sulfate, or the combination thereof. Commercially available calcium carbonate includes, but is not limited to, OMYACARB FT®, available from OMYA Inc. of Cincinnati, Ohio, or Supercoat®, from Imerys Performance Minerals Inc. of Alpharetta, Ga. One example of commercially available barium sulfate is BARITE 2075®, available from Polar Minerals in Mentor, Ohio.
When the at least one filler comprises a blend of high and low aspect ratio fillers, the filler mixture can include any suitable weight percentage of the high and low aspect ratio fillers. For example, the filler mixture can comprise at least 50 wt. % high aspect ratio filler. In one embodiment, the filler mixture can be from about 50 to about 80 wt. % high aspect ratio filler and from about 20 to about 50 wt. % low aspect ratio filler.
In accordance with one aspect, the polyolefin can be any suitable polyolefin. For example but without limitation, the polyolefin can be selected from the group consisting of polypropylene homopolymer, polypropylene impact copolymer, ethylene-propylene random copolymer, high density polyethylene, or combinations thereof. The polyolefin can be a blend of homopolymer polypropylene and impact copolymer polypropylene, in any desired weight percent, such as a 60/40 blend, or a blend ratio sufficient o achieve a desirable impact property of the composite.
In accordance with one aspect, the polymer composite can consist essentially of the polyolefin and the at least one mineral filler. However, the polymer composite can further comprise any additives known to one of ordinary skill in the art. For example, but without limitation, the additive can include colorants, processing aids such as those commonly used for processing composites, or combination thereof.
In accordance with one aspect, the disposable lid can be formed using a variety of conventional manufacturing and forming processes, including thermoforming or injecting molding processes, although a thermoforming process is employed herein. According to one method of manufacturing, pellets of a polyolefin resin are melted in a twin screw extruder. Powders of the at least one mineral filler are mixed with and/or added into the polyolefin melt to form a blend. The blend is extruded through a die to form an extruded sheet. The extruded sheet is then thermoformed to a desired shape of the disposable lid. Alternatively, a mineral-filled compound of high filler content in pellet form can be produced from a typical compounding process, and the pellets further diluted to a desirable filler content in the sheet extrusion process.
The thickness of the lid can be selected as desired, but is typically less than about 0.15 inches, preferably less than about 0.035 inches. Preferably, the lid can be about 0.01 to about 0.025 inches thick. The lid can be the natural color of the polyolefin/filler mixture, or a variety of colors or color combinations. The height, weight, shape, and design of the lid can be selected as desired to fit a suitable hot beverage container, such as a coffee cup, as is well known in the art. For example, the lid can weigh about 3 to about 4 grams. Exemplary lid designs include, but are not limited to, those described and shown in U.S. Pat. Nos. 7,819,271, 7,789,260, 7,691,302, D556,573, D544,793, D541,651 D541,650, D541,153, D540,675, D540,674, D540,673, D540,672, D540,166, D540,165, D539,646, D533,778, D635,855, 7,731,047, 7,513,382, 7,246,715, D540,167, D539,650, D539,649, D536,249, D535,561, 7,159,732, 7,156,251, 7,134,566, 7,131,551, D530,602, 7,063,224, D514,445, D514,444, 6,874,649, 6,732,875, D489,260, D485,758, 6,679,397, 6,644,490, D478,006, D477,223, D476,891, D476,566, 4,753,365, D287,919, 4,615,459, and 4,589,569, the contents of each of which is incorporated herein by reference in its entirety.
In accordance with one aspect of the disclosed subject matter, the heat deflection temperature (“HDT”) also known as the deflection temperature under load (“DTUL”) can be determined according to ASTM D648-06, Standard Test method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position (2006). For the purpose of illustration and not limitation, Table 1 includes the heat deflection temperature measured according to the ASTM D648-06 standard (2006) for neat high impact polystyrene, neat polypropylene (“PP”), neat high density polyethylene (“HDPE”), and various mineral filled polymer composites in accordance with the disclosed subject matter. The data provided in Table 1 is based on nominally 12.7 mm wide by 3.17 mm thick injection molded bars with a span of 101.6 mm. A load of 2.5N was applied to achieve a fiber stress of 0.455 MPa (66 PSI). The temperature of the heat-transfer medium was ramped at 2.0° C./min. The deflection was reset to zero at 30° C. to allow for any low temperature creep. The temperature at which the sample deflected an additional 0.25 mm was considered the heat deflection temperature. For the purpose of illustration and not limitation,
1High Impact Polystyrene, Total Petrochemicals 940E
2High Density Polyethylene, Density = 0.963 g/cc
3PP Homopolymer PP/Impact Copolymer blend. Blend ratio 60/40
4PP Impact Copolymer
5PP Homopolymer
6DTUL—Deflection Temperature Under Load (66 psi) per ASTM D648.
As can be seen in the data of Table 1 and
Examples 1-20 in accordance with the disclosed subject matter of Table 1 show the heat deflection temperatures of various polyolefin and mineral filler combinations at different levels of mineral filler. Of the different polyolefin and mineral filler combinations, the calcium carbonate filled polyolefins have a gradual increase in heat deflection temperature relative a respective non-filled (i.e. neat) polyolefin as the mineral content is increased. By contrast, the talc filled polyolefins have a much higher increase in heat deflection temperature as the mineral filler content is increased. Unexpectedly, the talc filled polypropylene has a more significant increase in heat deflection temperature, even with the talc content as low as about 10%.
As shown in the data of Table 1 and
As shown by Example 2, when the polyolefin includes high density polyethylene, the mineral filler includes a high aspect ratio mineral filler (e.g. talc), and the polymer composite comprises at least about 20% by weight of the mineral filler, the heat deflection temperature will be greater than that of high impact polystyrene. As shown by Example 10, when the polyolefin includes high density polyethylene, the mineral filler includes a low aspect ratio mineral filler (e.g. calcium carbonate), and the polymer composite comprises at least about 50% by weight of the mineral filler, the heat deflection temperature will be greater than that of high impact polystyrene. As shown by Example 12, when the polyolefin includes polypropylene, the mineral filler includes a high aspect ratio mineral filler (e.g. talc), and the polymer composite comprises at least about 10% by weight of the mineral filler, the heat deflection temperature will be greater than that of high impact polystyrene. As shown by Example 17, when the polyolefin includes polypropylene, the mineral filler includes a low aspect ratio mineral filler (e.g. calcium carbonate), and the polymer composite comprises at least about 20% by weight of the mineral filler, the heat deflection temperature will be greater than that of high impact polystyrene.
For the purpose of illustration and not limitation, Table 1 and
In accordance with another aspect, the polymer composite can have a carbon footprint lower than high impact polystyrene. For example, the polymer composite can have a greenhouse gas emission lower than high impact polystyrene. For the purpose of illustration and not limitation, Table 2 shows cradle-to-grave greenhouse gases emissions of lids in accordance with the disclosed subject matter as compared to lids of high impact polystyrene. The two lids have similar rigidity and perform similarly as a hot beverage cup lid. The comparative example was made from high impact polystyrene sheet of about 0.0214 inches thick and weighed about 3.83 grams. The example in accordance with the disclosed subject matter include 40% talc-filled polypropylene and was made from a 0.0167 inches thick sheet and weighed about 3.32 grams. A base unit of 10,000 pieces was used to calculate the greenhouse gases emissions. Several factors contributed to the much lower greenhouse gases emission of the example in accordance with the disclosed subject matter. These factors include polymer density, GHG emission of base polymers and minerals, and the amount of minerals incorporated in the composite. As can be seen in
While the present application is described herein in terms of certain preferred embodiments, those skilled in the art will recognize that various modifications and improvements can be made to the application without departing from the scope thereof. For example, which the present application describes a disposable lid for a hot beverage container such as a coffee cup, the polymer composites in accordance with the application could be used in applications other than lidding where the improved heat deflection temperature of a mineral filled polymer is desired. Thus, it is intended that the present application include modifications and variations that are within the scope of the appended claims and their equivalents. Moreover, although individual features of one embodiment of the application are discussed herein or shown in the drawings of one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment can be combined with one or more features of another embodiment or features from a plurality of embodiments.
In addition to the specific embodiments claimed below, the application is also directed to other embodiments having any other possible combination of the dependent features claimed below and those disclosed above. As such, the particular features presented in the dependent claims and disclosed above can be combined with each other in other manners within the scope of the application such that the application should be recognized as also specifically directed to other embodiments having any other possible combinations. Thus, the foregoing description of specific embodiments of the application has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the application to those embodiments disclosed.
This application claims the benefit of and priority to U.S. Provisional Application Ser. No. 61/477,886, filed Apr. 21, 2011, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61477886 | Apr 2011 | US |
