Patent Application
20080217346
The invention relates to tear-back thermoformed polystyrene lids having the specified amount of filler and tear-back portion configuration. The combination of the filler amount and tear-back configuration allows an improved tearability for the filled polystyrene lids so that the lids need not be pre-scored for use.
Polystyrene tear back lids are commonly used in foodservice applications, in particular as covers for hot cups. For example, U.S. Pat. Nos. 4,460,103, 5,490,609 and 5,699,927 (the disclosures of which are incorporated herein in their entireties by this reference) disclose various types of tear back lids. It is also known that the tearability of a polystyrene tear back lid can be improved by designing the lid such that the tear back portion is oriented in the direction of extrusion. U.S. Pat. No. 5,613,619 (the disclosure of which is incorporated herein in its entirety by this reference) discloses such a feature.
Recently, manufacturers of polystyrene lids for hot cups have begun to investigate inclusion of filler into the lids to reduce the costs of manufacturing such lids. Historically, polystyrene lids for hot applications have not included a significant amount of filler. This is due primarily to two reasons. First, polystyrene has traditionally been a low cost raw material and, as such, there was little motivation to include filler into a formulation. Further, polystyrene used in hot cup lid applications is generally high impact polystyrene (“HIPS”). HIPS is FDA compliant and exhibits good thermoformability due to its low brittleness. Since filler is known to increase the brittleness of polystyrene, it was not desired to negate the low brittleness of HIPS with the addition of filler, since this was a property for which HIPS was selected for use in thermoformed hot cup lid applications.
The inventors herein have surprisingly found that filler can be added within a specified range to provide a suitably tearable filled thermoformed HIPS container lid when the tearback portion of the lid is oriented in the extrusion direction of the polystyrene when the tear back lid comprises two sets of tear indentations and a tab portion.
In a significant aspect, a filled container lid is provided. The lid is prepared from a HIPS composition consisting essentially of from at least 10% to about 15% filler. The lid comprises a tear back portion defined by a left and a right notch cut into a skirt defined by an outer diameter of the lid and two sets of tear indentations, wherein the tear indentations comprise from 1 to 4 grooves thermoformed into the lid. The two sets of tear indentations are oriented in a machine direction of the extruded sheet. The left and right notches are substantially in alignment with at least one of each of the 1 to 4 grooves. The filler can specifically comprise calcium carbonate. In significant form, the filled HIPS lid exhibits excellent tearability without the need to pre-score the lid.
Still further aspects and advantages of the present invention will become readily apparent from the discussion which follows.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying drawing figures wherein:
The invention is described in detail below with reference to the Figures. Such description is for purposes of illustration only and is not limitative of the invention in any way. Numerous modifications within the spirit and scope of the present invention, set forth in the appended claims, will be readily apparent to those of skill in the at.
Unless otherwise indicated, “mil”, “mils” and like terminology refers to thousandths of an inch and dimensions appear in inches. Likewise, caliper is the thickness of material and is expressed in mils.
In this detailed description of the present invention, any patent or non-patent literature referenced herein and the disclosure contained therein is intended to be and is hereby incorporated by reference. All numerical ranges and amounts are understood to be modified by the term “about,” which shall have the intended meaning that all such ranges or amounts are approximately or substantially the value indicated. An indication that a numerical range or amount is greater than or less than is also understood to include values that are approximately or substantially equal to the given numerical range or amount.
The present invention is directed toward a filled polystyrene container lid that is not pre-scored. The polystyrene consists of high impact polystyrene or “HIPS” as such term is known to one of ordinary skill in the art. Importantly, the amount of filler in the HIPS composition is from at least 10% to about 15% by weight of the HIPS composition from which the lid is prepared. Further importantly, it was found that the area of the lid defining the tear back portion of the lid must be oriented in the direction that the HIPS composition is extruded into sheet form. That is, to comprise the invention herein, the tear back portion must be aligned in the machine direction of the extruded HIPS sheet from which the lid is prepared.
The inventors herein have surprisingly found that lids thermoformed from at least 10% to about 15% filled extruded HIPS sheets and comprising the tear back portion design herein exhibit improved tearability as compared to lids having from 0 to less than 10% filler. In particular, it was found that lids having at least 10 to about 15% filler were significantly easier to tear back than lids having less than at least 10% filler. Such improved ease of tearability is a desirable feature for hot cup lids in that, if less force is needed to tear the lid, the user will be less likely to exert too much force on the lid while opening the tear back portion. This, in turn, reduces the possibility that the hot beverage will spill from the container.
Also, it was found by the inventors herein that lids having less than at least 10% filler became disengaged from the container rim more readily when the user was opening the lid. In use, such disengagement is highly undesirable because of the possibility that hot beverage will spill on a consumer. Thus, the lids of the present invention provide an improved lid over those found in the prior art.
As noted, the filler amount in the lids of the present invention must be from at least 10 to about 15% of the amount of HIPS in an extruded sheet. The amount of filler can be at least 10, or 11, 12, 13, 14 or 15% by weight of the composition, as measured by total weight of the composition. It has been found that filler amounts of greater than about 15% up to about 25% filler also can provide good tearability. However, at these higher amounts, the lid shows more propensity to disengage from the container rim. Thus, the present invention addresses a HIPS lid prepared from an extruded sheet of a HIPS composition having from at least 10% to about 15% filler by weight of the composition, and no more or no less.
Without being bound by theory, it is believed that at lower amounts of filler, the HIPS resin is held tightly together. When filler is added within a certain amount, the HIPS resin polymer chains are released somewhat, thus making it easier to separate the polymer chains in the tearing action. At higher amounts of filler, it is believed that the lid becomes more brittle and less flexible. As such, the lid does not flex as well during tearing and will therefore be more likely to disengage from a container rim during use. So, although the amount of HIPS resin can be reduced at filler levels of greater than 15%, it is currently not desired to use such higher levels because of the higher possibility for lid failure during use.
HIPS is used as the base polymer in the present invention. HIPS is generally a styrene polymer that includes an elastomeric polymer wherein the elastomeric polymer is disbursed in a matrix of the styrene polymer. Elastomeric polymers are well known to improve the impact strength of the base polystyrene resin. The elastomeric polymer can be incorporated into the styrene polymer by graft copolymerization or by mechanical mixing of elastomer and styrene polymer to form a high impact polystyrene using methods well known in the art such as, for example, that disclosed in U.S. Pat. No. 4,049,595 (the disclosure of which is incorporated herein in its entirety by this reference).
HIPS can also comprise polystyrene and polybutadiene or polyisoprene mixture that exhibits improved impact resistance over standard polystyrene. Total 960E (Total Petrochemicals) and Chevron-Phillips EB6755 (Chevron-Phillips) are commercial HIPS resins that can be suitably used for the lids of the present invention.
Some examples of materials suitable for use in the present invention include any filler that would be suitable for food contact applications. Although mineral fillers such as calcium carbonate are preferred, pigments and other food safe materials can suitably be used herein. Mixtures of food safe fillers can also be used.
To provide the HIPS resin composition, a masterbatch can be prepared wherein the filler is mixed in a high level with a small amount of resin. The masterbatch can have greater than about 50% filler therein. The masterbatch will be “diluted” in a base resin to provide the desired filler end concentration.
In order to increase incorporation of filler in such high amounts in the masterbatch, mixing and processing aids can be used. For example, the filler can first be coated with a surfactant or similar processing aid to improve its dispersability into the base HIPS resin.
In addition to the use of a surfactant, a compatibilizer may also be used to improve mixing or compatibility of the filler with the HIPS.
Additives can be included in the filled HIPS compositions of the present invention. Suitable additives can include for example, antioxidants, dye, fire resistant materials, mold release agents, colorants, and other materials designed to improve the processibility of the polymer or the properties of the thermoplastic product. Such additives can be added directly into the master batch. Where additives are present, the total amount of filler is in relation to the total weight of the composition. For example, where there is 83% HIPS, 15% filler and 2% colorant as additive, a lid formed from this composition will fall within the scope of the invention herein.
When an additive is a colorant, various coloring agents can be utilized in order to make the food service product any desired color. The colorant can be in the form of a color concentrate or masterbatch as would be recognized by one of ordinary skill in the art, A suitable colorant can be is titanium dioxide, which is used to make a white end product. Other coloring agents include, for example, carbon black, which is used to make a product that is black in color.
Lids made according to the present invention are thermoformed. Thermoforming processes for shaping or molding thermoplastics into various useful products by forming a heated continuous sheet of thermoplastic material in a mold whereby the continuous sheet takes the shape of the mold are well known in the art. Commercially available machinery for such processes is designed so that the continuous sheet of filled HIPS, as in the present invention, is fed through an oven and heated to bring the continuous sheet of filled HIPS to a suitable thermoforming temperature. Alternatively, the continuous sheet can come directly from the extruder and can be brought to the proper thermoforming temperature by means of a series of rollers, which can either be heated or cooled, as appropriate. In either case, a thermoforming station comprises molds having the desired lid shape. The continuous sheet can either be draped over the mold or vacuum formed into the cavity to take the desired shape.
The lids of the present invention are formed from the continuous sheet that can then be cut or separated into individual thermoformed lids at a cutting station. Significantly, the tear back portion of the lid is not scored during the cutting process, nor is it scored at any other time in the lid preparation process. The fact that the lid is not pre-scored is a marked difference from prior art tear back lids, which typically include a scoring step in the cutting process so as to provide a tear back portion that can be suitably torn in use. Trim from the cutting process can be used as regrind material to be used in the feedstock of the lid forming process.
Referring now to
Lid 10 comprises sets 20 and 25 of tear back indentations, wherein each set 20 and 25 comprise grooves 22a, 22b and 22c and 27a, 27b and 27c that are oriented on either side of a latch 30. Sets 20 and 25 can each, independently, comprise 1, 2, 3 or 4 grooves, although 3 are shown in each of sets 20 and 25 in
Skirt 14 comprises a tab 50 in connecting relation therewith. Tab 50 comprises having notches 60a and 60b on either side thereof. The left and right sides of tab 50, which are sides 52a and 52b are in substantial alignment with notches 60a and 60b respectively. Notch 60a is in substantial aliment with at least one of grooves 22a, 22b or 22c and notch 60b is in substantial alignment with at least one of tear back grooves 27a, 27b or 27c. As used herein, “substantial alignment” means that when tab 50 is pulled to open tear back portion 50, there will be a single tear line on either side of tear back portion 50. These lines can be somewhat crooked after opening of tear back portion 50 by a user, however, when the tab sides 52a and 52b are in substantial alignment with notches 60a and 60b, and notch 60a is in substantial alignment with one of the grooves 22a, 22b or 22c and notch 60b is in substantial alignment with one of the grooves 27a, 27b or 27c, the tear back portion will be comfortable for a user drinking out of tear back portion 50.
Latch 30 can have a raised protrusion 35 formed in the lid surface; raised protrusion 35 can have latching members 37a and 37b associated therewith. Latch 35 is formed into the lid 10 surface by thermoforming of an extruded HIPS sheet (not shown) using a suitable mold (not shown). Latch 35 is hinged at hinge 38. Tear back portion 40 may be latched in the open position by inserting latch 35 into recess 70 having engagement members 75a and 75b so that latching members 37a and 37b of the latch 35 engage with engagement members 75a and 75b formed in opposing side walls of the recess 70.
As noted previously, it has been surprisingly found that if grooves 22a, 22b, 22c, 27a, 27b and 27c are oriented in the machine direction of the extruded HIPS sheet, the tearability of the tear back portion 40 is greatly improved.
In use, the filled HIPS lid 10 of the present invention is somewhat flexible in the range of fillers corresponding to the present invention so that, when the latch 35 is inserted into the recess 70, the latching members 37a and 37b are pushed past the corresponding engagement members 75a and 75b. Tear-back portion 40 is then latched in the open position because each first latching member 37a and 37b engages its respective second latching members 75a and 75b. To “unlatch” the tear-back portion 40, the user exerts an upward force on the tear-back portion 40 (for example, by pulling upward on the tab) to enable the latching members 37a and 37b to disengage the engagement members 75a and 75b. Tear back portion 40 can then be seated on the rim of the container (not shown) to approximate a seal such that a beverage will be less likely to spill from the container in use.
More particularly, latch 35 flexes, thereby allowing the latching members 37a and 37b to be more easily pushed past the engagement members 75a and 75b to latch the tear-back portion 40 in the open position. Also, after tear-back portion 40 is latched, latching members 37a and 37b resist disengagement from engagement members 75a and 75b. Upon unlatching of tear-back portion 40, latch 35 and, in particular, its upper portion, returns substantially to its original configuration.
Vent hole 90 can be present to allow venting of a hot liquid (not shown) from the container (not shown).
The following Examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the present invention is practiced, and associated processes and methods are constructed, used, and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is as specified or is at ambient temperature, and pressure is at or near atmospheric.
Lids were made from filled HIPS resin to provide lids having the configuration shown herein. The resin used was from Chevron-Phillips and comprised a mixture of EB6085 and EA3300.
The amount of filler was tested as set out below. No colorant was included in the noted samples, thereby providing a translucent lid. The depth of the grooves forming each set of tear back portions was also examined as a variable. The lids were formed as set forth in the diagram of
Dimensions:
Lid Fit Testing:
Tear Tab Testing:
Lid Dimensions:
Lids including colorant were tested at 0% CaCO3 and 15% CaCO3. The formula was as follows:
A masterbatch of colorant and CaCO3 was prepared with the EA3300, followed by dilution of the masterbatch in the EB6025.
Observations:
Lids not having CaCO3 weighed about 5% less than the lids with CaCO3.
The average BOD (bead outside diameter) of the two trial variables was within 0.001″ of each other.
The RID (restriction inside diameter) of the sample set without CaCO3 averaged 0.004″ smaller than the variable with CaCO3.
Lid Fit Testing:
Tear Tab Testing:
While the invention has been described in connection with one aspect, modifications within the scope of the appended claims will be readily apparent to those of skill in the art.
