CA1245412A - Containers - Google Patents
ContainersInfo
- Publication number
- CA1245412A CA1245412A CA000487610A CA487610A CA1245412A CA 1245412 A CA1245412 A CA 1245412A CA 000487610 A CA000487610 A CA 000487610A CA 487610 A CA487610 A CA 487610A CA 1245412 A CA1245412 A CA 1245412A
- Authority
- CA
- Canada
- Prior art keywords
- container
- sidewall
- heating
- thickness
- polystyrene
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Containers Having Bodies Formed In One Piece (AREA)
Abstract
ABSTRACT
A method of improving the stiffness of a polystyrene foam container having a sidewall and a bottom, said con-tainer having been prepared from a laminate of polysty-rene foam having generally spherical closed cells, and, on at least the outer surface thereof, a layer of solid polystyrene; said method comprising heating said con-tainer in the unrestrained state, said heating being suf-ficient to increase the thickness of the sidewall at least 10%, and cup produced by this method.
A method of improving the stiffness of a polystyrene foam container having a sidewall and a bottom, said con-tainer having been prepared from a laminate of polysty-rene foam having generally spherical closed cells, and, on at least the outer surface thereof, a layer of solid polystyrene; said method comprising heating said con-tainer in the unrestrained state, said heating being suf-ficient to increase the thickness of the sidewall at least 10%, and cup produced by this method.
Description
~2~
CONTAI~ERS
This invention relates to a foam cup which has been treated to improve the strength thereof. The cup is made from a foam resin sheet produced by the blown bubble technique to which a solid resin layer is applied to one or both sides of the foam.
Foam cups are widely used for individual servings of hot beverages, such as coffee and soup, and cold bever-ages such as soft drinks. Many millions are used everyday. Obviously, the cup must have sufficient strength to permit handling by the user, but, at khe same time, use a minimum amount of resin for the product. Polystyrene and other resins can be used to produce the cup although the majority are now made from polystyrene.
Broadly, the process of our invention resides in a method of improving the stiffness of a polystyrene foam container having a sidewall and a bottom, said container having been prepared from a laminate of polystyrene foam having generally spherical closed cells, and, on at least the outer surface thereof, a layer of solid polystyrene, said method comprising heating said container in the unrestrained state, said heating being sufficient to increase the thickness of the sidewall at least 10~.
The sidewall prior to heating has a thickness of 0.02 to 0.05 inch and said heating is carried out under conditions to provide an increase in thickness of from 10 to 30 percent. The heating can be applied by a variety of methods such as contact with hot water, steam, hot air, or infrared radiation. The cups produced by us in the work reported herein were produced on a G1000 VII
machine of Paper Machinery Corporation of Milwaukee, Wisconsin. This company is widely known as a major pro-ducer of machines for the production of paper cups. In the production system, the cups of this invention were prepared from single-side-coated roll stock produced according to the method of disclosure by Mazur 3,669,794 ~2~
--2~
(1972). Double-coated stock can also be used, this method being disclosed in Whelan, et al., 3,616,020 (1971).
In the Paper Machinery Corporation machine, a source of hot air is provided to seal the side seam resulting, after the sidewall is rolled into shape, and to seal the bottom of the cup with the si~dewall. In the machine, a source of air, heated by a flameless torch, blows the finished cup into a stacking device. It will be recog-nized that time and temperature of treatment are interre-lated, runs were made using a treatment time of 3 to 5 seconds with heated air in the range of 250 to 400F.
Heating foam cups has been disclosed as a method of improving the strength of containers. One example of this is Shapiro, et al., 3,344,222 (1967). In this patent~ foam cups produced by extrusion of foamable sheets of polystyrene are made, no solid layer being pre-sent, and the foam cups treated while holding the cup between restraining surfaces. This is said to provide a density gradient with denser foam near the surface of the cup, thus increasing the strength of the cup. According to the patentee, the thickness of the wall or walls of the container does not apparently change. The patentee also states that a wall gradient of two or three times the original thickness will severely impair the formation of the dense surface walls and the heat-insulating inte-rior æones.
It will be seen that the present process which heats the cup or container in the unrestrained state is directly contrary to the teaching of Shapirol et al.
Another patent which requires an increase in thick-ness when a foam cup is heated i8 Myers, et al., 4,359,160 ~1982), this patent being directed to a thermo-formed cup or container. The sheet for the thermoforming operation is produced by extrusion of molten polystyrene containing a blowing agent and a nucleating agent from a slit-ring orifice. This product, like the product of the invention, contains closed, generally spherical closed cells as extruded. In the process of Myers, et al., this sheet is thermoformed by a plug-system method which stretches the cells and produces a product containing "pancake"-shaped cells. Upon heating this thermoformed cup, as when hot liquid is added thereto, the cells tend to return to spherical shape.
Thus, the cup of Myers, et al., while probably being stronger after filling with hot liquid, is still defi-cient because it does not have the improved strengthprior to use by the user.
From the above description, it is obvious that the object of this invention is to provide a coated Eoam cup of improved strength.
lS A further object of this invention is to provide a method for producing this container. Other objects of this invention will become apparent to those skilled in the art upon reading this disclosure.
The following examples set forth currently preferred embodiment of the invention, but these examples should not be considered unduly limited.
Amoco R2 polystyrene resin was extruded by the blown bubble technique using butane in an amount of 4 wt% as a blowing agent and a talc nucleating agent in an amount of 0.5 to 0.75 wt~, all weights being based upon the amount of polystyrene. The production system is well-known.
After slitting and opening of the sheet to a flat struc ture, the sheet was fed between nip rollers into which nip was extruded a polystyrene solid resin. The solid resin was a 50-50 mixture of Amoco R2 and Amoco H2R poly-styrene, the mixture containing, as a pigment, 2 to 4 wt%
of TiO2. A good bond was obtained with this system. The foam thickness was slightly less than 0.03 inch and the solid resin thickness was approximately 0.002 inch.
The procedure for the showing of sidewall deflective strength improvement consisted of first measuring the untreated cup sidewall thickness and the sidewall deflective strength and then CaLrying out the heating procedure. For this exampler the heating consisted of pouring boiling water into the 9-oz. CUp5 brim full and covering each cup with another cup so that the covering cup was heated by the steam given off by the hot water.
These pairs of cups were left in -this position for 15 minutes to allow the foam to expand freely. After this time, the sidewall thickness and deflective strength were again measured.
The sidewall deElective strength test is made on the full cup. Each is placed on a platform on its side using a flat strip pressing against the upper portion of the rim. A gram scale is provided to apply a gradually increasing weight to the rim, and the deflection mea-sured. The data show the load required for a half-inch deflection of the cup.
The data are shown in the following table, Runs 1-3 being the bottom cups and Runs 4-6 being the upper cups which were exposed to the steam.
SIDEWALL DEFLECTIVE STRENGTH
SIDEWALL THICKNESS (~rams per 1/2") Run Untreated Heated ~ ~ntreated Heated ~
1 .028 .032 13 23~ 280 18
CONTAI~ERS
This invention relates to a foam cup which has been treated to improve the strength thereof. The cup is made from a foam resin sheet produced by the blown bubble technique to which a solid resin layer is applied to one or both sides of the foam.
Foam cups are widely used for individual servings of hot beverages, such as coffee and soup, and cold bever-ages such as soft drinks. Many millions are used everyday. Obviously, the cup must have sufficient strength to permit handling by the user, but, at khe same time, use a minimum amount of resin for the product. Polystyrene and other resins can be used to produce the cup although the majority are now made from polystyrene.
Broadly, the process of our invention resides in a method of improving the stiffness of a polystyrene foam container having a sidewall and a bottom, said container having been prepared from a laminate of polystyrene foam having generally spherical closed cells, and, on at least the outer surface thereof, a layer of solid polystyrene, said method comprising heating said container in the unrestrained state, said heating being sufficient to increase the thickness of the sidewall at least 10~.
The sidewall prior to heating has a thickness of 0.02 to 0.05 inch and said heating is carried out under conditions to provide an increase in thickness of from 10 to 30 percent. The heating can be applied by a variety of methods such as contact with hot water, steam, hot air, or infrared radiation. The cups produced by us in the work reported herein were produced on a G1000 VII
machine of Paper Machinery Corporation of Milwaukee, Wisconsin. This company is widely known as a major pro-ducer of machines for the production of paper cups. In the production system, the cups of this invention were prepared from single-side-coated roll stock produced according to the method of disclosure by Mazur 3,669,794 ~2~
--2~
(1972). Double-coated stock can also be used, this method being disclosed in Whelan, et al., 3,616,020 (1971).
In the Paper Machinery Corporation machine, a source of hot air is provided to seal the side seam resulting, after the sidewall is rolled into shape, and to seal the bottom of the cup with the si~dewall. In the machine, a source of air, heated by a flameless torch, blows the finished cup into a stacking device. It will be recog-nized that time and temperature of treatment are interre-lated, runs were made using a treatment time of 3 to 5 seconds with heated air in the range of 250 to 400F.
Heating foam cups has been disclosed as a method of improving the strength of containers. One example of this is Shapiro, et al., 3,344,222 (1967). In this patent~ foam cups produced by extrusion of foamable sheets of polystyrene are made, no solid layer being pre-sent, and the foam cups treated while holding the cup between restraining surfaces. This is said to provide a density gradient with denser foam near the surface of the cup, thus increasing the strength of the cup. According to the patentee, the thickness of the wall or walls of the container does not apparently change. The patentee also states that a wall gradient of two or three times the original thickness will severely impair the formation of the dense surface walls and the heat-insulating inte-rior æones.
It will be seen that the present process which heats the cup or container in the unrestrained state is directly contrary to the teaching of Shapirol et al.
Another patent which requires an increase in thick-ness when a foam cup is heated i8 Myers, et al., 4,359,160 ~1982), this patent being directed to a thermo-formed cup or container. The sheet for the thermoforming operation is produced by extrusion of molten polystyrene containing a blowing agent and a nucleating agent from a slit-ring orifice. This product, like the product of the invention, contains closed, generally spherical closed cells as extruded. In the process of Myers, et al., this sheet is thermoformed by a plug-system method which stretches the cells and produces a product containing "pancake"-shaped cells. Upon heating this thermoformed cup, as when hot liquid is added thereto, the cells tend to return to spherical shape.
Thus, the cup of Myers, et al., while probably being stronger after filling with hot liquid, is still defi-cient because it does not have the improved strengthprior to use by the user.
From the above description, it is obvious that the object of this invention is to provide a coated Eoam cup of improved strength.
lS A further object of this invention is to provide a method for producing this container. Other objects of this invention will become apparent to those skilled in the art upon reading this disclosure.
The following examples set forth currently preferred embodiment of the invention, but these examples should not be considered unduly limited.
Amoco R2 polystyrene resin was extruded by the blown bubble technique using butane in an amount of 4 wt% as a blowing agent and a talc nucleating agent in an amount of 0.5 to 0.75 wt~, all weights being based upon the amount of polystyrene. The production system is well-known.
After slitting and opening of the sheet to a flat struc ture, the sheet was fed between nip rollers into which nip was extruded a polystyrene solid resin. The solid resin was a 50-50 mixture of Amoco R2 and Amoco H2R poly-styrene, the mixture containing, as a pigment, 2 to 4 wt%
of TiO2. A good bond was obtained with this system. The foam thickness was slightly less than 0.03 inch and the solid resin thickness was approximately 0.002 inch.
The procedure for the showing of sidewall deflective strength improvement consisted of first measuring the untreated cup sidewall thickness and the sidewall deflective strength and then CaLrying out the heating procedure. For this exampler the heating consisted of pouring boiling water into the 9-oz. CUp5 brim full and covering each cup with another cup so that the covering cup was heated by the steam given off by the hot water.
These pairs of cups were left in -this position for 15 minutes to allow the foam to expand freely. After this time, the sidewall thickness and deflective strength were again measured.
The sidewall deElective strength test is made on the full cup. Each is placed on a platform on its side using a flat strip pressing against the upper portion of the rim. A gram scale is provided to apply a gradually increasing weight to the rim, and the deflection mea-sured. The data show the load required for a half-inch deflection of the cup.
The data are shown in the following table, Runs 1-3 being the bottom cups and Runs 4-6 being the upper cups which were exposed to the steam.
SIDEWALL DEFLECTIVE STRENGTH
SIDEWALL THICKNESS (~rams per 1/2") Run Untreated Heated ~ ~ntreated Heated ~
1 .028 .032 13 23~ 280 18
2 .027 .~36 25 265 310 15
3 .027 .034 21 260 310 16 ~ .028 .037 24 270 315 14 .027 .035 23 260 300 13 6 .027 .035 23 245 235 17 Ave. .027 .035 23 255 302 16 Cups made according to the procedure set forth in EXAMPLE 1 were treated wlth air heated with a flameless torch. With exposure times in the range of 3 to 5 sec-onds and air temperatures in the range of 250 to 400F, ~2~
increases in wall thickness and increased sidewall deflective strengths were obtained.
From the foregoing description, those skilled in the art will appreciate that the modification can be made without departing from the broad scope of the invention.
It is not intended to limit the broad scope of the inven-tion to those embodiments illustrated and described, but reasonable modifications can be made.
increases in wall thickness and increased sidewall deflective strengths were obtained.
From the foregoing description, those skilled in the art will appreciate that the modification can be made without departing from the broad scope of the invention.
It is not intended to limit the broad scope of the inven-tion to those embodiments illustrated and described, but reasonable modifications can be made.
Claims (8)
1. A method for providing a finished polystyrene foam container having a sidewall and a bottom, said con-tainer having improved stiffness and being suitable for use with hot beverages, said method comprising:
(1) forming a container from a laminate of polystyrene foam and, on at least the outer surface thereof, a layer of solid polystyrene by rolling said laminate into shape to form the sidewall and subsequently sealing the bottom of the container to the sidewall, and (2) heating said container in an unrestrained state at a temperature sufficient to increase the thickness of the sidewall at least 10 percent and form the finished container which is then stacked prior to use.
(1) forming a container from a laminate of polystyrene foam and, on at least the outer surface thereof, a layer of solid polystyrene by rolling said laminate into shape to form the sidewall and subsequently sealing the bottom of the container to the sidewall, and (2) heating said container in an unrestrained state at a temperature sufficient to increase the thickness of the sidewall at least 10 percent and form the finished container which is then stacked prior to use.
2. A method for providing a polystyrene foam con-tainer having a sidewall and a bottom, said container having improved stiffness and being suitable for use with hot beverages, said method comprising:
(1) forming a container from a laminate of polystyrene foam and, on at least the outer surface thereof, a layer of solid polystyrene by rolling said laminate into shape to form the sidewall and subsequently sealing the bottom of the container to the sidewall, and (2) heating said container in an unrestrained state by contacting said container with hot air or infrared radiation at a temperature in excess of 250°F, said heating being sufficient to increase the thickness of the sidewall at least 10 percent.
(1) forming a container from a laminate of polystyrene foam and, on at least the outer surface thereof, a layer of solid polystyrene by rolling said laminate into shape to form the sidewall and subsequently sealing the bottom of the container to the sidewall, and (2) heating said container in an unrestrained state by contacting said container with hot air or infrared radiation at a temperature in excess of 250°F, said heating being sufficient to increase the thickness of the sidewall at least 10 percent.
3. The method of Claim 1 wherein the sidewall, prior to heating, has a thickness of 0.02 to 0.05 inch, and said heating results in an increase in thickness of 10 to 30 percent.
4. The method of Claim 1 wherein said heating is effected by contact of said container with hot water, steam, hot air, or infrared radiation.
5. A container produced by the process of Claim 1.
6. The method of Claim 1 wherein said heating is effected by contact of said container with hot air or infrared radiation and at temperature in excess of 250°F.
7. The method of Claim 2 wherein said temperature is in the range of 250°F to 400°F.
8. The method of Claim 2 wherein the container is stacked after heating.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000487610A CA1245412A (en) | 1985-07-26 | 1985-07-26 | Containers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000487610A CA1245412A (en) | 1985-07-26 | 1985-07-26 | Containers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1245412A true CA1245412A (en) | 1988-11-29 |
Family
ID=4131069
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000487610A Expired CA1245412A (en) | 1985-07-26 | 1985-07-26 | Containers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1245412A (en) |
-
1985
- 1985-07-26 CA CA000487610A patent/CA1245412A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |