CA1314376C

CA1314376C - Container with a label and a method for manufacturing the same

Info

Publication number: CA1314376C
Application number: CA000580700A
Authority: CA
Inventors: Masatsugu Yoshida; Seishiro Maruyama; Hiroshi Ezawa; Takayuki Watanabe; Hiroaki Tsushima
Original assignee: Mitsui Toatsu Chemicals Inc
Current assignee: Mitsui Toatsu Chemicals Inc
Priority date: 1987-10-22
Filing date: 1988-10-20
Publication date: 1993-03-16
Anticipated expiration: 2010-03-16
Also published as: EP0313406A1; AU2406288A; NZ226616A; AU611723B2; KR890006371A; US4983238A

Abstract

ABSTRACT OF THE DISCLOSURE

A sheet made from a foamed polystyrene resin which is heat-shrinkable in one axial direction and has a heat-insulatingness is prepared. A printing process is applied to this sheet to produce a label.
A container made from a thermo-plastic resin is covered with said cylindrical label and is put in a furnace in order to heat-shrink the label to be fitted on the container.
The container with the label manufactured in accordance with the present invention has a superior heat-insulatingness, and thus can maintain the temperature of water contained therein for a longer time. Also, when it is used in a electronic-range, a temperature of an outer wall surface of the container can be prevented from increasing, and thus the container can be held by a bare hand even immediately after cooking.

Description

~ 3 1 -~376 A CONTAINER WITH A LABEL AND A METHOD FOR MANUFACTURING THE SAME
-FIELD OF T~E INVENTION
-The present invention relates to a container provided with a label made from a ~bam shrinkable i~rm heet. More specifically, the present invention relates to a container made from a thermoplastic resin provided with a label made from a heat shrinkable foam polystyrene sheet.

BACKGROUND OF INVENTION
When a container made from a thermoplastic resin is subjected to a process color pr:Lnting on its outer surface, it is generally required to provide a part of the barrel portion of the container with a flat portion to which the printing is applied. Thus, it has only been possible to print, merely a simple streching pattern on the outer surface of the container.
Often a heat-shrinkable film or sheet is used as a packing material for the container. However, when the film or sheet is subjected to printing and i9 heat-shrun~ onto the container, irregular strains are created on the film or sheet. Thus, merely a simple stretching pattern which permits a slight shift of the position of the stretching pattern can be printed on ths film or sheet.
Further, in recent years, many microwavable food containers have been developed, but none of the containers have a printed indication on the outer surface thereof. Also, during cooking of food stuffs in an micro-wave oven the container is heated to a high temperature due to heated food , .

~ 3, ~37 6 stuffs, and thus cannot be held with a bare hand, and therefore is incon-venient to be taken out from the microwave oven.
A heat-insulating container which is able to have a high-grade printing on the outer surface thereof has been desired which can list the contents o~ the food stuffs contained in the container and thus create added values to the container.
In the past, a heat-insulating container was made by adhering a heat-insulating sheet made from a foam sheet was adhered to the outer surface of the container.
The foam sheet has applied to the container, by the following method. The foam sheet is continuously extruded from an extruder while it is stretched, ln a direction perpendicular to the direction o the extru-sion to produce a sheet. The sheet is subjected to a printing process and then is cut along the direction of the extrusion to produce a long belt.
Then, the longitudinal side edges of the belt parallel to the extrusion ; direction are continuously adhered to each other to produce a cylinder.
The cylinder is cut to a desired length to produce a plural~ty of smaller cylinders. The container is covered with the cylinder and heated, and thus the cylinder is heat-shrunk and wrapped on the container. This method, however, has the following disadvantages.
' As a result of an investigation by the inventors, it was found that a large percent of such containers have defects where the edges of the sheet were adh~red to form a cylinder. One of the reasons causing the great percent defects may be the ~act that since the belt is made round so that the longitudinal direction of the belt may conform with the central axis of thecylinder and the both side edges of the belt are adhered to produce the cylinder, the cylindrical belt will be subjected to a great ` 1 31 ~376 restoring force tending to deform the belt from the cylindrical shape to the flat shape. However, the above reason is not enough to explain the large percent of defective containers. This is also apparent from the fact that, as will be described later in Comparison Example 1, even when the belt was cut out that the longitudinal direction of the belt is perpen-dicular to the extrusion direction to produce a rectangular belt and the both side edges of the belt parallel to the extrusion direction were adhered with each other to produce the cylinder, the defective adhesion was easily caused.
A process for cutting the cylinder and putting it on the container and heat-shrinking the cylinder îs preferably performed on an on-line system connected with a process for making the cylinder. Most preferably, the process for cutCing the cylinder and putting it on the container and heat-shrinking the cylinder is performed concurrently with the cutting of the foam sheet to the belt and the adhesion of the both side edges thereof.
In this case, however, the defective adhesion results in a defective heat insulating container. In order to avoid this disadvantage, the following method without using the on-line system may come to mind. A long cylinder in which the defective portions have been eliminated is first wound on a reel; then re-wound from the reel, cut, and then placed on the container and heat-shrunk onto the container. In this method, however, a fold or crease is formed on the cylinder during the winding operation, and this fold can not be removed even after the heat-shrinkage of the cylinder on the container. Thus the appearance of the container will be extremely impaired, and thus the value of the container as an article of commerce will be decreaæed.

-` 1 3 1 ~376 SUMMARY OF THE INV~NTION
It is an object of the present invention to overcome the above-described disadvantages of the prior art and to provide an inexpensive and very valuable container having a heat-shrinkable label that can be provided with various printing patterns and to provide a novel method for manufacturing the same.
The present invention provides a method for manufacturing a thermoplastic container with a label comprising:
extruding a resin sheet and stretching the resin sheet in the direction of extrusion;
cutting the sheet to a desired size to make a label;
forming the label into a cylinder having a circumference less than the maximum circumference of the container such that the circumference of the cylinder corresponds to the direction of stretching;
placin~ the formed cylindrical label onto the container : hy applying a sufficient force to stretch the portion of the label to be placed in contact with the area of the maximum circumference of the container, wherein the circumference of at least a portion of the label remains less than the maximum circumference of the container; and heating the cylindrical label to a temperature sufficient to heat shrink the label into adherence with the container.

-` 1 31 ~37~

As used herein, the "label" made of resin can be a sheet made only from a foam polystyrene sheet, or a sheet made by laminating the foam polystyrene sheet and a film of the polystyrene or an olefin resin (for example, high density polyethylene, low density polyethylene, polypropylene, a co-polymer of ethylene-vinyl acetate etc.). Also, the label has or has not a printed pattern thereon, and the cylinder means the label having a shape like a sleeve.
A method for manufacturing the container in accordance with the present invention is as follows.
The foam polystyrene sheet is extruded and stretchecl in the direction of extrusion to produce a sheet. Then, the sheet is cut ln a direction substantially parallel to the extrusion ~: direction and in a direction perpendicular to the extrusion direction. The label is formed into a cylinder such that the direction of stretching corresponds to the circumference of the cylinder. The overlapping portions of both side edges of the label are adhered. Hereafter "to adhere" means to join by heat-sealr ultrasonic-seal, high frequency-seal and seal by adhesive or solvent.
It has been found that the circumference of the cylinder, (i.e. the stretching direction of the sheat), is perpendicular to the extrusion direction, i.e. where the two side edges parallel to the extrusion direction are adherecl to each other, the adhesion of the edges is defective.

~' Further, in order to prevent shift of the position of the label during heat shrinkage it is recommended that, in forming the sheet into a cylindrical shape, the circumferential length of the cylinder is smaller ~han the maximum circumference of the container, and ~he label is stretched in an amount of from about 0.1% to about 5.0~ of its circumference during being placed onto the container, the outer wall surface of the container is - 5a -' ' .
.

l 3 1 !~ 3 7 6 adapted to be contacted with the inner surface of the cylinder in an area of at least about 1% of the height of the container. The container is then covered with the label, and the label ls heat-shrunk to contact the container.
Further, in order to prevent shift of the label during heat shrink-. age and fall off the label from the container after heat shrinkage, it is .. ~; .
also recommended to use a container that ~ has a flange at an open end thereof, and an outer circumference at a portion adjacent the flange which is from about 0.1% to about 30% less than the max-imum outer circumference of the container. Further, it is preferable that the axial distance between the maximum outer circumference portion and the flange portion is at least 1% of the height of the container.
Further, to prevent the cylindrical label from shifting relative to the container during the heat shrinking step, it is preferrea that the container have at least one groove or projection about the circumference thereof. Further, at least two grooves or projections may be intermit-tently formed about the circumference of the container or at least one or two or more grooves~or projectlons may extend continuously about the circumference of the container. When the grooves or pro~ections are intermittently formed, the number thereof is preferably at least two in order to prevent the cylindrical label from shifting relative to the container during the heat-shrinking step.
The foam polystyrene sheet for use in accordance with the invention may be made by the following steps:
plastisizing polystyrene; , adding to the resin a foaming agent such as a chemical ~3rm~ agènt ; generated by heat-deposition of carbon dioxide or nitrogen gas etc. in 1 31 ~-776 nlllo~lrlt oF from nbout 0.05X to ~bout 3.0X by ~elght, or nddin~ an org~nlc solvcnt havin~ a low boillng polnt, for exnmple, n hydrocnrbon compound such as butane, pentane etc. or a hydrogen fluorlde compound such ns freon Il, 12, 114 etc. ln nn nmounC of from nbollt 0.001 to nbout o.n~ mol/resln IOO ~; ~ixlng the components; and extruding them from an extruder to the air.
Sald poly~tyrene means general purpose polystyrene or c~poly~er o~
styrene snd butndiene, acrylonitrile, methacrylic acid, acrylic acid, or maleic anhydride etc.
When the sheet extruded from the extruder i9 stretched, the ~heet becomes heAt-ahrinknble ln the strechlng dlrection.
The sheet prefernbly has the thickneas of from about 0.1 mm to about 1,0 mm and an expan~lon ratlo of from nbout 2 to about 10, more preferably a thicknes3 of froDi about 0.2 mm to about 0.6 mm and the expansion ratio of from about 3 to about 8.
If the sheet thlckness 18 s~nller thnn about 0.1 mm, the sheet 1~8 lea~ lleat-lnsulMt~ng properties and when the con~ainer ls covered with the cyllndrical lnbel, the lnbel wlll be bent. To the contrary, lf the sheet thickness 19 larger than about 1.0 mm, the difference between the curva-tures Oe the lnner su~fnce of the sheet nnd of the outer ~urfnce of the shee~ la lncreAsed, ~nd thu~ when the cylindric~l label i8 hent-~hrunk, wrinkles or crenQe~ nre cre~ted on the sur~nce thereof.
Al~o, 1~ the expnnslon ratio is les~ than nbout 2, the sheet wlll be broken in bendin~ thereof and thus cnn not be formed into 8 cyllndrlcnl shApe. Further, when the contnlner 18 covered with such a cyllndrlcAl label, ~ald label wlil be bro1cen. Addltionally, the heAt-ins~latlng 1 31 ~376 properties of such a label is decreased since the heat-conductivity of such a label is increased.
I the expansion ratio is larger than about 10, a secondary foaming is increased during the heat-shrinkage of the label, resulting in an increased deformation of the label.
The heat-shrinkage factor of the sheet is determined by measuring the shrinkage of the sheet after it is immersed in an oil at 120C for 1 minute. Preferably, the heat-shrinkage factor is from about 30% to about 70~ in the direction of stretching and from about -15~ to about +15% (minus represents an elongation) in a direction perpendicular to the direction of stretching.
Printing may applied to the sheet if desired, further, the sheet can be cut parallel to and perpendicular to the stretching direction, namely extruding direction respectively, to thereby form a ~uadrilateral label.
The printing may be applied after cutting of the sheet.
The label is formed into a cylinder such that the circumference of the cylinder corresponds to the direction of str~e/tc ~ . The overlapping portion of the ends o~ the sheet can then be ~41~4~.
; The sheet may be laminated with a polystyrene film to produce a laminated shee~. It is pre~erred that this polystyrene film be oriented in one axial direction Preferably, the shrinkage factor of this polystyrene film is approximately the same as that of the foam polystyrene sheet.
Preferably, container made from ~he thermoplastic resin is employed.
Such a container generally formed by inJection-molding. However, it may be manufactured by applying a secondary processing to the sheet extruded through a die from the extruder by using a forming machine such as a vacuum forming machine, a compressed air forming machine, or a 1 31 ~376 vacuumcompressed air forming machine. The container may be made from any materials suitable to the above-described fo~ning process. For example, polypropylene, polyethylene, polyethylene terephtalate, polycarbonate, polyamide, polystyrene etc. are recommended, and a res~n having a thermal ~ deforming temperature (defined by ~IS K-6871) higher than 100C are parti-cularly preferred.
In addition, a resin which does not fulfill the above-described conditions by itself only may be used by laminating such resin with a resin having a higher thermal deforming temperature.
The container may be a cup, bowl, bottle, can so on.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig~ 1 shows a relation between the extrusion direction of the sheet and the stretching direction of the sheet according to the present invention;
Fig. 2 shows a process for forming a cylinder from a sheet;
Fig. 3 shows a relation between the extrusion direction of the sheet and the stretching direction of the sheet in a comparison example.
Fig. 4 shows a process for forming from a sheet Fig. 3.
Fig. 5 ls a schematic view showing a process of covering the con-tainer with the cylindrical label;
Fig. 6 is a side elevational and partly broken sectional view showing the container covered completely with the cylindrical label of Fig.

Fig. 7 is a schematic view of the con~ainer covered with the cylin-drical label, the label being heat-shrun~ in a furnace to thereby contact with the container throughout;

1 31 ~376 Figo 8 is a graph showing a relation between the temperatures of both containers with the label manufactured according to the present invention and without the label and the time for which the containers were maintained;
Fig. 9 is a longitudinal sectional view of another emobodiment of the invention wherein a cylindrical label is appl:Led the container having a flange at an open end thereof:
Fig. 10 is a schematic side view showing the label heat-shrunk in a furnace;
` Fig. 11 is a longitudinal sectional view showing another embodiment of the container according to the present invention, wherein the container is provided with a groove about the circumference thereof in order to prevent the cylindrical label from falling off the container;
Fig. 12 is a schematic partially broken side view showing a con-tainer of Fig. 13 being covered with the cylindrical label;
Fig. 13 is a partially broken schematic side view showing the label ,~
which has been heat-shrunk in a furnace;
Fig. 14 is a schematic partially broken side view of the container of Fig. 13, which has completely covered with the label heat shrunk in a furnace;
.
Figs. 15 - 22 are schematic side ~iews of the containers of the other embodiments of the present invention, respectively.

; ., PREFE~RED EMBODIMENTS OF THE PRESENT INVENTION
Referring to drawings, reference numerals 1 and 2 denote labels made from a foam polystyrene sheet, a su:Ltable pattern of printing being applied :

1 31 '~376 on the sheet. la and 2a denote overlapped por~ions of two ends of the sheet, 3 denotes a container made from a thermoplastic resin, 3a denotes a flange portion of the container. Fig. 8 is a graph showing a relation between the temperatures of both containers with the label according to the present invention and without the label and the time to be maintained. The ordinate shows the temperature (C), and the abslssa &hows the time (min.) for which the container were maintained. In Fig. 8, (A) denotes a curve showing a transition of the temperature of water after the container with the label was filled with a pre-determined temperature of water, (B) denotes a curve showing a transition of the temperature of water after the container without label was filled with a pre-determined temperature of water, (C) denotes a curve showing a transition of the temperature of the outer wall surface of the container without label in which a predetermined temperature of water was filled, and (D) denotes a curve showing a transition of the temperature of the outer-wall surface of the container with label in which a pre-determined temperature of water was filled. In Figs. 9 and 10, 3a denotes a flange portion of container 3, 3b denotes an opening, and 3c denotes a portion of maximum diameter of container 3, respectively. Further, in Figs. 11 - 22, 3d and 9a denote a grooves, 5a denotes a dent, and 4a, 6a, 7a, 8a, lOa and lla denote projections formed on the outer surface of containers 4, 6, 7, 8, 10 and 11, respectively.
First, Figs. 5 - 8 will be explained.
These drawings show sheet 1 made from a foam polystyrene sheet and formed in a cylindrical shape, the overlapped portions la of two ends of the sheets 1 being heat-sealed or adhered by adhesives. The above-described cylindrical label had a circumference smaller than the maximum circumference of the container 3. The sheet forming label 1 were elongated 131~1,376 by about 0.1% -- 5.0% and then the labels 1 were co~ered over the container 3. The cylindrical labels 1 and the container 3 were contacted with each other along an area of at least 1% of the height of the container 3.
If the elongation of the sheet is smaller than 1%, during the heat-shrinkage step the label will be shifted in position relative to the container. If the elongation of the sheet is larger than 5.0~, tke label can be injured or broken.
If the contact area between the cylindrical label 1 and the con-tainer 3 after the container was covered with the label 1 is smaller than 1% of the height of the container 3, then the label will be shifted in position relati~e to the container during the heat-shrinkage of the label.
In Fig. 6, the container 3 was forced -lnto the cylindrical label 1 until the upper end of the label 1 abutted the lower surface of the flange 3a. In this case, the width of the contact area between the cylindrical label 1 and the container 3 is required to be greater than 1% of the height of the container.
Then, when the container 3 covered with the cylindrical label 1 was put in a surface to heat-shrink the label 1, as shown in ~'ig. 7, the label 1 was fitted on the outer-wall surface of the container 3.
Then, the container 3 with the label and without the label each were filled with 250 ml of water having a temperature of 90C. The relation between the temperature of the filled water and the surface temperature of the container was compared. This comparison shows that the outer wall surface temperature of the container with the label was lower than that of the container without the label, and thus the container with the label can maintain a higher temperature of water container therein, thus demonstrat-ing a superior heat insulating properties.

1 31 ~376 Fig. 9 and 10 shows another process of covering the container 3 with cylindrical label 1.
The opening 3b of the container 3 was provided with the flange ~.
The container 3 was formed in a manner that the length of the outer circumference A of the container 3 adjacent the flange 3a was smaller than that of the maximum outer circumference ~ of the container 3 approximately by 0.1% to 30%, and that the distance C between the maximum outer circum-ference portion 3c and the flange~3~ was at least 1% of the height D of the conta~ner 3.
If the difference between the length of the outer circumference A of the container 3 adjacent the flange 3a provided around the opening 3b and that of the maximum outer circumference B of the container 3 was less than 0.}% of the maximum outer circumference B when the cylindrical label 1 i.e.
sleeve was wrapped on the container 3 and was heat-shrunk, said label 1 can be detached from the flange 3a, so that the label 1 can not be attached in a pre-determined position on the container 3. On the contrary, if said difference between both lengthes was more than 30%, when the label 1 was heat-shrunk on the container 3, the label 1 will come into unever contact with the flange 3a.
Also, if the distance between the maximum outer circumference por-tion 3c and the flange 3a was less than 1% of the height D of the container 3, when the label 1 was heat-shrunk on the container 3, the label 1 can be detached from the flange 3a, so that the label 1 can not be attached in a pre~determined position on the container 3.
It is recommended that the length of the outer circllmference A of the container 3 ad~acent the flange 3a provided around the opening 3b is smaller than that of the maxi~um outer circumference B of the container 3 . i ;~

7 ~

between the maximum outer circumference portion 3c and the flange 3a is within from about 5% to about 20~ of the height D of the container 3.
Thus, when the sleeve-shaped label 1 into which the container 3 was inserted was heat-shrunk, as shown in Fig. 10, the label 1 was wrapped in a pre-determined position on the outer surface of the container 1.

EXAMPLE
This method will be explained by way of example.

Example 1:
Referring to Fig. 1, a rectangular label 1 (length = 95 mm, width =
290 mm, thickness = O.3 mm,-e~m~g-expansion ratio = 4) made from a foam polystyrene sheet and stretched in the extrusion direction was prepared.
Both sides perpendicular to the extrusion direction were adhered by heat-sealing to produce a cylinder, as shown in ~ig. 2~ A cup-shaped container made from polyplopyrene (inner diameter = 90 mm, height = 80 mm) was covered with this cylinder and was put in a furnace having the inside temperature of 200C for 2 seconds. The cylinder was heat-shrunk into adherence with ~he container. One hundred such heat-insulating containers were manufactured. These containers were tested and no defective cylind-rical label were detected.

Comparison Example 1 Referring to Fig. 3, a rectangu,lar label 2 (length = 95 mm, width =
e~ o,~

290 mm, thickness = 0.3 mm, l~p~e~6i~n ratio = ~) which was made from a foam polystyrene sheet and stretched perpendicularly ~o the extrusion direction was prepared. Both sides parallel to the extrusion direction 1 31 ~376 were adhered in a manner similar ta in Example 1 to firm a cy-linder as shown in Figure 4. One hundred :insulating containers were manufactured in the manner set forth in Example 1. These containers were tested and 15 containers were found to be defective. Specifically adherence of the side edges was poor and were separated in 15 containers.
~xample 2:
general purpose polystyrene mixed with freon 0.025 mol per 100g of polystyrene extrude from the extruder stretching in the extrusion direction to produce a foam polystyrene shee-t, which had the thickness of 0.3 mm, the expansion ratio of 5.5, the shrinkage factor in the stretching direction of 60 %, and a shrinkage factor in the direction perpendicular to the stretching direction of +5 %. An impact resistance polystyrene film (shrink-age factor = 55 %~ which was oriented in one axial direction and `:
had the thickness of 0.02 mm was prepared. The foam polystyrene sheet was laminated with an impact resistant polystyrene film, with the stretching directions of them being the same to thereby produce a laminated sheet. This laminated shee-t was cut and cylindrically formed or shaped so that the extrusion direction corresponded to the circumference of the cylinder. The overlap-ped portion of the two ends of the sheet was heat-sealed to form a cylindrical label having the inner diameter of 89 mm.
Then, as shown in Figure 5, a cup-shaped container 3 (the height is 80 mm, the flange outer diameter is 96 mm, the bottom outer diameter i5 70 mm) made from polypropylene and 1 31 ~376 having the maximum outer diameter ~f 90 mm in:its barrel portion was co~ered with or inserted into said cylindrical label 1, and the upper end face of the label 1 was abutted with the flange 3a. The contact area hetween the inner surface of the cylindrical label 1 and - 15a -the outer surface of the container 3 was made along the width of 5 mm.
When the contalner with the label was put in the urnace to be heated, the label was shrunk without causing any shift in position relative to the container, as a result of which, the label was attached to the container at the desired position thereof.

Example 3:
The cylindrical label having an inner diameter of 86 mm was formed by using a foam polystyrene sheet having a thickness of 0.65 mm and the expansion ratio of 5. A cup-shaped container ~height of 80 mm~ made from polypropylene and having a maximum outer diameter of 90 mm on the barrel portion thereof was covered with the cylindrical label, and the upper end of the label was abutted against the flange. The width along which the inner surface of the cylindrical label contact~ with the outer surface of the container was 15 n~m. The container with the label was put in the surface, the insde temperature of which was 130C. In this case, the sheet was heated and shrunk without causing any shift in position relative to the container, as a result of which, the label was wrapped to the container at the desired position thereof.

Example 4:
The laminated sheet same as Example 2 was formed to the cylinder 1 having the inner diameter of 92 mm.
In the container shown in Fig. 9, the portion ad~acent to the lower surface of the flange 3a ha~ an outer diameter A of 90 mm, and a maxlmum outer diameter B of the barrel portion is 91 mm~ and the distance C between .

-~

-- 1 31 -~376 the opening 3b and the portion 3c of maximum diameter is 15 mm, and a neck-in is formed at the portion shown by C.
A cup-shaped container 3 (the height is 80 mm, the outer diameter of flange is 96 mm, the bottom outer diameter Is 70 mm) made from poly-~ L9 ~
~4~r-en~-was covered with the above-described cylindrical label 1, and the ~. ~J.
upper end face of the label 1 was abutted with the flange 3a (Fig. 9). In this state, the container with the label was put in the furnace, within which it was maintained at the temperature of 13~C for 5 seconds, result-ing in the heat-shrinkage of the label 1. This label 1, as shown in Fig.
10, was shrunk without departing from the surface of the flange 3a of the container, as a result of which the label was attached to the container at the desired position thereof.

~xample 5:
The container 3 covered with the label 1, same as Example 2 as shown in Fig. 11, had a groove 3d about the outer circumference thereof. The optimum size of said groo~e 3d depends upon the size and shape of the container 3 and the thickness of the label etc., and thus is difficult to be specified. In general, howe~er, it is preferred that the width measured in a direction of the height of the container is within 3 n~ - 5 mm and the maximum depth is within 1 mm - 5 mm.
Then, the container 3, as shown in Fig. 12, was covered with the cylindrical label 1, and the upper end face of the label 1 was abutted with the lo~er surface of the flange 3a as shown in Fig. 13, and in this state, the container with the label was put in the furnace and heated, as a result of which, the label was securely attached on the outer surface of the container 3 as shown in Fig. 14.

1 31 ~376 When the cylindrical label 1 was made from the foam polystylene sheet having a thickness o 0.3mm and an expansion ratio of 4, and the container 3 is made from a polypropylene sheet, it is preferred for the composite body to be heated to a temperature of 130C for 1 second.
When the cylindrical label 1 was heat-shrunk, a part of the sheet material entered or was forced into the groove 3d formed on the outer circumference of the container 3, so that the label was securely attached to the outer circumference of the container 3 without using any adhesive or solvent. Also, even if the label 1 had been attached in a deformed state to the container resulting in an inferior good, since label I could be easily removed from the container 3, and the container 3 could be re-used.
Figs. 15 - 22 shows further examples respectively. The container shown in Fig. 15 has a plurality of rectangular pro~ection 4a provided on the outer surface of the container 4, said projections being arranged along the circumference of the container at a pre-determined distance from adjacent projections. The containers 5 and 6 shown in Figs. 16 and 17 respectively have a plurality of rectangular dents 5a and 6a instead of the above-described projections on the outer circumferential surface thereof.
The container 7 shown in Fig. 18 similarly has a plurality of pro~ections 7a having a shape like ~ boomerang. ~le container 8 shown in Fig. 19 has a plurality of linear pro~ections 8a arranged in a pattern like a chain of mountains. The container 9 shown in Fig. 20 has a groove 9a having a triangu~ar cross section. The containers 10 and 11 shown in Figs.
21 and 22, respectively9 have a line of projections lOa and lla which have a triangular cross-section and a rectangular cross-section, respectively.
When these containers were covered with the cylindrical label and put in the furnace and heated, a part of the sheet material was forced in 1 31 ~376 the dents or grooves, or was fi~ted over the projections, and thus, the label was securely attached to the container wi~hout falling off the container. Also, even if the label was attached in a deformed state to the container so that it might result in an inferior good, since this label can be easily removed from the container, this container can be re-used.

Comparison example 2 A cylindrical label was made by a using a method similar to that used in Example 2 except that sodium bicarbonate/citric acld of 0.3% in weight was used instead of freon, and the foam sheet had an expansion ratio of 1.9 and a thickness of 0.3 mm. A container was covered with this label.
At this time, the sheet material was folded, resulting in crack extending about the circumference of the label. During heating of the label, the cracked portion extended to become a large split.

;~ .
Comparison example 3 A cylindrical label was made by using a method similar to that used in Example 2 except that 0.06 mol freon per 100 g of resin were added to the resin. The foam sheet had a thickness of 0.95 mm and an expansion ratio of 11 A container was covered with this label. In heating the label, the label expanded prior to shrinkage thereof and was deformed and shifted in position. Thus it was impossible to secure the label at a pre-determined position.

Comparison example 4 A cylindrical label was made under conditions similar to those of 1 3 1 ~t376 Example 2 except that the label was made from the sheet having a thickness of 0.09 mm and the take-off speed of the sheet was greater than in Example 1. This label was deformed while cover~ng the container, and thus could not be attached to a pre-determined posi~ion to the container.

Comparison example S
A cylindrlcal label was made under the conditions similar to those of Example 2 except that the sheet had the thickness of 1.1 mm and the take-off speed of the sheet was less than in Example 2. This label became folded during the process of covering the container, and the fold could not be removed through heat-shrinkage of the label.

Claims

1. A method for manufacturing a thermoplastic container with a label comprising:
extruding a resin sheet and stretching the resin sheet in the direction of extrusion;
cutting the sheet to a desired size to make a label;
forming the label into a cylinder having a circumference less than the maximum circumference of the container such that the circumference of the cylinder corresponds to the direction of stretching;
placing the formed cylindrical label onto the container by applying a sufficient force to stretch the portion of the label to be placed in contact with the area of the maximum circumference of the container, wherein the circumference of at least a portion of the label remains less than the maximum circumference of the container; and heating the cylindrical label to a temperature sufficient to heat shrink the label into adherence with the container.

2. The method of claim 1, wherein the extruded resin is a foam polystyrene resin.

3. The method of claim 1, wherein the sheet is extruded to a thickness of from about 0.1 mm to about 1.0 mm.

4. The method of claim 1, wherein the extruded sheet has an expansion ratio of from about 2 to about 10.

5. The method of claim 2, wherein the extruded sheet has a thickness of from about 0.1 mm to about 1.0 mm and an expansion ratio of from about 2 to about 10.

6. A method of claim 2, wherein the extruded sheet has a thickness of from about 0.2 mm to about 0.6 mm and an expansion ratio of from about 3 to about 8.

7. A method of claim 1, wherein the extruded sheet has a heat shrinkage factor of from about 30% to about 70% in the direction of stretching and heat shrinkage factor of from about -15% to about +15% in the direction perpendicular to the direction of stretching.

8. A method of claim 1, wherein the cylinder forming step includes the step of applying an adhesive to overlapping side edges of the sheet.

9. A method of claim 1, wherein the cylinder forming step includes the step of heat-sealing overlapping side edges of the sheet.

10. A method of claim 1, wherein the sheet is a foamed resin sheet containing a plasticizer.

11. A method of claim 1, wherein the resin is polystyrene or a copolymer of styrene and at least one other monomer selected from the group consisting of butadiene, acrylonitrile, methacrylic acid, acrylic acid and maleic anhydride.

12. A method of claim 1, wherein during the step of placing the cylinder onto the container, at least a portion of the cylinder is stretched from about 1% to about 5% about its circumference.

13. A method of claim 12, wherein after the cylinder is placed onto the container, the cylinder engages the container over an area of at least 1% of the height of the container.

14. A method of claim 1, wherein the container has an open end portion having a flange adjacent thereto.

15. A method of claim 14, wherein the container is a cup, bowl or bottle having a generally frustroconical shape with the open end having a larger diameter than that of a closed end.

16. A method of claim 14, wherein the container at the portion adjacent the flange is pinched inwardly so that the circumference of the container at the portion adjacent the flange is from about 0.1% to about 30% smaller than the maximum outer circumference of the container.

17. A method of claim 16, wherein the axial distance between the maximum outer circumference portion of the container and the portion adjacent the flange is at least 1% of the height of the container.

18. A method of claim 1, wherein the container has at least one groove or projection about the circumference thereof to prevent the cylinder from shifting relative to the container during the heat shrinking step.

19. A method of claim 18, wherein the groove or projection extends continuously about the circumference of the container.

20. A method of claim 18, wherein the groove or projection extends intermittently about the circumference of the container.

21. A method of claim 1, wherein the sheet is laminated with a film.

22. A method of claim 21, wherein the film is polystyrene and has been stretched in one direction.

23. A method of claim 1, wherein the container has a frustroconical shape and the cylinder has a circumference slightly less than the maximum circumference of the container and wherein during the step of placing the cylinder on the container, the cylinder is stretched to fit the shape of the container and stretches about and engages the container.

24. A method for manufacturing a cup with a label being made of a thermoplastic resin and having a generally frustroconical shape with an open end having a larger diameter than a closed end which comprises:
[A] extruding a sheet of a foamed resin and stretching the foamed resin sheet in the direction of the extrusion, wherein the resin is polystyrene or a copolymer of styrene and at least one monomer selected from the group consisting of butadiene, acrylonitrile, methacrylic acid, acrylic acid and maleic anhydride and the sheet has a thickness of 0.1 to 1.0 mm, an expansion ratio of from about 2 to about 10, a heat shrinkage factor of from about 30% to about 70% in the direction of the stretching and a heat shrinkage factor of from about -15% to about +15% in the direction perpendicular to the direction of the stretching:
[B] cutting the stretched sheet in both directions substantially parallel and perpendicular to the extrusion direction to a desired size to make a label;
[C] sealing both edges of the label to form a cylinder having a circumference less than the maximum circumference of the cup such that the circumference of the cylinder corresponds to the direction of the stretching;
[D] placing the formed cylindrical label onto the cup by applying a sufficient force to stretch the portion of the label in contact with the area of the maximum circumference of the cup, wherein the circumference of at least a portion of the label remains less than the maximum circumference of the cup; and [E] heating the cylindrical label to a temperature sufficient to heat shrink the label into tight contact with the container in substantially all areas of the cup.

25. A method of claim 24, wherein the container has an open end portion having a flange adjacent thereto.

26. A method of claim 25, wherein the container is a cup, bowl or bottle having a generally frustroconical shape with the open end having a larger diameter than that of a closed end.

27. A method of claim 24, wherein the container has at least one groove or projection about the circumference thereof to prevent the cylinder from shifting relative to the container during the heat shrinking step.

28. A method of claim 24, 25 or 26, wherein the container is made of a thermoplastic resin having a thermal deforming temperature higher than 100°C and is adapted for containing food to be cooked by a microwave oven while the food is in the container.

29. A method of claim 25, 26 or 27, which further comprises:
laminating the stretched foamed resin sheet produced in step [A] with a monoaxially stretched non-foamed film of polystyrene, polyethylene, polypropylene, ethylene/vinyl acetate copolymer or a copolymer of styrene and at least one monomer selected from the group consisting of butadiene, acrylonitrile, methacrylic acid, acrylic acid or maleic anhydride, so that the stretching directions of the stretched sheet and the monoaxially stretched film are the same, wherein the monoaxially stretched film is substantially thinner than the stretched sheet and has substantially the same heat shrinkage factors as the stretched sheet.