CA2044079A1 - Extrusion coated synthetic printing paper for in-mold label coupon applications - Google Patents
Extrusion coated synthetic printing paper for in-mold label coupon applicationsInfo
- Publication number
- CA2044079A1 CA2044079A1 CA 2044079 CA2044079A CA2044079A1 CA 2044079 A1 CA2044079 A1 CA 2044079A1 CA 2044079 CA2044079 CA 2044079 CA 2044079 A CA2044079 A CA 2044079A CA 2044079 A1 CA2044079 A1 CA 2044079A1
- Authority
- CA
- Canada
- Prior art keywords
- label
- bottle
- combination
- bottles
- density polyethylene
- 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.)
- Abandoned
Links
Abstract
Disclosed herein is a label stock for use in conjunction with bottles and containers, especially those made by an in-mold label process. The label stock includes a releasable label material and an adhesive layer of low density polyethylene. The label stock is particularly well-suited for use with coupons that can be peeled from the bottles and containers by the consumer for in-store redemptions and mail-in rebates.
Description
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Express Mail No. RB516880947 PATENT
EXTRUSION COATED SYNTHETIC PRINTING PAPER FOR IN-MOLD
BACKGROU~ OF_THE INVENTION
The present invention relates to a peelable, releasable label material for use with plastic bottles. More particularly, the present invention relates to a polypropylene/low density polyethylene laminate which can be adhered to a high density polyethylene bottle.
Consumer marketing is a multi-million dollar husiness today. Pac~aging plays a major role in this area. An infinite number of today's products are sold in plastic bottles. The variety of contents for these bottles ranges from motor oil, to laundry detergent to orange juice. Many of the bottles are made from high densi~y polyethylene.
20As part of the marketing strategy for these products, certain manufacturers like to use point of purchase and rebate coupons. These coupons are attached to the item, typically a glass or high density polyethylene (HDPE) bottle, peeled off by the consumer at the point of purchase and redeemed at the cash register for the value of the coupon. Post mold labeling is one type of method which has been developed for attaching these coupons to the bottled consumer products after the bottles have been produced. One execution of this method includes the use of multi-layered pressure sensitive paper labels which are affixed to the bottle by a pressure sensitive adhesive. The top one or two layers can be clearly peeled off and redeemed for cents off at the cash register or used for such things as game pieces for promotional games and sweepstakes. Examples of pressure sensitive systems are "Clean Dri" and "Double Dri" labèl constructions from Mid America Tag and Label a Division of Menasha Corporation of Neenah, Wisconsin.
7 ~
A second method of labeling is to use glue applied labels which have unglued perforated sections of the label which can be separated via the perforations and redeemed. Rough handling, however, can cause the labels to prematurely separate from the bottle or cause the labels to become ripped and torn.
A third method of affixing labels is to use a hang tag around the neck of the bottle. The hang tag can be attached by a piece of string or by a hole which is die cut into the tag. Once again such a method of labeling is subject to a high degree of damage and loss due to the nature of the construction and affixation.
While all of the above methods of labeling are adapted for post mold labeled bottles, there is a concerted effort to label bottles during the molding process because of the efficiencies which can be obtained by eliminating the step of labeling the bottle on the filling line. Labeling on the filling line is normally the slowest most inefficient step in the filling process. Given the inefficiencies of post mold label attachment, it would seem apparent to affix the label during the molding process, i.e., in-mold labeling. To date, however, a successful system has not been developed which will allow a label with a point of purchase coupon to be applied to a plastic bottle by the in-mold labeling process.
In-mold labeling is a process commonly used with bottle forming process such as blow molding. The blow molding machines used for producing high density polyethylene (HDPE) bottles conventionally include an extruder that extrudes a tube or parison of hot high density polyethylene between open sections of a mold. Closing of the mold then clamps the plastic parison and allows air to be blown into the tube such that the plastic parison assumes the shape of the mold. After suitable cooling has taken place, the mold sections are opened to allow ejection of the molded bottle.
In-mold labeling has been developed to provide an attachment of labels to bottles during the molding process.
This in-mold labeling is performed by inserting a label, ~ ~ ?
plastic or paper, within the mold prior to the extrusion of the hot HDPE parison and subsequent closing of sections of the mold in preparation of the blowing operation. The subsequent blowing operation forms the hot HDPE parison around the label and activates a heat sensitive adhesive, that bonds the label to the thus formed bottle.
If labels used in the in-mold labeling process are to be used for in-store redemption and mail-in rebates, they must be sufficiently adhered to the bottle to prevent loss, premature release and damage, yet the same labels must be easily removable from the exterior of the container by the consumer.
One type of label made for such applications is a thermoplastic polypropylene film adhered to the bottle with a water-based ethylene vinyl acetate adhesive. A problem with such water-based adhesives is their failure due to the water sensitivity of the adhesive. The water-based ethylene vinyl acetate adhesive (EVA) has the proper softening point and hot tack to allow attachment of the label to HDPE bottles during the blow molding process. Testing by the applicant indicates that the bond between the thermoplastic polypropylene film and the adhesive (150-580 g/15 mm)[ 90 peel adhesion test using an Instron Universal Testing Instrumen~ as described on page 7: lines 30-31 supra] was of the proper magnitude to allow the label to be cleanly peeled from the surface of the bottle.
The sensitivity of the adhesive and therefore the problem with the system resides in the fact that such labels will fall off the bottles when exposed to high moisture conditions as are encountered during a freeze-thaw cycle. Freezing and thawing most often occurs when products are shipped and or stored during the winter or stored in the freezer section of a grocery store. Typically a large amount of moisture will condense on a frozen bottle containing product when it is removed from the freezer or taken from a frozen state and placed in a room at normal reiative humidity (RH) of approximately 30 to 90% RH. The condensed moisture on the outside of the label wicks into the water sensitive adhesive ~ 3 from the edge of the label causing the adhesive to fail and the label to loosen and fall-off the bottle. As a result, labels which use EVA adhesives are seen to be less than desirable when used in conjunction with labels involved in the in-mold labeling process.
Other adhesives are available for attaching thermoplastic polypropylene film labels to HDPE bottles in the in-mold label process. Examples are the Adcote~ ethylene vinyl acetate gel lacquers from Morton International of Woodstock, Illinois.
The problem with these adhesives is that the bond strength between label material adhesive and the bottle is so high that the coupon portion of the label can not be cleanly removed from the bottle. Testing by the applicant indicates that bond strengths for these adhesives are in the order of 650-800 g/15 mm when using a 90 peel adhesion test. As a result, when att~mpting to remove such labels, the film tends to delaminate and tear thereby making the labels unsuitable for redemption.
A third type of adhesive which can be used in the in-mold labeling process is a low density polyethylene. Oji Yuka Synthetic Paper Company of Tokyo, Japan has prepared labels from a thermoplastic polypropylene film (Ximdura~) which is tie coated either with polyurethane or polyethyleneimine and extrusion coated with low density polyethylene. The tie coat serves to firmly bond the LDPE to the Kimdura~ and the LDPE
acts as the adhesive in the in-mold labeling process. While this material works well for permanent label applications, this material does not function properly as a coupon label becau~e the typical 650-900 g/15 mm bond strength between the Pilm adhesive and bottle is too high. The coupon portion of the label cannot be cleanly peeled from the bottle because the film tears and delaminates.
It is therefore the object of the present invention to provide a label material that will peel cleanly from a bottle without tearing or delaminating. It is another object of the present invention to provide a label material which will not come loose from the bottle until removal is affected by the consumer.
Express Mail No. RB516880947 PATENT
EXTRUSION COATED SYNTHETIC PRINTING PAPER FOR IN-MOLD
BACKGROU~ OF_THE INVENTION
The present invention relates to a peelable, releasable label material for use with plastic bottles. More particularly, the present invention relates to a polypropylene/low density polyethylene laminate which can be adhered to a high density polyethylene bottle.
Consumer marketing is a multi-million dollar husiness today. Pac~aging plays a major role in this area. An infinite number of today's products are sold in plastic bottles. The variety of contents for these bottles ranges from motor oil, to laundry detergent to orange juice. Many of the bottles are made from high densi~y polyethylene.
20As part of the marketing strategy for these products, certain manufacturers like to use point of purchase and rebate coupons. These coupons are attached to the item, typically a glass or high density polyethylene (HDPE) bottle, peeled off by the consumer at the point of purchase and redeemed at the cash register for the value of the coupon. Post mold labeling is one type of method which has been developed for attaching these coupons to the bottled consumer products after the bottles have been produced. One execution of this method includes the use of multi-layered pressure sensitive paper labels which are affixed to the bottle by a pressure sensitive adhesive. The top one or two layers can be clearly peeled off and redeemed for cents off at the cash register or used for such things as game pieces for promotional games and sweepstakes. Examples of pressure sensitive systems are "Clean Dri" and "Double Dri" labèl constructions from Mid America Tag and Label a Division of Menasha Corporation of Neenah, Wisconsin.
7 ~
A second method of labeling is to use glue applied labels which have unglued perforated sections of the label which can be separated via the perforations and redeemed. Rough handling, however, can cause the labels to prematurely separate from the bottle or cause the labels to become ripped and torn.
A third method of affixing labels is to use a hang tag around the neck of the bottle. The hang tag can be attached by a piece of string or by a hole which is die cut into the tag. Once again such a method of labeling is subject to a high degree of damage and loss due to the nature of the construction and affixation.
While all of the above methods of labeling are adapted for post mold labeled bottles, there is a concerted effort to label bottles during the molding process because of the efficiencies which can be obtained by eliminating the step of labeling the bottle on the filling line. Labeling on the filling line is normally the slowest most inefficient step in the filling process. Given the inefficiencies of post mold label attachment, it would seem apparent to affix the label during the molding process, i.e., in-mold labeling. To date, however, a successful system has not been developed which will allow a label with a point of purchase coupon to be applied to a plastic bottle by the in-mold labeling process.
In-mold labeling is a process commonly used with bottle forming process such as blow molding. The blow molding machines used for producing high density polyethylene (HDPE) bottles conventionally include an extruder that extrudes a tube or parison of hot high density polyethylene between open sections of a mold. Closing of the mold then clamps the plastic parison and allows air to be blown into the tube such that the plastic parison assumes the shape of the mold. After suitable cooling has taken place, the mold sections are opened to allow ejection of the molded bottle.
In-mold labeling has been developed to provide an attachment of labels to bottles during the molding process.
This in-mold labeling is performed by inserting a label, ~ ~ ?
plastic or paper, within the mold prior to the extrusion of the hot HDPE parison and subsequent closing of sections of the mold in preparation of the blowing operation. The subsequent blowing operation forms the hot HDPE parison around the label and activates a heat sensitive adhesive, that bonds the label to the thus formed bottle.
If labels used in the in-mold labeling process are to be used for in-store redemption and mail-in rebates, they must be sufficiently adhered to the bottle to prevent loss, premature release and damage, yet the same labels must be easily removable from the exterior of the container by the consumer.
One type of label made for such applications is a thermoplastic polypropylene film adhered to the bottle with a water-based ethylene vinyl acetate adhesive. A problem with such water-based adhesives is their failure due to the water sensitivity of the adhesive. The water-based ethylene vinyl acetate adhesive (EVA) has the proper softening point and hot tack to allow attachment of the label to HDPE bottles during the blow molding process. Testing by the applicant indicates that the bond between the thermoplastic polypropylene film and the adhesive (150-580 g/15 mm)[ 90 peel adhesion test using an Instron Universal Testing Instrumen~ as described on page 7: lines 30-31 supra] was of the proper magnitude to allow the label to be cleanly peeled from the surface of the bottle.
The sensitivity of the adhesive and therefore the problem with the system resides in the fact that such labels will fall off the bottles when exposed to high moisture conditions as are encountered during a freeze-thaw cycle. Freezing and thawing most often occurs when products are shipped and or stored during the winter or stored in the freezer section of a grocery store. Typically a large amount of moisture will condense on a frozen bottle containing product when it is removed from the freezer or taken from a frozen state and placed in a room at normal reiative humidity (RH) of approximately 30 to 90% RH. The condensed moisture on the outside of the label wicks into the water sensitive adhesive ~ 3 from the edge of the label causing the adhesive to fail and the label to loosen and fall-off the bottle. As a result, labels which use EVA adhesives are seen to be less than desirable when used in conjunction with labels involved in the in-mold labeling process.
Other adhesives are available for attaching thermoplastic polypropylene film labels to HDPE bottles in the in-mold label process. Examples are the Adcote~ ethylene vinyl acetate gel lacquers from Morton International of Woodstock, Illinois.
The problem with these adhesives is that the bond strength between label material adhesive and the bottle is so high that the coupon portion of the label can not be cleanly removed from the bottle. Testing by the applicant indicates that bond strengths for these adhesives are in the order of 650-800 g/15 mm when using a 90 peel adhesion test. As a result, when att~mpting to remove such labels, the film tends to delaminate and tear thereby making the labels unsuitable for redemption.
A third type of adhesive which can be used in the in-mold labeling process is a low density polyethylene. Oji Yuka Synthetic Paper Company of Tokyo, Japan has prepared labels from a thermoplastic polypropylene film (Ximdura~) which is tie coated either with polyurethane or polyethyleneimine and extrusion coated with low density polyethylene. The tie coat serves to firmly bond the LDPE to the Kimdura~ and the LDPE
acts as the adhesive in the in-mold labeling process. While this material works well for permanent label applications, this material does not function properly as a coupon label becau~e the typical 650-900 g/15 mm bond strength between the Pilm adhesive and bottle is too high. The coupon portion of the label cannot be cleanly peeled from the bottle because the film tears and delaminates.
It is therefore the object of the present invention to provide a label material that will peel cleanly from a bottle without tearing or delaminating. It is another object of the present invention to provide a label material which will not come loose from the bottle until removal is affected by the consumer.
2 ~
It is yet another object of the present invention to provide a label material which, when peeled, has a bond ~ailure which occurs between the label material and the adhesive thereby leaving a clean back surface to the label which can be written on by the consu~er.
It is still a further object of the present inventioh to provide a label material which can be printed by normal label printing methods such as flexography, offset lithography or rotogravure printing.
These and other objects of the present invention will become more apparent upon a further review of the following specification and claims.
SUMMARY OF THE INV_ENTION
The present invention relates to a label usable with plastic bottles and in particular with bottles made with exterior surfaces of high density polyethylene. The label itself is a laminate of label stock with an adhesive layer of low density polyethylene. In a preferred embodiment, the label stock is polypropylene.
When the label according to the present invention is attached to a bottle, such as a high density polyethylene bottle, the release strength between the label and the bottle should be between about 100 and 580 grams per 15 mm.
Preferably the release strength should be between about 150 and 400 grams per 15 mm. As a result of using such a label stock, the label/bottle combination should be able to be cooled to a temperature of at least -10~C for a period of at least 24 hours and the label should not self-release upon thawing. Furthermore, when the label is peeled from the bottle, the majority of adhesive should remain with the bottle and not with the label stock itself.
It is yet another object of the present invention to provide a label material which, when peeled, has a bond ~ailure which occurs between the label material and the adhesive thereby leaving a clean back surface to the label which can be written on by the consu~er.
It is still a further object of the present inventioh to provide a label material which can be printed by normal label printing methods such as flexography, offset lithography or rotogravure printing.
These and other objects of the present invention will become more apparent upon a further review of the following specification and claims.
SUMMARY OF THE INV_ENTION
The present invention relates to a label usable with plastic bottles and in particular with bottles made with exterior surfaces of high density polyethylene. The label itself is a laminate of label stock with an adhesive layer of low density polyethylene. In a preferred embodiment, the label stock is polypropylene.
When the label according to the present invention is attached to a bottle, such as a high density polyethylene bottle, the release strength between the label and the bottle should be between about 100 and 580 grams per 15 mm.
Preferably the release strength should be between about 150 and 400 grams per 15 mm. As a result of using such a label stock, the label/bottle combination should be able to be cooled to a temperature of at least -10~C for a period of at least 24 hours and the label should not self-release upon thawing. Furthermore, when the label is peeled from the bottle, the majority of adhesive should remain with the bottle and not with the label stock itself.
3 ~ .L i ~
DESCRIPTION OF TH~ PREFERRED EMBO~IMENT
The present invention relates to a releasable label material suitable for use as a label for containers in general and most preferably for thermoplastic containers such as high density polyethylene (HDPE). Materials suitable for bottles which are blow molded and in-mold labeled are polyesters such as polyethylene terephthalate (PET), polyvinylchloride, and polypropylene multi-layer bottles. As described in the background of the present invention, the label material of the present invention is best suited for use in the in-mold labeling process even though other processes are also contemplated as being within the scope of the present invention.
- The label material of the present invention includes a label stock which has been extrusion coated on one side with an adhesive layer of low density polyethylene (LDPE). LDPE
is a highly chain-branched polyethylene polymer produced by polymerizing ethylene under high pressure. Low density polyethylene can contain a variety of short and long chain branches and usually has densities ranging from about O.910 to about 0.940 grams per cubic centimeter (g/cm3). Melt flow indices for LDPE using ASTM standard Dl238-88 can range from about 0.15 to 15.0 grams per 10 minutes (g/10 min.) when measured at l90-C under a load of 2.16 kilograms (kg). The LDPE can be applied at a coating rate of about 9.32 to about 23.3 g/m2 with the preferred range being 11.7-18.4 g/m2.
This correlates to a coating thickness of approximately 10 to 25 microns.
The label stock itself can be any one of a number of materials well known to be used as label stock, however, a preferred material is a thermoplastic polyolefin film. Note that whatever label stock which is chosen should be compatible with the coating of LDPE. In particular, the label stock used in the example below is a thermo~lastic polypropylene film which has been biaxially oriented. When using such a polypropylene film, it will generally have a density between 2 ~3 . 3 ~
about 0.17 and 1.02 grams per cubic centimeter (g/cm3). The caliper of the label stock generally will be between about 60 microns and about lS0 microns and preferably between 60 microns and 95 microns. Basis weights for the label stock will range between about 50 g/m2 and about 116 g/m2 and preferably will be from 60 g/m2 to 82 g/m2. Several examples will now follow which will further demonstrate the present invention and its attributes.
A 76 cm wide web of polypropylene film (Kimdura~ KPK-80 from Kimberly-Clark Corporation of Neenah, Wisconsin) having a caliper of 80 microns, a basis weight of 81 g/m2 and a density of 1.02 g/cm3 was extrusion coated on one side with 11.7 g/m2 low density polyethylene (LDPE). The extrusion equipment included a Hexco 8.9 cm single screen extruder with a 24 to 1 L/D (length to diameter ratio), an EDI 91 cm die and a Gloucester Engineering Company, Inc. laminator with a steel chill roll and a silicone rubber back up roll. The LDPE
(Petrothene 1014 from Quantum Chemical Corporation of Cincinnati, Ohio) had a density of 0.918 g/m3 and a melt flow index of 7.0 g/10 min. No tie coat or precorona treatment was applied to the label stock prior to coating with the LDPE.
To extrude the LDPE onto the polypropylene label stock the LDPE was heated to 316~C.
The LDPE coated polypropylene label stock was printed with a label pattern on the surface opposite the LDPE label coating by rotogravure and then die cut into label shapes.
The labels were then applied to HDPE bottles by the in-mold labeling process on a wheel type blow molding machine by Continental Plastic Containers, 2375 Touhy Avenue, Elk Grove Village, Illinois 60007.
The labeled bottles were tested for label bond strength and for moisture resistance by a freeze thaw cycle test. To determine bond strength the label panels were cut from the bottle and the panels were then cut into lS mm wide strips L s t~ 7 s using a standard sample cutter. One end of the label was then peeled back on itself approximately 15 mm. The peeled end of the label film was placed in one jaw of an Instron Universal Testing Instrument(model 1122, Instron Corporation, Canton, MA 02021) and the other end of the bottle panel, opposite the peeled end, was placed in the other jaw. The sample to be peeled was held horizontally so the jaws peeled the label film from the bottle at so from the horizontal. Settings from the Instron were as follows:
Cross head speed - 30 cm/min.
Span - 2.54 cm Scale - 2 kg full scale Chart speed - 15 cm/min.
Three test samples were run and yielded peel strengths of 250g/15 mm, 240g/15 mm and 220 g/15 mm. The average of the three tests was 237g/15 mm.
To conduct the freeze/thaw test, bottles with labels were filled with warm water at 50C and placed in a freezer at -10C for 17 hours at which time the water was frozen. The bottles were then removed from the freezer and placed in a room at 23'C and 50~ relative humidity for six hours until the water was thawed. While a large amount of water condensed on the outside of the bottles, after thawing none of the bottles lost their labels and the bond strength using the previously described 90- peel adhesion was 180 g/15 mm after thawing.
In addition to the bond strength and freeze/thaw testing, labeled bottles were also peeled by hand as would happen during actual consumer use. Labels could be cleanly peeled from the HDPE bottles leaving the LDPE adhesive on the bottles thereby making it possible to write on the labels.
Furthermore, when the labels were peeled from the bottles they did not tear or delaminate.
~ t"J
A 84 cm wide roll of KPK-80 Rimdura~ polypropylene label stock was extrusion coated with 13 microns of low density polyethylene extrusion resin (Petrothane 1014, melt flow index 7.0g/10 min., density 0.918 g/cm3) at a temperature of 316C.
No tie coat or precorona treatment was applied to the KimduraX
film befcre extrusion coating. Labels were die cut from this low density polyethylene adhesive polypropylene label film laminate. They were applied to HDPE bottles using an in-mold labeling process by Graham Container Corporation, York, PA on a wheel type blow molding machine manufactured by the same company.
A label panel was cut from one of the bottles and the bond strength tested at 579 g/ls mm by 90 peel on an Instron using a 15 mm wide strip. Instron settings were as follows:
Cross head speed - 30 cm/min.
Span - 2.54 cm Scale - 2 kg full scale Chart speed - 15 cm/min.
One bottle was filled with warm water at 47-C and frozen in a freezer at -10-C for 23 hours. It was taken from the freezer and placed in a room at 22'C and 50% RH for 24 hours.
A large amount of moisture collected on the surface of the bottle and label as it thawed. After 24 hours the bottle had warmed to room temperature and the label was still firmly attached to the bottle. The bond strength was 480 g/15 mm using the previously described 90- peel adhesion test. The label could be cleanly removed from the bottle.
Labels prepared by the Oji-Yuka Synthetic Paper Company of Tokyo, Japan from a thermoplastic polypropylene film ~Kimdura~) which was tie coated either with polyurethane or polyethyleneimine and extrusion coated with low density polyethylene w~re evaluated. The tie coat served to firmly bond the LDPE to the ~imdura~, in fact, firmly enough that the label could not be removed from the bottle without tearing and delaminating after in-mold labeling.
The present invention provides a labèl material which is extrusion coated with low density polyethylane without prior use of a tie coat or corona treatment. This provides a label material that will peel cleanly from a bottle without tearing or delaminating. It is desirable to be able to test the bond strength of the extrusion coated low density polyethylene to the label film material before in-mold labeling to determine if this bond strength is in a range which will allow it to peel cleanly from the bottle after in-mold labeling.
Consequently, Dennison Standard Paper Testing Waxes (series No. 39-330 from Dennison Manufacturing company, Framingham, Mass., using ASTM Method D2482-86T) was used to measure the bond strength of the LDPE adhesive film to the Kimdura~ label film. The Dennison waxes are a numbered series of waxes with graded adhesive powers used to test bond strength of coatings to web materials. Higher numbers indicate stronger bonding.
A 8 1/2" x 11" sheet of Kimdura0 KPK-80 extrusion coated with 11.7 g/m2 of low density polyethylene (Petro-theme 1014 from Quantum Chemical Corporation of Cincinnati, Ohio) was tested by placing waxes, which had been heated until the end was molten, firmly on the LDPE surface of the sample. Waxes having ratings of 5 through 3 were used. After cooling, the wax was pulled from the sample with a quick jerk. Bond strength was determined by finding the wax numbers between which the coated surface was not disrupted and where it became detached. In this case, the LDPE did not pick with a #5 wax and did pick with a #6 wax. For Oji-Yuka LDPE coated Kimdura~
label material, the LDPE coating did not pick with a #8 wax but did pick with a #9 wax.
Thus for a coupon application the LDPE extrusion coating should have a bond strength corresponding to a wax pick of at least a #5 wax to ensure good bonding to the bottle but a bond 2~ '?
strength below that corresponding to a #8 wax to ensure a clean peel from the bottle.
Having thus described the invention in detail it should be apparent that various modifications and changes can be made in the present invention without departing from the spirit and scope of the following claims.
DESCRIPTION OF TH~ PREFERRED EMBO~IMENT
The present invention relates to a releasable label material suitable for use as a label for containers in general and most preferably for thermoplastic containers such as high density polyethylene (HDPE). Materials suitable for bottles which are blow molded and in-mold labeled are polyesters such as polyethylene terephthalate (PET), polyvinylchloride, and polypropylene multi-layer bottles. As described in the background of the present invention, the label material of the present invention is best suited for use in the in-mold labeling process even though other processes are also contemplated as being within the scope of the present invention.
- The label material of the present invention includes a label stock which has been extrusion coated on one side with an adhesive layer of low density polyethylene (LDPE). LDPE
is a highly chain-branched polyethylene polymer produced by polymerizing ethylene under high pressure. Low density polyethylene can contain a variety of short and long chain branches and usually has densities ranging from about O.910 to about 0.940 grams per cubic centimeter (g/cm3). Melt flow indices for LDPE using ASTM standard Dl238-88 can range from about 0.15 to 15.0 grams per 10 minutes (g/10 min.) when measured at l90-C under a load of 2.16 kilograms (kg). The LDPE can be applied at a coating rate of about 9.32 to about 23.3 g/m2 with the preferred range being 11.7-18.4 g/m2.
This correlates to a coating thickness of approximately 10 to 25 microns.
The label stock itself can be any one of a number of materials well known to be used as label stock, however, a preferred material is a thermoplastic polyolefin film. Note that whatever label stock which is chosen should be compatible with the coating of LDPE. In particular, the label stock used in the example below is a thermo~lastic polypropylene film which has been biaxially oriented. When using such a polypropylene film, it will generally have a density between 2 ~3 . 3 ~
about 0.17 and 1.02 grams per cubic centimeter (g/cm3). The caliper of the label stock generally will be between about 60 microns and about lS0 microns and preferably between 60 microns and 95 microns. Basis weights for the label stock will range between about 50 g/m2 and about 116 g/m2 and preferably will be from 60 g/m2 to 82 g/m2. Several examples will now follow which will further demonstrate the present invention and its attributes.
A 76 cm wide web of polypropylene film (Kimdura~ KPK-80 from Kimberly-Clark Corporation of Neenah, Wisconsin) having a caliper of 80 microns, a basis weight of 81 g/m2 and a density of 1.02 g/cm3 was extrusion coated on one side with 11.7 g/m2 low density polyethylene (LDPE). The extrusion equipment included a Hexco 8.9 cm single screen extruder with a 24 to 1 L/D (length to diameter ratio), an EDI 91 cm die and a Gloucester Engineering Company, Inc. laminator with a steel chill roll and a silicone rubber back up roll. The LDPE
(Petrothene 1014 from Quantum Chemical Corporation of Cincinnati, Ohio) had a density of 0.918 g/m3 and a melt flow index of 7.0 g/10 min. No tie coat or precorona treatment was applied to the label stock prior to coating with the LDPE.
To extrude the LDPE onto the polypropylene label stock the LDPE was heated to 316~C.
The LDPE coated polypropylene label stock was printed with a label pattern on the surface opposite the LDPE label coating by rotogravure and then die cut into label shapes.
The labels were then applied to HDPE bottles by the in-mold labeling process on a wheel type blow molding machine by Continental Plastic Containers, 2375 Touhy Avenue, Elk Grove Village, Illinois 60007.
The labeled bottles were tested for label bond strength and for moisture resistance by a freeze thaw cycle test. To determine bond strength the label panels were cut from the bottle and the panels were then cut into lS mm wide strips L s t~ 7 s using a standard sample cutter. One end of the label was then peeled back on itself approximately 15 mm. The peeled end of the label film was placed in one jaw of an Instron Universal Testing Instrument(model 1122, Instron Corporation, Canton, MA 02021) and the other end of the bottle panel, opposite the peeled end, was placed in the other jaw. The sample to be peeled was held horizontally so the jaws peeled the label film from the bottle at so from the horizontal. Settings from the Instron were as follows:
Cross head speed - 30 cm/min.
Span - 2.54 cm Scale - 2 kg full scale Chart speed - 15 cm/min.
Three test samples were run and yielded peel strengths of 250g/15 mm, 240g/15 mm and 220 g/15 mm. The average of the three tests was 237g/15 mm.
To conduct the freeze/thaw test, bottles with labels were filled with warm water at 50C and placed in a freezer at -10C for 17 hours at which time the water was frozen. The bottles were then removed from the freezer and placed in a room at 23'C and 50~ relative humidity for six hours until the water was thawed. While a large amount of water condensed on the outside of the bottles, after thawing none of the bottles lost their labels and the bond strength using the previously described 90- peel adhesion was 180 g/15 mm after thawing.
In addition to the bond strength and freeze/thaw testing, labeled bottles were also peeled by hand as would happen during actual consumer use. Labels could be cleanly peeled from the HDPE bottles leaving the LDPE adhesive on the bottles thereby making it possible to write on the labels.
Furthermore, when the labels were peeled from the bottles they did not tear or delaminate.
~ t"J
A 84 cm wide roll of KPK-80 Rimdura~ polypropylene label stock was extrusion coated with 13 microns of low density polyethylene extrusion resin (Petrothane 1014, melt flow index 7.0g/10 min., density 0.918 g/cm3) at a temperature of 316C.
No tie coat or precorona treatment was applied to the KimduraX
film befcre extrusion coating. Labels were die cut from this low density polyethylene adhesive polypropylene label film laminate. They were applied to HDPE bottles using an in-mold labeling process by Graham Container Corporation, York, PA on a wheel type blow molding machine manufactured by the same company.
A label panel was cut from one of the bottles and the bond strength tested at 579 g/ls mm by 90 peel on an Instron using a 15 mm wide strip. Instron settings were as follows:
Cross head speed - 30 cm/min.
Span - 2.54 cm Scale - 2 kg full scale Chart speed - 15 cm/min.
One bottle was filled with warm water at 47-C and frozen in a freezer at -10-C for 23 hours. It was taken from the freezer and placed in a room at 22'C and 50% RH for 24 hours.
A large amount of moisture collected on the surface of the bottle and label as it thawed. After 24 hours the bottle had warmed to room temperature and the label was still firmly attached to the bottle. The bond strength was 480 g/15 mm using the previously described 90- peel adhesion test. The label could be cleanly removed from the bottle.
Labels prepared by the Oji-Yuka Synthetic Paper Company of Tokyo, Japan from a thermoplastic polypropylene film ~Kimdura~) which was tie coated either with polyurethane or polyethyleneimine and extrusion coated with low density polyethylene w~re evaluated. The tie coat served to firmly bond the LDPE to the ~imdura~, in fact, firmly enough that the label could not be removed from the bottle without tearing and delaminating after in-mold labeling.
The present invention provides a labèl material which is extrusion coated with low density polyethylane without prior use of a tie coat or corona treatment. This provides a label material that will peel cleanly from a bottle without tearing or delaminating. It is desirable to be able to test the bond strength of the extrusion coated low density polyethylene to the label film material before in-mold labeling to determine if this bond strength is in a range which will allow it to peel cleanly from the bottle after in-mold labeling.
Consequently, Dennison Standard Paper Testing Waxes (series No. 39-330 from Dennison Manufacturing company, Framingham, Mass., using ASTM Method D2482-86T) was used to measure the bond strength of the LDPE adhesive film to the Kimdura~ label film. The Dennison waxes are a numbered series of waxes with graded adhesive powers used to test bond strength of coatings to web materials. Higher numbers indicate stronger bonding.
A 8 1/2" x 11" sheet of Kimdura0 KPK-80 extrusion coated with 11.7 g/m2 of low density polyethylene (Petro-theme 1014 from Quantum Chemical Corporation of Cincinnati, Ohio) was tested by placing waxes, which had been heated until the end was molten, firmly on the LDPE surface of the sample. Waxes having ratings of 5 through 3 were used. After cooling, the wax was pulled from the sample with a quick jerk. Bond strength was determined by finding the wax numbers between which the coated surface was not disrupted and where it became detached. In this case, the LDPE did not pick with a #5 wax and did pick with a #6 wax. For Oji-Yuka LDPE coated Kimdura~
label material, the LDPE coating did not pick with a #8 wax but did pick with a #9 wax.
Thus for a coupon application the LDPE extrusion coating should have a bond strength corresponding to a wax pick of at least a #5 wax to ensure good bonding to the bottle but a bond 2~ '?
strength below that corresponding to a #8 wax to ensure a clean peel from the bottle.
Having thus described the invention in detail it should be apparent that various modifications and changes can be made in the present invention without departing from the spirit and scope of the following claims.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A releasable label/bottle combination comprising:
a high density polyethylene (HDPE) bottle, and, a label releasably adhered to said bottle with an adhesive layer of low density polyethylene, said label having a release strength of between about 100 and about 580 grams/15 millimeters.
a high density polyethylene (HDPE) bottle, and, a label releasably adhered to said bottle with an adhesive layer of low density polyethylene, said label having a release strength of between about 100 and about 580 grams/15 millimeters.
2. The combination of claim 1 wherein said label is a thermoplastic polypropylene film.
3. The combination of claim 2 wherein the adhesion of said adhesive layer to said label is less than a Dennison wax pick of 8.
4. The combination of claim 3 wherein upon exposure of said label/bottle combination to a temperature of at least -10°C
for a period of at least 24 hours, said label will not self-release upon thawing.
for a period of at least 24 hours, said label will not self-release upon thawing.
5. The combination of claim 4 wherein said release strength of said label from said bottle is between about 150 and about 400 grams/15 millimeters.
6. The combination of claim S wherein said adhesive layer has a coating weight of approximately 9.32 g/m2 to 23.3 g/m2.
7. The combination of claim 6 wherein upon peeling said label from said bottle, the majority of said adhesive remains with said bottle.
8. A label for use in such molding processes as in-mold labeling comprising:
a piece of label stock and a layer of low density polyethylene adhered to at least one side of said label stock, said adhesive layer having a coating weight of approximately 9.32 g/m2 to 23.3 g/m2.
a piece of label stock and a layer of low density polyethylene adhered to at least one side of said label stock, said adhesive layer having a coating weight of approximately 9.32 g/m2 to 23.3 g/m2.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US58269290A | 1990-09-14 | 1990-09-14 | |
| US582,692 | 1990-09-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2044079A1 true CA2044079A1 (en) | 1992-03-15 |
Family
ID=24330136
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2044079 Abandoned CA2044079A1 (en) | 1990-09-14 | 1991-06-07 | Extrusion coated synthetic printing paper for in-mold label coupon applications |
Country Status (3)
| Country | Link |
|---|---|
| BR (1) | BR9103587A (en) |
| CA (1) | CA2044079A1 (en) |
| MX (1) | MX9100679A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6159568A (en) * | 1992-02-21 | 2000-12-12 | Avery Dennison Corporation | Peelable label |
| US6716501B2 (en) | 2002-07-18 | 2004-04-06 | Avery Dennison Corporation | Multilayered film |
| US6756095B2 (en) | 2001-01-10 | 2004-06-29 | Avery Dennison Corporation | Heat-sealable laminate |
| US6758000B2 (en) | 2001-01-10 | 2004-07-06 | Avery Dennison Corporation | Livestock security tag assembly |
| US6773653B2 (en) | 2001-10-05 | 2004-08-10 | Avery Dennison Corporation | In-mold labeling method |
-
1991
- 1991-06-07 CA CA 2044079 patent/CA2044079A1/en not_active Abandoned
- 1991-08-15 MX MX9100679A patent/MX9100679A/en unknown
- 1991-08-21 BR BR9103587A patent/BR9103587A/en unknown
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6159568A (en) * | 1992-02-21 | 2000-12-12 | Avery Dennison Corporation | Peelable label |
| US6165576A (en) * | 1992-02-21 | 2000-12-26 | Avery Dennison Corporation | Peelable label |
| US6756095B2 (en) | 2001-01-10 | 2004-06-29 | Avery Dennison Corporation | Heat-sealable laminate |
| US6758000B2 (en) | 2001-01-10 | 2004-07-06 | Avery Dennison Corporation | Livestock security tag assembly |
| US6773653B2 (en) | 2001-10-05 | 2004-08-10 | Avery Dennison Corporation | In-mold labeling method |
| US6716501B2 (en) | 2002-07-18 | 2004-04-06 | Avery Dennison Corporation | Multilayered film |
Also Published As
| Publication number | Publication date |
|---|---|
| MX9100679A (en) | 1992-05-04 |
| BR9103587A (en) | 1992-05-12 |
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| Date | Code | Title | Description |
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| FZDE | Dead |