CA1128004A

CA1128004A - Peelable seal

Info

Publication number: CA1128004A
Application number: CA310,386A
Authority: CA
Inventors: William E.R. Watt; John R. Herb
Original assignee: Pharmachem Corp
Current assignee: Pharmachem Corp
Priority date: 1977-09-02
Filing date: 1978-08-31
Publication date: 1982-07-20
Also published as: GB2003449A; GB2003449B; FR2401847A1; SE432561B; NL7808006A; SE7809238L; DE2837505A1

Abstract

Abstract of the Disclosure Containers for storing food, medicaments, blood and the like having a peelable and/or burstable seal formed by sealing together an oxidized surface of a polyolefin film.

Description

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This invention relates to a peelable seal for use in connection with containers including containers for storin~ blood platelets and to a process for producing the same.

It is well known in the art to utilize plastic bag containers in packaging because of their low cost and ease in manufacture. The plastic bag containers hav~ found their use in packaging frozen foods, tobacco, hardware, medicaments, blood components, articles of manufacture, as boilable cooking bags, and the like. At the present time, various methods are utilized to seal the container either at a time prior to filling so as to maintain its integrity or after filling with the desired product. The sealing of the container takes place by various methods such as weld sealing with heat and/or pressure, utilizing various adhesives, etc. Such sealing of the container provides a disadvantage in that separation without tearing or particle formation is difficult and re-sealing when necessary is not possible in all cases without additional equipment or sealing components. There are many applications wherein a peelable seal on the container is mo~t advantageous. Until now, only polyvinyl chloride film could be utilized to form a container having a peelable seal. The utilization of the polyvinyl chloride film has been found to be disadvantageous wherein human consumption or medical use of the product takes place due to the fact that there is a leaching out of certain chemicals from the film which are harmful when consumed by humans. Additionally, polyvinyl chloride has the disadvantage of requiring additional ingredients to form the seal or when opened leaves a residue about the peeled area which can cause contamination.
It is known to produce a peelable seal on containers formed from plastic material by applying only a slight pressure during heat sealing. However, such prior art methods require precision and

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controlled heat sealing operations which prevent the commercial-ization of the method. Furthermore, such sealing is inconsistent and not reliable.
Although various methods have been made to provide a flexible plastic container with a peelable seal utilizing an inert plastic substance,none have resulted in a container which can be utilized both at a low temperature and a high temperature range.
According to the present invention, an oxidized polyolefin film is utilized in the formation of containers so as to render the container with a peelable seal. More particularly, the present invention relates to the treatment of a polyolefin film which in itself forms a container or where tlle polyolefin is utilized in combination with other materials such as other plastics or metal.
~ dditionally, according to the present invention there is provided a blood component storage bag in the form of a container having a peelable seal formed from a polyolefin having at least one surface oxidized so as to be peelably sealed. Preferably, each port of the container is provided wlth a peelable seal tab forming a protective closure. Also, at least one of the ports is provided with a burstable seal below the port.
The term "burstable seal" refers to a low strength peelable seal which can be broken by the application of fluid pressure.
In a blood storage bag the burstable seal is preferably of a strength wherein the squeezing of the bag with liquid and/or entrapped air provides sufficient pressure to open or break the seal.
It has now been found that polyolefin can be made to form a peelable seal if at least one surface is oxidized by either an application of an open flame which is an oxidizing flame, such as a propane flame, or corona discharge under the conditions disclosed by R.M. Sonkin in "Corona-Discharge Treatment of Polyolefin Films", ~ ~ ~ 8Q~ ~

Plastics Engineering, Feb. 1977, pages 50-52 prior to heat sealing. Tl~e oxidized surface results in an interface which resists fusion of the film during heat sealing. It is understood that the term "heat sealing" as used herein refers to the technique of sealing by the heat and pressure together.
With reference to the drawings:
Fig. 1 is a diagrammatic representation of a process for pro-ducing a container with a peelable seal according to the present invention;
Fig. 2 illustrates a polyolefin bag containing a peelable seal on one side;
Fig. 3 illustrates a polyolefin bag containing several peelable portions of different strength;
Fig. 4 illustrates the application of the present invention to a container formed in combination with other materials;
Fig. 5 illustrates the application of the present invention to a dispensing container for medicaments;
Fig. 6 illustrates the application of the present.invention to one form of a blood storage bag;
Fig. 7 is a face view of one specific form of platelet storage bag according to the present invention;
Fig. 8 is a similar view of a still further form of platelet storage bag according to the present invention having a modified form of peelable seal and burstable seal;
Fig. 9 is a simllar view of another form of platelet storage bag according to the present invention, and Fig. 10 is a similar view of still another form of platelet storage bag according to the present invention.
Description of the Preferred Embodiments Fig. 1 illustrates one method of forming flexible containers witn peelable seals in accordance with the present invention.

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Polyolefin film is fed from supply rolls 10, 10' and is oxidized on a surface being subjected to corona discharge by lamps 12, 12'.
The treated films are then passed through rolls 14, 14' and into a platen press 16 wherein the sealing occurs utilizing selected temperatures and pressures which depend upon the particular density of the polyolefin utilized and ~he permanency of the seal. The individual containers are then cut from the rolls by means of a cutter 18.
In lieu of corona treatment, the surfaces of the polyolefin film may be oxidized utilizing an open flame. Typically, the treated polyolefin film has a surface energy of 30 - 50 dynes/cm.
The sealing pressure by the platen press is generally 500 - 1500 lbs. per square inch of sealing area and at a temperature of about 200 - 500F. Besides the use of a platen press, forming rolls may be utilized in the conventional method of producing plastic con-tai.ners. Also, it has been found to be advantageous to form the polyethylene containers utilizing impulse sealing techniques.
It can be readily seen that the treated polyolefin can be utilized to form containers having a wide variety of uses. As shown in Fig. 2, a polypropylene bag 30 i8 formed wherein there is a permanent seal 32 along the edge of three sides only with the remaining portion having a peelable seal 36 so that upon tlle application of a force by means of free end flaps or tabs 33, 38', the peelable seal 36 is peeled apart so as to form an access into the container. Such a container is suitable for use when the container's integrity is to be maintained prior to filling with an article such as food.
In Fig. 3 there is shown a polyethylene container 40 which is provided with a plurality of compartments 44a, 44b, 44c that are formed by means of seals 46a, 46b, 46c, 46d. Each of the seals 46a, 46b, 46c, 46d have a different peel strength. There is ~ 1 2 ~

further provided free ends 48, 48' which serve as gripping means for peeling apart the seal 46a. Container 40 is especially adaptable for utilization as a mixing bag wherein the contents of the container are to be kept separated and mixed only prior to use, such as in the case with epoxy cements.
Fig. 4 shows the utiliæation of a peelable seal 56 in connection with a metallic can 50 having a metallic body portion 52 and a treated polyethylene lid 54.
Fig. 5 illustrates the adaptability of the peelable seal 61 for use in packaging such articles as medicaments 62 wherein individual compartments are formed in the container 60 so as to permit easy access when required by peeling the edges of each com-partment by the application of a peeling force with free end tabs 63, 63'. The compartments may be formed by the selective heat sealing of two films or alternately, by heat sealing a plurality of films over a single film.
Fig. 6 shows a steriliza~le, flexible oxidized polyethylene bag 70 with holes 71 for hanging the bag either in an upright or in an inverted position. Bag 70 also includes a first hollow outward protrusion 77, welded onto said bag, a second hollow outward pro-trusion 78 such as for use in introducin~ plasma into t~.le bag, and a third hollow protrusion 79, such as for introducing platelets into the bag, formed at the upper periphery of the bag. Alon~ the per-iphery of the bag is provided a weld seal 74. Further, each of the protrusions 77, 78 and 79 are provided witll a protective closure which forms a bag and is provided with tabs 73, 73'. Each of the bag portions over the protrusions is formed by means of a weld seal 74 at its base and by a peelable seal between the base portion and the tab or free end portions 73, 73'. The tab portions 73, 73' serve as a gripping means for opening the peelable seal.
It has been further found to be advantageous to provide a l~Z~Qq~

peelable seal in a platelet bag close to the plasma inlet 78 and platelet inlet 79 as illustrated by 76a, 76a' and 76b, 76b'.
By providing the seal close to the tubes 78 and 79, there is created an air pressure which prevents the occurrence of a capillary action if only one of the inlets 78 or 79 is utilized.
Optionally, after utilization, the bag may be resealed below the inlets. Also, to prevent flow of material into tuba 77, a punctur-able membrane 80 is provided.
Fig. 7 shows a sterilizable, flexible, oxidized polyethylene bag selected for illustration herein comprises a pair of poly-ethylene sheets 113, 113' and is optionally provided with corner holes 111 for hanging the bag either in an upright or in an invert-ed position. The confines of the bag 110 are defined by weld seal 114, which seals the sheets 113, 113' together. Bag 110 as shown also includes a hollow delivery tube 118, such as for use in evacuating the bag, inlet tube 119, such as for use in introducing plasma into the bag, and another similar inlet tube 117, such as for introducing platelets into the bag. The tubes 117J 118 and 119 can be used lnterchangeably.
Further, each of the tubes 117, 118 and 119 is provided with a protective closure which forms a bag 117a, 118a and ll9a, respectively, over each of the tubes. Each of the bag portions 117a, 118a and ll9a over the tubes is formed by means of a weld seal at its base and by a peelable seal116 between the base portion and the tab or free ènd portions of the sheets 113, 113'. The tab or free end portions of the sheets 113, 113' serve as gripping means for opening the peelable seal.
The tear strength of the seal is dependent upon many factors, including the density of the polyethylene film, the temperature ~1280~4 and pressures applied, etc. The surface treatment of the poly-ethylene with corona discharge has been found to be effective by producing a surface energy of about 30-50 dynes/cm.
It has been found to be desirable to include a burstable seal 120 below the evacuation port 118. The seal 120 bridges diagonally across below the port 118 to prevent backflow into the port after the bag has been filled. I~hen the bag is ready for evacuation, the bag is squeezed sufficiently to cause the internal pressure of either the trapped air and/or liquid to break the low strength seal and permit the contents of the bag to flow out through the port.
It has been further found to be advantageous to provide additional peelable seals in protective closures 118a and ll9a, one positioned close to the plasma inlet 118 and the other close to the platelet inlet 119, as illustrated in Fig. 7 by the members 116a, 116a' and 116b'. By positioning the seals close to the tubes 11~ and 119, an air pocket is created within the protective closures 118a and ll9a which prevents the unwanted flow of fluid by capillary action when only one of the inlets 118 or.119 is being utilized. Alternatively, after filling, the bag may be resealed below the inlets 11~, 119 to prevent any back-flow.
Optionally, the weld seal 114 at the lower portion of the bag 110 may be extended beyond the periphery of the bag so as to include portions 114a which provide supporting strength about the area of the lower holes 111.
Tube 117 may be provided Witil a puncturable membrane 122 to prevent back-flow of material into the tube. However, the use of a burstable seal has been found to be preferable to prevent back-flow since inadvertent punctures are avoided.
Slits 123, 124 are provided so as to permit independent opening of the protective enclosures.

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The free end portions 113, 113' of the s'neets serve as a gripping means for the medical technician so as to break the seal of each of the enclosures 117a, 118a, 119a, and permit access to tile tubes 117, 118, 119 as required.
The tubes 117, 118, 119 may also include a ridge or spherical enlargement on its outer diameter so as to provide a convenient and simple means for adapting the bag to any of a variety of blood storage applic&tions, including the storage of various blood com-ponents and the freeze storage of red blood cells.
Fig. 8 illustrates a further embodiment of the present invention wherein there i9 shown a platelet freezing bag having a bag portion 132 that is formed by folding an oxidized polyethylene film and appropriately sealing in the desired manner. The bag 132 contains at its upper periphery an evacuation tube 142 about one upper corner with a burstable seal 128 bridging diagonally across below the tube 142. Inlet tubes 140 and 141 are formed about the other upper corner with a burstable seal 128' bridging diagonally across below tube 140. Each of the tubes 140, 141 and 142 is covered by a protect-ive enclosure 140a, 141a, 142a, respectlvely, which is ~ormed by the selective formation of peelable seals 136, 138 and 139 as shown in the drawing together with the weld seal 133 at the upper portion of the bag 132. The seals 135, 136, 138 and ].39 are then selectively slit so as to form individual enclosures 140a, 141a, 142a for each of the tubes 140, 141 and 142. By forming a selective pattern of a peelable seal and selectively slitting the bag there is formed an individual protective enclosure for each of the openings into the bag. Thus, tubes 140, 141 and 142 are provided with a protective closure by means of the weld seal 133 at their base and peelable seal portions 135, 138 and 139 that are made into individual units by slits 136', 138' and 139'. Slits 136' and ~ Q~ ~

138' are placed into the seal portion such as to result in the formation on an individual pocket 137 havin~ a peelable seal portion 136 that is suitable for holding a label. If desired, the bag may be provided with holes 137a for placing the bag on a holding rack. Each of the enclosures 140a, 141a, 142a, is pro-vided with tab portions 143, 143' which serves as a gripping means for opening the peelable seal. It has been found to be further advantageous to have one tab portion 143 shorter than the other tab portion and to form the peelable seal into a configuration having a narrow portion or point as shown so as to faciliate gripping of the tabs and opening of the peelable seal.
Fig. 9 illustrates a furtl~er embodiment of the present in-vention wherein there is shown a platelet freezing bag 140 with a weld seal 141 along its periphery of the bag which joins oxidized polyethylene sheets 142, 142' into bag form. Formed on the upper portion of the bag 140 is a platelet inlet tube 143 with a burst-able seal 143' along its lower portion, plasma inlet tube 144 with a burstable seal 144' at its lower portion, and an evacuation tube 145 with a burstable seal 148 along its lower portion. A peelable seal 146 ls provided above and along the sides of the tubes 143, 144, 145 so as to form protective enclosures 143a, 144a, 145a together with the weld seal 141 at the upper portion of the bag 140 around eacll of the tubes 143, 144, 145. Slits 147 separate each of the protective enclosures from one another and the seal 146 has a pointed config~lration so that the medical technician is able to easily utilize either tube 143, 144, 145 without disrupting the integrity of the other ports. Also, each of the burstable seals 143', 144' and 148 seal below the tubes to protect the integrity of the bag and to prevent flow into the unused tube after the bag has been filled. The seals 143', 144' and 148 are made low strength 2 8~ ~ ~

so as to permit breaking of the seal by squeezing the bag with its contents and air acting as the breaking force. Each of the seals 143', 144' and 148 may be of variable strengths so that one seal could be broken without disrupting the other seals.
As seen in Fig. 10, a platelet freezing bag having a bag portion 152 is formed by folding an oxidized polyethylene film and appropriately sealing in the desired manner. The bag 152 contains at its upper periphery a tube 153 for use in evacuating the bag after filling, and a pair of tubes 154 and 155 for use as inlets.
Eacll of the tubes 153, 154 and 155 is covered by a protective enclosure 153', 154' and 155' which is created by the selective formation of a peelable seal 156 as shown in the drawing. If desired, the peelable seal between eac'n tube 153, 154, 155 is slit along point 161a, 161b, 161c so as to form individual enclosures having the individual gripping means 162, 162' formed from the free end portions of the sheet. Thus, tube 153 is provided with a pro-tective closure by means of the weld seal 157 at its base and the peel-able seal portion 156 that i8 separated from the enclosure 154' by means of a slit 161b. The tube 154 is provided with a protective closure 154' by means of the weld seal at its base 157 and the peelable seal 156 that i9 slit at 161a and 161b. ~ pocket 158 may be formed that i9 suitable for holding identification means by including additional weld seals 158a and 158b in the free end portion as shown in the drawing. Also, seals 157a, 157b may be provided, bridging diagonally across below the tubes 154 and 155 to prevent back-flow after the bag has been filled. Seals 157a and 157b may be either burstable, peelable or weld seals depending upon further use of the tubes 154, 155. A burstable seal 153a encloses the bottom of tube 153 to protect the integrity of the tube until used.
The ports may also include a ridge or spherical enlargement on its outer diameter so as to provide a convenient and simple means for adapting the bag to any of a variety of blood storage appli-cations, including the storage of various blood components and the freeze storage of red blood cells.
It is understood that the present invention may be utilized in connection with other blood pack systems such as in the collect-ion, preparation, storage or administration of whole blood or blood components.
It is further understood that the term "weld seal" as used herein refers to ei~her a peelable seal of high strength or a permanent seal.

Claims

CLAIMS:
WE CLAIM:

1. In a process for forming a peelable seal with at least two extruded polyolefin film members by the simultaneous application of controlled heat and pressure to said film members at the portion to be sealed, the improve-ment which comprises oxidizing by corona discharge treatment at least one surface of at least one of the polyolefin film members at the portion to be sealed so as to modify by oxidation the structure of the surface crystals formed by extrusion and then simultaneously applying controlled heat and pressure to soften the modified cyrstals at the contacting surface to partially fuse the crystals at the contacting surface while maintaining the integrity of the crystals so that the modified crystals form an interface between the polyolefin film members at the seal portion and a peelable seal is thereby formed.

2. A process according to Claim 1 wherein at least two polyolefin film members having a surface oxidized by corona discharge treatment are sealed together so that the oxidized surface of each film member forms the interface therebetween.

3. The process according to Claim 1 wherein said polyolefin film members are peelably sealed across the opening of a container.

4. The process according to Claim 1 wherein a portion of said oxidized polyolefin film members are heat sealed to form a peelable seal and another portion of said oxidized polyolefin film members are heat sealed to said surface so as to form a weld seal.

5. The process according to Claim 1, wherein the treated polyolefin film members are subjected to pressure between 500-1500 psi of sealing area and sealing is conducted at a temperature of about 200-500°F.

6. The process according to Claim 1, wherein said treated polyolefin film members are heat sealed at selective portions so as to form compartments.

7. A peelable seal which is formed with at least two extruded polyolefin film members by the simultaneous application of controlled heat and pressure to said film members at the portion to be sealed, wherein at least one surface of at least one of the polyolefin film members at the portion to be sealed is oxidized by treatment with corona discharge so that the surface crystals formed by extrusion are modified whereby the simultaneously applying of controlled heat and pressure softens the modified crystals at the contacting surface to partially fuse the crystals at the contacting surface while maintaining the integrity of the crystals, and the modified crystals form an interface between the polyolefin film members at the seal portion.

8. The peelable seal according to Claim 7, wherein said treated polyolefin film members are subjected to pressure of about 500-1500 psi of sealing area and sealing is conducted at a temperature of about 200-500°F.

9. The peelable seal according to Claim 7 wherein said polyolefin is polyethylene.

10. The peelable seal according to Claim 7 wherein said polyolefin film members are sealed across the opening of a container.

11. A flexible container comprising a polyolefin film and a peelable seal according to Claim 7 said container having a substantial portion of its periphery weld sealed.

12. A sterilizable, closed container including an inlet at the top thereof forming a part of said closed container, said inlet being composed of a peelable seal according to Claim 7.

13. A packaging unit comprising polyolefin films having an oxidized surface sealed together at selective portions of said films so as to form compartments, the seal portions comprising a peelable seal according to Claim 7 so as to remove an article within a single compartment.