Field of the Invention

The present invention relates to an insert for reinforcement of plastic bags, an improved three-dimensional plastic bag and production thereof. The improvement comprises a plastic insert that reduces the risk of fatigue due to handling or packaging of plastic bags. The plastic bag may be used for any purpose but a preferred use is within the bioprocessing industry or hospitals where plastic bags are used as disposable containers.

Background of the Invention

The bioprocessing industry has traditionally used stainless steel systems and piping in manufacturing processes for fermentation and cell culture. These devices are designed to be steam sterilized and reused. Cleaning and sterilization are however costly labor-intensive operations. Moreover, the installed cost of these traditional systems with the requisite piping and utilities is often prohibitive. Furthermore, these systems are typically designed for a specific process, and cannot be easily reconfigured for new applications. These limitations have led to adoption of a new approach over the last ten years - that of using plastic, single-use disposable bags and tubing, to replace the usual stainless steel tanks.

In particular bioreactors, traditionally made of stainless steel, have been replaced in many applications by disposable bags which are rocked or stirred to provide the necessary aeration and mixing necessary for cell culture. These single-use bags are typically sterile and eliminate the costly and time-consuming steps of cleaning and sterilization. The bags are designed to maintain a sterile environment during operation thereby minimizing the risk of contamination.

Bags containing sterile fluids are used in the bioprocessing industry for formulation, storage, transfer, processing, and transportation. Sterile conditions must be maintained during these operations, and the bags are usually sealed to prevent contamination. Commonly used bags are of the "pillow style," mainly because these can be manufactured at low cost by seaming together two flexible sheets of plastic. Thus, the most conventional bags are two-dimensional.

In many applications, the components contained in a bag must be mixed before use. For example, a product may be formulated from the blending of a dry powder into a fluid. In other situations, the product contained in a bag may separate during transport or storage, and require mixing before use. The mixing situation puts extra demands on the bag in relation to strength.

In the corners of conventional three-dimensional plastic bags, three films meet and are joined together, usually by heat-sealing. Every corner of a three dimensional bag has a risk of leak due to two reasons: improper seal process and fatigue of the heat-sealed area. The root cause is lack of material at the spot where three films are sealed together.

Therefore, there is a need for an improved three-dimensional plastic bag which resists fatigue (and leakage) during handling and packaging and is easy to produce.

Summary of the Invention

According to the present invention a plastic part or insert is used that can reinforce the sealing area between the films of a plastic bag to mitigate the risk of fatigue due to handling or packaging.

In a first aspect, the invention relates to an insert for reinforcement of bags made of plastic film, comprising a star-like plastic part having at least three jaws, wherein the insert is adapted to be arranged at a junction of a three-dimensional bag where at least three plastic films meet, so that each jaw extends in a direction between two films. The insert may for example be heat-sealed or glued at the junction.

The radius between the jaws shall preferably not be smaller than the minimum allowable bending radius of the film. The insert may be one, two or three-dimensional.

In one embodiment, the insert comprises three jaws. In this embodiment one insert is used for each three-way junction of the films of a plastic bag. Thus, in this embodiment, the plastic part looks like a star with three jaws. This part reinforces the junction where at least the three films meet and is heat-sealed or glued to the respective films along its jaws.

In another embodiment, the insert comprises four jaws. In this embodiment one and the same insert is used for a four- way junction of the films of a plastic bag. This embodiment can also be seen as two integrated three jaws-inserts. This embodiment has a variable center portion to fit to any desired bag size. Thus, the insert may comprise a center portion which is variable in length to be adopted to various bag designs. Optionally, the center portion of the insert is provided with ports.

In a second aspect, the invention provides a three dimensional bag made of plastic film comprising reinforcement inserts in each junction where at least three plastic films are joined, wherein the reinforcement inserts each comprise a star-like plastic part having at least three jaws, wherein the insert is adapted for insertion and sealing at a junction of the three-dimensional bag where at least three plastic films meet, so that each jaw extends in a direction between two films. The reinforcement inserts may be part of the plastic films before they are heat-sealed together or the parts may be added to a ready made plastic bag.

The bag may comprise an adhesive material between the films in the case the films are not compatible (sealable directly to) with each other.

In a third aspect, the invention provides a method of producing a three-dimensional bag made of plastic films, comprising sealing of the plastic films along their edges to form a three- dimensional bag, and re-enforcing the inner film junctions where at least three plastic films meet with a star-like plastic insert having at least three jaws, so that each jaw extends in the direction between two films.

Brief Description of the Drawings

Figure 1 A is a schematic cross-sectional view of a plastic insert according to the invention having three jaws.

Figure IB is a schematic cross-sectional view of a plastic insert according to the invention having four jaws.

Figure 2A is a schematic view of the film junctions of four films suitable to be used together with the plastic insert according to Figure 1 A.

Figure 2B is a schematic view of the film junctions of four films suitable to be used together with the plastic insert according to Figure IB.

Figure 3 A is a schematic detail view of the film edges of a plastic bag provided with two plastic inserts of the invention.

Figure 3B is a schematic view of a three dimensional plastic bag incorporating the detail from Figure 3 A.

Detailed Description of the Invention

The corner of a three dimensional bag has a risk of leak due to two reasons: improper seal process and fatigue of the heat-sealed area. The root cause is lack of material and stiffness resulting in bending at a radius that is smaller than the minimum allowable bending radius of the film at the spot where the three films are sealed together.

With reference to Fig. 1A, the invention provides a plastic insert 1, provided with three jaws 2 with jaw tips 3, and a center body 4. The jaw tips may or may not be of the same material as the rest of the plastic insert.

According to the invention a plastic part or insert (Figure 1A-1B) is used that can reinforce the junctions between the films to mitigate the risk of fatigue due to handling or packaging of plastic bags. The plastic part/insert may have the appearance like a star with three jaws (Figure 1A). This part fills the junction where the three films meet together and is heat- sealed to the films along its jaws (Figure 2A). The critical dimension of the plastic insert is the radius between the three jaws. Because the objective is to reduce the risk of fatigue due to bending, the radius shall not be smaller than the minimum allowable bending radius of the film. In the example shown in the drawings (Figure 1A-1B), the minimal allowable bending radius is 1/32" (0.8 mm). The minimum bending radius is specific to the film material. The criteria to determine the minimum bending radius is not to create any crease or kink of the film. In the examples, the film used is Solmed Infuflex 9101. The film has three major layers, PE (polyethylene) on the outside and EVOH (ethylene vinyl alcohol) in the middle. Tie layers are used to bond the layers together. For other films, the minimum bending radius could be different.

The plastic insert may also be designed as a single piece with four jaws (Figure IB) that can be provided in the area where all the four films meet (Figure 2B). In this case the center body 4 may be of variable length. The center body or bridging jaw may be of the same or different material as the rest of the insert. The center body 4 may be provided with ports (not shown). This design according to Fig IB only requires one step of heat seal for the sealing of four films to each other.

In alternative embodiments, functionality may be added to the plastic insert. For example, the molded part may include a handle that can be used to maneuver the bag into position within a drum or tank. Another possibility is the addition of one or more ports through the center of the part, making it somewhat analogous to a boat fitment with thin wings of plastic that would serve the originally described function of aiding in the three-film sealing process.

Figure 3A-3B shows where the plastic inserts of the invention are positioned. Figure 3A is an enlarged view of two three-jaws inserts, and Figure 3B shows where these inserts are positioned in a plastic bag. The two three-jaws inserts may be replaced by one four-jaws insert with an extended center portion.

In the embodiments of the invention, the inserts may be made of the same material as the plastic films. In other embodiments the inserts may be of the same material as the adhesive material on the sealing surface of laminate films. Best sealing effect is achieved when identical material are melted onto each other. Examples of plastic are polyolefms (polyethylene, polypropylene, ethylene vinyl acetate copolymers etc), PVC, perfluorinated polymers (e.g. FEP, ECTFE etc), thermoplastic elastomers and laminate where these polymers are present in a surface layer.

It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.