JPS6136942B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for protecting plastic film containers used at liquid nitrogen temperatures as low as -196°C, and particularly for blood used to preserve blood or one of its components at low temperatures of -170°C to -196°C. This invention relates to a method for protecting plastic film containers for storage or transportation. In recent years, blood preservation in liquid nitrogen (-
Rapid freezing at 196℃ (196℃) has attracted attention, while traditional refrigerated storage (4 to 6℃, glass bottles, soft vinyl chloride containers, polypropylene containers) and slow freezing (-80 to -90℃, soft Compared to vinyl chloride containers), the blood freezing time is shorter (5 hours for the slow method vs. 2 to 3 minutes for the rapid method), the recovery rate of red blood cells is better, the quality of the collected red blood cells is better, and the storage period is significantly longer. Due to its advantages such as stretchability, the amount of blood transfusions actually used is increasing, and the demand for blood containers for rapid cryogenic storage is also increasing. However, the vinyl chloride container mentioned above is-
It is not resistant to temperatures as low as 196°C, and cracks occur even with the slightest impact, making it unusable. Stainless steel containers have been used experimentally for frozen blood, but they are difficult to seal, liquid nitrogen flows into the container and destroys red blood cells, and the container is not transparent, making it difficult to determine the condition of the stored blood. Furthermore, it has disadvantages such as being difficult and expensive to process. For this reason, bags made of highly biaxially oriented polyolefin materials and bags made of fluorine-based resins with low temperature resistance and blood suitability for the inner layer have been proposed in recent years. Because it is vulnerable to shock, it is necessary to freeze it by sandwiching it with an aluminum holder or wire mesh, and even when using fluorine resin, which is said to have good low temperature resistance, careful operation is required.
Cracks may occur in the heat-sealed part at the bottom of the bag when it is placed in a stocker filled with liquid nitrogen for storage, or the bag may break due to a strong impact at low temperatures due to uneven temperature and pressure during sealing. There is a problem when this happens. The present invention has been made in view of the above circumstances, and it is possible to prevent valuable blood from being lost due to damage to the container during the preservation operation, and to ensure stability without interfering with normal rapid freezing operations. This is what I gained in my pursuit of being able to do the work. Furthermore, in the pursuit of materials that do not lose their flexibility or strength even at temperatures as low as -196°C, the present invention has developed fabrics that have a cloth or net shape, as well as highly stretched fibers. The inventors have discovered that the present invention has a strength at low temperatures that is not found in continuous bodies such as films and plates made of the same material, and does not break when subjected to bending or impact. be. That is, the present invention provides a method for storing a substance in a packaging bag made of a thermoplastic synthetic resin having low-temperature resistance in liquid nitrogen. This is a method for protecting a packaging bag for low temperature freezing, which is characterized by protecting it with a cloth-like or net-like protective sheet. First, the thermoplastic synthetic resin packaging bag to be protected may have an inner layer of, for example, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, chlorinated trifluoroethylene resin, or ethylene-tetrafluoroethylene trifluoride copolymer. These include single-layer or multi-layer film packaging bags having a certain low temperature resistance and having one kind of ethylene copolymer. Since this method freezes and preserves the target blood or a component of the blood, it is hygienic and compatible with blood.
And complete sealing is possible by heat fusion,
It is also required to maintain a certain level of flexibility and strength even in liquid nitrogen at -196°C, and the above resin satisfies these requirements. The packaging bag may be a single layer, but it is usually required to be as thin as possible in terms of heat conduction, and consideration must be given to strength, and in addition, other strong heat-resistant synthetic resins are used to ensure stability of heat sealing. Used by laminating with film. As shown in FIG. 1, the bag is heat-sealed with the above-mentioned resin inside, and a spout member for injection and dispensing is attached to form a blood storage bag. Next, the packaging bags obtained in this way are made of chemical fibers, natural fibers, synthetic resin tapes stretched and strengthened in a uniaxial direction, cords (thin wires), split fibers, and are made of cloth or net-like materials through which liquid nitrogen can freely pass. The sheet covers the entire or part of the packaging bag, including the entire lower part of the fused portion at the end of the packaging bag, in such a way that the sheet protrudes outside the end of the bag body. The chemical fibers constituting the cloth-like or net-like sheet mentioned here include recycled fibers such as rayon, semi-synthetic fibers such as acetate, synthetic fibers such as nylon, vinylon, acrylic, inorganic fibers such as glass fiber, and natural fibers. These include vegetable fibers such as cotton and hemp, animal fibers such as wool and silk, and asbestos-mineral fibers. Further, the cloth-like or net-like sheet may be composed of a tape or split fibers formed by uniaxially stretching a thermoplastic resin such as polyethylene or polypropylene, or a cord. These cloth-like and net-like sheets are required to have appropriate opening properties so that liquid nitrogen can pass through freely and the rate of freezing of blood is not delayed, and so that they can absorb shocks applied to the packaging bag at low temperatures. Blood needs to be frozen evenly in a short time of 2 to 3 minutes, and the packaging bag is flat and placed vertically in liquid nitrogen to prevent heat conduction from decreasing due to the gases contained in the blood. The stress and impact are concentrated at the bottom of the packaging bag. For this reason, the protective sheet referred to in the present invention is rarely used, and the entire or part of the packaging bag, including the entire lower part of the fused portion at the end of the co-packaging bag, is formed so that the protective sheet protrudes outside the end of the packaging bag. The coating prevents the packaging bag from directly touching the walls of the freezing tank or storage tank during freezing and storage. This, combined with the low-temperature resistance that the packaging originally had, makes it less susceptible to cracks and cracks caused by impact.
There is no damage and blood freezing can be performed easily. Furthermore, the methods of covering the packaging bag with a protective sheet include placing the packaging bag into a bag with a protective sheet that has been sewn before use, and joining the protective sheets together on the outside of the packaging bag, or wrapping the bag during use. Sandwich the bag with a protective sheet as shown in Figure 2 and cover it so that it is fixed at points around the periphery of the packaging bag, and even though the protective sheet is in close contact with the surface of the packaging bag, it is not fixed at all. or partially fixed to a part of the periphery. This is to ensure that the protective sheet receives as much of the applied impact as possible, and to prevent the fibers or stretched plastic from losing their flexibility and elasticity due to being fixed. In addition, blood storage packaging bags must be autoclaved for 20 minutes at 121°C or 200°C before use.
-Due to 30 minutes of dry heat sterilization, some fibers and stretched plastics may melt, lose their elasticity and strength, and lose their low-temperature resistance. For this reason, the packaging bag must be covered with a protective sheet after sterilization and immediately before normal use. As described above, the protection method according to the present invention can be used with cloth made of almost any type of fiber or mesh made of stretched polyolefin, and is easy to operate because the bag body is simply covered with cloth or mesh. It has great advantages such as greatly reducing damage to packaging bags at low temperatures. Also, since the cloth/mesh has coarse mesh, it is possible to see through the inner bag, and a window can be added if necessary. Examples will be described below. Example 1 One side is corona discharge treated and further coated with 3 g/m ² of polyester isocyanate adhesive.
A 0.05mm ethylene-tetrafluoroethylene copolymer film and a 0.05mm-thick crosslinked polyethylene resin film are bonded together to form a two-layer film, and an injection and pouring spout member is attached to the ethylene-tetrafluoroethylene copolymer film. A copolymer film was placed on the inner surface and heat sealed to obtain a blood storage bag (containing 400 c.c.). This is then folded in half with a net-like non-woven fabric made of split fibers of high-density polyethylene film that has been stretched and reinforced, and then machine-sewn to cover the lower part, and the upper part is joined with a polyethylene fastener to create an adhesive composite. Ta. (Figure 3) Fill this composite bag with water:glycerin = 1:1, heat seal the opening, and place it vertically into a liquid nitrogen bath according to the usual blood cryopreservation procedure, and freeze for 3 minutes. Immediately after it had cooled, it was drawn out and placed in a stocker filled with liquid nitrogen. The same operation was performed on both the bags protected by the present invention and the packaging bags alone, but about 20% of the bags not protected by the present invention had cracks in the lower seal, and 4% of the bags had cracks. When the bags were torn and thawed, the contents leaked out, but in the present invention, cracks occurred in the seals of 2% of the bags, but no leakage of the contents occurred. Further, no damage occurred to the protective sheet. Example 2 One side is corona discharge treated and further coated with 3 g/m ² of polyester isocyanate adhesive.
A 0.05 mm chloride trifluoride ethylene resin film and a 0.025 mm thick biaxially stretched polyethylene terephthalate film are bonded together to form a two-layer film.
An injection and dispensing opening member was attached to this, and an ethylene chloride trifluoride film was placed on the inner surface and heat sealed to obtain a blood storage bag (400 c.c.). Next, fabric (rayon) 70g/m ² glass cloth (surface coated with polytetrafluoroethylene)
Extruded stretched PE net 40g/ ^m2 Cotton cloth 80g/m
A protective sheet bag was made by sewing 35 g/m ² of m ² nylon net with the ears exposed using a sewing machine. Water in the above blood storage packaging bag: Glycerin =
Fill with 1:1 liquid, heat seal the mouth, put it into a protective sheet bag from the bottom side, and point suture the top of the protective sheet with nylon thread. A similar operation was performed. The results are shown below.

[Table] As described above, the specimens protected according to the present invention exhibited much better low-temperature resistance than the specimens that were not protected.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a plan view of a packaging bag, FIG. 2 is a perspective view of a protective sheet, and FIG. 3 is a plan view of the packaging bag protected by the protective sheet. 1... Packaging bag, 2... Seal part, 3... Mouth part,
4...protective sheet, 5...perforation, 6...fastener.

Claims (1)

[Scope of Claims] 1. When a substance is placed in a packaging bag and stored in liquid nitrogen, the packaging bag is made of synthetic fiber, natural fiber, uniaxially stretched plastic tape, cord, or cloth or net-like material made of split fibers. A method for protecting a packaging bag for low temperature freezing, characterized by protecting it with a protective sheet. 2. The protection method according to item 1 above, characterized in that at least the entire lower part of the packaging bag is covered with a protective sheet. 3. A single layer or a single layer having as an inner layer one of the following resins: ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, chlorotrifluoroethylene resin, or ethylene-chlorotrifluoroethylene copolymer 3. The protection method according to item 1 or 2, characterized in that a multilayer plastic film packaging bag is used. 4. The protection method according to any one of items 1 to 3 above, characterized in that the method is coated immediately before dropping into liquid nitrogen.