DETAILS OF INVENTION

This invention refers to manufacturing method for medical plastic bag used for drawing, or storing, blood or for preserving physiological saline solutions.

Plastic sheeting used in the manufacture of this medical bag can be of the type manufactured by the calender method, or by Ti-Die or cylindrical die: however, sheeting manufactured by means of the calender method of the Ti-Die process require the use fo large facilities, making dust control difficult leading to the creation of many pinholes, in addition to the disadvantage of requiring reforming into bag medical bag is, therefore, generally manufactured by means of cylindrical die.

If bag is manufactured using a cylindrical die, investment can be reduced and, since the bag is preduced in cylindrical shape, no separate marufacturing process is required to make cylindrical. In addition to these advantages, the inner side of the bag is not exposed, preventing the ingress of any foreign substance, like dust. However, the bag is rendered somewhat flat due to cohesiveness of the inner part, creating difficulties in the manufacturing process, in that one end of the bag should be closed, and other end connected to a hose. Also, other potential medical problems may arise ^: e.g.bag contents may leak through pinholes created • ^* may be infected by a virus, or liquid contents may evaporate due to bag breathability, causing content properties to change.

Therefore, other types of bag have been developed, in which the bag is made of more than two layers, to close pinholes and eliminate cohesiveness of the inner layer, cr the inner surface is coated with silicone, or vertical

patterns are formed on the inner surface, to prevent the inner walls from sticking together and prevent the plasticizer migreate.

However, it was found non-worthwhile to coat the inner surface with silicone or to form vertical patterns on the inner surface : neither of which eliminated pinholes or improved the breathability problem.

This invention therefore, reters to method by which dorble-layered cylindrical sheeting, measuring 0.3-^-0.4mm in thickness and 24-^-60cm in circumference are manufactured for use as medical containers, using a cylindrical die for double-layer molding which has closed pinholes and reduced breathability to suppress evaporation of bag contents. Furthermore the inner layer of the cylindrical sheeting mads in two layers is formed through high-temperature gelling and non-migreate P.V.C compound in which if both the interior and exterior layers are formed through extrusion molding based no the temperature conditions affecting the exterior layer extrusion molding, the interior layer will have a higher extrusion molding temperature, resulting in al lesser degree of gelling. This, is trun, causes somewhat imperfect molding, creating a fine embossing on the interior surface.

Cylindrical sheeting with embossing and non-migreated plasticizer thus created prevents the interior surfaceds from sticking together, eliminating other difficulties caused by adhesion of the interior surfaces.

In order to, make the interior layer of the double-layered cylinrical sheeting of a higher get state than the exterior layer, the exterior layer can be made using a general type of resin composite which a slightly less smount of plasticizer than that used in the exterior layer is mixed in the interior layer to increase the processing temperature marginally above that of the general resin composite : or the degree of polymerization can be increased in the making of urethene rubber which is non-migreate plasticizer mixed : or, conversely, an amount of process accelerator may be mixed in the exterior

part, making the gelling temperature of the exterior layer lower than that of the interior layer.

Details of this invention, bassed on experimental results, are given in the following :

Experiment No. 1 In making interior and exterior resin composites, DOP plasticizer was added to 100 parts(weight ratio to be the same thereafter) PVC : 6 parts epoxy soybean oil 2 parts CA-ZA stabilizer and 0.3 parts wax : all having in common, the polyme ization degree 2000 : which 60 parts and 58 parts were added to the exterior layer and interior layer respectively and extrusion effected under the condition of gelled extrusion molding (tempe reture of extruding machine: 170°C, and temperature of die : 185°C), after reducing by 2 parts the amount of plasticzer mixed in the interior layer. This process resulted in the formation of a fine embossing on the inner, surface of the interior layer, while no phenomenon of the interior walls sticking together was exhibted due to this embossing.

Experiment No. 2 In making the interior and exterior resign layers, 60 parts DOP, 5 parts epoxy soybean oil, one aprt CA-ZA stabilizer and 0.2 parts wax were mixed in 100 parts PVC '• and PVC of polymerization degree 1300 was used for the exterior layer, while PVC, of polymerization degree 1700 was mixed in the interior layer, and extrusion molding was completed under the conditions of gelled extrusion molding(temperature of extruding machine : 170 ^* 0, temperature of die : 185C) for the interior layer. This process created a fine embossing on the inner surface of the inte ior layer, and this embossing prevented the interior surfacess from sticking together.

Experiment No. 3

In making the interior and exterior resin layers, 55 parts DOP, 5 parts

epoxy soybean oil, one part CA-ZA stabilizer, and 0.3 parts wax, were mixed in 100 parts (Polymerization degree 1800) PVC, and 2 parts PA (Acrylic process accelerator) was added to the exterior layer, reducing the gelling temperature of the exterior layer '. and extrusion molding of the bag was completed after setting the extrusion temperature to 170°C and die teπperature to 185°C, to satisfy the reduced gelling temperature of the exterior layer.

Experiment No. 4

In making the interior and exterior resin layers, 55 parts DOP 5 parts of epoxy soybean oil 2 parts CA-ZA stabilizer and 0.2 parts was were mixed in 100 partss PVC for the exterior resin layer, however, the DOP used for the exterior layer was replaced by 40 parts uretene rubber (non-migreate high-polymer plasticizer) to form the interior resin layer: and extrusion molding was effected under conditions of extruding machine temperature : 170 °C, and die temperature : 185°C

Approximately 40 parts of urethane rubber, which is a non-migreate high-polymer plasticizer, or a plasticizer of the ester group, is recommended for the interior resin layer, while the nytril rubber may be replaced by a urethane rubber or a plasticizer of the ester group (p-200 name of product manufactured by Asai Denga industrial Co., Ltd., 2 Jung Mok, Marino Woo-Chi, Nihon Bashi, Juo-ku, Tokyo, Japan).

It is advisable that medical bag to be manufactured according to the method of this invention has a thickness of 0.3-0.4mm and width of 12-30mm as a result of extruding the interior part with a mixture of malterials having a little higher gelling temperature, the interior part is marginally insufficiently molded, creating a fine embossing on the interior surfaces.

Because of this embossing, and the non-migreating characteristics, there is no sticking phenomenon exhibited in the interior surfaces.