FIELDOF INVENTION:
This invention relates to the development of Polyvinyl chloride based containers plasticised using di-(isononyl)-cyclohexane 1,2 dicarboxylate, which are nontoxic and have extremely lpw leachability characteristics which are suitable for the collection and storage of bloocfand blood components and more particularly suited for the collection and storage of platelet rich plasma and platelet concentrates.
PRIOR ART
Plasticised PVC bags have a number of advantages over glass containers. Not only are they easier to handle and store, but also safer. A very significant advantage is that contact with outside air is not necessary during the collection of blood and during transfusion which ensures the sterility of blood. Another important advantage is that soft PVC blood bags can be pressed together by hand for rapid infusion of blood which is necessary in certain emergencies.Yet another advantage is that blood can be separated into various fractions by centrifuging and transferred to different bags in a multiple bag system without opening the system, thus preserving the sterility and integrity of blood.
Blood transfusion became safe, dependable and convenient as a result of certain important developments - the landmark discovery of blood groups by Prof. Carl Landsteiner (1900), the safety and effectiveness of citrate for intravenous administration by Hustin (1914) crossmatching between the donors and patients to exclude incompatibility by Hekt0en(i907) and the development of the anticoagulant solution ACD by Loutit and Mollison (1943). Modern blood banking, however, was initiated with the pioneering work of development of PVC Bags for blood collection and storage started by Prof. Carl .W.Walter of Harvard Medical school in 1947. He had to face several problems in developing his design to a commercial product. After extensive trials conducted in the USA, he finally got permission to manufacture this item in 1962.
Plasticised PVC containers possess a number of advantages which makes it the material of choice for medical and more particularly for blood contact applications. Its more important features are:- ability to be welded together by high frequency
jt * which enables the production of leak free products and offers infinite design possibilities, steam sterilisability even at i2i°C, favourable cost/ performance ratio and low bulk density offering low storage and distribution costs. The plasticisers used in the compounding of PVCare mainly responsible for buildinginthedesirable characteristics for medical applications such as low toxicity, transparency,
flexibility, strength, elongation, stability at low and high temperatures, permeability ^
to water, oxygen andcarbondioxide in the desired range. While a wide range of plasticisers are available for food contact &nd medical applications, the choice for blood contact applications is very limited. The principal plasticiser used is di,(2-ethyl hexyl)phthalate (DEHP) which offers the benefits of overall performance, ready availability at high purity and cost effectiveness.
The Migration Of The Plasticiser DEHP into blood and blood products and its effects is herein described.
DEHP is not covalently bonded to PVC and so could migrate out of the plastic. This is particularly so in the presence of solubilising lipids, lipoproteins and albumin. Jaegar and Rubin(i970) reported the leaching of DEHP into stored human blood. Several studies conducted subsequently demonstrated the extractability of DEHP from PVC blood bag into whole blood, platelet concentrates and plasma during storage. Concern have been expressed about the adverse effects of DEHP leached into blood and blood products and extensive studies have been made to assess every facet of the problems reported. There are several excellent reviews evaluating the significances and implications of the studies conducted. PVC materials plasticised with DEHP have been used in patient healthcare for over soyears and there are over 3000 published papers discussing its potential toxicological hazards. A blue ribbon Panel Report by Dr.Everett Koop (June 1999) former Surgeon General and Chairman of an expert panel convened by the American Council on Science and Health sums up the present position succinctly "DEHP in medical devices is not harmful to even highly exposed people, those who undergo certain medical procedures like regular haemodialysis or extracorporeal membrane oxygenation The panel concluded that "DEHP imparts a variety of important physical characteristics that are critical to the function of medical devices and eliminating DEHP in these products could cause harm."
> The Collection and Storage of Platelet Concentrates in DEHP Plasticised Bags
It became established that platelets could be stored with reasonable post transfusion recovery and survival for up to 72 hours in DEHP plasticised blood bags. In an earlier study it was demonstrated that thin walled DEHP plasticised PVC containers behaved better indicating thereby that higher oxygen and carbondioxide permeabilities were desirable.
The effect of DEHP plasticiser on stored platelets was studied in detail by Zoltan Racz and Clara Barotti (1995) who found that : Platelet aggregation was the only parameter that was slightly inhibited in DEHP plasticised bags indicating that the presence of DEHP had no harmful effect during storage.
Another significant observation made was that platelets from 400ml donor blood could be stored in DEHP plasticised bags meant for storage of platelets from 450ml of blood without deterioration for four days. Such platelets were not inferior to platelet concentrates stored for sdays in PL 732(polyolefin) or PL 1240(TEHTM) containers. These studies indicate that DEHP plasticised bags could be more effectively used for platelet storage if higher permeabilities are ensured .
In vitro studies, showed that DEHP reduced platelet functions such as aggregation responses and percentage of hypotonic shock responses. It also Prevented morphological changes in platelets which are frequently seen in TOTM and BTHC plasticised PVC bags. These changes have been explained on the basis of the DEHP leached into the plasma stabilizing platelet membrane and thereby preventing changes as in the case of RBC.
TEHTM PLASTICISED PVC;
Grode etal ( 1985 ) studied the storage of platelet concentrates in PVC bags plasticised with tri-2ethyl hexyl mellitate plasticiser (TEHTM) and showed that such bags possessed sufficient gas permeability to be suitable for the extended storage of platelets for atleast 5 days. They also found a 30 fold reduction in plasticiser accumulation in platelet concentrates as compared to DEHP plasticised bags. Studies made subsequently confirm that such bags may be used for storing platelet concentrates for atleast sdays at 22°C. While TEHTM plasticised containers were
Jt > found satisfactory for storage of most platelet concentrates, it may be desirable to use c more permeable containers if platelet yields are routinely very high. A distinct
advantage of TEHTM is its low migration and volatility characteristics.M/s Baxter Healthcare corporation.USA, (PL-1240), M/s Cutter laboratories.USA,(CLX), M/s Tuta Laboratories,Australia and others have been using TEHTM as plasticiser for platelet storage bags.
BTHC Plasticised PVC:-
Blood bags made with n-butyryl tri n-hexyl citrate (BTHC) plasticisers have been shown to be effective for storing platelets and their behaviour was similar to TEHTM plasticised bags. Measurements of pH, pC02, p02 , glucose, lactate, ATP , total adenine nucleotide, lactate dehydrogenase and platelet factor - 4(PF4) showed similar results for BTHC and TEHTM plasticised bags during 5 days storage of platelets. Results of invivo studies were similar.
An interesting observation, however has been made while statistically significant higher values have been obtained for BTHC plasticised containers than for TEHTM, for pH, p02 and glucose, the higher pH levels obtained for BTHC is similar to the high pH levels observed during the storage of platelets in blow moulded polyolefin bags which have high permeability. This observation indicates that while BTHC and Polyolefin containers ensures sufficient oxygenation to maintain an aerobic metabolism, the carbondioxide permeability is too high and allows too much escape of the gas as indicated by the low partial pressure of carbondioxide.
Modified Polyolefines:-
This material was introduced by M/s Baxter Healthcare Corporation, USA under the trade name PL -732 plastic. This material has high gas permeability and has been shown to be suitable for the storage of platelets up to seven days. This material is reported to be free of plasticisers. However, this being of polyolefin it is possible that it contains an antioxidant added to prevent oxidative deterioration. Polyolefin materials are also prone to leaching. Polypropylene has been shown to release many low molecular weight oligomers while polyethylene releases higher molecularweight oligomers. So even polyolefins cannot be said to be free of leachable materials.

Other Plasticisers:-
The search for non leaching plasticisers has resulted in the development and assessment of various organic compounds, but only the following has found some acceptance for making non toxic medical grade PVC products:- (i) Di nonyl phthalate (ii) Di iso nonyl phthalate, (iii) Di n-decyl phthalate and (iv) Di octyl terephthalate. The availability of these chemicals at high purity levels at acceptable prices has been a problem. In addition, they could not come up to the levels of performance as plasticiser for PVC.
EP1393759 discloses a medical working material based composition comprising of 1000 parts of PVC with K value between 65 and 100, 350-750 parts of DINCH, 100- 180 parts of epoxidised vegetable oil, 0.5-4 parts of calcium stearate, 0.5 - 4 parts of zinc stearate and 5-15 parts of amide wax. The composition of the cited document is used for preparing children's toys, medical devices, in particular tubes for dialysis, infusion and drainage and food packaging. However the cited prior art uses amide wax and high amount of epoxidised vegetable oil which leads to decreased transparency of the sheets which arise out of the formulation. Further the cited patent has not envisaged or taught the essential levels of permeability for the fabricated products as it was not important for the purpose covered in the cited patent.
Description of the invention
Soft medical grade PVC is used for the manufacture of blood bags, millions of which are being used in blood banks and hospitals everyday. These bags are capable of withstanding exposure to the high temperatures required for sterilization -upto i2i°C and low temperatures down to -8o°C required for certain processing operations and for storage of blood and blood components. They are also permeable allowing oxygen from the atmosphere to get into the blood bags to meet the breathing requirements of blood components and more particularly the platelets and allow the carbondioxide produced during the metabolism to diffuse out
Di(2-ethyl hexyl) phthalate, the most widely used phthalate plasticiser for blood bags has only slight solubility in water. The solubility is higher in blood plasma because of the presence of lipids, lipoproteins and albumin.
Blood itself is a key but scarce resource. Di(2-ethyl hexyl)phthalate(DEHP), the main phthalate used in medical devices has a further and a unique role in blood bags because it has a protective effect on red cell membrane and helps to prolong the life of the blood itself. Without these products blood supplies would be substantially reduced.
k * Di,(2-ethyl hexyl) phthalate(DEHP) besides being available in high purity and high volumes, has been intensively studied regarding its properties and mode of metabolism in the human body. There are over 3000 research papers published in addition to several excellent reviews relating to DEHP and its properties, performance characteristics and metabolism in animals and humans. DEHP also has protective effect on the cell membranes of erythrocytes which results in the preservation of red blood cells in blood and red cell concentrates separated there from and stored in DEHP plasticised PVC containers.
While whole blood, red cell concentrates and plasma could be stored effectively in DEHP plasticised PVC containers, platelets are not so well preserved. This difference has been traced to the lower permeability to Oxygen and Carbondioxide in di (2-ethyl hexyl)phthalate plasticised PVC bags. This results in insufficient supply of oxygen to platelets stored in such bags. Also, the carbondioxide resulting from the metabolism of platelets is unable to diffuse out in sufficient quantities resulting in the development of undesirable pH levels.
Various studies are reported in literature to increase the permeability of Polyvinyl chloride containers by the use of plasticisers such as tri octyl trimellitate(TEHTM), modified polyolefines, various citrate based plasticisers and notably by the use of n- butyryl,tri -n-hexyl citrate(BTHC). PVC bags made using these plasticisers have been shown to be capable of maintaining the viability of platelets stored in them for up to six days. TOTM has the additional advantage of ensuring low leachability. Citrate based plasticisers however have high leachability. It is however not clear whether the higher leachability of the citrate plasticised bags is advantageous or has any deleterious effects on platelets stored in PVC bags plasticised by them. Published research papers indicate that platelets are better preserved in tri octyl tri mellitate plasticised bags. It is also well realized that citrate plasticised bags could be used for the storage of whole blood, red cell concentrates and platelets.
Tri octyl tri mellitate plasticised bags, however, do not maintain the viability of red cells in blood and red cell concentrates. The viability is not far better than the blood stored in glass bottles. This is due to the fact that TEHTM has low leachability and so cannot stabilize RBC membranes unlike in the case of DEHP.
Plasticisers such as mellitates and citrates are markedly more expensive than DEHP which makes containers made using these plasticisers significantly costlier. It is found possible to use DEHP plasticised bags for storage of platelets provided appropriate changes are made in:-
- The composition
- The design of the bags and,
- The characteristic of the sheets and tubes used.
The composition needs to be so formulated that leaching of di ,(2-ethyl hexyl) phthalate is maintained at low levels. Also each additive incorporated should pass appropriate chemical and physiological tests particularly tests regarding toxicity described in International standards ISO - 3826. Also the final material namely sheets and tubes and also the containers fabricated there from should pass all the tests specified under:-
- International Standards Organisation -ISO3826
- British Standards
- German Standards
- United States pharmacopeia
- Indian Pharmacopeia
- European pharmacopeia
for containers for blood components.
Platelets are characterized by their very high metabolic rate with rapid ATP turn rate several times higher than that of other blood cells and remarkable ability to aggregate particularly under the influence of aggregating agents such as ADP, Epinephrine, Collagen and Thrombin. Platelets however lose their ability to aggregate and adhere during storage which may be associated with the general decrease in platelet sensitivity to their functions such as shape change, aggregation and secretion. There is some evidence that the decrease in sensitivity may be reversed after infusion.
Various studies of platelets stored in DEHP plasticised blood bags indicates that when platelet membranes are stabilized by leached DEHP, their readiness to
4 ^ aggregate is adversely affected, eventhough temporarily. Platelets stored in non leaching plasticisers function much better.
A new plasticiser manufactured by M/s BASF has recently become available in commercial quantities. The-eempeund is 1,2-cyclo irexane -dicarbojylic acid, di iso nonyl ester( CAS No: 166412-78-8) and is put on the market as Di iso Nonyl Cyclohexane (DINCH). This compound is reported to have very low solubility in water and hence low migration characteristics, low toxicological profile, no environmental hazards, no peroxisome proliferation, no reproductive hazards and has been found safe for food contact applications.
DINCH is distinct from other plasticisers presently in use for medical and food applications, because of the following characteristics:-
(i) Low leachability and hence low migration into water, solutions containing electrolytes, solutions containing fatty material and blood plasma.
(ii) It has low volatility as compared to other plasticisers.
(iii) It has high compatibility with PVC which is very similar to that of DEHP.
(iv) Tensile strength of DINCH plasticised PVC is similar to that of DEHP at equal concentrations.
(v) Permeability to Oxygen and Carbondioxide of DINCH plasticised PVC are also very similar to that of DEHP.
(vi) DINCH plasticised PVC sheets have low cold flexibility upto - 40°C which is very low as compared to existing plasticisers.
These characteristics indicate that DINCH could prove to be a good plasticiser for making CAPD bags, containers for storing parenteral solutions and containers for storing blood and blood components.
In the case of CAPD bags, large volumes of solutions are used for dialysis. Such solutions have to be sterilized in large volume containers thus exposing the solutions in the container to temperatures upto 1210 C.Hence the need for a plasticiser of low leachability.
RecenTtrends indicate that there is increasing demands for blood plasma. Plasticised PVC is probably the best material for plasma containers. DINCH plasticised PVC should prove very useful for this purpose. Yet another possibility is for containers for
the storage of plasma for the recovery of cryoprecipitate. The low cold flex temperatures of DINCH plasticised PVC upto -40° C is of great advantage for this purpose.
From the properties of this compound as available, we felt that DINCH should prove good as a plasticiser for PVC for making platelet storage bags. Hence we made studies to develop suitable formulations using this compound as plasticiser. The compounds were extruded into sheets and tubes and tested for chemical, physical and biological characteristics. Since all the requirements were met, we fabricated blood bags and tested them for compliance to the standards of International Standards Organisation - ISO -3826. The bags fully met the requirements.
Hence we made a series of studies in which platelet rich plasma separated from blood was stored in the blood bags made using DINCH as plasticiser and the changes in the platelets were monitored over seven days. We found that the platelet characteristics were well maintained for upto seven days.
This invention therefore, relates to the development of platelet storage bags using Polyvinyl Chloride plasticised with DINCH (ie, 1,2 - cyclohexane dicarboxylic acid di isononyl ester).
The formulation developed as per the invention for the platelet storage container consists of :-
1) 1000 parts by weight of suspension polymerized Polyvinyl chloride resin of K -value ( 1% cyclo hexanone)-6o to 80,
2) 400 to 650 parts by weight of 1,2 cyclohexane dicarboxylic acid di iso nonyl ester,
3) Upto 200 parts by weight of di,(2-ethyl hexyl)phthalate,
4) Upto 200 parts by weight of di ,(2-ethyl hexyl) adipate,
5) Upto 30 parts by weight of a non toxic stabilizer being salts of metals such as calcium, and zinc with fatty acids containing 8 to 18 carbon atoms,
6) 30 to 100 parts of an epoxidised vegetable oil rich in linoleic acid containing not less than 6.0% by weight of oxirane oxygen,
1) Upto 40 parts by weight of an ester having the stru
CH3(CH2)n COO R where n is 10-16 and R is an alkyl group containing 4 to 10 carbon atoms, and
2) Upto 10 parts by weight of saturated aliphatic hydrocarbon having 12 - 20 carbon atoms , preferably containing branched side chains and having an average molecular weight in the range of 200 to 300
The component (5) referred to above, may be selected from calcium palmitate, calcium stearate, zinc octanoate, zinc laurate, zinc myristate, zinc palmitate or zinc stearate or blends of the above which may be dispersed in an epoxidised vegetable oil.
The component (6) may be selected from the epoxidised soyabean oil or linseed oil or a mixture thereof.
The component (7) may be selected from butyl stearate, ocyl stearate and nonyl stearate.
The component ( 8) may be medical grade liquid paraffin.
The PVC composition according to this invention may be prepared as per one of the preferred embodiments herewith described below:-
The polyvinyl chloride powder is first charged into a high speed blender. The stirrer is operated at low speed and component (5) is added and the stirring is continued for upto 5minutes. The stirrer speed is increased and when the temperature has attained 50°C, component (6) is added gradually. When the temperature of the mixture attains 70°C, component (2) is added followed by the components (3) and (4) as necessary . The addition should be completed before the temperature attains ioo°C . The components (2),(3) and (4) may be blended and the blend added in place of (2). When the temperature reaches no°C ,the component^) is added followed by (8) and the muring continued till the temperature reaches 120°C. The contents of the blender is then rapidly discharged into a cooler mixer where it is continuously mixed till the temperature fells to 40°C and then discharged into receptacles.
The process is essentially a blending operation involving physical factors such as absorption of additives and their penetration into the pore structure of the PVC and consequent swelling of the granules.
The polyvinyl chloride composition so obtained is then extruded into strands of 2- 3mm diameter, air cooled and then cut into pellets in a rotary cutter. The pellets are freed from fine particulate in a suitable cyclone separators. The pellets are then extruded into tubes and sheets of appropriate dimensions. The sheets , tubes and other components are then joined by high frequency welding to form containers of required design. It has been found that characteristics of the PVC material could be varied over a wide range by varying proportion of plasticiser 2,3,4 an(l other additives particularly components ( 6) and (7).
Our observations clearly show that PVC based containers meant for storing platelet rich plasma or platelet concentrates recovered from 45omiUi litres of human blood should provide for transmission upto 40 milli litre of oxygen , and upto 222 milli litre of carbondioxide per 24hours of storage. If the PVC(blood bags) container are designed so that factors such as capacity of the container, its surface area, the thickness and permeability characteristics of sheet provide the above mentioned transmission figures upto 40 milli litres of oxygen and upto 220 milli litres of carbondioxide per container of platelets per 24 hours at 25°C are achieved, platelets could be stored in them without significant damage for atleast seven days.
The thickness of the sheet used for making PVC containers plays a vital role in its permeability to gases such as oxygen and carbondioxide. We find that the optimum results are obtained when 0.30 to 0.45 mm thick sheets are used. The thickness of sheet has to be considered in conjunction with various other factors such as tensile strength, elongation at break, puncturability, the likelihood of developing pinholes and other defects which might promote the entry of microorganisms into the bag and the requirements for centrifugation of such bags.
Yet another critical factor is the total internal surface area of the PVC containers. When 1 unit blood ( 450 ml) is processed for the recovery of platelet concentrates, the resulting concentrates would have an average volume in the range of 60 - 70 ml and the platelet count should be atleast 5.5 to 1010 The PVC container should provide sufficient internal surface area to enable upto 40 milli litres of oxygen and upto 250 milli litres of carbondioxide to permeate the bag in 24 hrs at latmosphere and at 25 0 C. Our studies show that an internal surface area of 300 to 500 sq.cms is required. This range of surface area would be sufficient to take care of the normal variations in platelet count encountered in blood banks.
When units of blood other than 450ml are to be collected routinely and platelet concentrates are recovered there from, the surface area of bags in which platelets are stored have to be modified suitably to obtain the optimum performance. The bags should be capable of enabling upto 40 millilitres and preferably in the range of 25- 40ml of oxygen and upto 250 millilitres and preferably in the range of 150-250111I of carbondioxide to permeate the surface of the container every 24hours for platelets recovered from one unit (450ml) of blood.
The permeability requirement of the containers for the storage of whole blood, plasma enriched RBC, cord blood and plasma will be in the range of 27-31 ml for oxygen to permeate and 152-202 ml for carbon dioxide to permeate the surface of the container from one unit (450ml) of whole blood, which range falls well within the range of the platelet containers of the present invention. Hence the containers of the present invention are well suited for the fabrication of paediatric bags, blood plasma bags and cord blood bags also.
The invented process thus consists of using 1,2-cyclohexane dicarboxylic acid, di isononyl ester (DINCH) plasticised PVC bags of composition essentially as described earlier for the storage and preservation of platelet concentrates for periods upto seven days, the said bags fabricated in such a manner as to provide permeability upto 40 mllilitres of oxygen and upto 250 milli litre of carbondioxide every 24 hours at one atmosphere at 25° C.
The proposed patent involves two inventive steps.
1. usage of medical grade paraffin as lubricant which is the only chemical that distinctly enhances the transparency of PVC sheets prepared from the composition.
2. restricting the amount of epoxidised soya bean oil to only 10 parts also assist in enhancing the transparency of the sheet prepared from the composition.




The resultant Platelet storage containers do possess Die uemicu pciineduuay ana——- desired level of transparency as detailed in the table above under the heading characteristics of the bags.
Example 2 Paediatric bags:
Composition

^ The resultant Paediatric bags do possess the desired permeability and desired level of transparency as detailed in the table above tinder the heading characteristics of the bags.
Example a Containers for the storage of whole blood and plasma enriched RBC.


The resultant cord blood bags will possess the desired permeability and desired level of transparency as detailed in the table above under the heading characteristics of the bags.
Although the invention has been described above with reference to the disclosed embodiments, those skilled in the art will readily appreciate that the specific experiments detailed are only illustrative of the invention. It should be understood that various modifications can be made without departing from the spirit of the invention.

WE CLAIM:
1. A polyvinyl chloride based formulation for use in making a platelet storage container and blood bag by compounding 1000 parts of polyvinyl chloride resin made by suspension polymerization process having K value as determined using cyclohexane - 1 % by weight, of 60 to 80, characterized in containing atleast
a) 400 - 650 parts by weight of a diester of cyclohexane dicarboxylic acid with isononylalcohol,
b) 30 to 100 parts by weight of an epoxidised vegetable oil rich in linoleic acid, and having oxirane oxygen content of not less than 6.0 percent by weight,
c) Upto 30 parts by weight of a non- toxic stabilizer being salts of calcium and zinc with fatty acids containing 8 to 18 carbon atoms,
d) Up to 40 parts by weight of an ester having the structural formula CH3(CH2)n. COOR where n is 10 - 16 and R is alkyl group containing 4 to 10 carbon atoms, and
e) Up to 10 parts by weight of a saturated aliphatic hydrocarbon having 12 to 20 carbon atoms, preferably containing branched side chains and having an average molecular weight in the range 200 - 350.
2. A platelet storage container, said container made from a polyvinyl chloride formulation as claimed in claim 1.
3. A process for making blood bags suitable for the collection and storage of platelet rich plasma or platelet concentrates, the said bags being made using a formulation as claimed in claim 1. by compounding of 1000 parts of polyvinyl chloride resin made by suspension polymerization process having K value as determined using cyclohexane -1% by weight, of 60 to 80, with :-
(a) 400 - 650 parts by weight of a diester of cyclohexane dicarboxylic acid with isononyl alcohol,
(b) 30 to 100 parts by weight of an epoxidised vegetable oil rich in linoleic acid , and having oxirane oxygen content of not less than 6.0 percent by weight,
(c) Upto 30 parts by weight of a nontoxic stabilizer being salts of calcium and zinc with fatty acids containing 8 to 18 carbon atoms,
(d) Upto 40 parts by weight of an ester having the structural formula CH3(CH2)n.COOR where n is 10 - 16 and R is alkyl group containing 4 to 10 carbon atoms, and
(e) Up to 10 parts by weight of a saturated aliphatic hydrocarbon having 12 to 20 carbon atoms, preferably containing branched side chains and having an average molecular weight in the range 200 - 350.
4. The polyvinyl chloride based formulation as claimed in claims 1, wherein the diester of cyclohexane dicarboxylic acid is di -(iso nonyl)- cyclohexane 1,2 dicarboxylate.
5. The polyvinyl chloride based formulation as claimed in claims 1, wherein the epoxidised vegetable oil is epoxidised soyabean oil, epoxidised linseed oil or a mixture thereof.
6. The polyvinyl chloride based formulation as claimed in claims 1, wherein the salts of metals claimed is calcium palmitate, calcium stearate, zinc octanoate, zinc laurate, zinc myristate or a mixture thereof.
7. The polyvinyl chloride based formulation as claimed in claims 1, wherein the hydrocarbon claimed is liquid paraffin of medical grade.
8. The polyvinyl chloride based formulation as claimed in claims 1, where the ester used may be selected from butyl stearate, octyl stearate and nonyl stearate.
9. The platelet storage container for the storage of platelets as claimed in claims 2, wherein the container has thickness in the range 300 to 450 microns.
10. The platelet storage container as claimed in claims 2, wherein the container can allow 25-40 milli litres of oxygen to permeate in 24 hours at one atmospheric pressure at 25°C for platelets separated from 450 ml of blood.
li. The platelet storage container as claimed in claims 2, wherein the container can allow 150- 250 milli litres of carbondioxide to permeate in 24 hours at one atmospheric pressure at 25°C for platelets separated from 450 ml of blood.