Title of Invention

MIGRATION RESISTANT PLASTICIZED POLY (VINYL CHLORIDE) (PVC)

Abstract

57) Abstract:- This invention relates to a process for the preparation of migration resistant polyvinyl chloride (PVC) comprising in the steps of treating cleaned plasticized PVC tubing with a solution of an alkali metal salt of a nucleophile selected from thiosulphate and sulphide, in the presence of a phase transfer catalyst (PTC) such as herein described, at a temperatixre in the range of 60 to 80** C for 5 hrs. followed by washing the tubings and drying to obtain migration resistant polyvinyl chloride wherein said alkali metal salt is selected from sodium, potassium and ammonium salt. PRICE: THIRTY RUPEES

Full Text

The present invention relates to a process for the preparation of migration resistant plasticized poly (vinyl chloride) (PVC). Plasticized PVC is one of the most widely used polymeric material in the medical field for the manufacture of blood bags, trans¬fusion tubings, urine bags, crystalloid sets, etc. and also for packaging food stuffs and pharmaceuticals. Plasticizers are chemicals that are added to a polymer to increase its work¬ability, distensibi1ity, flexibility and low temperature proper¬ties. A plasticizer is a molecule which modifies a resin so that one can start with a basic resin, develop different products with different properties and applications. Briefly, piasticization on the molecular level is the weakening or masking of selective bonds between polymer chains, while leaving others strong, to make possible the shaping, flexing or molding of the material. This is accompanied by an increase in intermolecular space, which allows the change in shape. There are many different kinds of plasticizers and di- DEHP which is a moderately high molecular weight plasticizer ( M W 390) is commonly employed in the production of plasticized PVC. Without plasticizer P^C is a rigid plastic. Plasticized PVC usually contains upto 40% by weight of this plasticizer (Ljunggren, Artif. Organs., 8, 99, 1984). Plasticizers often possess, high mobility, and they can easily migrate from PVC to the environment. This not only results in the deterioration of PVC, but also in the contamination of the product by the plas— ticizer if PVC is used in food packaging or medical applications such as blood bag. DEHP can produce adverse effects in putuitary gland tissues, liver abnormalities, testicular damage (Lake et al.. Environ. Health, pers., 67, 203, 1986) and also can act as a potential carcinogen (Kluwe et al., Toxicol. Environ. Health, 10, 797, 1982). Several different approaches have been made to retard or prevent the migration of DEHP from plasticized PVC. Coating the PVC surface with various polymers, crosslinking PVC during processing using peroxides, irradiation in presence of multifunctional monomers (See for eg. Duvis et al., J Appln. Polym. Sci., 42, 191, 1991 and reference therein), grafting hydrophilic monomers onto the surface of PVC by gamms irradiation (Krishnan et al. , Biomaterials, 12, 489, 1991) plasma treatment of PVC surface (Iriyama and Yasuda, J Appl. Polym. Sci., Appl. Polym. (Symp., 42, 97, 1986), coating with dithiocarbamate substituted PVC and heating to crosslink the surface of PVC (Levinf US Patent 4806393, 1986) are some of the methods reported in the published and patent literature to retard the migration of the plasticizer. However, all these techniques have severe limitations and none of them prevents the migration completely or near completely. An object of this invention is to propose a process for the preparation of miciration resistant polyvinyl chloride by surface modification using phase transfer catalysis. Thus according to this invention is provided a process for the preparation of migration resistant polyvinyl chloride (PVC) comprising in the steps of treating cleaned plasticized PVC tubing with a solution of an alkali metal salt of a nucleophile selected from thiosulphate and sulphide, in the presence of a phase transfer catalyst (PTC) such as herein described, at a o temperature in the range of 60 to 80 C for 5 hrs. followed by washing the tubings and drying to obtain migration rf polyvinyl chloride wherein said alkali metal salt is selected from sodium, potassium and ammonium salt. In accordance with this invention, there iS, provided a process for the preparation of migration-resJ«tant poly(vinyl chloride) (PVC) by the nucleophilic substitution of the chlorine atoms on PVC by nucleophiles such as thiosulphate and sulphide on plasti- cizers PVC by phase transfer catalysis. PTCs are those wich can transfer one reactant from its normal phase ir«;o the normal phase of the second reactant and that the transferred reagent will be available in a highly active form. The reaction is conducted using any alkali salts of the said nucleophiles such as sodium, potassium or ammonium salts. The plasticized PVC is in a physical form such as sheets, tubings or any devices made out of sheets, and tubings or plasticized PVC molded in any physical form. By way of example, the plasticized PVC tubes or sheets are claned by sonication in a bath type sonicator and treated with the alkali metal solution of thio-sulphate or a sulphide in water in presence of a PTC. The PTC is Euch as tetrsbutyl ammonium hydrogen sulphate (TBAH), or any other compound which has the characteristics of a typical PTC such as tetrabutyl ammonium iodide (TABI), tetrabutyl ammonium bromide (TBAB), he>:a—decyl trimethyl ammonium bromide v'HTMAB), benzyl tri ethyl ammo-nium chloride (BTAC) and 1.8 crown-6 (1SC6) . The concentration of the aqueous alkali metal salt solution of thiosulphate is 2.5 to 5.0li, preferably 5.0li and the concentra¬tion of the alkali metal salt solution of sulphide is 4.0M to 9.0M, preferably 7.0M. The reaction is carried out in the tempe- o rature range of 60—80 C for various periods of time. Here, the 2-PTC (TBAH) will bring S O Na or S. groups from the aqueous 2 3 phase to the solid PVC, where exchange of anions with chlorine atom takes place. These chlorine atoms are taken to the aqueous phase by PTC. A concentration of PTC from 0.05 to 0.30M is used with the alkali metal thiosulphate and from 0.01 to 0.20M is used with the alkali metal sulphide solution. The treated PVC tubings or sheets are finally washed and dried in a vacuum oven at room temperature. It is presumed that -S-S- type or crosslinking is formed on the surface of PVC using thiosulphate and —S- type in the case of sodium sulphide. SURFACE MODIFICATION WITH SODIUM THIOSULPHATE Example Medical grade PVC tubing was cleaned by sonication in a bath type sonicator in distilled water for 5 mins.. Pieces of tubes having approximately 1.5 cm in length were treated with a solution of sodium thiosulphate having a concentration of 3.(3M in the o presence of 0-15M TBAH in 10 ml distilled water at 30 C for 5 hrs. with occasional shaking. After the reaction, the tubes were washed well with water. SURFACE MODIFICATION WITH SODIUM SULPHIDE Example About 1.5 cm long PVC tubes were treated with 10 mL of 7M sodium o sulphide 0.15M TBAH 80 C for 5 hrs.. The tubes were then washed well with water and dried in a vacuum oven at room temperature. WE CLAIM: 1. A process for the preparation of migration resistant polyvinyl chloride plasticized PVC tubing with a solution of an alkali metal salt of a nucleophile selected from thiosulphate and sulphide, in the presence of a phase transfer catalyst (PTC) such as herein o described, at a temperature in the range of 60 to 80 C for 5 hrs. followed by washing the tubings and drying to obtain migration resistant polyvinyl chloride wherein said alkali metal salt is selected from sodium, potassium and ammonium salt. 2. A process as claimed in claim 1 wherein said plasticized PVC is in a physical form such as sheets, tubings or any devices made out of sheets and tubings or plasticized PVC molded in any physical form. 3. A process as claimed in claim 1 wherein said PVC tubings are cleaned by sonication in a bath type sonicator. 4. Vt process as claimed in claims 1 or 2 wherein said step of sonication is carried out for 5 mins. in distilled water. 5. A process as claimed in claim 1 wherein said solution of the alkali metal salt is an aqueous solution. 6. A process as claimed in claim 1 wherein the concentration of said aqueous alkali metal salt solution of thiosulphate is 2.5 to 5.0M, preferably 5.0M. 7. A process as claimed in claim 1 wherein the concentration of said aqueous alkali metal salt solution of sulphide is 4.0 to 9.0M, preferably 7.0M. 8. A process as claimed in claims 1 or 7 wherein said temperature is 80 - *?. A process as claimed in claim 1 wherein said phase transfer catalyst is selected from tetrabutyl ammonium iodide (TBAI), tetrabutyl ammonium bromide (TBAB), hexadecyl trimethyl ammonium bromide (HTMAB), benzyl triethyl ammonium chloride (BTAC) and IS crown-6 and tetrabutyl ammonium hydrogen sulphate (TBAH). 10. A process as claimed in claim 1 wherein said PTC is TBAH, TBAB- 11. A process as claimed in claim 1 wherein a concentration of said PTC of .05 to .30li is used with the alkali metal thio-sulphate solution. 12. A process as claimed in claim 1 wherein a concentration of said PTC of 0.01 to .20M is used with the alkali metal sulphide solution. 13. A processes claimed in claims 1,9 or 10 wherein the concen¬tration of PTC used is .15M. 14. A process as claimed in anyone of the aforementioned claims wherein the treated PVC tubings are washed and dried in a vacuum oven at room temperature. 15. A process for the preparation of migration resistant poly¬vinyl chloride Dated this 3rd day of SEPTEMBER, 1996.

Documents:

709-mas-95 abstract.pdf

709-mas-95 claims.pdf

709-mas-95 correspondences-others.pdf

709-mas-95 correspondences-po.pdf

709-mas-95 description (complete).pdf

709-mas-95 form-1.pdf

709-mas-95 form-26.pdf

709-mas-95 form-4.pdf

709-mas-95 form-6.pdf