Title of Invention	A PROCESS FOR PREPARING A PREPOLYMER ADHESIVE
Abstract	57) Abstract:- A process for preparing a prepolymer adhesive comprising preparing a hydroxyl terminated polyurethane prepolymer (component A) by reacting cycloaliphatic diisocyanate and a polyol component and drying said component A; Subjecting said dried component A to the step of treatment with a diisocyanate (component B) to obtain a resinous prepolymer adhesive. PRICE: THIRTY RUPEES

Full Text

The presnt invention relates to a process of preparing a prepolymer adhesive. The use of plasticised poly (vinyl chloride) for biomedical applications is mainly as extracorporeal tubings and blood bag. The performance of the products manufactured from the plasticized poly (vinyl chloride) is dependent generally upon the interaction between the product and the surrounding medium. In most of the applications, plasticized poly (vinyl) chloride is in contact with some kind of surrounding liquid medium. During manufacture of plasticized poly (vinyl chloride) sheet di-2 ethyl hexyl phthalEte (DEHP) is added as plasticizer to plasticize the rigid poly (vinyl chloride) polymer and to get the desired product- But with time, this plasticizer migrate to the surrounding liquid medium leading to create brittleness and early failure of the product. In application where no liquid medium is in contact with the product, migration of plasticizer takes place due to environ¬mental ageing, and known as. sweating. The migration of undesirable event, because the plasticizer DEHP is metabolished to give monoethyl hexylphthalate (MEHP) in vivo and cause cardie-toxic effect on human heart muscle. Hypotension and cardiac arrest occurred in rats following the infusion of MEHP when circulating blood levels exceeded 75 ug per ml.. In this connec¬tion, reference is invited to (6.ROCK, Transfusion 30(8), 767(1990). The therapeutic level of DEHP for human at no effect level is 60 ug/kg body weight per day. (A S Chawla and I Hinberg Biomat. Art Cell h Immob. Biotech 19(4) 761-783(1991). Higher doses of DEHP have been found to be mutagenic and teratogenic. Therefore, the performance of the products manufactured from plasticized poly (vinyl chloride) largely depends on its resis¬tance to leach DEHP into the surrounding medium. OBJECTS OF THE INVENTION An object of this invention to propose a process for chemical treatment of polyvinyl chloride materials which is not only reliable but also simple and economical. Further objects and advantages of this invention will be more apparent from the ensuing description. At the outset of the description which follows, it is to be understood that the ensuing description only illustrates a parti¬cular form of this invention. However, such a particular form is only an exemplary embodiment and without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and reading of the invention and not intended to be taken restrictively. DESCRIPTION OF THE INVENTION According to this invention, there is provided a process for preparing a prepolymer adhesive comprising preparing a hydroxyl terminated polyurethane prepolymer (component A) by reacting cycloaliphatic diiosocyanate and a polyol component and drying said component A; subjecting said dried component A to the step of treatment with a diisocyanate (comonent B) to obtain a resinous prepolymer adhesive. According to this invention is provided a process for the prepa¬ration of a resinous prepolymer adhesive. In accordance with this invention, the PVC material is subjected to 3 first step of cleaning with s non-polar solvent, and then to a second step of cleaning in an ultrasonic cleaner using a detergent solution which is then dried. Basically, the steps of cleaning and chemical treatment are broadly carried out on an experiments basis as follows : I. Initially, cleaning of plasticized poly product is carried out using s non-polar organic solvent for 1-5 mins. to remove surface—adhered plasticizers and lubricants, etc. followed by cleaning in an Itrasonic cleaner using B detergent solution and deionised water, and then dried at the temperature o of 30-70 C for 10-40 hrs,. II. Chemical treatment of cleaned snd dried PVC product is carried out using a prepolymer adhesive of polyurethane. (a) An aliphatic prepolymer adhesive of polyurethane was prepared by reacting two component mixtures containing component A and component B. Component A is a hydroxyl terminated polyurethane prepolymer and Component B is a diisocyanate. Component A was prepared with the reaction between a cycloaliphatic diisocyanate and excess polyol having trifunctionality and nitrogen atom in the presence of a tin catalyst at 70-150°C for a duration of 30-180 mins. in an inert atmosphere using an amide solvent. The resin was dried. This dried resin A was reacted with Component B at 40-100 C for a duration of 2-20 mins.. The resinous prepolymer adhesive was used for coating the PVC product. (b) The clean PVC product was dipcoated for 1-10 mins. using the prepolymer adhesive of polyurethane immediately after the preparation of prepolymer adhesive. Dipcoating was moderated using a ketone solvent. (c) Dipcoated products were then cured at 40-120"C for a duration of 10-50 hrs.. (d) The chemically modified PVC product is then cleaned in running water, deionized water and dried at 40-70°C for 1-4 hrs. . EXAMPLE For an experimental study, we used plasticized poly (vinyl chloride) sheet and tube containing of 30 phr of diethyl hexyl phthalate and 10 phr of dioctyl adipate plasticizers. Calendered PVC sheet (0.35mm thickness) and extruded PVC tube were chemically treated as detailed above. The coating thickness is 0.18mm in each side of a PVC sheet. The chemically treated PVC products were exposed to hexane (a 'hard' solvent capable of extracting good amount of DEHP), liquid paraffin (a 'soft' solvent) and blood (with anti-coagulant) for a period 552 h at 28/4 C. The weight loss in these media were determined by drying the solvent-exposed modified PVC product. Unmodified commercially available PVC products were used as control. The amount of loss of plasticizer in the modified and unmodified PVC products are shown below : a. Treatent with PVC tubes: b. Treatment with PVC sheet : During the exposure in the media, the modified materials remain transparent and flexible. The modified materials exposed to hexane and blood did not harden as could be observed in unmodified materials. The modified PVC materials are compatible with blood as the haemolytic potential is within the acceptable limit. Ininially cleaning of plasticized poly (vinyl chloride) product! is carr5ed out using a non-polar organic solvent for 1-5 minutes Go remove surface - adhered plastlcizers and lubricants etc. followed by cleaning in an ultrasonic cleaner using a detergent solution and deionised water, and then dried at the temperature of 30-70°C for 10-40 h. II. Chemical treatment of cleaned and dried PVC product is carried out using a prepolymer adhesive of polyurethane. (a) An aliphatic prepolymer adhesive of polyurethane was prepared by reacting two component mixture containing component A and component B. Component A is a hydroxyl terminated polyurethane prepolymer and component B is a dtisocyanate. Component A was prepared with the reaction between a cycloaliphatic dtisocyanate and excess polyol having trifunctionallty and nitrogen atom in the presence of a tin catalyst at 70-150°C for a duration of 30-180 min. In an Inert atmosphere using an amide solvent. The resin was dried. This dried resin A was reacted with component B at 40-100°C for a duration of 2-20 min. The resinous prepolymer adhesive was used for coating the PVC product. (b) The clean PVC product was dipcoated for l-l0 min using the prepolymer adhesive of polyurethane Immediately after the preparation of prepolymer adhesive. Dipcoatlng was moderated using a ketone solvent. (c) Dipcoated products were then cured at 40-120°C for a duration of 10-50 h. (d) The chemically modified PVC product is then cleaned in running water, deionized water and dried at 40-70°C for 1-4 h. Example t For an experimental study we used plasticized poly (vinyl Chloride) sheet and tube containing of 30 phr of diethyl hexyl phthalate and 10 phr of dloctyl adlpate plasticizers. Calendered pvc sheet (0.35mm thiokness) and extruded PVC tube were chemically treated as detailed above. The coating thickness Is 0.18 mm in each side of a PVC sheet. The chemically treated PVC products were exposed to hexane (a 'hard' solvent capable of extracting good amount of DEHP), liquid paraffin (a 'soft' solvent) and blood (with anti coagxilant) for a period 552 h at 28/4°c. the weight loss in these media were determined by drying the solvenr -exposed modified PVC product. Unmodified commercially available PvC products were used as control. The amount of loss of plasticizer in the modified and unmodified PVC products are shown below: a. Treatment with PVC tubes: b. Treatment with PVC sheet: During thosed to hexane and blood did not harden as could be observed in inmodified materials. The modified Pvc materials, are compatible with blood as the haemolytic potential is within the acceptable limit. WE CLAIM : 1. A process for prepsring a preparation hesive comprising preparing a hydroxyl terminated polyurethane prepolymer (component A) by reacting cycloaliphatic dlisocyenate and a polyol component and drying said component A; subjecting said dried component A to the step of treatment with a diisocyanate (component B) to obtain a resinous prepolymer arihesi ve. 2. A process as claimed in claim 1 wherein said polyol is in excess of the cycloaliphatic diisocyanate . 3. A process as claimed in claim 1 wherein said polyol has tri-f functional i ty and nitrogen atom. 4. A process as claimed in anyone of claims 1-3 wherein said process for the preparation of component A is carried out in an amide solvent in the presence of a catalyst in an inert atmosphere. 5. A process as claimed in anyone of claims 1-4 wherein the preparation of component A is carried out at a temperature of 70- 150° C. 6. A process as claimed in anyone of claims 1-5 wherein the preparation of component A is carried out for a period of time ranging from 30-180 mins.. 7. A process as claimed in claim 1 wherein for the preparation of component A, a tin catalyst is used. 8. A process as claimed in claim 1 wherein the step of treating dried component A with component B is carried out at a tempera- ture of 40-1øø°C 7. A process as claimed in claim I wherein the step of treating dried component A with component B is carried out for a period of 2-20 mins., 10. A process for preparing a prepolymer adhesive substantially 35 herein described with reference to the example.

Documents:

316-mas-95 abstract.pdf

316-mas-95 claims.pdf

316-mas-95 correspondence-others.pdf

316-mas-95 correspondence-po.pdf

316-mas-95 description (complete).pdf

316-mas-95 form-1.pdf

316-mas-95 form-26.pdf

316-mas-95 form-4.pdf

316-mas-95 form-5.pdf

316-mas-95 form-6.pdf

316-mas-95 others document.pdf