Title of Invention

"POLYURETHANE PREPOLYMER FORMULATION FOR ORTHOPAEDICS CASTING TAPE"

Abstract

This invention relates to polyurethane prepolymer formulation for orthopaedics casting tape comprising a water-activatable polyurethane prepolymer resin mix impregnated in a knitted-weave fibrous substrate, said prepolymer comprising a prepolymer (A) having a aromatic diisocyanate, polyol and a solvent and a prepolymer (B) having a aromatic diisocyanate, a polyol and solvent in the ratio of from 10:90 to 90:10, 0.5% to 2% based on the weight of prepolymer, of dimorpholinodiethylether as a catalyst, 0.5% of stabilizer benzoyl chloride and 0.5% of antifoaming agent poly (dimethylesiloxane).

Full Text

FIELD OF INVENTION The present invention relates to polyurethane prepolymer for orthopedic synthetic casting tape which comprises an isocyanate terminated polyurethane prepolymer along with catalyst, stabilizer, antifoaming agent etc. embedded in a fiber matrix. PRIOR ART Plaster of Paris casts have been used to immobilize body members for some time. These bandages are made by depositing Plaster of Paris on a reinforcing scrim material such as gauze. When the Plaster of Paris is dipped in water, the alpha hemihydrate of calcium sulfate is converted to calcium sulfate dehydrate, which results in the hardening of the cast. Plaster of Paris casts, however, suffers from a number of disadvantages. Prolonged time of setting restricts the movement of the fractured part, X-ray transmission through the cast to determine whether a fracture has been properly set is very difficult. In addition, the cast is quite heavy and restricts the mobility of the patient cast, which may result in skin irritation beneath the cast.wearing the cast. The casts are also very sensitive to water and may seriously loose their load-bearing capacity if they become wet. In addition, the air permeability of the Plaster of Paris cast is very limited, and, as a result, they do not allow evaporation of moisture from the skin beneath the A number of catalysts, though available to catalyze the water-isocyanate reaction of the prepolymer, are not suitable for use in a cast bandage due to their reactivity in packed condition with poor shelf stability. OBJECTS OF THE PRESENT INVENTION An object of present invention is to propose a storage stable orthopedic cast bandage comprising water cross linkable polyurethane prepolymer resin based formulation impregnated in knitted glass or polypropylene tape substrate. Another object is to propose tape for use in orthopedics applications by dipping in water to activate the resin to harden. STATEMENT OF INVENTION According to this invention there is provided polyurethane prepolymer formulation for orthopaedics casting tape comprising a water-activatable polyurethane prepolymer resin mix impregnated in a knitted-weave fibrous substrate, said prepolymer comprising a prepolymer (A) having a aromatic diisocyanate, polyol and a solvent and a prepolymer (B) having a aromatic diisocyanate, a polyol and solvent in the ratio of from 10:90 to 90:10, 0.5% to 2% based on the weight of prepolymer, of dimorpholinodiethylether as a catalyst, 0.5% of stabilizer benzoyl chloride and 0.5% of antifoaming agent poly (dimethylesiloxane). The present invention relates to a polyurethane cast material, which comprises a fibrous substrate impregnated with water activated polyurethane prepolymer, prepared using polyols and diisocynantes, stabilizers, cross linking catalysts and antifoaming agents etc. The polyols employed either difuctional or trifunctional aliphatic and/or aromatic polyether and/or polyester polyols. A molar excess of isocyanates and polyols are reacted to get the desired isocyanate terminated polyurethane prepolymer. Various stabilizers, catalysts and antifoaming ag used in the formulation. I n order to overcome the disadvantages of Plaster of Paris casts, numerous attempts have been made to develop plastic or plastic reinforced materials as a replacement for Plaster of Paris. U.S. Patent nos. 3,241,501 and 3,881.473 disclose casts, which are made with, a flexible fabric impregnated with a polymer which is capable of being cured by ultraviolet light. Although this casting material overcomes some of the disadvantages of Plaster of Paris cast material, it requires a different technique in its application and also requires the use of the ultraviolet light source in order to cure the cast. These casts also require significantly longer time for the cast to set before they will be load bearing. More recent attempts to produce substitutes for Plaster of Paris include the polyurethane polymers disclosed in German Offenlegenschrift nos. 2353212 and 2357931, U.K. Patent no. 1,578,895 and PCT application no. W081/00671. These bandages are open-weave fabrics coated with polyurethane prepolymers. that is, reaction products of isocyanates and polyols. The bandages are dipped into water in the same manner as the Plaster of Paris and then applied to the limb of a patient. The water causes the prepolymer to polymerize and form a rigid polymer structure. In order to obtain the desired rapid hardening or setting of the bandage, it is necessary to have a catalyst system incorporated in the prepolymer formulation. The casting material disclosed in U.K. Patent no. 1,578,895 employs amino polyols as catalysts and as the polyol components. The casting material disclosed in W081/00671 employs dimethyl ethanolamine (DMEA) or a mixture of DMEA and bis (2-dimethylaminoethyl) ether. These catalyst systems provide acceptable time of heardening by catalyzing the water-isocyanate reaction. However, the presence of these catalysts in the prepolymer system result in short shelf life in the bandage package. The inadequate shelf stability makes the cast difficult to bandage. Cast bandage of shelf life more the 12 months, are yet to be available commercially. A number of catalysts, though available to catalyze the water-isocyanate reaction of the prepolymer, are not suitable for use in a cast bandage due to their reactivity in packed condition with poor shelf stability. OBJECTS OF THE PRESENT INVENTION An object of present invention is to propose a storage stable orthopedic cast bandage comprising water cross linkable polyurethane prepolymer resin based formulation impregnated in knitted glass or polypropylene tape substrate. Another object is to propose tape for use in orthopedics applications by dipping in water to activate the resin to harden. STATEMENT OF INVENTION According to this invention there is provided a storage-stable orthopedic cast bandage comprising a water-activatable polyurethane prepolymer resin mix impregnated in a knitted-weave fibrous substrate, said prepolymer comprising a prepolymer (A) and a prepolymer (B) in the ratio of from 10:90 to 90:10. The present invention relates to a polyurethane cast material, which comprises a fibrous substrate impregnated with water activated polyurethane prepolymer, prepared using polyols and diisocynantes, stabilizers, cross linking catalysts and antifoaming agents etc. The polyols employed either difuctional or trifunctional aliphatic and/or aromatic polyether and/or polyester polyols. A molar excess of isocyanates and polyols are reacted to get the desired isocyanate terminated polyurethane prepolymer. Various stabilizers, catalysts and antifoaming agents are used in the formulation. Isocyanates: Both the aromatic/aliphatic isocyanates are suitable for prepolymer system of the present invention. The aromatic polyisocyanates include tolylene diisocyanate (TDI), such as the 80/20 or the 65/35 isomer mixture of the 2,4 and 2,6 isomeric forms, diphenylmethane diisocyanate (MDI) such as the 4,4' the 2,4' and the 2,2' isomeric forms or isomeric mixture thereof; modified MDI containing additional functional groups such as carbodiimide groups, urethane groups and allophanate groups and polymethylene polyphenylisocyanates (Polymeric MDI). Most preferred polyisocyanate is the carbodiimide containing MDI which is readily available commercially, e.g., Isonate RTM.143L and Rubinate RTM.XI-168. Amongst aliphatic isocyanates like 1,6 1 Iexamethylene diisocyanate (HMDI), Isophorone diisocyanate (IPDI), etc. are suitable for the prepolymer. Polyols ; The polyols are selected for the present invention include polyether polyols and polyester polyols. The polyether polyols are regarded as the polymerization of epoxides, such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide, or mixtures thereof in the presence of the catalysts. The polyester polyols include the reaction products of polyhydric alcohols and polybasic carboxylic acids, acid anhydrides. Polyesters of lactones, such as epsilon-caprolactone may also be used. Most preferred polyols are the poly (oxypropylene) glycols (PPG) and triols, having a molecular weight of 400 to 2,000. Examples of polyols are Pluracol. RTM. PI010 and Poly G.RTM.36-232. The preferred polyurethane prepolymer is made from diphenylmethanediisocyanate containing carbodiimide groups. These diisocyanates are reacted with a polyol containing two to three functional groups. The polyols may be diols or triols or mixtures of diols and triols. The preferred polyols are poly (oxypropylene) glycol having a hydroxyl number of 105 and poly (oxypropylene) triols having a hydroxyl number of 232. The molecular weight of the polyols is usually below 2,000, preferably in the range of 700 to 1500 and most preferably between 700 and 1,100. Polyethylene glycol (PEG) with varying molecular weight ranging from 200 to 2000 and copolymer polyol based on ethylene-propylene oxide with varying ratio from 65:35 to 95:5 are suitable polyol for the prepolymer. Catalysts The series of catalysts used for formulation are Bis (2-dimethylaminoethyl) ether, Triethylenediamine (DABCO), Cyclohexylamine (polycat 9), Cyclohexylamine (polycat 70), Cyclohexylanine (polycat 77), Dimethylethanolamine, Substituted morpholine. dimethylpiperazine, dimethylaminoethyl-3 -dimethyl aminopropylether, dimorpholinoethane, tetraethylethyleneamine. Imidazole, triethanol amine, 1,3 bis (dimethylamino) 2-propanol, dimethylaminoethoxy ethanol, dimorpholiethylether, dimorpholinodiethylether, dimorpholinodiethylether etc. The prepolymer also contains from 0.1 to 10% by weight based on the weight of the total mixture of the dimorpholinodiethylether catalyst. The preferred amount of catalyst is from 1% to 4% based on the weight of total mixture. A small amount of co-catalyst like dimorpholinodiethylether is used alongwith the prime catalyst such as tertiary amine or a metal catalyst. In addition to the polyisocyanate, the polyol and the catalyst, the prepolymer reactants may also include a small amount 0.01% to 1% by weight, of a stabilizer such as benzoyl chloride and a surfactant agent such as a silicone liquid used as an antifoam agent. The surfactant or antifoam would be present in an amount of from 0.01% to 1% by weight. WORKING EXAMPLES EXAMPLE 1 TDI, PEG and PPG succinic anhydride (SA) based prepolymer 25.52 g of TDI was taken in a 250 ml three necked round bottom flask, kept in a water bath and purged with nitrogen for 10 minutes. A thermometer was fitted to the one neck of the flask to record the temperature and over-headed stirrer was kept on stirring 66.18 g PEG-1000, 7.30 g of PPG-1000 and 3.0 g Succinic anhydride were mixed thoroughly and added dropwise at room temperature (30°C) over a period of half an hour, the exotherm of about 10°C was observed. The temperature had been raised to 45°C and was maintained for half an hour, the sample was withdrawn to check isocyanate content. On achieving required isocyanate content of 6.6%, the reaction was stopped and cooled down to room temperature. The set time of the bandage made with this prepolymer on polyester/cotton fabric was about 5 minutes. EXAMPLE 2 TDI, MDI, PPG, PEG, TMP and succinic anhydride based prepolymer 18.19 g of TDI and 26.16g of MDI was taken in a 250 ml three necked round bottom flask, placed in a water bath and purged with nitrogen for 10 minutes. A thermometer was fitted to the one neck of the flask to record the temperature and over headed stirrer was kept on stirring 3.65g of TMP was added and NCO content was checked periodicals After achieving the desired NCO content, the temperature was brought down to 40°C. 30.0 g of PPG and 20.0g of PEG 600 were premixed and added dropwise. The temperature was raised to 55°C and maintained for an hour to achieve the desired isocyanate constant. The set time of the bandage made with this prepolymer on polyester/cotton fabric was about 5 minutes. EXAMPLE 3 MDI, PPG, PEG, TMP and succinic anhydride based prepolymer 52.1 0g of MDI was taken in a 250-ml three necked round bottom flask, placed in a water bath and purged with nitrogen for 10 minutes. A thermometer was fitted to the one neck of the flask to record the temperature, over heated stirrer was kept on stirring. Temperature was raised to 45°C. After complete melting of MDI, 4.59g of TMP was added and the temperature was raised to 70°C. After holding for one hour at 70°C the temperature was brought down to 55°C. 25.0g of PPG-1000, 16.65g of PEG-600 and 1.65g of succinic anhydride were premixed and added drop wise over a period of half an hour. After 45 minutes, the required isocyanate value was achieved. After cooling down to room temperature, 50 g toluene was added to dilute the high viscous prepolymer. The set time of the bandage made with this prepolymer on polyester/cotton fabric was about 5 minutes. EXAMPLE 4 Parti 59.68g of TDI was taken in a 3 necked, 250 ml round bottomed flask fitted with stirrer and a water condenser and placed in a water bath. 25.0g of ethyl acetate was added and mixed thoroughly under nitrogen at 40-45°C. 15-32g of TMP flakes were added step wise, 3-4g portions each at an interval of 10 minutes, to control the exotherm. After complete addition, the temperature had been raised to 72°C and maintained until the required NCO content was achieved. The NCO content had been checked for every 30 minutes. After achieving required NCO content, the reaction flask was cooled down to room temperature and the prepolymer resin was collected in a dry, clean, and air tight glass bottle. Part 2 25.0g of MDI was taken in a 3 necked 250 ml round bottom flask fitted with stirrer, water condenser and placed in a water bath. 25.0g of ethyl acetate was added dropwise and stirred under dry nitrogen at 45-50°C. 50.0g of polyol (PPG-1000) was added in 30 mintues. After complete addition, temperature was raised to 75-80°C and maintained until the required NCO content. Part 1 and Part 2 were mixed in ratios like 10:90. 20:80, 30:50, 40:60, 50:50, 60:40. 70:30, 80:20, and 90:10 along with lphr DMDEE, 0.5phr PDMS and 0.5 phr Benzoyl chloride in nitrogen atmosphere. The properties in Table 1 guided the suitability in casting tape formulation. Table 1 (Table Removed) EXAMPLE 5 The fiber tape was impregnated with calculated amount (10-90%) by weight preferably 40-60%) to resin mix as mentioned in Example 6, dipped into the water surface, taken out, excess of water was squeezed out and various specimen prepared as per ASTM standards D5083 and F 1536-95. Ta ble 1 Based on glass fiber (Table Removed) WE CLAIM: 1. Polyurethane prepolymer formulation for orthopaedics casting tape comprising a water-activatable polyurethane prepolymer resin mix impregnated in a knitted-weave fibrous substrate, said prepolymer comprising a prepolymer (A) having a aromatic diisocyanate, polyol and a solvent and a prepolymer (B) having a aromatic diisocyanate, a polyol and solvent in the ratio of from 10:90 to 90:10, 0.5% to 2% based on the weight of prepolymer, of dimorpholinodiethylether as a catalyst, 0.5% of stabilizer benzoyl chloride and 0.5% of antifoaming agent poly (dimethylesiloxane). 2. Polyurethane prepolymer formulation as claimed in claim 1 wherein prepolymer mix wherein prepolymer A and prepolymer B is present in the ratio to 30:70 to 60:30 and more specifically from 60:40 to 50:50 respectively. 3. Polyurethane prepolymer formulation as claimed in claim 1 wherein toluene diisocyanate is a mixture of 80% of 2, 4-isomer and 20%o of 2, 6-isomer. 4. Polyurethane prepolymer formulation as claimed in claim 1 wherein the polyol is 1,1,1 tris hydroxymethyl propane and acts as cross linking agent in said prepolymer resin mix. 5. Polyurethane prepolymer formulation as claimed in claim 4 which contains an aromatic monomeric diisocyanate, methylene di-p-phenylene-di-isocyanate, a polyol, poly propylene glycol. 6. Polyurethane prepolymer formulation as claimed in claim 1 wherein the prepolymer A and prepolymer B contains solvent as dilutent namely methylene chloride, ethyl acetate, butyl acetate, iso amyl acetate, isopropyl acetate, toluene, xylene, benzene, dimethyl formamide, dimethyl acetamide etc. 7. Polyurethane prepolymer formulation for orthopaedics casting tape substantially as herein described and illustrated in the example.

Documents:

1533-DEL-2005-Abstract-(13-04-2009).pdf

1533-del-2005-abstract.pdf

1533-DEL-2005-Claims-(13-04-2009).pdf

1533-del-2005-claims.pdf

1533-del-2005-Correspondence-Others-(05-04-2010).pdf

1533-DEL-2005-Correspondence-Others-(13-04-2009).pdf

1533-del-2005-Correspondence-Others-(22-03-2010).pdf

1533-DEL-2005-Correspondence-Others-(25-03-2010).pdf

1533-del-2005-correspondence-others.pdf

1533-del-2005-correspondence-po.pdf

1533-DEL-2005-Description (Complete)-(13-04-2009).pdf

1533-del-2005-description (complete).pdf

1533-del-2005-form-1.pdf

1533-del-2005-form-18.pdf

1533-DEL-2005-Form-2-(13-04-2009).pdf

1533-del-2005-form-2.pdf

1533-DEL-2005-Form-3-(13-04-2009).pdf

1533-DEL-2005-GPA-(25-03-2010).pdf