Title of Invention	A PROCESS FOR THE PREPARATION OF BIS-GMA,
Abstract	This invention relates to a process for the preparation of disphenol a-glycidyl methacrylate by condensation reaction between diglycidyl ether of bisphenol a and met acrylic acid int eh presence of a catalyst such as herin described at a temperature in the range of 75 to 85 c for a period of 8 to 12 hrs. and recovering the pure bis-gma in a manner such as herein described.

Full Text

This invpnticn relates tn a process for the preparation of bisphenoi H- giycidyi methacrylate for use in a visible light cured composite for dental restorat ive purposes. This application has been divided out of parent- patent applica¬tion Na.279/Mas/93 of 26.4.93. Visible light cured composites are used as an aesthetic dental restorative. Such composites comprise a single paste system which is activated by exposing to intense blue light of the spectrum. Once it is activated) the paste gets cured in a few minutes. The system is widely accepted as it has several advantages) such as excellent shelf life, ease of handlingi less discoloration from ini tlator and an unlimi ted working time. An object or this invention is to propose an improved process for the preparation of a visible light cured composi te for dental restorst ive purposes. Another object of this invention is to propose a process for the preparation of a visible light cured composite having a di ametral tensile strength of 35-37 MPa• Still another object of this invention is to propose a process for the preparation of'a visible light cured composite having a compress!ve strength of 220-240 MPa. Yet another object of this invention is to propose a process for the preparation of a visible light cured composite which has an aesthet ic appearance. According to this invention, there is provided a process for the preparation of bisphenol A-glyeidyl methacrylate (bis-GMA) by condensation reaction between Diglycidyl ether of Bisphenol A and Methacryl ic acid in the1 presence, of a catalyst such as herein o described at a temperature in the range of 75 to 85 C for a period of S to 12 hrs. and recovering the pure b is-GMA in a manner such as herein described. The bisphenol A-glye idyl mathaery late ibis—8MA> thus prepared is used for the preparation of visible light cured composi fce materials* which can be used for restorati ve and orthodontic applications in dentistry. Preparation of the visible light cured composite comprises in the steps of s x■ preparing a resin mixture by the- addition of resins such as bisphenolA-glycidyl methacrylate (Bis-SfIA), its derivatives or any aromatic dimethacryiates and at least an initiator and accelerator, said accelerator selected from aromatic amines such as herein described j ii, preparing a visible light.curing paste by adding said resin •nixture to a filler such as silane treated quartz and mixing in the absence of sunliqht; 'iii. subjecting the paste to exposure in a visible light source emitting blue light. This is in the form of a high viscous paste which is applied directly to the site of application and cured in situ with the help of a light source. Resin Synthesis The base resin can be 2,2-bis /_4- oxy-propoxy)-7 phenyl propane or Bis-GMA>, its derivatives or any aromatic dimethacrylates. Bis-SMA is synthesised by the condensation reaction of Diglycidyl ether of Bisphenol-A and methacrylic acid by taking in trie molar ratio 1 s2. 1« "f he reaction is. catalysed by aromatic terti ary amines like N,N Dimethy1-p-toluidine at 60 C in an inert atmosphere. The reaction proouct is diluted with extra pure methylene chloride and washed with dilute sodium hydroxide and hydrochloric acid followed by distilled water, followed by drying by standard procedure such as tui th anhydrous sodium sulphate or by vacuum distillation. The resin solution in iiiuLiiyj-ene cnioiriQe xs tnen mnioitect with bU ppm of hydroquxnone, its derivatives or any hindered phenols. The .methylene chloride is removed by a flash evaporator under vacuum at a temperature of 60 °C. Filler Preparation Several kinds of fillers are employed in Bis-GMA based composites, said fillers selected from Quartz, Borosilicate glasses, lithium aluminium silicates and various aluminosilicate glasses. Also glasses containing radiopaque salts, rnicrofine fillers like fumed silica or silicon dioxide can be employed as fillers. The filler must be inert, hard, without colour and reinforcing. Depending upon the source it may require purification/ grading, etc. The purified material may be treated with coupling agents to improve interfacial bonding between the filler and the resin. The coupling agents generally used are silanes. The quartz obtained from local source is graded by using a seiving mechine/sedimentation, purified by washing with 75% hydrochloric acid and calcination at 800°C. The graded quartz powder of particle size below 20 microns are treated with trimethoxyl silyl propyl methacrylate (1% w/w of filler) from low volatile solvents like acetone. The acetone has been removed -by stirring and subsequent drying at 70°C or any appropriate temperature. Resin mixture preparation Since the resin is a highly viscous fluid/ the handling and incorporation of filler will be difficult. So it is essential to add low viscosity reactive diluents like di~or multifunctional methacrylates or similar monomers with unsaturation. Initiators can be alpha diketones which will be activated with visible light. Rate of initiation may be speeded up by adding electron donating species like tertiary amines. The premature polymerisation is prevented by adding inhibitors like quinones* hindered ph-anbls etc. Also stability to UV light and colour may be achieved by adding phenyl salicylate or 2-Hydroxy-4-methoxi bensophenone. Here 70 parts of Bis-GMA is mixed with 30 parts of triethylene glycol dimethacrylate. 0.25 parts each of camphorquinone and N,N-dimethyl-p-toluidine are 'i added as the .initiator system. The mixture is then inhibited with 0.09 parts of butylated hydroxy toluene. 0.09 parts of phenyl salicylate and 0.04 parts of 2-hydroxy-4-methoxy benzophenone are added as stabilizers. The resulting mixture is thoroughly mixed to di3solve the additives and to get a homogenous mixture. This is termed as resin mixture. Preparation of visible light curing paste 25 parts of the above resin mixture is taken and mixed with 72 parts of silane treated quartz. An amount of 3 parts by weight of silane treated pyrogenic silica is added to prevent the filler sedimentation and i thoroughly in the absence of sunlight to get a homogenous paste. Composite The paste thus prepared is subj ected to exposure in a visible light source emitting blue light of wave length in the region 440-480 nm resulting in a hardened composite. The composite when tested for mechai properties according to American Dental Association Specification No.27 gives a Diametral Tensile Strength 35-40 MP a and Compressive Strength of 200-230 MPa. The process of the present invention will be better understood by a reference to Fig.l accompanying drawing. Fig. 1 illustrates the flow chart of the process of the present invention. The composite prepared by the process of the present invention and as described herein has the follow: properties: WE CLAIMS . 1. A process for the preparation of PisphenoL a—glycidyl methaerylate (bis-GMA) by condensation react ion between diglycidyl ether of Bisphenol A and Methacrylic acid in the presence of a catalyst such as 'herein described at a temperature o in the range of 75 to B5 G for a period of 8 to 12 hrs. and recovering tHe pure bis-GMA in a manner sucH as herein described. 2. A process as claimed in c: la i.m 1 wherein said preparation of Bis-GMA is catalysed by tertiary amines such.as N»N~dimethy1-p- toluidine or ammonium salts such as benzyl triethyI ammonium chloride . 3. A process as claimed in claim i where in Bis-SrfA is synthesised in an inert atmosphere of nItrogen at a temperature of, for eg. o 60-60 C. 4. A process as c 1 aimed in claim l wherein Bis-6fiA is puri f ied by dissolving in dichloromethane and washing the dichloromethane solution with sodium hydroxide followed by hydrochloric acid to remove the catalyst and unreacted methacrylic acid > washing the dichloromethane solution with distilled water to make it ac id free, removing the water by decantatian> traces of , water being removed by drying wi th anhydrous sodium sulphate or by vacuum distill at ion to obtain pure bis-SflA. 5. A process as claimed in claim 5 wherein £is-6HA is optionaly inhibi ted by dissolv ing hydroquinone in it.

Documents:

1615-mas-1997 abstract.pdf

1615-mas-1997 claims.pdf

1615-mas-1997 correspondence others.pdf

1615-mas-1997 correspondence po.pdf

1615-mas-1997 description (complete).pdf

1615-mas-1997 form-1.pdf