Title of Invention

"A PROCESS FOR PREPARATION OF TITANIUM BASED METALPRIMER COMPLEX"

Abstract

This invention relates to a process for preparation of Titanium based metal-primer complex wherein the said process comprises of reacting in the ratio of 2:1 resol solution prepared in spirit with polyvinyl formal prepared in a mixture of ratio of 5:2 of spirit and xylene to form polymer blend, said etching is carried by reacting a mixture of nitric acid, hydrofluoric acid and water in the ratio of 20:5:75 of titanium as transition metal and water surface, applying said polymer blend onto said surface of said transition metal, curing as herein described of said metal surface coated with said polymer blend.

Full Text

FIELD OF THE INVENTION This invention relates to a process for preparation of Titanium based metal-primer complex. PRIOR ART OF THE INVENTION The adhesive bonding is one of the engineering practice used for joineries. The stability of the adhesive bonds is very important in this area of specialised application. The strength of the adhesive bonds decides on the suitability, particularly on the long term application of the metal surfaces coated with the adhesive. The metal surface is generally coated with the adhesive, which in-turn forms the metal adhesive bonds, inorder to make the metal surface, preferably, more inert to the corrosive environment, more particularly to the water, ever more particularly to the sea water environment. Therefore, the suitability, particularly the long-term applicability, of the metal is generally enhanced by coating it with the adhesive. This technique of coating the metal surface with adhesive is more generally used for underwater application, more particularly for under sea-water applications. In order to achieve this objective generally adhesive is applied directly on to the metal surface after sand blasting or etching with acid such, as with hydrochloric acid or with hydrofluoric acid. Such known methods of generating the metal-adhesive bonds, generally results in the poor bonding that is to say the metal-adhesive bond thus fromed in very weak. Still another major drawback of such metal-adhesive bonds generated on direct application of adhesive onto the metal surface after sand blasting or after etching with acid, such as hydrochloric acid or hydrofluoric acid, as stated herein above is that, the peel strength of such bonds is of the order of 2 to 3 kg/cm. Such metal-adhesive bonds formed on direct application of adhesive on to the metal surfaces are generally not chemical in nature, more particularly are not covalent in nature. Therefore, the major drawback of such bonds between metal and adhesive is their unsuitability for long-term application particularly in corrosive environment, more particularly in under-water, even more particularly in under seawater applications. OBJECTS OF THE INVENTION A primary object of this invention is to propose a process for preparation of metal-primer complex to enhance the metal-adhesive bond strength. A further object of the present invention is to propose a method of preparation of metal surface, which can form a strong metal-adhesive bond for long-term applications, particularly for underwater applications. Another object of the present invention is to propose a process for preparation of metal-primer complex which is more suitable to form chemical bond, particularly covalent bond with the adhesive. A further object of this invention is to propose a process for preparation of metal-primer complex and of the products thereof, which have higher peel strength after forming the metal-adhesive bond. Still another object of this invention is to propose a process for preparation of metal-primer complex and for the products thereof, which obviates the disadvantages of the known art of applying the adhesive directly onto the metal surfaces for such purpose as described herein above. According to this invention there is provided a process for preparation of Titanium based metal-primer complex wherein the said process comprises of: i) reacting in the ratio of 2:1 resol solution prepared in spirit with polyvinyl formal prepared in a mixture of ratio of 5:2 of spirit and xylene to form polymer blend, ii) said etching is carried by reacting a mixture of nitric acid, hydrofluoric acid and water in the ratio of 20:5:75 of titanium as transition metal and water surface, iii) applying said polymer blend onto said surface of said transition metal, iv) curing as herein described of said metal surface coated with said polymer blend. The process of the present invention comprises in four steps. The first step comprises of preparation of polymer blend by blending the solutions of resol and polyvinyl formal. The metal surface is prepared by conventional method followed by reaction with mixture is nitric acid, hydrofluoric acid and water in the second step of the process of this invention. The third step of the presently disclosed invention comprises of applying coating of polymer blend, prepared in first step in accordance to the present invention, onto the metal surface after reaction of second step of this invention. The fourth step of the presently disclossed invention is characterised by curing of the metal surface coated with polymer blend to result in metal- primer complex. The cured metal-primer complex is reacted with the desired adhesive, which in turn results in the stable bond even in underwater application. In accordance to the preferred embodiment of the present invention the polymer blend is formed on reaction of solution of resol and polyvinyl formal. According to the most preferred embodiment of this invention the solution of resol is prepared in spirit and that of polyvinyl formal is prepared in mixture of spirit and xylene. Still according to this preferred embodiment the spirit and xylene are most preferably taken in 5:2 ratio for preparing the solution of polyvinyl formal . The solutions of resol and polyvinyl formal, as prepared in accordance to the preferred embodiment of this invention, are taken in a ratio so that the ratio of resol and polyvinyl formal is most preferably maintained at 2:1. According to the preferred embodiment of this invention the polymer blend, prepared in accordance to the preferred embodiments of the present invention, as desired herein above, has viscosity of 80 to 115 cps, preferably of 90 to 105 cps. According to another preferred embodiment the metal surface after treatment with conventional technique is reacted with the reaction mixture of nitric acid, hydrofluoric acid and water followed by washing with water and air drying. In accordance to the most preferred embodiment of this invention the ratio of reaction mixture of nitric acid, hydrofluoric acid and water is essentially 20:5:75. The conventional technique, as referred herein above, is the sand blasting followed by degreasing with organic solvent, preferably trichloroethylene. The polymer blend prepared in accordance to the most preferred embodiment of this invention is applied onto the etched surface after the etched surface has been washed and dried, as stated herein above. The coated metal surface is cured in accordance to the most preferred embodiment of this invention. The curing of etched metal surface coated with the polymer blend is essentially carried out in-situ. In accordance to the most preferred embodiment of this invention the in-situ curing is carried out by stepwise curing. The stepwise curing is characterised by first heating at temperature of 65 to 75 degree centrigrade for hour followed by second heating at temperature of about 115 to 125 degree centigrade for 5 hours preferably, subsequently followed by conditioning at room temperature for about 24 hours. The cured metal-primer complex formed on the metal can find application in the area, where so ever the strong bonding is required to be formed with the adhesive particularly for underwater applications. In accordance to the preferred embodiment of this invention the cured surface of the metal-primer complex formed onto the metal is roughened, preferably with fine emery paper, cleaned, preferably with alcohol, more preferably with isopropanol and kept at room temperature for 1 hour prior to bonding with the adhesive. The metal-primer complex formed in accordance to the process of this invention definitely provides a good environmental protection to the metal-adhesive interface. The strong bonding is formed at interfaces between metal and primer, and between primer and adhesive. Therefore, the water can not displace the strong bond formed at the two interfaces, as disclosed herein, and hence, establishing the superiority of the metal-primer complex formed in accordance with the present invention. A comparative study of the adhesive bonds made with the metal-primer complex, prepared in accordance to the present invention, and with metal directly, with the valucanised styrene butadiene rubber using particular ly epoxy adhesive has shown that, the peel strength of the adhesive-metal (unprimed) bond is of the order of 2 to 3 kg/cm and whereas, that of, the adhesive-metal (orimed in accordance to the process of the present invention) bond is of the order of 7 to 8 kg/cm. The metal, as referred herein this description is preferably transition metal, more preferably inert metal, even more preferably titanium. The metal- primer complex, as referred herein this description means the complex formed between the etched metal and the polymer blend, which in turn are prepared in accordance to the most preferred embodiments of this invention as described herein above. The titanium-metal primer complex as referred herein this description, is the complex formed on reaction of polymer blend, referred as primer in general and "metal primer" in particular and prepared in accordance to the preferred embodiments of the present invention, with titanium. The foregoing description has been particularly referred to the titanium, however, this metal-primer complex can be prepared using any such metal as referred herein above. The applications of the presently disclosed products, that is, metal-primer complex have been stated in formation of bonding with adhesive for underwater, particularly under sea water applications. However, the products of the present invention may find application in any such area requiring the strong bonding between metal-primer and adhesive. The specific ratios of various reactants have been disclosed as these specific ratios definitely result in formation of stable meta l-primer-adhesive complex as disclosed herein above. WE CLAIM; 1. A process for preparation of Titanium based metal-primer complex wherein the said process comprises of:- i) reacting in the ratio of 2:1 resol solution prepared in spirit with polyvinyl formal prepared in a mixture of ratio of 5:2 of spirit and xylene to form polymer blend, ii) said etching is carried by reacting a mixture of nitric acid, hydrofluoric acid and water in the ratio of 20:5:75 of titanium as transition metal and water surface, iii) applying said polymer blend onto said surface of said transition metal, iv) curing as herein described of said metal surface coated with said polymer blend. 2. A process as claimed in claim 1 wherein the curing is essentially carried-out in-situ. 3. A process as claimed in claim 1 wherein said curing is done stepwise:- (a) first heating at 65 to 75 degree centigrade preferably for 1 hour, (b) second heating at 115-125 degree centigrade preferably for 5 hours. (c) Conditioning at room temperature for about 24 hours. 4. A process as claimed in claim 1 to 3 wherein the said conditioning is done at room temperature preferably for 1 hour. 5. A process for preparation of Titanium based metal-primer complex substantially as herein described.

Documents:

420-del-1997-abstract.pdf

420-del-1997-claims.pdf

420-del-1997-correspondence-others.pdf

420-del-1997-correspondence-po.pdf

420-del-1997-description (complete).pdf

420-del-1997-form-1.pdf

420-del-1997-form-19.pdf

420-del-1997-form-2.pdf

420-del-1997-form-3.pdf

420-del-1997-gpa.pdf