Title of Invention

"A NOVEL ADHESIVE AND A PROCESS FOR PREPARING THE SAME"

Abstract

The present invention provides a novel hydrophobic transparent colorless ready to use and with nothing to mix prior to application viscous adhesive comprising a polymerized styrene wherein the styrene is polymerized using chlorinated olefins in presence of initiator and plasticizer. The adhesive has viscosity in the range of 50 to 200 poise and has a shelf life of at least three months. The adhesive has a high strength of bond and is capable of bonding varied materials such as paper, glass, ceramics, decorative or precious stones without affecting their appearance and economic value. The adhesive also can be used to fix optical lenses so as to prepare high-refractive index glasses. The adhesive of the present invention has the unique feature of restoring its viscous property after solidification, which can be restored by subjecting the adhesive to indirect heat such as exposing the container containing the adhesive to steam or boiling water till it liquefies.The invention also discloses a process comprising polymerizing, by known methods, styrene using chlorinated olefins as an organic additive, benzoyl peroxide or 2,2'-azo-bis-isobutyrylnitrile (AIBN) as an initiator and phthalate as a plasticizer. the chlorinated olefin employed is C2 series with boiling point in the range of 80 C to 100 C, and selected from C2Cl4 CCl4, C2CL6, more preferably C2Cl4.

Full Text

THE PRESENT INVENTION RELATES TO A NOVEL ADHESIVE AND A PROCESS FOR PREPARING THE SAME. FIELD OF INVENTION: Particularly, the invention relates to an adhesive that is transparent, colorless and ready to use. As such there is no need to mix the adhesive with any thing prior to application. More particularly, the invention relates to an adhesive that is hydrophobic in nature and gives improved smooth appearance to the bonded product. Still more particularly, the invention relates to an adhesive with a high strength of bond and which is capable of bonding varied materials such as paper, glass, ceramics, stones, preferably decorative or precious, without affecting their appearance and economic value. Particularly, the adhesive can be used to fix optical lenses so as to prepare high-refractive index glasses. Yet more particularly, the invention relates to an adhesive that is viscous in nature. Further, one of the unique features of this adhesive is that the thickened adhesive after its shelf life can be restored for application by subjecting the adhesive to indirect heat. BACKGROUND OF THE INVENTION: Adhesives are the materials used for joining various components and often replace routine mechanical fixing methods due to certain inherent advantages. A number of adhesives are already in the market. These adhesives are drawn from natural substances, synthetic resins, or polymers and thus have their own limitations for application. Key types in today's industrial scene are: Anaerobics: Generally based on acrylics, these adhesives are useful for securing seals in close fittings. However, absence of air is essential for its working. Cyanoacryiates: Special type of acrylics that cure through reaction with moisture available on the bonding surfaces. Normally, these are suitable for bonding plastic to rubber. Toughened Acrylic/Methacrylates: Fast curing high strength and toughness adhesives are usually supplied in two parts, which need to be mixed just prior to application. Requires proper surface preparation for fixing. UV curable: Modified acrylic and epoxy adhesives, which are cured on exposure to UV radiation and require one substrate to be UV transparent. Epoxies: Consist of epoxy resin and hardener. These adhesives are available in one or two parts. They can form extremely strong bonds and bear gap filling capability up to 25mm. Polyurathanes: These adhesives are commonly one part moisture curing and are found useful for glass-fibre reinforced plastics. Modified Phenolics: These adhesives find application in metal bonding. However, they require heat and pressure for curing. Hot-melt adhesives, Rubber adhesives, Plastisols, Polyvinyl acetates and pressure sensitive adhesives are few more adhesives that are marketed on high scale. The prior art, as known to the within inventor, additionally, includes US 2002,0153086 dated October 24, 2002. The invention relates to fabrication of elastic webs using hot-melt adhesives. Though the adhesive has an advantage of not using liquid carrier thereby reducing cost on drying, the shortcoming associated with these adhesives is their less durability. They are, usually, susceptible to extreme temperatures. The aforesaid invention teaches use of hot-melt, pressure sensitive adhesive. It advocates use of two different adhesives for two substrates to be fixed. Styrene- isoprehe-styrene based adhesive is applied to one substrate and polyurethane based adhesive to the other substrate. This makes the process complex and time consuming. Further, the joint thus obtained lacks durability, as the adhesives used are susceptible to extreme temperatures and pressures. Recently, a number of patents as exemplified below have been granted in the field of adhesive formulations and their applications for varied types of materials: > Polymer bonding grains of sand using styrofoam fluff as an adhesive (US 5, 041,250) > Adhesive blends for polystyrene (US 5,597,865) > Polystyrene-ethylene/butylene-polystyrene hot-melt adhesive (US 5,459,193) > Adhesive blend of polyolefins and grafted block copolymer of polystyrene (US 5,070,143) > CO'CXtrudable adhesive for polystyrene, and products there from (US 4,861,677) > Hot-melt adhesive compositions containing a polystyrene resin (US 4,338,414) All these adhesives suffer from one or the other disadvantage such as lacking transparency, durability, requirement of stringent curing conditions, very specific applicability, and sensitivity to temperatures etc. As can be noted, these adhesives are either water or solvent based and thus require long spells of drying. Another draw back is that they develop yellow tinge on drying and thus reduce the economic value when used for fixing decorative objectives or precious stones. Yet another disadvantage is that most of these adhesives lack transparency and thus they are found unsuitable for optical glasses. Still yet another disadvantage is that these adhesives cannot be made reusable after the expiry of shelf life. Yet another draw back of some of the existing adhesives is the requirement of two-coat adhesive system thereby resulting in weak adhesion. There is an imperative need to develop an adhesive that can be successfully used for fixing optical glass, ceramics, inorganic glass, decorative objectives and precious stones without losing their appearance and/or functional property and thereby affecting their economic value. The main object of the present invention is to prepare and provide an adhesive that is transparent, colorless and ready to use and with nothing to mix prior to application. Other object of the present invention is to prepare and provide an adhesive that is hydrophobic in nature, thereby preventing the strength of the bond from getting affected on contacting with water at ambient temperatures. Another object of the present invention is to prepare and provide an adhesive that gives an improved smooth appearance to the bonded product. Further objective of this invention that all the ingredients used are readily available commercially. The polystyrene can also be prepared easily. Still another object of the present invention is to prepare and provide an adhesive that is highly durable, strong and is capable of bonding varied materials such as paper, glass, ceramics, decorative or precious stones without affecting their appearance and/ or economic value. Yet another object of the present invention is to prepare and provide an adhesive that is useful for the preparation of high-refractive index glasses, for optical applications, by sandwiching the adhesive layer between two lenses. Still another object of the present invention is to prepare and provide an adhesive that is viscous in nature and having a good shelf life. Further object of the present invention is to prepare and provide an adhesive whose shelf life can be restored and the adhesive can be used for applications beyond its prescribed shelf life. One of the objects of the present invention is also to provide an improved process for preparing the adhesive as herein before described. The improvement may be achieved by selectively using appropriate ingredients as hereinafter described. After considerable experimentation, it was observed that the properties of polystyrene change when certain chemical additives are present during its formation. The polystyrene is relatively inert chemically; quite resistant to alkalis, halide acids, oxidizing and reducing agents; highly transparent; has a high refractive index; durable; hydrophobic; environmentally safe and can be easily produced. The observation of sticky nature of the polymeric solution that sets quickly gave an idea of exploring polystyrene for making an adhesive by sustaining its viscosity and regulating the state of its polymerization to desired level. The process of the present invention aims at using the additives selectively that would help in retaining viscosity without hampering the properties of the adhesive. In the course of experiments on reaction-injection molding of polystyrene, serendipity led to a couple of organic additives originally intended to serve as blowing agents, but instead providing the key function for the present novel adhesive product. Carbon tetrachloride, a widely used blowing agent, when present during the preparation of polystyrene imparts yellow color to the polymer and is thus found unsuitable as an additive even though it helps in retaining the viscosity. After prolonged research, which included evaluation of chlorofluorocarbons (CFC), pentanes, carbon dioxide and water etc., it was noticed that the use of chlorinated olefins as an organic additive produced a good quality polymer obviating most of the disadvantages such as the effects on ozone layer, being the cause of low-level smog, green house effect or resulting in poor quality product. It was also noticed that chlorinated olefins, when used in combination with conventional plasticizers and initiators, improved the quality of the polymer as an adhesive. Accordingly, the present invention provides a novel adhesive comprising a polymerized styrene wherein the styrene is polymerized using chlorinated olefins in presence of initiator and plasticizer such as herein described. According to one of the embodiment of this invention, the adhesive is transparent colorless and ready to use and with no requirement to mix with any other ingredient/ substance (s) prior to it's application. According to other embodiment of this invention, the adhesive is hydrophobic in nature and gives improved smooth appearance to the bonded product. According to another embodiment of this invention, the adhesive has a high strength of bond and is capable of bonding varied materials such as paper, glass, ceramics, decorative or precious stones without affecting their appearance and economic value. According to yet other embodiment of this invention, the adhesive can be used to fix optical lenses so as to prepare high-refractive index glasses. According to yet another embodiment of this invention, the adhesive is viscous in nature, has viscosity in the range of 50 to 200 centipoise. According to still other embodiment of this invention, the unique features of this adhesive is that the thickened adhesive after its shelf life can be restored for application by subjecting the adhesive to indirect heat such as exposing the container containing the adhesive to steam or boiling water till it liquefies. According to still another embodiment of this invention, the adhesive has adhesion close to commercially available adhesive. Accordingly the present invention also provides a process for preparing the adhesive as herein before described, which comprises polymerizing, by known methods, styrene using chlorinated olefins as an organic additive, benzoyl peroxide or 2,2'-azo-bis-isobutyrylnitrile (AIBN) as an initiator and phthalate as a plasticizer. Chlorinated olefin employed may be such as C2 to C3 series, preferably C2 series with boiling point in the range of 80 C to 100 C, exemplified by C2Cl4_ CCI4, C2CL6, more preferably C2CI4 [tetrachloroethylene]. The ratio of chlorinated olefin to styrene may vary from 0.5 to 1.0 v/v. Phthalate such as diethyl phthalate (soluble) or potassium hydrogen phthalate (insoluble) may be used as a plasticizer and may range from 0.8 to 1.2 g per 10 ml of styrene. The initiator employed should not exceed 20% w/v of styrene and preferably may be added between 10 and 20% w/v of styrene. The reaction may be carried out at a temperature between 80°C to 95°C for a period of about two hours. The adhesive, prepared by the method of the present invention, has a quality of restoring its viscous nature. The bonding time is usually one day. However, prolonged bonding time of a week results in doubling the strength. The bond strength is about 1800 kgf/m as against 200 to 1550 kgf/m of the commercially available adhesives such as paper glue, fevi-stick and quick-fix. Moreover, the adhesive is transparent, colorless, and hydrophobic and has a high refractive index. The visocity of the adhesive varies from 50 to 200 poise. The curing and application of the adhesive does not require stringent conditions. The adhesive can be well stored at a wide range of temperature ranging from 0°C to 50°C without affecting its property. ADVANTAGES: 1. The adhesive of the present invention is transparent, colorless and ready to use. 2. The adhesive of the present invention is highly durable, hydrphobic and has a high refractive index. 3. The adhesive of the present invention is environmentally safe. 4. The adhesive of the present invention has a high strength of bond. 5. The adhesive of the present invention can be made reusable after expiry of its shelf life. 6. The process for preparing the adhesive of the present invention is economical, environment friendly, industrially feasible and easy to operate. We Claim: 1. A novel hydrophobic transparent colorless viscous adhesive comprising a polymerized styrene wherein the styrene is polymerized using chlorinated olefins in presence of initiator and plasticizer such as herein described. 2. The adhesive as claimed in claim 1, wherein the viscosity of the adhesive is in the range of 50 to 200 poise. 3. The adhesive as claimed in claim 1, wherein the shelf life of the adhesive is of at least three months. 4. A process for preparing the adhesive as claimed in preceding claims comprising polymerizing, by known methods, styrene using chlorinated olefins as an organic additive, benzoyl peroxide or 2,2'-azo-bis-isobutyrylnitrile (AIBN) as an initiator and phthalate as a plasticizer. 5. A process as claimed in claim 4 wherein the chlorinated olefin employed is C2 series with boiling point in the range of 80 C to 100 C, and selected from C2C14, CCl4, C2CL6, more preferably C2Cl4. 6. A process as claimed in claim 4 wherein the ratio of chlorinated olefin to styrene varies from 0.5 to 1.0 v/v. 7. A process as claimed in claim 4 wherein the phthalate such as diethyl phthalate (soluble) or potassium hydrogen phthalate (insoluble) is used as a plasticizer. 8. A process as claimed in claim 4 wherein the amount of phthalate added ranges from 0.8 to 1.2 g per 10 ml of styrene. 9. A process as claimed in claim 4 wherein the initiator employed should not exceed 20% w/v of styrene and preferably be added between 10 and 20% w/v of styrene. 10. A process as claimed in claim 4 wherein the polymerization is carried out at a temperature between 80°C to 95°C for a period of about two hours. 11. A novel adhesive substantially as herein described. 12. A process for preparing the adhesive as claimed in claim 1 substantially as herein described.

Documents:

1646-DEL-2003-Abstract-(14-03-2012).pdf

1646-del-2003-abstract.pdf

1646-DEL-2003-Claims-(14-03-2012).pdf

1646-del-2003-claims.pdf

1646-DEL-2003-Correspondence Others-(14-03-2012)..pdf

1646-DEL-2003-Correspondence Others-(14-03-2012).pdf

1646-del-2003-correspondence-others.pdf

1646-del-2003-correspondence-po.pdf

1646-del-2003-description (complete).pdf

1646-del-2003-description (provisional).pdf

1646-del-2003-form-1.pdf

1646-del-2003-form-18.pdf

1646-del-2003-form-2.pdf

1646-del-2003-gpa.pdf

1646-DEL-2003-Petition-137-(14-03-2012).pdf