WO1986002317A1

WO1986002317A1 - Immobilizer composition

Info

Publication number: WO1986002317A1
Application number: PCT/US1985/001724
Authority: WO
Inventors: Travis W. Honeycutt
Original assignee: Isopedix Corporation
Priority date: 1984-10-19
Filing date: 1985-09-09
Publication date: 1986-04-24
Also published as: EP0198845A1

Abstract

A method of bonding complementary threaded members comprising applying to at least some of the threads of a first member over which a second is intended to pass a quantity of a gelled thixotropic alpha-cyanoacrylate monomer containing composition. This is followed by applying the second member to the first so that it passes over the threads of the first member which have been applied with a gelled thixotropic alpha-cyanoacrylate monomer containing composition.

Description

Description Immobilizer Composition

Technical Field

The present invention deals with a method of bonding complementary threaded members such as a nut and bolt by chemical means. Although the prior art has recognized the need for such materials and has suggested various chemical compositions, prior art solutions have involved certain inherent drawbacks which have made the widespread acceptance of such bonding agents unachievable.

Background of the Invention

Those involved in the metal fabrication and construction trades have long sought a convenient-to- use chemical bonding agent for complementary threaded members. Ideally, such an agent should be easily handled, capable of gap filling threaded members and, when properly applied, result in a chemical bond between the threaded members along their threaded area of contact.

In the late 1950s, Krieble invented a system comprising an acrylate acid diester polymerized by a hydroperoxide which became the subject of U.S. Patent No. 2,895,950. Krieble made certain improvements to this composition which were the subject of U.S. Patent Nos. 3,043,820, as well as 3,046,262 and 3,218,305. Krieble's work was carried on by Gorman et al and Nordlander, whose work resulted in U.S. Patent Mos. 3,425,988 and 3,435,012, respectively. In each instance, the. various inventors described and claimed a chemical composition possessing anaerobic curing characteristics—i.e. compositions which would polymerize upon the exclusion of air or oxygen from the compound.

Being anaerobic, it became apparent that the various acrylate or methacrylate acid diesters polymerized with hydroperoxide could be used as a means of chemically bonding complementary threaded members. It was envisioned that the diester containing composition would be used to coat the threads of a bolt and application of a nut to the threaded area would exclude air or oxygen, thus encouraging polymerization. To some degree, the various compositions disclosed and claimed in the cited prior art have been employed to chemically lock together a nut and threaded bolt and, in fact, these compositions have been employed by Loctite Corporation, which vends a commercial product containing among other constituents acrylate acid diesters for this purpose. However, the use of such materials has not been without its drawbacks. More specifically, being anaerobic, the compositions of the prior art do not polymerize on the threaded bolt at any location other than beneath the nut. As a result, one is left with a liquid monomer containing composition throughout the length of the bolt which must be wiped from the threads in exposed areas. In addition, the above-described prior compositions require a polymerization or set-up time of approximately 30 minutes or longer which can be too long for certain industrial applications. Lastly, the prior anaerobic compositions generally only perform adequately on threaded members comprised of ferrite surfaces. These compositions do not work well on non- ferrites such as ceramics, stainless steel or plastics, etc.

It is thus an object of the present invention to provide a method for bonding complementary threaded members while avoiding the limitations of prior art compositions used for the same purpose.

It is yet a further object of £he present invention to provide a method of bonding complementary threaded members employing compositions which are not anaerobic and thus do not remain liquid in uncovered areas.

It is yet a further object of the present invention to provide a method of bonding complementary threaded members wherein substantially none of the bonding composition remains on the threads of one of the members after passage of the complementary member thereover. As such, thread to thread interstices are substantially filled by employing the present composition.

Summary of the Invention

The present invention comprises a method of bonding complementary members. To at least some of the threads of, for example, a bolt over which a nut is intended to pass, a quantity of a gelled thixotropic α-cyanoacrylate monomer containing composition is applied and the nut is passed over the threads so coated. The α-cyanoacrylate monomer containing composition is of such a viscosity and thixotropicity that substantially none of the composition remains on the threaded bolt in areas over which the nut has passed.

Detailed Description of the Invention

It is paramount in the practice of the present invention to employ a hardening agent which possesses certain well defined physical and chemical properties. The composition should possess a reasonably high viscosity, i.e. at least 20,000 cps, and exhibit certain thixotropic properties. Further, the composition should polymerize or harden quickly and yet be capable of some movement in the event that one wishes to remove one member from its threaded counterpart after the hardening agent has polymerized. By the selection of the proper hardening agent, the details of which will be fully described hereinafter, not only could the above-referenced attributes be achieved, but also the hardening agent could be maintained solely at the interface between the threaded members for as one of the members is applied to its complement over threads which have been coated with the hardening agent substantially none of the hardening agent remains on the threads in areas over which the member has passed. It was found that the objects of the present invention could be achieved by providing a thixotropic gel composition containing an α-cyanoacrylate monomer, a dry colloidal fumed silica, a plasticizer, a stabil¬ izer, free radical scavenger, filler and viscosity enhancer. The filler is ideally in the form of fibers or spheres, each taken alone or in combination with the only requirement being that the material comprising the filler be composed of material which is insoluble in and inert to the α-cyanoacrylate monomer containing composition. . ^!

The fibers and spheres must not have any significant amounts of residual catalyst, such as peroxides, which are used in certain manufacturing techniques for polyolefins etc. Thus, although not an absolute requirement, it is preferable to employ fibers and spheres which were thermally polymerized and not catalytically polymerized in their manufacture. In view of their inertness and relative availability, it has been found that polypropylene and polyethylene are preferred materials for the composition of the fibers and spheres. It has been found that thermally polymerized polypropylene spheres sold under the trade designation Type 6501 from Himmont U.S.A., Inc. and fibers of spun polypropylene sold under the trade designation Type 153 from Hercules Chemical Co. which are produced from thermally polymerized feed stock are most advantageous for use in practicing the present invention.

Although a wide latitude can be employed in the selection of fibers and spheres of varying physical dimension, it has been found that spheres between approximately 40 to 180 mesh are most preferable in practicing the present invention, while spheres of 170 mesh are ideal. Concerning concentrations, between approximately 1 to 50 percent by weight of filler is appropriate while between 5 and 25 weight percent is more preferable, while between 10 and 20 weight percent is ideal.

The α-cyanoacrylate monomer should be of the following formula H C = C - C - 0 - R

CN 0 wherein R is a member selected from the group consist¬ ing of an alkyl from approximately 1 to 16 carbon atoms; phenyl, cyclohexyl,^'' alkoxy, allyl, furfuryl and mixtures thereof. Examples of appropriate alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl and amyl. Various alkoxy groups include methoxyethyl and ethoxyethyl. These include α- cyanoacrylate monomers which are well known in the prior art as adhesives and can be employed herein in an amount between approximately 45.0 to 98.5 percent by weight and more preferably between 71.0 and 94.25 percent by weight and most ideally between approximately 78.0 and 89.0 percent by weight. Added to the α-cyanoacrylate monomer is a dry colloidal fumed silica, a plasticizer, a stabilizer and free radical scavenger. When proper amounts of these materials are combined, as more fully explained hereinafter, a thixotropic gel composition is achieved which is ideally suited as a hardening agent for the bonding of complementary threaded parts.

Although virtually any α-cyanoacrylate monomer recognized by the prior art as being useful as an adhesive can be employed in practicing the present invention, it has been found that the present invention be limited to the use of only a dry colloidal fumed silica as the thickening agent. More specifically, this ingredient is preferably a hydrophobic silated silica, as the inclusion of any water will decrease the stability and shelf-life of the composition. It has been found that a product sold under the trademark CAB-0-SIL N 70 TS available from Cabot Corporation is most adequate in practicing the present invention. It is preferable that a plasticizer be employed in the composition for without one, phase separation occurs during storage. Plasticizers for use herein comprise one or more members selected from the group consisting of monofunctional aliphatic esters, such as butyl acetate and butyl cyanoacetate, difunctional aliphatic esters, such as dibutyl phthalate, phosphate esters and phosphonate esters. Although dibutyl and dioctyl phthalate are preferable in carrying out the present invention, one could use 3,4,5-dihydroxybenzoic acid and its esters as taught in U.S. Patent No. 4,139,693 among others known, in the trade. It is preferable that the plasticizers be employed between approximately 0.5 to 5.0 percent by weight and more preferably between 0.75 to 4.0 percent by weight and most preferably between 1.0 to 2.0 percent by weight. As a means of controlling the viscosity of the thixotrope under shear, certain viscosity modifiers can be included in the formulation. Ex-amples of such materials are polyethyl cyanoacrylate or other poly- meric cyanoacrylates, polymethylmethacrylate and cellulose esters. These materials can be incorporated in the composition in amounts between approximately 0.1 to 6.0% by weight. Approximately 3.0% by weight is preferred.

To further enhance the stability of the composition, a suitable stabilizer is incorporated therein. Examples of appropriate stabilizers include sulfur dioxide, hydrogen fluoride, nitrogen oxide, phosphoric acid, phosphorous acid, boron trifluoride, stannic chloride, ferric chloride, sultones and aromatic sulfonic acids. The stabilizing agent should be employed in amounts between approximately 0.0005 to 0.10 percent by weight and more preferably between 0.001 to 0.020 percent by weight and most ideally between approximately 0.007 to 0.010 percent by weight. As α-cyanoacrylates can polymerize via the free radical route, to enhance shelf-life, it is preferable that a free radical scavenger be included in the composition. Such scavengers include hydroquinone, monoethyl ether of hydroquinone, butylated hydroxyanisole, butylated hydroxytoluene and t-buty.l hydroquinone. Hydroquinone is the preferred free radical scavenger for use herein and should be included in amounts between approximately 0.001 to 0.15 parts by weight.

Although the above-recited ingredients can be combined by virtually any well known technique, it is preferable that means be employed to minimize the amount of water in the system contained e-ither hygroscopically as a contaminant or as an azeotrope. The presence of even small amounts of water will destabilize the composition and greatly reduce its shelf-life. To most efficiently eliminate water in the composition, it is recommended that the various ingredients be added to the composition in a common solvent which could then be removed by vacuum, etc., to eliminate azeotropic water from the final mixture. A suitable solvent should be non-ionic and have a boiling point no higher than approximately 80^βC. Examples of suitable materials include benzene, toluene, xylene, hexane, chloroform, dichloromethane, acetone, ethyl dichloride and ethyl acetate. These solvents are known to form azeotropes with water and their low boiling points facilitate their removal from the final composition.

Example 1

A flask was fitted with a magnetic stirrer and charged with 500 mis of benzene. Approximately 80.0 parts by weight of the α-cyanoacrylate monomer was employed in the form of ethoxyethyl α-cyanoacrylate which was stabilized with approximately 0.003 parts by weight sulfur dioxide and 0.07 parts by weight hydroquinone employed as a free radical scavenger. The viscosity of the composition under shear was regulated by the addition of 0.5 parts by weight polymethylmethacrylate powder as well as 2.0 parts by weight dibutylphthalate as a plasticizer. While being agitated, 6 parts by weight CAB-0-SIL N 70 TS was slowly added. The above-recited composition was continuously stirred in a flask for approximately 30 minutes whereupon the solvent was stripped off by fitting the flask with dry nitrogen gas and vacuum lines, whereupon the pressure was reduced to approximately 2 mm/Hg while sparging the vessel with dry nitrogen gas to facilitate stripping of the solvent. To enhance solvent removal, it is noted that the composition can be warmed to increase the vapor pressure of the ---solvent. Although the amount of each of the materials can be somewhat varied within acceptable ranges, the solvent should be used in amounts between approximately 0.1 to 50 times the weight of the final composition and, more preferably, between approximately 5 to 25 times, and most preferably between 5 and 10 times the weight of the final composition.

Example 2

A 3/8"—16 size threaded zinc plated bolt and complementary nut were selected. The composition of Example 1 was liberally applied to the end of the bolt filling approximately 1/4 inch of threads with the hardening composition. The nut was then applied to the bolt and screwed thereon in the normal fashion. While the bolt was being applied, little resistance was noted over and above the normal resistance one would expect during the screwing operation. However, it was observed that virtually none of the hardening composition remained on the threads of the bolt over which the nut had passed and in approximately two minutes, polymerization had taken place to the point where the nut could not be removed from the bolt by ordinary hand manipulation.

Example 2 was repeated using nylon nuts and bolts, brass nuts and bolts, aluminum nuts and bolts, as well as cadmium nuts and bolts. In each instance, results similar to those reported for the zinc plated nut and bolt of Example 2 were achieved.

Because of the thixotropic gelled nature of the present composition, it is ideally suited as a vehicle for the bonding of two complementary threaded members. Hov/ever, the composition is capable of bonding non- threaded members such as metal rivets and threaded members which are applied to solid or non-threaded bodies—such as the application of «a threaded screw to wood or an aluminum screw to sheet metal, etc.

Claims

1. A method of bonding first and second complementary threaded members comprising applying to at least some of the threads of the first member over which the second is intended to pass, a quantity of a gelled thixotropic α-cyanoacrylate monomer containing composition followed by applying the second member to the first so that the second passes over the threads of the first which have been applied with the gelled thixotropic α-cyanoacrylate monomer containing composition.

2. The method of claim 1 wherein said α-cyanoacrylate monomer containing composition is of such a viscosity and thixotropicity that substantially none of the composition remains on the threaded first member in areas over which the second member has passed.

3. The method of claim 1 wherein said gelled thixotropic composition comprises an α-cyanoacrylate monomer of the formula *^■

H„C = C - C - 0 - R

² I II CN 0 wherein R is a member selected from the group consisting of an alkyl from approximately 1 to 16 carbon atoms; phenyl, cyclohexyl, alkoxy, allyl and furfuryl groups and mixtures thereof; a plasticizer; dry colloidal fumed silica; a stabilizer; a free radical scavenger; a filler in the form of fibers or spheres or mixtures of fibers and spheres substantially insoluble in and inert to said α-cyanoacrylate monomer; and a viscosity modifier.

4. The method of claim 3 wherein said filler comprises one or more members selected from the group consisting of polyolefins, polyesters, polytetrafluoroethylene and polyamides. t

5. The method of claim 4 wherein said cellulose has been treated with triethylchlorosiloxane.

6. The method of claim 3 wherein said plasticizer comprises a member selected from the group consisting of monofunctional aliphatic esters, difunctional aliphatic esters, difunctional aromatic esters, phosphate esters and phosphonate esters.

7. The method of claim 3 wherein said stabilizer comprises a member selected from the group consisting of sulfur dioxide, hydrogen fluorid-e, phosphorous acid, boron trifluoride, stannic chloride, ferric chloride, sultones and aromatic sulfonic acids.

8. The method of claim 3 wherein said free radical scavenger comprises a member selected from the group consisting of hydroquinone, monoethylether of hydroquinone, butylated hydroxyanisole, butylated hydroxytoluene and t-butyl hydroquinone.

9. The method of claim 4 wherein said polyolefins comprise a member selected from the group consisting of polypropylene and polyethylene.

10. The method of claim 3 wherein said viscosity modifier is a member selected from the group consisting of polymeric cyanoacrylates, polymethylmethacrylates, and cellulose esters.

11. The method of claim 1 wherein said first member comprises a threaded bolt and said second member comprises a complementary threaded nut.

12. A method of bonding first and second comple¬ mentary threaded members comprising applying to at least some of the threads of the f rst member over which the second is intended to pass, a quantity of a gelled thixotropic α-cyanoacrylate monomer containing composition followed by applying the second member to the first so that it passes over the threads of the first member which have been applied with the composi¬ tion, said composition comprising an α-cyanoacrylate monomer of the formula

wherein R is a member selected from the group consisting of an alkyl from approximately 1 to 16 carbon atoms; phenyl, cyclohexyl, alkoxy, allyl, furfuryl groups and mixtures thereof; a plasticizer; dry colloidal fumed silica; a stabilizer; a free radical scavenger; a filler in the form of fibers or spheres or mixtures of fibers and spheres substantially insoluble in and inert to said α-cyanoacrylate monomer; and ^! a viscosity modifier.

13. The method of claim 12 wherein said α-cyanoacrylate monomer is present in said composition in an amount between approximately 45 to 98.5 percent by weight based upon the weight of the entire composition.

14. The method of claim 12 wherein said α-cyano¬ acrylate monomer is present in said composition in an amount between approximately 71 to _"94.25 percent by weight based upon the weight of the entire composition.

15. The method of claim 12 wherein said α-cyanoacrylate monomer is present in said composition in an amount between approximately 78.0 to 89.0 percent by weight based upon the weight of the entire composition.

16. The method of claim 12 wherein said filler comprises spheres between approximately 40 to 180 mesh in size.

17. The method of claim 12 wherein said filler comprises spheres approximately 170 mesh in size.

18. The method of claim 12 wherein said filler is present in an amount between approximately 1 to 50 by weight based upon the weight of the entire composition.

19. The method of claim 12 wherein said filler is present in an amount between approximately 5 to 25 percent by weight based upon the weight of the entire composition.

20. The method of claim 12 wherein said filler is present in an amount between approximately 10 to 20 percent by weight based upon the weight of the entire composition.

21. The method of claim 12 wherein said stabilizer comprises sulfur dioxide which is-present in an amount between approximately 0.0*005 to 0.10 weight percent based upon the weight of the α-cyanoacrylate monomer, plasticizer and filler.

22. The method of claim 21 wherein said sulfur dioxide is present in an amount between approximately 0.001 to 0.020 weight percent based upon the weight of the α-cyanoacrylate monomer, plasticizer and filler.

23. The method of claim 21 wherein said sulfur dioxide is present in an amount between approximately 0.007 to 0.010 weight percent based upon the weight of the α-cyanoacrylate monomer, plasticizer and filler.

24. The method of claim 12 wherein said plasticizer is present in an amount between approximately 0.5 to 5.0 percent by weight based upon the weight of the entire composition.

25. The method of claim 12 wherein said plasticizer is present in an amount between approximately 0.75 to 4.0 percent by weight based upon the weight of the entire composition.

26. The method of claim 12 wherein said plasticizer is present in an amount between approximately 1.0 to 2.0 percent by weight based upon the weight of the entire composition.

27. A method of bonding a threaded member to a receiving body comprising applying to at least some of the threads of the threaded member,_* a quantity of gelled thixotropic α-cyanoacrylate monomer containing composition followed by screwing the threaded member into the receiving body so that at least some of the threads which have been applied with the gelled thixotropic α-cyanoacrylate monomer containing composition are in contact with the receiving body.