WO1986006738A1

WO1986006738A1 - Composition and method for inhibiting the cure of cyanoacrylate adhesives and cure inhibted cyanoacrylate adhesive compositions

Info

Publication number: WO1986006738A1
Application number: PCT/US1986/001047
Authority: WO
Inventors: Warren Gregory Lazar
Original assignee: Warren Gregory Lazar
Priority date: 1985-05-17
Filing date: 1986-05-14
Publication date: 1986-11-20
Also published as: EP0222888A1; KR880700040A; KR910001027B1; EP0222888A4; JPS63500247A

Abstract

Compositions and methods for inhibiting the cure of cyanoacrylate adhesives and cure inhibited cyanoacrylate adhesive compositions. The cure inhibited compositions comprise an organic carboxylic acid; and a hydrated or anhydrous metal chloride, fluoride, bromide or iodide.

Description

COMPOSITION AND METHOD FOR INHIBITING THE CURE OF CYANOACRYLATE ADHESIVES AND CURE- INHIBITED CYANOACRYLATE ADHESIVE COMPOSITIONS

Background of the Invention

Field of the Invention

This invention relates to compositions containing cyanoacrylate adhesives that are temporarily inhibited from polymerizing and curing even in the presence of activating substances, such as metals, which normally catalyse polymer¬ ization of cyanocrylate adhesive compositions. This invention also relates to compositions and methods for inhibiting polymerization and curing of cyanoacrylate adhesives.

Description of the Prior Art

A major drawback of cyanoacrylate compounds is their tendency to polymerize rapidly and often uncontroll¬ ably when contacted or mixed with various activating sub- stances, especially substances that form ions in solution. Even trace quantities of such activators as organic salts, inorganic salts, metals, water, urea, oxides, etc., sub¬ stantially increase the rate of cyanoacrylate polymeriza¬ tion. This tendency has limited the usefulness of cyano- acrylate compounds to ordinary adhesive applications. If cyanoacrylate compounds could be mixed with sufficient quantities of various activating substances without polymerizing immediately, they would be useful in a wide variety of additional applications. The development of cyanoacrylates, such as methyl-2-cyanoacrylate, ethyl-2-cyanoacrylate, proρyl-2- cyanoacrylate, 2-ethylhexyl-2-cyanoacrylate, isobutyl-2- cyanoacrylate, n-butyl-cyanoacrylate, hexyl-, heptyl-, and octyl-cyanoacrylate, etc., represented a major technological advance in the bonding and adhesive art.

The preparation of cyanoacrylates is well-known. It is described in such U.S. Patents as No. 2,467,926; No.

2,794,788; No. 2,912,454; and No. 2,926,188, the disclosures of which are incorporated by reference. The use of cyano¬ acrylate polymers as adhesives is described in such U.S. Patents as No. 2,776,232; No. 2,794,788; and No. 2,467,926, 0 also incorporated by reference. The cyanoacrylate adhesives are fast-drying, high tensile-strength glues and bonding agents. Their use in bonding or joining materials together is very widespread in industry, in the household, and in special applications such as surgery (as tissue adhesives), 5 dentistry, etc.

Various inorganic substances have been proposed as fillers or thickeners for cyanoacrylate monomer composi¬ tions. For example, U.S. Patent No. 3,663,501 of Adams, et al. issued on May 16, 1972 discloses preparation of a 0 dental cement containing finely divided sodium fluoride, fused silca, quartz, and alumina fillers. U.S. Patent No. 3, 607,542 of Leonard, et al. issued on September 21, 1971 discloses the preparation of water-resistant cyanoacrylate paste containing insoluble inert fillers (such as various 5 salts of calcium, titanium, zinc, tin, aluminum and iron) for use as adhesives in submerged applications and as fillings for teeth. Neither reference is concerned with the polymerization rate of cyanoacrylate adhesives or with its control.

3_Q Incorporation of acid inhibitors in cyanoacrylate compositions is known. For example, U.S. Patent NO. 4,182,823 of Schoenberg issued on January 8, 1980 teaches that acid additives called "stabilizers" in the patent) including acid gases, other acids (such as acetic) or

_ various Lewis acids (such as FeCl-, SnCl- and BF-) inhibit polymerization of cyanoacrylate compositions. The patent warns, however, that such additives must be used with caution because strong acids "over-stabilize" the monomer and weak acids do not "stabilize" it sufficiently. Schoen- berg further observes that the acids (which are said to act as anionic polymerization inhibitors) interfere with the cure of the adhesive.

U.S. Patent No. 2,794,788 of Coover issued on June 4, 1957 states that sulfur dioxide is effective as a stabilizer for cyanoacrylate monomers, that boron trifluo- ride and hydrogen fluoride are also effective, but that carbon dioxide is less effective.

U.S. Patent No. 4,460,759 of Robins issued July 17, 1984 discloses a two-part cyanocrylate adhesive compo¬ sition. One part of this composition contains weakly acidic or weakly ionic compounds as accelerators for polymerization, particularly when these compositions are used on wood substrates. Such accelerators are said to include metal halides. The first part contains acid gases and free-radical compounds as inhibitors.

Although many of the above references recognize the need to control the rate of polymerization of cyano¬ acrylate adhesives, the additives they propose are inade¬ quate as inhibitors because their inhibitory effect cannot be well-controlled.

As stated in Schoenberg, supra, too little acid inhibitor is not effective and two much can interfere with polymer cure. In addition, many acid additives cause polymer decomposition, and shorten the useful life of the cyanoacrylate polymer.

Accordingly, it is an object of the present invention to provide novel compositions useful as inhibitor- stabilizers for cyanoacrylate compounds and compositions.

Another object is to provide novel inhibiting- stabilizing compositions for cyanoacrylates that effective¬ ly delay onset and propagation of polymerization reations even in the presence of activators for such reactions.

Another object is to provide cyanoacrylate compo¬ sitions that are temporarily or permanently rendered non- reactive to activating substances.

SUBSTITUTE S -4- Another object of the invention is to provide cyanoacrylate compositions that are temporarily or perma¬ nently inhibited from polymerizing in which the inhibitor does not cause premature decomposition of the polymer. Another object is to provide cyanoacrylate compositions that are temporarily or permanently inhibited from polymerizing to a controlled extent although they contain substantial amounts of substances that act as catalysts for cyanoacrylate polymerization. Another object is to provide cyanoacrylate compositions that are electrically or thermally conductive and have such polymerization and stability characteristics or mechanical properties as make them suitable for use in the manufacture of electronic and microelectronic components Another object is to expand the uses to which cyanoacrylate adhesive compositionis can be put by provid¬ ing compositions comprising cyanoacrylate monomers that are controllably inhibited towards polymerization and at the same time yield polymers with the desired degree of cure and stability.

A further object is to prepare cyanoacrylate adhesive compositions that can be spray-coated in place using inter alia on artists' air brush.

Yet another object is to provide methods for inhibiting the polymerization of cyanoacrylate compounds and for preparing polymerization-inhibited and stabilized compositions containing cyanoacrylate compounds and activa¬ tors. Summary of the Invention One aspect of this invention is directed to a composition comprising at least one organic acid and at least one hydrated or anhydrous base metal fluoride, chloride, bromide or iodide. The composition is useful in inhibiting-stabilizing cyanoacrylates. Another aspect of the invention is directed to a cyanoacrylate composition temporarily or permanently inhibited from polymerizing, the composition including an organic acid and at least one hydrated or anhydrous metal fluoride, chloride, bromide or iodide. The composition may include a filler that is ordinarily an activator of cyano¬ acrylate polymerization. Yet another aspect of the invention relates to a method for inhibiting cyanoacrylates against polyme ization by incorporating either to said cyanoacrylates or to an activator additive thereof an inhibitor comprising a liquid organic acid and an anhydrous or hydrated metal fluoride, 0 chloride, bromide or iodide, prior to mixing said cyanocry- late with said activator-additive, or simultaneously therewith.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, unpo- 5 lymerized (or partially polymerized) cyanoacrylate composi¬ tions can be temporarily (or permanently) inhibited from reacting with polymerization-activating materials (activa¬ tors) and at the same time stabilized against incomplete cure and/or premature decomposition. 0 This inhibition-stabilization of the cyanoacryl¬ ate is accomplished by incorporating an inhibitor-stabilizer either in the unpolymerized (or partially polymerized) cyanoacrylate or in an activator that will serve as an additive or filler of the final composition, said inhibitor- 5 stabilizer comprising:

(a) an organic carboxylic acid; and

(b) a hydrated or anhydrous metal chloride, fluoride, bromide or iodide.

The inhibitor-stabilizer is preferably incorpo- _Q rated in the cyanoacrylate adhesive (monomer or prepolymer) prior to exposure of the latter to an activator, such as a metal, oxide, ionic solvent, salt, water or urea. However, it can also be incorporated to the activator prior to mixing it with the cyanoacrylate. The ingredients of the - inhibitor-stabilizer must be premixed and may not be separately incorporated in the cyanoacrylate or activator. Preferably, the inhibitor-stabilizer also in¬ cludes a polar solvent to facilitate mixing with and solubility in the cyanoacrylate (or activator additive). In fact, unless the two active ingredients of the inhibitor- stabilizer are fully compatible with the cyanoacrylate (or activator-additive), use of a solvent is particularly desirable. Additional solvent may be used when the in¬ hibitor-stabilizer is mixed with the cyanoacrylate to facilitate mixing. This additional solvent may but need not be a polar solvent; it can be any suitable organic solvent.

Suitable solvents for the inhibitor include polar organic and inorganic solvents, such as water, lower aliphatic alcohols, lower aliphatic ketones, lower aliphatic ethers of carboxylic acids, lower alkylene glycols, lower alkylene glycol ethers, lower aliphatic esters of carboxylic acids, carboxylic acid nitriles, and mixtures thereof. Methyl chloride, formaldehyde and dimethyl sulfoxide are also useful as solvents in the present invention. Preferred solvents are: water; acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, ethyl butyl ketone, acetyl acetone; methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and hexanol, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and methyl-CELLOSOLVE^R-acetate (methyl-2-ethoxy- ethanol acetate; CELLOSOLVE^R is a trademark of Union Carbide Corporation); ethyl ether, dimethyl ether, and diethylene glycol ethyl ether (diethyl-CARBITOL^R; a trade¬ mark of Union Carbide Corporation); methyl-CELLOSOLVE, butyl CELLOSOLVE, methyl glycol ether, butoxy triglycol, methoxy triglycol, glycol methyl CARBITOL; and acetonitrile. The most preferred solvents for use in the present invention are: water, acetone, ethanol, ethyl acetate, dimethyl ether, glycol methyl CARBITOL, and acetonitrile.

Preferred acids for the inhibitor-stabilizer are formic acid, acetic acid, propionic acid, butanoic acid, lactic acid, pentenoic acid, carbonic acid, etc. Most preferred is formic acid.

Preferred metal halide salts are: FeCl_; FeCl₃.6H₂0; LiF; CdCl₂; CdCl₂.2-1/2H₂0; MgBr.6H_H0; SnBr₄; GeCl₄; MgCl₂; ZnCl₂; ZnBr; MnCl₂.4H₂0;

LiI.3H₂0; LiI.H₂0; SnCl₂.6H₂0; and SnCl₂.2H₂0. Magnesium bromide hexahydrate, tin cloride hexahydrate and ferric chloride hexahydrate are most preferred.

Non-polar solvents that can be added to the in- hibited cyanoacrylate composition include without limita¬ tion plasticizers, such as dibutyl phthalate, tricresyl phosphate, dimethyl phthalate, etc.

Generally suitable relative proportions of the ingredients of the inhibitor-stabilizer, i.e. the acid, salt and solvent (if any) are: acid — about 0.002 - 55%; salt — about 0.002 - 50%; and solvent — about 0 - 75% by weight.

As a weight percentage of the cyanoacrylate monomer the inhibitor-stabilizer can be about 0.10-55%. The above proporltions are given by way of guide¬ lines. The actual amount of the inhibiting-stabilizing composition will depend on how long it is desired to delay the onset of polymerization for the final cyanoacrylate mixture (i.e. after addition of the activating substance) and, to a lesser extent, on the ability of the activator to catalyze cyanoacrylate polymerization. It should be noted that as the percentage compositive of acid and salt is increased, the cure time of the adhesive composition increases. The duration of the stabilization or inhibition provided by a given stabilizer/acrylate formulatin is also dependent upon the ambient temperature to which the material is exposed. Storage of an inhibited cyanoc rylate compound of the present invention at 120^*F for 3 weeks would result in some curing of the adhesive, however, if the same composition were stored at 40^βF for 3 months little or no curing would take place. By varying the ratio of inhibitor ingredients to cyanoacrylate constituents in the present invention, it is possible to inhibit curing for periods varying between a few minutes and several months.

The incorporation of the inhibitor-stabilizer renders the cyanoacrylate non-reactive to activating substances for a period of time at least long enough to permit mixing of the cyanocrylate with the activator and any processing, storage, or fabrication necessary for the particular end application envisioned.

By the present invention, a multitude of applica¬ tions become possible. The following are listed for illustration purposes only. 1) Electrically Conductive Cyanoacrylate

Compositions and Materials

Incorporation of a metal with high conductivity (in powder or other particulate form) as a filler can render a cyanoacrylate composition electrically conductive. Before the present invention, it was impossible to incorpo¬ rate sufficient metal as a filler to render the polymer electrically conductive because rapid polymerization of the cyanoacrylate would begin immediately following addition of even minute quantities of metal. This made further addition of metal impossible. Moreover, rapid polymeriza¬ tion of the metal-filled cyanoacrylate would interfere with the processing or fabrication of the finished product.

Metal-filled cyanoacrylate polymers can be used in die and wire bonding of microelectronic circuits instead of solder. In addition, they can be used as conductive terminals for resistors, as electrodes for capacitors and for a variety of functions in thick-film hybrid microelectronic circuits. The metal-filled cyano¬ acrylate compositions can be applied to circuit boards by conventional screening methods. Electrically conductive cyanoacrylate compositions preferably contain about 0.5 - 7.0% of inhibitor, 0.05 - 0.4% acid, 0.08 to 0.8% salt and about 0.4% to 10.0% solvent by weight of the cyanoacrylate monomer.

Other applications for conductive cyanoacrylates are in high-conductivity metallization films and coatings for plastics, paper, mica, ceramics and other non-conductive materials. The metallized films and coatings allow direct soft-soldering without the use of flux and may be further metal-coated by electroplating. Such films and coatings are useful in electronic and microwave applications as connectors, contacts, magnetic shields, especially in metal shields that are used to protect from Radio Frequency Interference (RFI) and Electro Magnetic Interference (EMI) and capacitor terminals. They can be applied by brushing, dipping, or spraying, or by conventional screening tech¬ niques using standard 180 to 200 mesh screens.

These conductive, film-forming cyanoacrylate compositions preferably contain about 1.0 - 7.0% inhibitor- stabilizer (0.07 to 0.6 acid, 0.2 to 1.3% salt) and about 1.0 - 10.0% solvent.

Suitable metal fillers for electrically conduc¬ tive cyanoacrylates, in general, include one or more of palladium, silver, copper, tin, gold, and platinum and other high-conductivity metals. The metal filler may first be combined with the inhibitor composition and the metal- containing inhibitor may subsequently be introduced into the cyanocrylate. This makes it possible to package these constituents separately for mixing by the consumer just prior to use (as an A&B component system). 2) Thermally Conductive Cyanoacrylate

Compositions and Materials

Incorporation of fillers can also produce thermo- conductive materials that can be used as heat sinks for the base and mounting stud of transistors, diodes, and rectifiers; and as coupling agents to reduce thermal contact resistance. Suitable fillers for this purpose include base metals, such as iron, aluminum, tin, and metal oxides that are not electrically conductive, etc. ^ Another use for thermally conductive cyanoacryl¬ ates is for application between, e.g., semiconductor power devices and heat sinks; power resistors and chassis mounts; thermostats and mounting surfaces; and anywhere else where

5 the efficient transfer and removal of heat are necessary or desirable. Finally, they can be used in thermoelectric devices (e.g. in transformers as anti-static layers and heat sinks) and in heat dissipaters for electronic devices. Suitable fillers for this purpose are base metal oxides

10 (especially alumina) and iron, graphite, titanium, tin; gold, silver, copper and all heavy metals.

Thermally conductive cyanoacrylate compositions according to this invention preferably contain about 1.0 to 7.0% inhibitor 0.07 to 0.6% acid, 0.2 to 1.3% salt and

15 about 1-11% solvent.

The thermally conductive cyanocrylates of the present invention can be used in place of other thermocon- ductive plastic materials including thermoconductive expoxies containing alumina or other metals. These thermal

20 cyanoacrylates may be employed to join heat sinks and other components to printed circuit boards and in like applica¬ tions.

3) Photoconductive Cyanoacrylate Compositions and Materials

25 In general, these are liquid or screenable paste

(slurry) compositions that can be used in the manufacture of photocells used for light sensors, light-controlled relay operations, exposure meters, fire detectors, photo¬ meters, lamp controls, liquid level indicators and a

30 variety of other detectors. Suitable fillers include cadmium sulfide, cadmium selenide and cadmium-sulfoselenide. Compositions used in these applications preferably contain about 0.5 - 0.2% acid about 0.08 - 0.24% salt and about 1 - 11% solvent.

35 It will be understood by those skilled in the art of the present invention that a variety of other fillers can be incorporated to the inhibited-stabilized cyanoacryl¬ ates contemplated herein. These include one or more of plasticizers, silicones, silica, polymeric fillers, fibers, magnetic resins, pharmaceuticals, dyes, water, non-polar solvents, radioactive materials, viscosity modifiers, human and animal skin, etc.

This invention is for use with any cyanoacrylate monomer (or prepolymer) including but not limited to those set forth in the Background of the Invention, or mixtures thereof.

The invention will be further described below by reference to specific examples, which are intended to illustrate it without limiting its scope. Thus, the scope of the present invention is not to be limited to the cyanoacrylates, fillers, acids, salts and solvents or proportions disclosed in the Examples, below. EXAMPLE 1

A stabilizing-inhibiting composition with or without a solvent is formed by mixing the following ingredients:

Formula (A) Formula (B)

40.7% SnCl₂.6H₂0 15.9% MgB ₂.6H₂0 40.7% Water 15.9% Water 18.6% Formic Acid 7.3% Formic acid 30.5% Acetone 30.5% Ethyl Cellosolve

Formula (C) Formula (D) 23.5% FeCl₃.6H₂0 50.0% SnCl₂.6H₂0 23.5 Acetone 53.0% Formic Acid 50.0% Acetic Acid

Formula (E)

15.9% SnCl₂.6H₂0

30.5% Butoxyethylene glycol

15.9% H₂0

7.3% Formic acid 30.5% Acetone EXAMPLE 2

An inhibited-stabilized methyl-2-cyanoacrylate composition is made by mixing one of the stabilizing- inhibiting compositions according to Example 1 with methyl- 2-cyanoacrylate monomer and a solvent to improve mixing. The resulting compositions in weight percent are shown in the table below: Inhibited Cy.anoacrylate I II III IV

Composition No.

Inhibitor (Any one of Ex. 1 ) 0.05 0.5 18.0 0.8

Acetone 2.0 2.0 3.0 0.8

Methyl Cy.anoacrγlate 97.95 97.5 76.0 98.2

Methyl-CKr.TanSQLVE^R 0.2

Ethyl Acetone 3.0

EXAMPLE 3

An electrically conductive cyanoacrylate composi¬ tion is formed from the inhibited-stabilized compositions No. II of Example 2 and the following ingredients:

Inhibited-stabilized CA. 84.0 (II) 50.0 (II) 35.0 (II) Gold Powder 16.0

Silver Powder 37.0

Tin Powder 65.0

Copper Powder 13.0

100.00 100.00 100.00

These compositions will not polymerize for about 24 hours from incorporation of the metal powders. EXAMPLE 4

A thermoconductive cyanoacrylate composition is formed from the inhibited-stabilized cyanoacrylate composi¬ tions No. Ill of Example 2 and the following ingredients: Inhibited-stabilized CA. 50.0 (III) 49.0 (III) 54.0 (III)

Copper Powder 50.0

Iron Powder 40.0 Thulium Powder 36.0

Tungsten Powder 21.00 10.0

The thermoconductive compositions will not polymerize for about 24 hours from incorporation of the metal powders. EXAMPLE 5

A fiber-filled cyanoacrylate composition is prepared as outlined above, except that the cyanoacrylate compositions No. IV and II were used. Inhibited-stabilized CA. 85.0 (IV) 92.0 (II)

Paper Fiber 5.0

Wool Fiber 10.0 8.0

These compositions will not polymerize for about 24 hours after incorporation of the fibers. They can be used as 0 adhesives, especially in high impact resistant applications and in joining sheet and cloth materials (e.g. textile fabrics, leather and vinyl sheets). EXAMPLE 6

A flexible plasticized cyanoacrylate composition 5 for use as a caulking material is prepared by mixing the inhibitor-stabilized cyanoacrylate of Example 2 with the following ingredients:

Inhibited-stabilized A. 99.2 (IV) 90.0 (II) Plasticizer 0 [Propylene carbonate] 0.8 5.0

Plasticized polyvinyl acetate 5.0

EXAMPLE 7

A sprayable cyanoacrylate composition containing 5 finely divided silver particles was prepared by admixing a stabilized-inhibited cyanoacrylate composition (Formula I of Example 2 prepared with inhibitor Formula E of Example 1 ) with 30 percent by weight of the stabilized inhibited cyanocrylate composition of finely divided metallic silver 0 particles (average size 200-300 mesh). The siler powder is stirred in with a single blade electric laboratory mixer until an essentially homogeneous silver dispersion is obtained. The silver containing cyanoacrylate mixture is loaded into the reservoir of a Badger brand artists' air _ brush. The brush is connected to a source of pressurized air (30-40 psi). Plastic sheets (each approximately 2" x 2" x 1/4") of Styrene, ABS and acrylic (plexiglass) were laid on a flat surface. A solution of 5% toluidine was coated on the upper surface of the ABS plastic sheet and allowed to dry at room temperature (15^*C).

The silver-containing cyanoacrylate composition was sprayed across the entire upper surface of the three plastic sheets (with the nozzle of the air brush held approximately eight inches from the surface of each sheet) using broad sweeping strokes.

At the conclusion of the spraying operation, a second sheet of styrene was applied to the cyanocrylate sprayed surface of the first styrene sheet and pressed down momentarily (using band pressure).

The cyanocrylate on the ABS sheet cured in approximately 3 minutes. The cyanoacrylate joining the styrene sheets cured to working condition (i.e. to a condition in which the sheets could not be pulled apart by hand) in approxi¬ mately fifteen minutes.

The cyanoacrylate on the acrylic sheet cured within one hour.

The method for making the compositions of the present invention employed in the specific embodiments described above is basically the same regardless of the particular cyanoacrylate, activator-filler and inhibitor- stabilizer used.

As those skilled in the art will appreciate, many modifications, additions, omissions and substitutions can be made, all within the scope and spirit of the present invention as claimed below.

Claims

What is claimed is:

1. A composition useful in inhibiting polymerization of cyanoacrylate in the presence comprising from about 0.002 to about 55% of an organic acid or mixture of organic acids and from about 0.002 to about 50% of a salt selected from the group consisting of hydrated and anhydrous base metal chlorides, fluorides, bromides and iodides and mixtures thereof, said percentages being by weight.

2. The composition of claim 1 also comprising from 0 to about 75% of a polar solvent.

3. The composition of claim 2, said solvent being selected from the group consisting of water, aliphatic alcohols, lower alkylene glycols, lower alkylene glycol ethers, carboxylic acid nitriles and mixtures thereof.

4. The composition of claim 1, said acid being selected from the group consisting of formic acid, acetic acid, propionic acid, lactic acid, pentenoic acid, butyric acid, carbonic acid, and mixtures thereof.

5. The composition of claim 1, said salt being selected from the group consisting of: FeCl^; FeCl-.6H_0; LiF; CdCl₂; CdCl₂.2-1/2 H₂0; MgBr.6H₂0; SnBr₄; GeCl₄; MgC ; ZnCl₂; ZnBr; MnCl₂.4H₂0; LiI.3H₂0; LiI.H₂0; SnCl₂.6H₂0; SnCl₂.2H₂0; and mixtures thereof.

6. The composition of claim 3 said acid being selected from the group consisting of formic acid, acetic acid, propionic acid, lactic acid, pentenoic acid, butyric acid, carbonic acid and mixtures thereof.

7. The composition of claim 6, said salt being selected from the group consisting of: FeCl₃; FeCl-.6H₂0; LiF; CdCl₂; CdCl₂.2-1/2 H₂0; MgBr.6H₂; SnBr₄; GeCl₄; Mg ; ZnCl₂; ZnBr; MnCl₂.4H₂0; LiI.3H₂0; LiI.H₂0; SnCl₂.6H₂0; and SnCl₂.2H₂o and mixtures thereof.

8. The composition of claim 4, said salt being selected from the group consisting of: FeCl₃; FeCl₃.6H₂0; LiF; CdCl ; CdCl₂.2-1/2 H₂0; MgBr.6H ; SnBr₄; GeCl₄; MgCl₂; ZnCl₂; ZnBr; MnCl₂.4H₂0; LiI.3H₂0; LiI.H₂0; SnCl₂-6H₂0; and SnCl₂.2H₂0 and mixtures thereof.

9. The composition of claim 1, said acid being formic acid.

10. The composition of claim 1, said salt being selected from the group consisting of SnCl₂.6H₂0; MgBr.6H₂0; FeCl₃.6H₂0; and mixtures thereof.

11. The composition of claim 3, said acid being formic acid.

12. The composition of claim 3, said salt being selected from the group consisting of SnCl₂.6H₂0; MgBr.6H₂0; FeCl-.δH^O; and mixtures thereof.

13. The composition of claim 11, said salt being selected from the group consisting of SnCl₂.6H_;?0; MgBr.6H₂0; FeCl₃.6H₂0; and mixtures thereof.

14. The composition of claim 9, said salt being selected from the group consisting of SnCl₂.6H_0; MgBr.6H-,0; FeCl₃.6H₂0; and mixtures thereof.

15. The composition of claim 14, said solvent being selected from the group consisting of water, acetone, acetoni¬ trile, ethanol, ethylene glycol, ethyl acetate, dimethyl ether, and glycol methyl carbitol.

16. The composition of claim 15 comprising about 1 - 55% of said acid and about 1 - 45% of said salt.

17. The composition of claim 16 comprising about

5 - 40% of said acid, about 5 - .40% of said salt and about 1 - 60% of said solvent.

EET

18. An adhesive composition comprising:

(a) a monomeric ester of cyanoacrylic acid; and

(b) an inhibitor comprising:

(i) an organic acid and (ii) a metal halide salt; said composition being inhibited from polymerizing when mixed with polymerization-activating substances.

(ii) a metal salt selected from the group consisting of Fed..; FeCl₃.6H₂0; LiF; CdC1₂; CdC1₂.2-1/2 H₂0; MgBr. 6H 0; SnBr₄; GeCl₄; MgCl₂; ZnCl₂; ZnBr; MnCl₂.4H₂0; LiI.3H₂0; LiI.H₂0; SnCl₂.6H₂0; SnCl₂. 2H₂0; and mistures thereof; said composition being inhibited from polymerizing when mixed with polymerization-activating substances.

19. The composition of claim 18 wherein said acid is selected from the group consisting of formic acid, acetic acid, propionic acid, lactic acid, pentenoic acid, butyric acid, carbonic acid, and mixtures thereof.

20. The composition of claim 19, wherein said solvent is selected from the group consisting of water, acetone, aceton¬ itrile, ethanol, ethylene glycol, ethyl acetate, dimethyl ether, and glycol methyl carbitol.

21. The composition of claim 20, wherein said inhibitor is present in an amount between about 0.1% and about 50% by weight based on said cyanoacrylic acid monomer.

22. The composition of claim 21, wherein said inhibitor is present in an amount between about 1 and about 20% by weight based on said cyanoacrylic acid monomer.

23. A composition according to claim 22 further comprising a solvent selected from the group consisting of water, acetone, acetonitrile, ethanol, ethylene glycol, ethyl acetate, dimethyl ether, and glycol methyl carbitol.

SUBST

24. A composition according to claim 23 wherein said inhibitor is present in an amount between about 1 and about 25% and said solvent is present in an amount between 0 and about 60% based on said monomer.

25. A composition according to claim 24, said composition further comprising a substance selected from the group consisting of activators that would catalyze polymerization of said monomer but for the presence of said inhibitor.

26. A composition according to claim 25, said composition being an electrically conductive composition.

27. A composition according to claim 26, said composition being a thermally conductive composition.

28. A composition according to claim 27, said composition being a photoconductive composition.

29. A method for stabilizing a cyanoacrylate adhesive composition so that said composition is inhibited from polymer¬ izing when mixed with substances activating said polymerization, said method comprising: adding to said composition in an amount effective to inhibit said polymerizatin an inhibitor comprising:

(a) an organic said selected from the group consisting of formic acid, acetic acid, propionic acid, lactic acid, pentenoic acid, butyric acid, carbonic acid, and mixtures thereof;

(b) a salt selected from the group consist¬ ing of FeCl₃; FeCl₃.6H₂0; LiF; CdCl₂; CdCl₂.2-1/2 H₂0; MgBr.6H₂0; SnBr₄; GeCl₄; MgCl₂; ZnCl₂; ZnBr; MnCl₂.4H₂0; LiI.3H₂0; LiI.H₂0; SnCl₂.6H₂0; SnCl₂.2H₂0; and mixtures thereof; prior to or simultaneously with addition of an activating substance

ITUTE SHEET