CA1057880A - Debondable cyanoacrylate adhesive compositions - Google Patents
Debondable cyanoacrylate adhesive compositionsInfo
- Publication number
- CA1057880A CA1057880A CA248,111A CA248111A CA1057880A CA 1057880 A CA1057880 A CA 1057880A CA 248111 A CA248111 A CA 248111A CA 1057880 A CA1057880 A CA 1057880A
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- Canada
- Prior art keywords
- composition
- acid
- percent
- ester
- plasticizer
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
DEBONDABLE CYANOACRYLATE
ADHESIVE COMPOSITIONS
By Victoria R. Allies and William D. Zimmermann A B S T R A C T
Adhesive compositions based on polymerizable esters of .alpha.-cyanoacrylic acids are provided with controlled bond strength and debondable characteristics by incorporating therein a plasti-cizer and a carboxylic acid.
ADHESIVE COMPOSITIONS
By Victoria R. Allies and William D. Zimmermann A B S T R A C T
Adhesive compositions based on polymerizable esters of .alpha.-cyanoacrylic acids are provided with controlled bond strength and debondable characteristics by incorporating therein a plasti-cizer and a carboxylic acid.
Description
1()5'78i~
BACKGROUND OF THE INVENTION
Field of the Invention , - This invention relates to a-cyanoacrylate adhesive compositions, more specifically, to such compositions for-mulated so as to produce bonds which are relatively weak and can be debonded relatively easily.
, Description of the Prior Art Adhesive compositions based upon esters of a-cyano- ~ ;;
acrylic acid are well known in the art and have found exten-10 sive use, because of their rapid cure speed and excelle,nt ~ -long-term bond strength, to a wide variety of surfaces. For instance, tensile shear strength of a steel-to-steel bond typically is greater than about 2,200 psi for ethyl cyano-acrylate, and significantly higher in pure -tensile strength.
;, Cyanoacrylate adhesive bonds also tend to be relatively "~
brittle; therefore, the adhesive compositions are often ;! plasticized. Typical plasticizers include the various alkyl esters and diesters, alkyl and aromatic phosphates an~ phos-phonates of Kodak U.S. Patent 2,784,127 issued March 5, 1957;
the diallyl phthalates of Kodak U.S. patent 3,354,128, issued November 21, 1967; and the aryl and diaryl ethers of Loctite U.S. Patent 3,699,127, issued October 17, 1972. These ref-erences indicate that, in general, plasticizer concentrations of more than 15-20 percent by weight of the adhesive composi-: . . . .
tion should be avoided since at higher concentrations, the . , , bond strength would be significantly reduced.
Cyanoacrylate monomer is believed to polymerize primarily by an anionic mechanism. To control premature : ,.;
polymerization, theref~re, ionic inhibitors are customarily used. These inhibitors are most commonly strong acids, e.g., ` acidic gases such as nitrogen oxide and sulfur dioxide, at a ;'', ~)5~
, , level of about 0.001 to about 0.06 percent by weight (see, e.g~, Kodak U.S. Patent 2,794,788, issued June ~, 1957).
Other known strong acidic inhibitors are soluble organic acids, e.g., aryl sulfonic acids, which are typically used at a level of about 0.001 to about 0.06 percent by weight.
While the use of strong acids such as thosle just mentioned, is important in obtaining good shelf life for the cyano-acrylate monomer~ the disadvantage inherent in their use is that they tend to retard the rate of polymerization, there-by interfering with the effectiveness of the adhesive.
Obviously, the prior art has been directed tomaximizing bond strength and shelf life. While xapid reaction rate and good storage stability are always important in a commercial product, it has not heretofore been recognized that a high level of bond strength may not always be desirable.
Thus, it would be quite beneficial to have an adhesive formu-lation which combines the rapid bonding associated with cyano-acrylates with reduced and controlled bond strength, along with the ability to be readily debonded, when desired.
Summary of the Invention According to the present invention, such an advantageous adhesive composition is provided. This composition, having controlled bond strength and adapted for debonding, comprises in admixture:
; (a) at least one polymerizabla ester of an a-cyanoacrylic acid, (b) from about 20 percent to about 60 percent -by weight of the composition of a plasticizer which is miscible with the ester of part (a);
(c) from about 0.015 percent to about 0.15 percent by weight of the composition of a
BACKGROUND OF THE INVENTION
Field of the Invention , - This invention relates to a-cyanoacrylate adhesive compositions, more specifically, to such compositions for-mulated so as to produce bonds which are relatively weak and can be debonded relatively easily.
, Description of the Prior Art Adhesive compositions based upon esters of a-cyano- ~ ;;
acrylic acid are well known in the art and have found exten-10 sive use, because of their rapid cure speed and excelle,nt ~ -long-term bond strength, to a wide variety of surfaces. For instance, tensile shear strength of a steel-to-steel bond typically is greater than about 2,200 psi for ethyl cyano-acrylate, and significantly higher in pure -tensile strength.
;, Cyanoacrylate adhesive bonds also tend to be relatively "~
brittle; therefore, the adhesive compositions are often ;! plasticized. Typical plasticizers include the various alkyl esters and diesters, alkyl and aromatic phosphates an~ phos-phonates of Kodak U.S. Patent 2,784,127 issued March 5, 1957;
the diallyl phthalates of Kodak U.S. patent 3,354,128, issued November 21, 1967; and the aryl and diaryl ethers of Loctite U.S. Patent 3,699,127, issued October 17, 1972. These ref-erences indicate that, in general, plasticizer concentrations of more than 15-20 percent by weight of the adhesive composi-: . . . .
tion should be avoided since at higher concentrations, the . , , bond strength would be significantly reduced.
Cyanoacrylate monomer is believed to polymerize primarily by an anionic mechanism. To control premature : ,.;
polymerization, theref~re, ionic inhibitors are customarily used. These inhibitors are most commonly strong acids, e.g., ` acidic gases such as nitrogen oxide and sulfur dioxide, at a ;'', ~)5~
, , level of about 0.001 to about 0.06 percent by weight (see, e.g~, Kodak U.S. Patent 2,794,788, issued June ~, 1957).
Other known strong acidic inhibitors are soluble organic acids, e.g., aryl sulfonic acids, which are typically used at a level of about 0.001 to about 0.06 percent by weight.
While the use of strong acids such as thosle just mentioned, is important in obtaining good shelf life for the cyano-acrylate monomer~ the disadvantage inherent in their use is that they tend to retard the rate of polymerization, there-by interfering with the effectiveness of the adhesive.
Obviously, the prior art has been directed tomaximizing bond strength and shelf life. While xapid reaction rate and good storage stability are always important in a commercial product, it has not heretofore been recognized that a high level of bond strength may not always be desirable.
Thus, it would be quite beneficial to have an adhesive formu-lation which combines the rapid bonding associated with cyano-acrylates with reduced and controlled bond strength, along with the ability to be readily debonded, when desired.
Summary of the Invention According to the present invention, such an advantageous adhesive composition is provided. This composition, having controlled bond strength and adapted for debonding, comprises in admixture:
; (a) at least one polymerizabla ester of an a-cyanoacrylic acid, (b) from about 20 percent to about 60 percent -by weight of the composition of a plasticizer which is miscible with the ester of part (a);
(c) from about 0.015 percent to about 0.15 percent by weight of the composition of a
- 2 -;~:
i - ~57B8~
carboxylic acid which is soluble in the ester of part (a).
The invention also relates to a method for preparing the above adhesive composition by mixing the component ingredients or dissolving the plasticizer and carboxylic acid in the cyanoacrylate. The invention further relates to the use of such adhesive composition for bonding objects and subsequently debonding them by applying the composition to a surface of one of the objects, placing that surface in abutting relationship with a mating surface until the adhesive cures, then subjecting the bond to heat or solvent action to effect debonding.
Description of the Preferred Embodiments The monomeric a-cyanoacrylate esters of this invention are those well known to the art and conform to the general formula~
CN
CH2=C-C-O-R
o wherein R is a C1 to about C16 alkyl, alkenyl, cyclohexyl, phenyl, haloalkyl, arylalkyl, acylalkyl group, and the like, and mixtures thereof. Preferably, a single ester will be used and R will be a Cl to about C5 alkyl, alkenyl or cyclohexyl group, most preferably, methyl or ethyl.
The above monomers are generally prepared by the condensation of an ester of cyanoacetic acid with formaldehyde, followed by thermal depolymerization and fractional distilla-tion under vacuum to separate the monomer. Appropriate ~-procedures are described in, for example, Xodak U.S. Patent 3a No. 2,721,858, issued October 25, 1955; and other references.
The second required ingredient in the adhesive , :
~ .
~ .. _ . . . .. . . . . . . ~, ., 7~
composition is a plasticizer. The key property of the plasticizer is that it be fully miscible, and compatible, within the concentration range noted below, with the cyanoacrylate. By the term "compatible" :is meant that the material does not cause gellation or sett:Ling of the mixture.
The function of the plasticizer is to wea]cen the ultimate bond strength of the cured adhesive; therefore, the plastici-zer is to be used in relatively high concentration, namely, from about 20 percent to about 60 percent by weight of the total adhesive composition~ Preferably, the plastici~er content will be about 30 percent to about 40 percent by weight. A considerable variety of plasticizers are suitable for use in this invention and their selection accordin~ to the criteria above stated will be a matter of straightforward experimentation in any given case. The preferred plasticizers ; fall into various broad classes, as follows:
(a) aryl and diaryl ethers, such as diphenyl ether ~` ;t and its halogen-substituted derivatives; each . .~ , , .
aryl ring with its substituents, if any, may contain up to about 20 carbon atoms;
(b) alkyl and alkenyl esters of acids of the fumaric acid series, such as dialkyl fumarate and diallyl maleate; each alcoholic portion ;~
may contain up to about 12 carbon atoms, but preferably about 4 to 8 carbon atoms - (c) alkyl and alkenyl esters of acids of the ; oxalic acid series, such as diallyl oxalate, dioctyl azelate, and diallyl sebacate; the number of carbon atoms in the alcoholic portion will preferably be as in (b), above;
:, .
~ (d) alkyl and alkenyl esters of acids of the , ~ ~
.~ -- 4 ~;
" ~ :
: ., ~ ~1)57~38 phthalic acid series, whether ortho, meta or para, such as diallyl phthalate, dibutyl ;
phthalate, isobutyl phthalate, and ethyl hexyl phthalate; again the number of carbon atoms in the alcoholic portion will preferably be as in :
(b), above;
(e) alkyl and alkenyl esters of various other unsaturated dicarboxylic acids, such as diallyl itaconate. ;
Of the above plasticizers, those of groups (a~, ~c) and (d) are especially preferred. Mixtures of the above ~`
plasticizers can also be used. It will be understood that ,~
the above list of plasticizers is not intended to be llmiting.
Other plasticizers can be used, provided that they meet the miscibility and compatibility criteria described above.
The third required ingredient in the adhesive composition is a carboxylic acid or polycarboxylic acid. The key property of the acid is that it be soluble, within the concentration range noted below, in the cyanoacrylate. The acid should be relatively weak, that is, its pRA should not be~
below about 1.0 and preferably should be in the range of about 1.3 to about 6Ø The precise function of the carboxylio ~;
acid is not well understood; however, without intending to be bound to any particular theory, it is believed that the acid tends to limit polymer chain length. However, the acid may ; ~ also provide surface effects which tend to enhance adhesion and thereby regulate the weakening effect of the plasticizer.
i , . ~ . .
, The most desirable acids are those which, in addition to being ~
., . :. ~
soluble, do not substantially contribute to degradation of bond strength during storage of bonded par~ts over pexiods - of days or weeks, or substantially increase fixture or cure '~ time. The acid also appears to aid in disassembly of the .~ ~
. ' , , .
., , ' .- ~'~, `- 1~3S~
bond, as by application o~ solvent, where desired.
The concentration of -the carboxylic acid may vary from about 0.015 percent to about 0.15 percent by weight of the adhesive composition. The acid concentration chosen for any given situation will depend on the particular properties of the acid in relation to the above criteria. The preferred concentration, however, will usually be in the range of about 0.025 percent to about 0.075 percent by weight. It will also be appreciated that since the acid and the plasticizer ha~e a certain degree of individual ability to control bond strength, a considerable range of adhesive properties can be obtained by varying the proportions of these ingredients, as will be found by straightforward experimentation.
The preferred soluble organic acids fall into the following categories:
(a) alkyl and alkenyl monocarboxylic acids and their halo and cyano derivatives, such as mono- and dichloroacetic acid, cyanoacetic acid, and oleic acid; the alkyl or alkenyl moiety preferably will have from 1 to about 25 carbon atoms, more preferably from 1 to about 17 carbon atoms;
(b) aromatic monocarboxylic acids, such as benzoic acid and phenyl acetic acid, and the halo and lower alkyl and alkenyl derivatives (e.g., from 1 to about 4 carbon atoms) of such acids, for example, toluic acid and chlorobenzoic acid;
(c) aliphatic dicarboxylic acids of the oxalic acid series, such as oxalic acid and malonic acid, 3Q wherein the aliphatic portion may be substituted with halo and lower alkyl and alkenyl groups ', :
.. ...
11)5'i'~
(e.g., from 1 to about 4 carbon atoms).
A variety of additional materials may also be present in the adhesive composition. As has been mentioned, the cyano-acrylate monomer will usually contain an inhibitor of anionic polymerization , such as an acidic gas. More recently, sultone stabilizers have been developed (see Kodak U.S. Patent 3,742,018, issued June 26, 1973). It is also usually desirable to include an inhibitor of free radical polymerization, such as compounds of the phenolic type, for example, hydroquinone, its monomethyl ether, p-tert.-butyl catechol, and the like. In some applica-tions it may be advantageous to include dyes and viscosity modifiers as well. These materials, as well as the concentra-tions of their use, are known in the art and form no part `
of the present invention. A worthwhile summary of known ~ ;
formulations may be seen in U.S. Patent 3,699,127 issued October 17, 1972.
As has been indicated, a particular advantage of the - adhesive compositions of this invention is that their bonds ;
can be destroyed relatively easily, thereby permitting disass-20 embly of bonded parts. This property is highly desirable in applications where, for instance, rapid fixturing but weak ultimate strength is desired or where a small object is to be adhered to a jig or fixture ~or machining but is subsequently ~- to be detached from the jig or fixture. The compositians of this invention are uniquely adapted to such needs since they quickly (e.g., within one hour or less) form a secure bond -having tensile strength of 1,000 psi or more, but yet the parts can be very rapidly debonded, typically within 10 minutes or less. This combination of properties greatly improves efficiency in certain manufacturing operations.
Debonding can be readily accomplished thermally, such as by heating the bond line to 200-300F by oven or induction heat.
-, ' . , .
.,, ~, ;~'.
,,, . , :. . .
lVS788~
A variety of solvents, such as nitromethane, ac~tone, acetonitrile or dimethyl~ormamide, will also dissolve the bond. A particularly desirable feature of the present compositions is that the adhered parts may also be debonded by an aqueous surfactant solution containing, e.g., about 1 to about 5 percent by weight of the surfactant. A wide variety of water-soluble surfactants may be employed, but a preferred surfactant is a potassium aryl alkyl sulfonate sold under the trademark "Minate 415" manuEactured by Stepan Chemicals, Inc., Northfield, Illinois.
Mild heating (e.g.~ about 50C) of the solution is helpful. The presence of the carboxylic acid has been found to be beneficial in this context. While the mechanism :is not ; understood, it appears that it reduces the water resistance of the bond. Whether a solvent or aqueous bath is used, the ; ~ bath should be agitated. An especially effective form of agitation is provided by an ultrasonic transducer.
The following examples illustrate the invention but are not intended to be limiting in any way.
EX~PLE 1 An adhesive composition solution was prepared as follows. 2.5 gxams of a phenolic free radical inhibitor and 0.25 gram of oxalic acid were dried for about 2 hours at 60C
; and ~mm Hg pressure. These dried ingredients were weighed : ~:
into a clean, dry polyethylene container. Then 175.0 grams of dibutyl phthalate and 322.25 grams of ethyl cyanoacrylate ~; monomer were weighed into the container. Shaking accelerated the dissolving of the solids. This composition is referred to as "A".
The same procedure was followed using dried cyano- ;
acetic acid instead of oxalic acid and diphenyl ether instead . , .
.. .
' ' ' .. .~,, , ~ . . :
1~5'7~
of dibutyl phthalate. This composition is referred to as "B".
A third composition, referred to as "C"~ was prepared using the same procedure except that 0.37 gram dried benzoic acid was substituted for the oxalic acid.
Typical strength properties for these adhesive formulations are reported in Table I below for the room temperature cure times shown. The tensile lap shear test was ; performed according to AST~l A109. This test involves 10 adhering together overlapping surfaces of two steel test ;~
strips. The ends of the so-assembled specimens are pul:Led with a measuring device such as an Instron tester, and the tensile shear strength of the bond is measured. A compressive shear test was used to measure the fixture strength of the adhesive on various mixed substrates. This test involves adhering together overlapping surfaces of two test strips tglass, steel, aluminum, vinyl). One end of the so-assembled ~ ;
specimens is pushed against a "Chattillon" hand gauge and ~ : -~ the compression force to break the bond is measured.
; 20 TABLE I
Tensile Shear (psi) Compressive Shear (psi) Adhesive 24~hr. cure 15-min. cure 30-sec. cure (steel/glass) c A 1765 916 more than 15 (glass substrate failure) B 1265 890 more than 15 (glass, substrate failure) ; C 1490 850 more than I5 (glass substrate failure) D* 2200 1350 more than 15 (glass substrate failure) " ` '' `:' .. ..
*Control: ethyl cyanoacrylate without plasticizer and acid ! . ~
, ` ' ' :~ _ 9 _ :~ ' ' ~ ' ., ' ', ~
~ llS'~8~
Using the above adhesives, glass discs (about S/8"
to l" diameter) were bonded to mating steel surfaces. Bonds were fully cured (30-60 minutes at room temperature) and the parts were then debonded by the following ~ethods. Method A
involves immersing the bond in a 2 percent solution of a surfactant ("CONTR~D 70" ~ a proprietary anionic surfactant manufactured by Harleco, Inc., Philadelphia, Pennsylvania) in water at about 150F in an ultrasonic tank of about 400-500 watt output. Method B involves using an oven or an induction heater and elevating the temperature of the bondline to about 250F. Method C involves immersing the bond in solvents such as nitromethane, acetone or dimethylformamide in a 400-500 watt output ultrasonic tank. Typical times for disassembly o~ these adhesive bonds are listed in Table II, below.
TABLE II
_ _ ; Time to Debond, minutes Adhesive Method AMet_od B Method C
A about 2-3less than l about 2-3 2Q B about 1-2less than l about 1-2 '. ~
C less than l less than l about l D* more than 20 more than lO more than 20 :, ' ;
*Control: ethyl cyanoacrylate without plasticizer and acid .~ .
.
: -- 10 --" : . .
i - ~57B8~
carboxylic acid which is soluble in the ester of part (a).
The invention also relates to a method for preparing the above adhesive composition by mixing the component ingredients or dissolving the plasticizer and carboxylic acid in the cyanoacrylate. The invention further relates to the use of such adhesive composition for bonding objects and subsequently debonding them by applying the composition to a surface of one of the objects, placing that surface in abutting relationship with a mating surface until the adhesive cures, then subjecting the bond to heat or solvent action to effect debonding.
Description of the Preferred Embodiments The monomeric a-cyanoacrylate esters of this invention are those well known to the art and conform to the general formula~
CN
CH2=C-C-O-R
o wherein R is a C1 to about C16 alkyl, alkenyl, cyclohexyl, phenyl, haloalkyl, arylalkyl, acylalkyl group, and the like, and mixtures thereof. Preferably, a single ester will be used and R will be a Cl to about C5 alkyl, alkenyl or cyclohexyl group, most preferably, methyl or ethyl.
The above monomers are generally prepared by the condensation of an ester of cyanoacetic acid with formaldehyde, followed by thermal depolymerization and fractional distilla-tion under vacuum to separate the monomer. Appropriate ~-procedures are described in, for example, Xodak U.S. Patent 3a No. 2,721,858, issued October 25, 1955; and other references.
The second required ingredient in the adhesive , :
~ .
~ .. _ . . . .. . . . . . . ~, ., 7~
composition is a plasticizer. The key property of the plasticizer is that it be fully miscible, and compatible, within the concentration range noted below, with the cyanoacrylate. By the term "compatible" :is meant that the material does not cause gellation or sett:Ling of the mixture.
The function of the plasticizer is to wea]cen the ultimate bond strength of the cured adhesive; therefore, the plastici-zer is to be used in relatively high concentration, namely, from about 20 percent to about 60 percent by weight of the total adhesive composition~ Preferably, the plastici~er content will be about 30 percent to about 40 percent by weight. A considerable variety of plasticizers are suitable for use in this invention and their selection accordin~ to the criteria above stated will be a matter of straightforward experimentation in any given case. The preferred plasticizers ; fall into various broad classes, as follows:
(a) aryl and diaryl ethers, such as diphenyl ether ~` ;t and its halogen-substituted derivatives; each . .~ , , .
aryl ring with its substituents, if any, may contain up to about 20 carbon atoms;
(b) alkyl and alkenyl esters of acids of the fumaric acid series, such as dialkyl fumarate and diallyl maleate; each alcoholic portion ;~
may contain up to about 12 carbon atoms, but preferably about 4 to 8 carbon atoms - (c) alkyl and alkenyl esters of acids of the ; oxalic acid series, such as diallyl oxalate, dioctyl azelate, and diallyl sebacate; the number of carbon atoms in the alcoholic portion will preferably be as in (b), above;
:, .
~ (d) alkyl and alkenyl esters of acids of the , ~ ~
.~ -- 4 ~;
" ~ :
: ., ~ ~1)57~38 phthalic acid series, whether ortho, meta or para, such as diallyl phthalate, dibutyl ;
phthalate, isobutyl phthalate, and ethyl hexyl phthalate; again the number of carbon atoms in the alcoholic portion will preferably be as in :
(b), above;
(e) alkyl and alkenyl esters of various other unsaturated dicarboxylic acids, such as diallyl itaconate. ;
Of the above plasticizers, those of groups (a~, ~c) and (d) are especially preferred. Mixtures of the above ~`
plasticizers can also be used. It will be understood that ,~
the above list of plasticizers is not intended to be llmiting.
Other plasticizers can be used, provided that they meet the miscibility and compatibility criteria described above.
The third required ingredient in the adhesive composition is a carboxylic acid or polycarboxylic acid. The key property of the acid is that it be soluble, within the concentration range noted below, in the cyanoacrylate. The acid should be relatively weak, that is, its pRA should not be~
below about 1.0 and preferably should be in the range of about 1.3 to about 6Ø The precise function of the carboxylio ~;
acid is not well understood; however, without intending to be bound to any particular theory, it is believed that the acid tends to limit polymer chain length. However, the acid may ; ~ also provide surface effects which tend to enhance adhesion and thereby regulate the weakening effect of the plasticizer.
i , . ~ . .
, The most desirable acids are those which, in addition to being ~
., . :. ~
soluble, do not substantially contribute to degradation of bond strength during storage of bonded par~ts over pexiods - of days or weeks, or substantially increase fixture or cure '~ time. The acid also appears to aid in disassembly of the .~ ~
. ' , , .
., , ' .- ~'~, `- 1~3S~
bond, as by application o~ solvent, where desired.
The concentration of -the carboxylic acid may vary from about 0.015 percent to about 0.15 percent by weight of the adhesive composition. The acid concentration chosen for any given situation will depend on the particular properties of the acid in relation to the above criteria. The preferred concentration, however, will usually be in the range of about 0.025 percent to about 0.075 percent by weight. It will also be appreciated that since the acid and the plasticizer ha~e a certain degree of individual ability to control bond strength, a considerable range of adhesive properties can be obtained by varying the proportions of these ingredients, as will be found by straightforward experimentation.
The preferred soluble organic acids fall into the following categories:
(a) alkyl and alkenyl monocarboxylic acids and their halo and cyano derivatives, such as mono- and dichloroacetic acid, cyanoacetic acid, and oleic acid; the alkyl or alkenyl moiety preferably will have from 1 to about 25 carbon atoms, more preferably from 1 to about 17 carbon atoms;
(b) aromatic monocarboxylic acids, such as benzoic acid and phenyl acetic acid, and the halo and lower alkyl and alkenyl derivatives (e.g., from 1 to about 4 carbon atoms) of such acids, for example, toluic acid and chlorobenzoic acid;
(c) aliphatic dicarboxylic acids of the oxalic acid series, such as oxalic acid and malonic acid, 3Q wherein the aliphatic portion may be substituted with halo and lower alkyl and alkenyl groups ', :
.. ...
11)5'i'~
(e.g., from 1 to about 4 carbon atoms).
A variety of additional materials may also be present in the adhesive composition. As has been mentioned, the cyano-acrylate monomer will usually contain an inhibitor of anionic polymerization , such as an acidic gas. More recently, sultone stabilizers have been developed (see Kodak U.S. Patent 3,742,018, issued June 26, 1973). It is also usually desirable to include an inhibitor of free radical polymerization, such as compounds of the phenolic type, for example, hydroquinone, its monomethyl ether, p-tert.-butyl catechol, and the like. In some applica-tions it may be advantageous to include dyes and viscosity modifiers as well. These materials, as well as the concentra-tions of their use, are known in the art and form no part `
of the present invention. A worthwhile summary of known ~ ;
formulations may be seen in U.S. Patent 3,699,127 issued October 17, 1972.
As has been indicated, a particular advantage of the - adhesive compositions of this invention is that their bonds ;
can be destroyed relatively easily, thereby permitting disass-20 embly of bonded parts. This property is highly desirable in applications where, for instance, rapid fixturing but weak ultimate strength is desired or where a small object is to be adhered to a jig or fixture ~or machining but is subsequently ~- to be detached from the jig or fixture. The compositians of this invention are uniquely adapted to such needs since they quickly (e.g., within one hour or less) form a secure bond -having tensile strength of 1,000 psi or more, but yet the parts can be very rapidly debonded, typically within 10 minutes or less. This combination of properties greatly improves efficiency in certain manufacturing operations.
Debonding can be readily accomplished thermally, such as by heating the bond line to 200-300F by oven or induction heat.
-, ' . , .
.,, ~, ;~'.
,,, . , :. . .
lVS788~
A variety of solvents, such as nitromethane, ac~tone, acetonitrile or dimethyl~ormamide, will also dissolve the bond. A particularly desirable feature of the present compositions is that the adhered parts may also be debonded by an aqueous surfactant solution containing, e.g., about 1 to about 5 percent by weight of the surfactant. A wide variety of water-soluble surfactants may be employed, but a preferred surfactant is a potassium aryl alkyl sulfonate sold under the trademark "Minate 415" manuEactured by Stepan Chemicals, Inc., Northfield, Illinois.
Mild heating (e.g.~ about 50C) of the solution is helpful. The presence of the carboxylic acid has been found to be beneficial in this context. While the mechanism :is not ; understood, it appears that it reduces the water resistance of the bond. Whether a solvent or aqueous bath is used, the ; ~ bath should be agitated. An especially effective form of agitation is provided by an ultrasonic transducer.
The following examples illustrate the invention but are not intended to be limiting in any way.
EX~PLE 1 An adhesive composition solution was prepared as follows. 2.5 gxams of a phenolic free radical inhibitor and 0.25 gram of oxalic acid were dried for about 2 hours at 60C
; and ~mm Hg pressure. These dried ingredients were weighed : ~:
into a clean, dry polyethylene container. Then 175.0 grams of dibutyl phthalate and 322.25 grams of ethyl cyanoacrylate ~; monomer were weighed into the container. Shaking accelerated the dissolving of the solids. This composition is referred to as "A".
The same procedure was followed using dried cyano- ;
acetic acid instead of oxalic acid and diphenyl ether instead . , .
.. .
' ' ' .. .~,, , ~ . . :
1~5'7~
of dibutyl phthalate. This composition is referred to as "B".
A third composition, referred to as "C"~ was prepared using the same procedure except that 0.37 gram dried benzoic acid was substituted for the oxalic acid.
Typical strength properties for these adhesive formulations are reported in Table I below for the room temperature cure times shown. The tensile lap shear test was ; performed according to AST~l A109. This test involves 10 adhering together overlapping surfaces of two steel test ;~
strips. The ends of the so-assembled specimens are pul:Led with a measuring device such as an Instron tester, and the tensile shear strength of the bond is measured. A compressive shear test was used to measure the fixture strength of the adhesive on various mixed substrates. This test involves adhering together overlapping surfaces of two test strips tglass, steel, aluminum, vinyl). One end of the so-assembled ~ ;
specimens is pushed against a "Chattillon" hand gauge and ~ : -~ the compression force to break the bond is measured.
; 20 TABLE I
Tensile Shear (psi) Compressive Shear (psi) Adhesive 24~hr. cure 15-min. cure 30-sec. cure (steel/glass) c A 1765 916 more than 15 (glass substrate failure) B 1265 890 more than 15 (glass, substrate failure) ; C 1490 850 more than I5 (glass substrate failure) D* 2200 1350 more than 15 (glass substrate failure) " ` '' `:' .. ..
*Control: ethyl cyanoacrylate without plasticizer and acid ! . ~
, ` ' ' :~ _ 9 _ :~ ' ' ~ ' ., ' ', ~
~ llS'~8~
Using the above adhesives, glass discs (about S/8"
to l" diameter) were bonded to mating steel surfaces. Bonds were fully cured (30-60 minutes at room temperature) and the parts were then debonded by the following ~ethods. Method A
involves immersing the bond in a 2 percent solution of a surfactant ("CONTR~D 70" ~ a proprietary anionic surfactant manufactured by Harleco, Inc., Philadelphia, Pennsylvania) in water at about 150F in an ultrasonic tank of about 400-500 watt output. Method B involves using an oven or an induction heater and elevating the temperature of the bondline to about 250F. Method C involves immersing the bond in solvents such as nitromethane, acetone or dimethylformamide in a 400-500 watt output ultrasonic tank. Typical times for disassembly o~ these adhesive bonds are listed in Table II, below.
TABLE II
_ _ ; Time to Debond, minutes Adhesive Method AMet_od B Method C
A about 2-3less than l about 2-3 2Q B about 1-2less than l about 1-2 '. ~
C less than l less than l about l D* more than 20 more than lO more than 20 :, ' ;
*Control: ethyl cyanoacrylate without plasticizer and acid .~ .
.
: -- 10 --" : . .
Claims (13)
1. A cyanoacrylate adhesive composition having controlled bond strength and adapted for debonding, comprising in admixture:
(a) at least one polymerizable ester of an .alpha.-cyanoacrylic acid;
(b) from about 20 percent to about 60 percent by weight of the composition of a plasticizer which is miscible with the ester of part (a);
(c) from about 0.015 percent to about 0.15 percent by weight of the composition of a carboxylic acid which is soluble in the ester of part (a).
(a) at least one polymerizable ester of an .alpha.-cyanoacrylic acid;
(b) from about 20 percent to about 60 percent by weight of the composition of a plasticizer which is miscible with the ester of part (a);
(c) from about 0.015 percent to about 0.15 percent by weight of the composition of a carboxylic acid which is soluble in the ester of part (a).
2. A composition of claim 1 wherein the ester of .alpha.-cyanoacrylic acid has the formula wherein R is a C1 to C16 alkyl, alkenyl, cyclohexyl or phenyl group.
3. A composition of claim 1 wherein the plasticizer is an aryl or diaryl ether.
4. A composition of claim 1 wherein the plasticizer is an alkyl or alkenyl ester of an acid of the fumaric acid series.
5. A composition of claim 1 wherein the plasticizer is an alkyl or alkenyl ester of an acid of the oxalic acid series.
6. A composition of claim 1 wherein the plasticizer is an alkyl or alkenyl ester of an acid of the phthalic acid series.
7. A composition of claim 1 wherein the carboxylic acid is an alkyl or alkenyl monocarboxylic acid or derivative thereof.
8. A composition of claim 1 wherein the carboxylic acid is an aromatic monocarboxylic acid.
9. A composition of claim l wherein the carboxylic acid is an aliphatic dicarboxylic acid of the oxalic acid series.
10. A composition of claim 1 which additionally contains an inhibitor of anionic polymerization.
11. A composition of claim 10 which additionally contains an inhibitor of free radical polymerization.
12. A method of preparing a cyanoacrylate adhesive composition having controlled bond strength and adapted for debonding, comprising dissolving in at least one polymerizable ester of an .alpha.-cyanoacrylic acid (a) from about 20 percent to about 60 percent by weight of the composition of a plasticizer, and (b) from about 0.015 percent to about 0.15 percent by weight of the composition of a carboxylic acid.
13. A method of debondably adhering and subsequently debonding objects, comprising:
I. applying to a mating surface of one of said objects a cyanoacrylate adhesive composition having controlled bond strength and adapted for debonding, comprising in admixture:
(a) at least one polymerizable ester of an .alpha.-cyanoacrylic acid;
(b) from about 20 percent to about 60 percent by weight of the composition of a plasticizer which is miscible with the ester of part (a);
(c) from about 0.015 percent to about 0.15 percent by weight of the composition of a carboxylic acid which is soluble in the ester of part (a);
II. placing mating surfaces of said objects in abutting relationship until the adhesive compositions has cured;
and III. debonding the objects by subjecting the bond to heat or solvent action.
I. applying to a mating surface of one of said objects a cyanoacrylate adhesive composition having controlled bond strength and adapted for debonding, comprising in admixture:
(a) at least one polymerizable ester of an .alpha.-cyanoacrylic acid;
(b) from about 20 percent to about 60 percent by weight of the composition of a plasticizer which is miscible with the ester of part (a);
(c) from about 0.015 percent to about 0.15 percent by weight of the composition of a carboxylic acid which is soluble in the ester of part (a);
II. placing mating surfaces of said objects in abutting relationship until the adhesive compositions has cured;
and III. debonding the objects by subjecting the bond to heat or solvent action.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56145875A | 1975-04-14 | 1975-04-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057880A true CA1057880A (en) | 1979-07-03 |
Family
ID=24242056
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,111A Expired CA1057880A (en) | 1975-04-14 | 1976-03-17 | Debondable cyanoacrylate adhesive compositions |
Country Status (6)
| Country | Link |
|---|---|
| AU (1) | AU509875B2 (en) |
| CA (1) | CA1057880A (en) |
| DE (1) | DE2612546A1 (en) |
| FR (1) | FR2313435A1 (en) |
| GB (1) | GB1529105A (en) |
| IT (1) | IT1118851B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4196271A (en) | 1975-12-24 | 1980-04-01 | Toagosei Chemical Industry Co., Ltd. | Adhesive composition |
| BR9711198A (en) | 1996-08-16 | 1999-08-17 | Loctite Ireland Ltd | Adhesive cyanoacrylate compositions for glass junction |
| US6977278B1 (en) | 2001-01-08 | 2005-12-20 | Loctite (R&D) Ltd. | Cyanoacrylate compositions curable to flexible polymeric materials |
| US8071675B2 (en) | 2005-12-19 | 2011-12-06 | Loctite (R&D) Limited | Cyanoacrylate composite forming system |
| DE102009012187A1 (en) * | 2009-02-26 | 2010-09-02 | Aesculap Aktiengesellschaft | Medical adhesive composition |
| PT2511355E (en) | 2011-04-12 | 2014-01-28 | Henkel Ireland Ltd | Cyanoacrylate adhesive with improved water resistance |
-
1976
- 1976-03-17 CA CA248,111A patent/CA1057880A/en not_active Expired
- 1976-03-22 AU AU12227/76A patent/AU509875B2/en not_active Expired
- 1976-03-23 IT IT4868076A patent/IT1118851B/en active
- 1976-03-24 DE DE19762612546 patent/DE2612546A1/en not_active Withdrawn
- 1976-03-24 FR FR7608454A patent/FR2313435A1/en active Granted
- 1976-03-24 GB GB1182176A patent/GB1529105A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2313435A1 (en) | 1976-12-31 |
| FR2313435B1 (en) | 1980-02-15 |
| IT1118851B (en) | 1986-03-03 |
| AU1222776A (en) | 1977-09-29 |
| DE2612546A1 (en) | 1976-10-14 |
| AU509875B2 (en) | 1980-05-29 |
| GB1529105A (en) | 1978-10-18 |
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