Anaerobically curable adhesive compositions

Abstract

An anaerobically curable adhesive composition comprising: an anaerobically curable component; a cure inducing component; and a stabiliser component comprising one or both of the following compounds glutamic acid diacetic acid tetrasodium salt (Na4GLDA); and / or methylglycine N,N-diacetic acid trisodium salt (Na3MGDA). Such stabiliser component(s) either alone, or in combination, act as potent metal ion chelators in anaerobic formulations at levels significantly lower than typically effective for Na4EDTA.

Description

Title Anaerobically curable adhesive compositions Field

[0001] The present invention relates to anaerobically curable adhesivecompositions, method of anaerobically curing such compositions and cured products thereof. Background

[0002] Anaerobically curable compositions are well known. Anaerobicallycurable compositions remain uncured when exposed to air (oxygen) and cure under suitable anaerobic conditions. The uses of anaerobically curable compositions are broad and continue to be developed. For example, anaerobically curable compositions can be useful as threadlockers, for gasketing, for adhesion to oily substrates, as pipe sealants, and for joint repair.

[0003] Typically, anaerobic adhesive compositions are mixtures ofpolymerizable acrylate ester monomers and peroxy polymerization initiatorstherefor. Preferably, at least a portion of the acrylate monomer is a di- or otherpolyacrylate ester. Suitable polyacrylate ester monomers are di-, tri- -andtetraethyleneglycol dimethacrylate; dipropyleneglycol dimethacrylate; polyethyleneglycol dimethacrylate; polypropyleneglycol dimethacrylate; di(pentamethyleneglycol) dimethacrylate; tetraethyleneglycol diacrylate; tetraethyleneglycol di(chloracrylate); diglycerol diacrylate; diglycerol tetramethacrylate; tetramethylene dimethacrylate; ethylene dimethacrylate; butyleneglycol dimethacrylate; neopentylglycol diacrylate; and trimethylolpropane triacrylate.

[0004] Monofunctional acrylate esters (esters containing one acrylate group)may also be used in anaerobic adhesives, and preferably the esters are those with a relatively polar alcoholic moiety. Typical examples of compounds within this category are cyclohexylmethacrylate; tetrahydrofurfuryl methacrylate; hydroxyethyl acrylate; hydroxypropyl methacrylate; t-butylaminoethyl methacrylate; cyanoethylacrylate and choroethyl methacrylate.

[0005] Another class of polyacrylate ester monomers utilized in anaerobicadhesive compositions are the isocyanatemonoacrylate reaction products described in U.S. Patent No.3424988 (Toback / Gorman).

[0006] It is generally known that anaerobically curable compositions can beunstable and lose adhesion performance over time. Accordingly, it is common to employ stabilisers in the composition to obtain anaerobically curable compositions with increased stability. These stabilisers, however, can reduce the performance of the anaerobically curable compositions.

[0007] All anaerobic adhesives are sensitive to the presence of metal ions in theirformulations, in particular Cu and Fe metal ion contaminants. There are often small (ppm) levels of metal ions present in the raw material ingredients or acquired through the processing of the formulations. A critical component of all anaerobic formulations therefore is a stabiliser which can sequester such metal ions before they begin to destabilise the anaerobic adhesive itself. Such stabilisers are known as metal chelators. At present, commercially available anaerobically curable compositions employ tetrasodium EDTA (ethylene diamine tetra-acetic acid), referred to henceforth as Na4EDTA, as a stabiliser which is shown below:

[0008] European patent application no. EP 0 282 292 describes a metal ionchelator N-hydroxyethylenediamine triacetic acid trisodium salt (HEDTA Na3) for use in anaerobic acrylate ester sealants or adhesives.

[0009] Notwithstanding the prior metal ion chelators there remains a need foralternatives. Desirably such alternatives would be good stabilisers. Particularly ofinterest are alternative stabilisers which are capable of stabilizing anaerobic compositions. Furthermore, it is desirable that such stabilisers are effective at low concentrations, for example, even lower concentrations than a stabiliser such as Na4EDTA. And of course, it is also desirable that any such alternative stabiliser does not deleteriously affect the cure of the anaerobic adhesive, for example does not impede cure speed or impact bond strength such as tensile bond strength.

[0010] Accordingly, it is an objective of the present invention to provide metal ionchelators for use in anaerobic adhesives which are soluble in anaerobic adhesive compositions and can effectively chelate and deactivate contaminating metals without substantially interfering with the curing or cured properties of such adhesives. Summary

[0011] In one aspect, the present invention provides an anaerobically curableadhesive composition comprising: (i) an anaerobically curable component;(ii) a cure inducing component; and(iii) a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6acyl, carboxyl, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N- thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O- carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido;M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, carboxyl, ester, or carbonyl;m is an integer selected from 3-n.Thus, where n is less than 3, one or two substituents about the N may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6acyl, carboxyl, ester, or carbonyl.

[0012] Herein, carbonyl refers to any functional group containing a carbonyl groupwhich can include but is not limited to aldehydes, ketones, carboxylic acids, and amides. Thiocarbonyl refers to any functional group containing a thiocarbonyl group which can include but is not limited to thioaldehydes and thioketones.

[0013] The anaerobically curable adhesive composition may comprise:(i) an anaerobically curable component;(ii) a cure inducing component; and(iii) a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1and R2are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9cycloalkynyl, C5-C9heteroaryl, C3-C9heteroalicyclyl, C6-C12aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato,nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ramay be selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C7-C12 aralkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6acyl, linear or branched C1-C6carboxylate, ester, or carbonyl;m is an integer selected from 3-n.Thus, where n is less than 3, one or two substituents about the N may be selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6acyl, linear or branched C1-C6carboxylate, ester, or carbonyl.

[0014] Possible alternatives for C(R1)(R2)-COOM shown in the structures above,includewhere M is a cation such as H+ or a metal cation, for example Na+, Li+, K+; and R1and R2are each independently as defined above.

[0015] The present invention also provides an anaerobically curable adhesivecomposition wherein the stabiliser component may comprise one or both compounds of following structures: (i) glutamic acid diacetic acid tetrasodium salt (Na4GLDA) of thestructure:and / or (ii) methylglycine N,N-diacetic acid trisodium salt (Na3MGDA) of thestructure:

[0016] Glutamic acid diacetic acid tetrapotassium salt (K4GLDA) is within thepresent invention also.

[0017] Methylglycine N,N-diacetic acid tripotassium salt (K3MGDA) is within thepresent invention also.

[0018] Advantageously, the stabiliser component Na4GLDA is bio-based, forexample derived from monosodium glutamate (MSG) (which is a common food ingredient) as disclosed by the manufacturer, NouryonTM. The stabiliser component Na3MGDA is biodegradable, as disclosed by the manufacturer, Nouryon. Therefore, both the stabiliser components offer environmentally sustainable alternatives for curing of anaerobic products.

[0019] Advantageously, the composition of the present invention excludes (thenecessity to have) Na4EDTA as a component of the composition.

[0020] Suitably, the stabiliser component(s), such as glutamic acid diacetic acidtetrasodium salt (Na4GLDA) and / or methylglycine N, N-diacetic acid trisodium salt (Na3MGDA), are in the form of diluted mixtures or premixes upon addition to an adhesive composition.

[0021] Suitably, the stabiliser component(s) are in the form of solutions havingconcentrations of the stabiliser component(s) ranging from about 2% to about 10%, such as about 3.5%, prior to their addition to the adhesive composition.

[0022] Suitably, the stabiliser component(s) can be used at a variety ofconcentrations in the adhesive composition, ranging from about 2 ppm to about 1000 ppm, such as from about 5 ppm to 500 ppm or from about 10 ppm to 1000 ppm, for example from about 10 ppm to about 100 ppm.

[0023] Surprisingly, the stabiliser component(s) of the invention, either alone, orin combination, act as potent metal ion chelators in anaerobic formulations at levels significantly lower than typically effective for Na4EDTA.

[0024] In another aspect, the present invention provides a method ofanaerobically curing an anaerobically curable adhesive composition comprising the steps of: (A) providing an anaerobically curable adhesive composition comprising: (a) an anaerobically curable component; (b) a cure inducing component; (c) a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12heteroaralkyl, C6-C12(heteroalicyclyl)alkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6 acyl, carboxyl, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O- carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido;M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6alkenyl, linear or branched C2-C6alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C7-C12 aralkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, carboxyl, ester, or carbonyl;m is an integer selected from 3-n; and(B) exposing the anaerobically curable adhesive composition to an anaerobic environment for a time sufficient to cure the composition.

[0025] The present invention also provides a method of anaerobically curing ananaerobically curable adhesive composition comprising the steps of: (A) providing an anaerobically curable adhesive composition comprising: (a) an anaerobically curable component; (b) a cure inducing component; (c) a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, mercapto,alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido;M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl,C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate,ester, or carbonyl;m is an integer selected from 3-n; and(B) exposing the anaerobically curable adhesive composition to an anaerobic environment for a time sufficient to cure the composition.

[0026] More specifically, in this aspect, the present invention provides a methodof anaerobically curing an anaerobically curable adhesive composition comprising the steps of: (A) providing an anaerobically curable adhesive composition comprising: (a) an anaerobically curable component; (b) a cure inducing component; (c) a stabiliser component comprising one or both of the following compounds:(i) glutamic acid diacetic acid tetrasodium salt (Na4GLDA) of the structure:and / or (ii) methylglycine N,N-diacetic acid trisodium salt (Na3MGDA) of the structure:and; (B) exposing the anaerobically curable adhesive composition to an anaerobic environment for a time sufficient to cure the composition.

[0027] In yet another aspect, the present invention provides the cure / curedproduct formed by the curing of an anaerobically curable adhesive composition of the invention.

[0028] In still yet another aspect, the present invention provides a bondedassembly comprising a first substrate bonded to a second substrate by the cure / cured product formed by the curing of an anaerobically curable adhesive composition of the invention.

[0029] The present invention also relates to use of a stabiliser component of thestructure: N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6alkenyl, linear or branched C2-C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12heteroaralkyl, C6-C12(heteroalicyclyl)alkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6 acyl, carboxyl, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N- thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O- carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl,sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ramay be selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C7-C12 aralkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6acyl, carboxyl, ester, or carbonyl;m is an integer selected from 3-n,as a stabiliser for an anaerobically curable adhesive composition .

[0030] The present invention also relates to use of a stabiliser component of thestructure: N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, mercapto,alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl,C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate,ester, or carbonyl;m is an integer selected from 3-n,as a stabiliser for an anaerobically curable adhesive composition.

[0031] In this respect, the stabiliser component may comprise at least one of:glutamic acid diacetic acid tetrasodium salt (Na4GLDA) of the structure:or methylglycine N,N-diacetic acid trisodium salt (Na3MGDA) of the structure:as a stabiliser for an anaerobically curable adhesive composition.

[0032] As discussed above the stabiliser component(s) may be used incombination with each other. As discussed below additional stabilisers may be utilised.

[0033] The present invention also relates to a method of stabilising ananaerobically curable adhesive composition by providing an effective amount of a stabiliser component of the structure: N–[C(R1)(R2)-COOM]n(Ra)mwherein R1and R2are each independently selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12heteroaralkyl, C6-C12(heteroalicyclyl)alkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6 acyl, carboxyl, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N- thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O- carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ramay be selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6alkenyl, linear or branched C2-C6alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C7-C12 aralkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, carboxyl, ester, or carbonyl;m is an integer selected from 3-n.

[0034] The present invention also relates to a method of stabilising ananaerobically curable adhesive composition by providing an effective amount of a stabiliser component of the structure: N–[C(R1)(R2)-COOM]n(Ra)mwherein R1and R2are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9cycloalkynyl, C5-C9heteroaryl, C3-C9heteroalicyclyl, C6-C12aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato,nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ramay be selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C7-C12 aralkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6acyl, linear or branched C1-C6carboxylate, ester, or carbonyl;m is an integer selected from 3-n,

[0035] More specifically, the method of stabilising an anaerobically curableadhesive composition provides an effective amount of at least one of: (a) glutamic acid diacetic acid tetrasodium salt (Na4GLDA) of the structure:or (b) methylglycine N,N-diacetic acid trisodium salt (Na3MGDA) of the structure:as a stabiliser component of the anaerobically curable adhesive composition .

[0036] Accordingly, the present invention offers significant advantages over thestate-of-the-art which include being biodegradable, non-hazardous, and / or bio- based and having better stabilising performance at significantly lower concentrations.

[0037] Suitable anaerobically curable adhesive compositions which mayinclude one or both of the above mentioned stabiliser component(s) include those components described above (including those discussed under “Background”) and below.

[0038] Included within the invention is a monoamino polycarboxylic acid / saltas a stabiliser component within an anaerobically curable adhesive composition . Desirably there are 3 or 4 carboxylic acid / salt groups in the monoamino polycarboxylic acid / salt stabiliser component. Optionally the monoamino polycarboxylic salt is a potassium or sodium salt. Polymerizable (meth)acrylate ester monomers

[0039] The (meth)acrylate ester monomers may be utilised as ananaerobically curable component. (Meth)acrylate monomers suitable for use in the anaerobically curable adhesive compositions described herein may be chosen from a wide variety of materials, such as those represented by H2C═CGCO2R4, where G is hydrogen, halogen or alkyl groups having from 1 to about 4 carbon atoms, and R4is selected from C1-C6alkyl, C3-C9cycloalkyl, alkenyl, C4-C9 cycloalkenyl, C6-C12 alkaryl, C6-C12 aralkyl or C3-C9 aryl groups having from 1 to about 16 carbon atoms, any of which may be optionally substituted or interrupted as the case may be with silane, silicon, oxygen, halogen, carbonyl, hydroxyl, ester, carboxylic acid, urea, urethane, carbonate, amine, amide, sulfur, sulfonate, sulfone and the like.

[0040] One class of monomers suited for use in this invention comprisespolyacrylate esters represented by the formulawhere here R4is a radical selected from hydrogen, halogen or alkyl of from 1 to about 4 carbon atoms; q is an integer equal to at least 1, and preferably equal to from 1 to about 4; and X is an organic radical containing at least two carbon atoms and having a total bonding capacity of q plus 1. With regard to the upper limit for the number of carbon atoms in X, workable monomers exist at essentially any value. As a practical matter, however, a general upper limit is about 50 carbon atoms, preferably 30, and most preferably about 20.

[0041] For example, X can be an organic radical of the formula:wherein here each of Y1and Y2is an organic radical, preferably a hydrocarbon group, containing at least 2 carbon atoms, and preferably from 2 to about 10 carbon atoms, and Z is an organic radical, preferably a hydrocarbon group, containing at least 1 carbon atom, and preferably from 2 to about 10 carbon atoms.

[0042] Other classes of useful monomers are the reaction products of di- or tri-alkylolamines (e.g., ethanolamines or propanolamines) with acrylic acids, such as are disclosed in French Patent No.1,581,361.

[0043] Examples of useful acrylate ester oligomers include those having thefollowing general formula:where here R5represents a radical selected from hydrogen, lower alkyl of from 1 to about 4 carbon atoms, hydroxy alkyl of from 1 to about 4 carbon atoms, andwhere here R4is a radical selected from hydrogen, halogen, or lower alkyl of from 1 to about 4 carbon atoms; R6is a radical selected from hydrogen, hydroxyl, orm is an integer equal to at least 1, e.g., from 1 to about 15 or higher, and preferably from 1 to about 8; n is an integer equal to at least 1, e.g., 1 to about 40 or more, and preferably between about 2 and about 10; and p is 0 or 1.

[0044] Typical examples of (meth)acrylate ester oligomers corresponding to theabove general formula include di-, tri- and tetraethyleneglycol dimethacrylate;di(pentamethyleneglycol)dimethacrylate; tetraethyleneglycol diacrylate; tetraethyleneglycol di(chloroacrylate); diglycerol diacrylate; diglycerol tetramethacrylate; butyleneglycol dimethacrylate; neopentylglycol diacrylate; and trimethylolpropane triacrylate.

[0045] While di- and other polyacrylate esters, and particularly the polyacrylateesters described in the preceding paragraphs, can be desirable, monofunctional acrylate esters (esters containing one acrylate group) also may be used. When dealing with monofunctional acrylate esters, it is highly preferable to use an ester which has a relatively polar alcoholic moiety. Such materials are less volatile than low molecular weight alkyl esters and, more important, the polar group tends to provide intermolecular attraction during and after cure, thus producing more desirable cure properties, as well as a more durable sealant or adhesive. Desirably, the polar group is selected from labile hydrogen, heterocyclic ring, hydroxy, amino, cyano, and halo polar groups. Typical examples of compoundswithin this category are cyclohexylmethacrylate, tetrahydrofurfuryl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, t-butylaminoethyl methacrylate, cyanoethylacrylate, and chloroethyl methacrylate.

[0046] Another useful class of monomers is prepared by the reaction of amonofunctionally substituted alkyl or aryl (meth)acrylate ester containing an active hydrogen atom on the functional substituent. This monofunctional, (meth)acrylate-terminated material is reacted with an organic polyisocyanate in suitable proportions so as to convert all of the isocyanate groups to urethane or ureido groups. The monofunctional alkyl and aryl acrylate esters are preferably the acrylates and methacrylates containing hydroxy or amino functional groups on the non-acrylate portion thereof. Acrylate esters suitable for use have the formula:where here X is selected from --O-- or and R9 is selected from hydrogenor lower alkyl of 1 through 7 carbon atoms; R7is selected from hydrogen, chlorine or methyl and ethyl radicals; and R8is a divalent organic radical selected from lower alkylene of 1 through 8 carbon atoms, phenylene or naphthylene. These groups upon proper reaction with a polyisocyanate, yield a monomer of the following general formula:where n is an integer from 2 to about 6; B is a polyvalent organic radical selected from alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, aralkyl, alkaryl or heterocyclic radicals both substituted and unsubstituted; and R7, R8and X have the meanings given above in this paragraph.

[0047] Examples of suitable hydroxyl-functional (meth)acrylates includehydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate (“HEMA”), hydroxypropyl methacrylate (“HPMA”), hydroxybutyl methacrylate and mixtures thereof. Other examples of suitablehydroxy functional (meth)acrylates include 2-hydroxyethyl acrylate, 2- hydroxypropyl acrylate, 2-hydroxyethyl methacrylate (“HEMA”), pentaerythritol triacrylate (“PETA”), and 4-hydroxybutyl acrylate.

[0048] The hydroxy-functional (meth)acrylate can have a number averagemolecular weight of about 80 to about 1,000 grams / mole, or about 100 to about 800 grams / mole, or about 110 to about 600 grams / mole.

[0049] Of course, combinations of such (meth)acrylate monomers may also beused.

[0050] Still other (meth)acrylate monomers that may be used herein includesilicone (meth)acrylate moieties (“SiMA”), such as those taught by and claimed in U.S. Patent No.5,605,999 (Chu).

[0051] The polymerisable (meth) acrylate ester monomers may be present inthe composition in an amount from about 10 to about 90 weight percent, suitably about 30 to about 70 weight percent, based on the total weight of the composition.

[0052] The anaerobic cure-inducing compositions ordinarily include freeradical initiators, co-accelerators, and free radical inhibitors, as well as metal catalysts.

[0053] A number of well-known free radical initiators may be used including,without limitation, peroxide compounds such as hydroperoxides, like cumene hydroperoxide ("CHP"), para-menthane hydroperoxide, t-butyl hydroperoxide ("TBH"), diisopropylbenzene hydroperoxide and t-butyl perbenzoate. Other useful peroxides include benzoyl peroxide, dibenzoyl peroxide, 1,3-bis(t- butylperoxyisopropyl)benzene, diacetyl peroxide, butyl 4,4-bis(t- butylperoxy)valerate, p-chlorobenzoyl peroxide, t-butyl cumyl peroxide, t-butyl perbenzoate, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t- butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butyl-peroxyhex-3-yne, 4-methyl-2,2- di-t-butylperoxypentane and combinations thereof.

[0054] Such peroxide compounds are typically employed in the presentinvention in the range of from about 0.1 to about 10 percent by weight, based on the total weight of the composition, with about 1 to about 5 percent by weight being desirable.

[0055] As noted, conventional accelerators of free radical polymerization mayalso be used in conjunction with the cure accelerators used in the presentinvention, though in amounts less than that used in the past. Such accelerators (referred to herein as co-accelerators) are typically of the hydrazine variety (e.g., APH), as disclosed in U.S. Patent Nos.4,287,350 (Rich) and 4,321,349 (Rich). When APH is chosen as a co-accelerator for use herein, maleic acid would usually be added as well. One benefit of the present invention is that the anaerobic cure accelerators render the use of such acids unnecessary in preparing anaerobic adhesive compositions.

[0056] Other co-accelerators may also be used in the compositions of thepresent invention including, without limitation, organic amides and imides, such as benzoic sulfimide (also known as saccharin) (see U.S. Patent No.4,324,349).Of course, THQ as well could be used as a co-accelerator.Redox-Active Metal Catalyst

[0057] Further, the cure inducing component / agent of the anaerobicallycurable adhesive composition can be a redox-active metal catalyst comprising a transition metal when the anaerobically curable adhesive composition is contacted with the plastic substrate under anaerobic conditions. The redox-active metal catalyst enhances the strength of cure, speed of cure, and combinations thereof of the compositions described herein.

[0058] The transition metal included in the redox-active metal catalyst may betitanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, silver, vanadium, molybdenum, ruthenium, and combinations thereof. Further, the transition metal can be provided in the form of a salt. For example, the transition metal salt may be selected from cobalt (II) naphthenate; copper carbonate; copper (II) acetylacetonate; silver nitrate; vanadium (III) acetylacetonate and combinations thereof. Suitably, the redox-active metal catalyst is iron (II) naphthenate, copper disodium ethylenediamine tetraacetic acid (EDTA.2Na.Cu(II)), or copper naphthenate, vanadium acetylacetonate, vanadyl acetylacetonate, iron (II) acetate, or a combination thereof.

[0059] The redox-active metal catalyst may be included in the composition inan amount from about 0.0001 to about 2, suitably about 0.0002 to about 0.5 weight percent, based on the total weight of the composition.Stabiliser Component

[0060] Stabilizers and inhibitors (such as phenols including hydroquinone andquinones) are useful to control and prevent premature decomposition and polymerization of the composition of the present invention.

[0061] Beyond the stabiliser component(s) of the invention mentioned above,optionally a composition of the invention may include one or more additional stabilisers. Such additional stabiliser(s) may include a benzoyl functionalizedcompound. A benzoyl functionalized compound in a composition of the inventionis desirable because the inclusion of a benzoyl functionalized compound stabilizes the composition, for example it may stabilize the redox-active metal catalyst.

[0062] The benzoyl functionalized compound can be a photoinitiator. Forexample, those photoinitiators available commercially from BASF Chemical, Germany, under the “IRGACURETM” and “DAROCURTM” tradenames are desirable, specifically “IRGACURETM” 184 (1-hydroxycyclohexyl phenyl ketone), 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propan-1-one), 369 (2- benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone), 500 (the combination of 1-hydroxy cyclohexyl phenyl ketone and benzophenone), 651 (2,2-dimethoxy-2-phenyl acetophenone), 1700 (the combination of bis(2,6- dimethoxybenzoyl-2,4,4-trimethyl pentyl phosphine oxide and 2-hydroxy-2- methyl-1-phenyl-propan-1-one) and “DAROCURTM” 1173 (2-hydroxy-2-methyl-1- phenyl-1-propane) and 4265 (the combination of 2,4,6-trimethylbenzoyldiphenyl- phosphine oxide and 2-hydroxy 2-methyl-1-phenyl-propan-1-one). Of course, combinations of such materials may also be employed herein. The structures of preferred photoinitiators are shown below.

[0063] IrgacureTM 651

[0064] IrgacureTM 184

[0068] The benzoyl functionalized compounds may be included in thecomposition in an amount from about 0.1 to about 5 weight percent, suitably about 0.5 to about 2 weight percent, based on the total weight of the composition.Desirably the benzoyl functionalized compound is present in an excess amountrelative to the redox-active metal catalyst. On a weight basis, based on the totalweight of the composition, the benzoyl functionalized compound is desirablypresent in an excess amount relative to the redox-active metal catalyst. Forexample, the benzoyl functionalized compound is desirably present in an excessamount relative to the redox-active metal catalyst at a ratio of at least about 3:1; for example, at least about 4:1 such as at least about 5:1.Optional components

[0069] Additional / optional components can be included in the anaerobicallycurable adhesive compositions disclosed herein such that such additional components do not interfere with the functionality of the components described above.

[0070] For example, acrylic acid can be included in the composition toenhance the cure and adhesion in an amount from about 0 to about 20 weight percent, suitably from about 1 to about 10 weight percent, based on the total weight of the composition.

[0071] (Meth)acrylate oligomers can further optionally be included in thecomposition. (Meth) acrylate oligomers can be included to improve fully curedpeel strengths of the compositions described herein. For example,(meth)acrylate capped polyurethane oligomers can be included. A variety ofcommercial urethane (meth)acrylate oligomer resins are known. Suitably, thiscomponent is, or includes, a block resin such as described in U.S. Patent No. 4,309,526, comprising at least one polyether block derived from a polyether polyol and at least one hard block derived from an aromatic or cycloaliphatic diisocyanate and an aromatic or cycloaliphatic polyol. Especially preferred are such resins in which the polyether polyol is an aliphatic polyether having a number average molecular weight of from about 400 to about 10,000, more suitably about 700 to about 3,500.

[0072] If included, (meth)acrylate oligomers can be present in theanaerobically curable adhesive composition in an amount from about 5 to about 90 weight percent, suitably from about 10 to about 50 weight percent, based on the total weight of the composition.

[0073] Amines can optionally be included in the composition to cause themonomer to polymerize in the absence of oxygen and prevent polymerization of the monomer in the presence of oxygen.

[0074] The nature of the amine is not critical for purposes of the anaerobicallycurable adhesive compositions disclosed herein, i.e., primary, secondary, tertiary, aliphatic or aromatic amines can be used. For example, primary aliphatic amines such as ethyl, n-butyl, n-propyl, isopropyl, n-hexyl and t-butyl amines conveniently can be used. Also primary aromatic amines, such as aniline, p-toluidine, or p-naphthylamine, xylidine, benzylamine or p-benzylaniline can be used. Aliphatic or aromatic secondary amines also can be used. Typical examples of acceptable secondary amines are diethylamine, dipropylamine,diisopropylamine, diphenylamine, N-phenyl benzylamine and N-allylaniline.

[0075] Tertiary amines are organic amines wherein all three valences of thenitrogen atom are satisfied by carbon atoms. Tertiary amines are also suitable for use in the compositions described herein. The carbon atoms in the tertiary amines may be part of alkyl, carbocyclic or heterocyclic groups, either unsubstituted or hydroxyl-substituted. Generally, the trialkylamines and dialkylanilines are most suitably employed. However, alkaloids and other compounds within the scope of the above definition are also suitable for the present invention. Exemplary of the various tertiary amines that may be utilized are triethylamine, tripropylamine, tributylamine, triamylamine, triphenylamine, dimethylaniline, ethyldiethanolamine, triethanolamine and piperidine.

[0076] Generally, amines suitable for use in the compositions describedherein can be represented by the formula R”-R-NH, wherein R" is a hydrocarbon radical containing up to about 14 carbon atoms, suitably an aliphatic or aromatichydrocarbon group containing up to about eight carbon atoms, and R is eitherhydrogen or R. Naturally, either R” or R can contain any substituent or linkage, hydrocarbon or otherwise, which does not affect the condensation product adversely for the purpose disclosed herein.

[0077] The amine or amines used in the compositions described herein aresuitably liquid at room temperature for ease in handling and mixing, although gaseous and solid compounds may be employed by dispersing them in the monomer.

[0078] A variety of secondary and tertiary organic amines, suitably secondaryaromatic amines can be included in the anaerobically curable adhesive compositions disclosed herein.

[0079] Amines, suitably secondary aromatic amines, can be included in thecomposition in an amount up to about 5 weight percent, suitably about 0.001 to about 2 weight percent based on the total weight of the composition.

[0080] Silica and inorganic fillers can also optionally be included in thecomposition. Such fillers can be added to make the composition more viscous,i.e. thixotropic. This is beneficial for non-flow and non-sag properties such as foruse in gasket sealing. Suitably, when silica and / or inorganic fillers are included in the composition they are included in an amount of up to about 10 weight percent, suitably up to about 5 weight percent, based on the total weight of the composition.

[0081] Additional resins can also optionally be included in the composition.Such additional resins can include but are not limited to polyester and polyurethanes. Such resins can be included in the composition in an amount of up to about 50 weight percent, suitably up to about 20 weight percent, based on the total weight of the composition.

[0082] Some components that have been included in traditional anaerobicadhesives can also be added to the present anaerobic adhesive composition to alter the physical properties of either the formulation or the reaction products thereof. For instance, one or more of maleimide components, thermal resistance- conferring co reactants, diluent components reactive at elevated temperatureconditions, mono- or poly-hydroxyalkanes, polymeric plasticizers, and otherchelators (see U.S. Patent No.6,391,993, incorporated herein by reference) may be included to modify the physical property and / or cure profile of the formulation and / or the strength or temperature resistance of the cured adhesive.

[0083] When used, the maleimide, co-reactant, reactive diluent, plasticizer,and / or mono- or poly-hydroxyalkanes, may be present in an amount within therange of about 1 percent to about 30 percent by weight, based on the total weight of the composition.

[0084] Other additives such as thickeners, non-reactive plasticizers, fillers,toughening agents (such as elastomers and rubbers) and other well-known additives may be used in the inventive compositions where the art-skilled believes it would be desirable to do so. Detailed Description

[0085] The experimental details as given herein below are exemplary ofthe anaerobically curable adhesive compositions according to the present invention.

[0086] Cure performances of the stabiliser component(s) at differentconcentration levels within anaerobic adhesives were tested in anaerobic adhesives as set out below.

[0087] Na4GLDA and Na3MGDA are each commercially available from Nouryonof 1101 BZ, Amsterdam, The Netherlands.

[0088] 3.5% solutions in 1:3 volume ratio of water / propanediol of each ofNa4GLDA and Na3MGDA were prepared so that they could be easily added to adhesive formulations. Equivalent formulations utilising Na4EDTA were used for direct comparative testing.

[0089] A stock anaerobically curable adhesive composition was used which hasthe composition outlined in Table 1: Model Component ExampleFormulation A (%) Methacrylate3,3,5 – TrimethylcyclohexylMonomer methacrylate 27.1 Dimethacrylate Polyethyleneglycol Monomer Dimethacrylate 30.13 *Polyurethane methacrylateResin resin with weight average Mol. Weight 1,000-5,000 17.90 g / mol Filler Propoxylated Bisphenol A Fumarate 20.70 Anaerobic Cure PackageSaccharin, APH, CHP 2.18Adhesion Promoter Maleic Acid 2Metal Chelator StabiliserNa4GLDA / Na3MGDA 0Total 100Table 1 * Made in sequential steps from the reaction of diols and carboxylic acids for form polyester diols, followed by reaction with toluene diisocyanate and finally capping with hydroxy propyl(meth)acrylate. See e.g. U.S. Patent Nos. 3425988 and 4309526.

[0090] A control formulation based on the stock anaerobically curable adhesivecomposition of Table 1 with no stabiliser was prepared. This is included in Table2 below.

[0091] A comparative formulation with Na4EDTA was also prepared based on thestock anaerobically curable adhesive composition of Table 1 to give thecomposition set out in Table 2 below.

[0092] Na4GLDA, and Na3MGDA, were each converted to 3.5 weight percentsolutions in 1:3 volume ratio of water / propanediol. These were then mixed with the stock anaerobically curable adhesive composition of Table 1 to give thecompositions in Table 2 below.Composition Number StabiliserStabiliser Component Amount A1 (Control) None 0 ppmA2 (Comparative) Na4EDTA 315 ppmA3 Na4GLDA 236 ppmA4 Na4GLDA 315 ppmA5 Na4GLDA 394 ppmA6 Na4GLDA 473 ppmA7 Na3MGDA 236 ppmA8 Na3MGDA 315 ppmA9 Na3MGDA 394 ppmA10 Na3MGDA 473 ppmTable 2

[0093] The formulations of Table 2 containing either Na4EDTA (control) orNa4GLDA / Na3MGDA were each tested for thermal stability (82 °C in a 10mm x75mm test-tube and / or 55 °C in a lidded 25ml glass jar), shear strengthperformance and torque strength performance (According to standard test ASTM D5649). The thermal stability test results are most indicative of the presence and performance of the chelating stabiliser in the formulation.

[0094] With no stabiliser present, it was found that the control formulation (A1)gelled in less than 10 mins when exposed to 82 °C in a test tube.

[0095] With EDTA (A2) or with the stabiliser component(s) of the inventionpresent (A3-A10), this extended to beyond 7 days under the same conditions and a gel time was not observed as an end-point.

[0096] Likewise, for the 55 °C lidded glass jar test, over 6 weeks had passedwithout the observation of gelling in any of the samples A3 to A10. This isindicative of a highly stabilised product, above the target specification of >3h at 82 °C or >3 days at 55 °C in a glass jar.

[0097] The adhesive performance data (shear strength at 1h and 24h, torquestrength at 1h, 4h, and 24h) for all formulations was measured according to test standard ASTM D4562 and ASTM D5649.

[0098] A noticeable trend emerged for the formulations made with both Na4GLDAand Na3MGDA at concentrations of 236, 315, 394 and 473 ppm (A3 to A10). The cure strengths decreased in line with the increase in amounts of stabiliser. This indicates an over-stabilised formulation, where the metal chelator is present in abundance and can compete with the adhesive for the metal substrate, resulting in decreased cure strengths. The two new stabiliser component(s) are extremely potent chelators.

[0099] The two new stabiliser component(s), Na4GLDA and Na3MGDA, were veryeffective at stabilising the composition of Table 1 across all concentrationsexamined. The cure performance indicates that these should be considered at lower concentrations as they are potent stabiliser component(s) and may be effective at levels much lower than the control material, Na4EDTA. Testing was subsequently repeated with a stock anaerobically curable adhesive composition which had the composition shown in Table 3: Model Component ExampleFormulation B (%) Methacrylate Monomer3,3,5 – Trimethylcyclohexylmethacrylate 28.5 Dimethacrylate Monomer Polyethyleneglycol Dimethacrylate 26.58 *Polyurethane methacrylate Resin resin with weight average Mol. Weight 1,000-5,000 17.6 g / mol Filler Propoxylated Bisphenol A Fumarate 22 Anaerobic Cure Package Saccharin, APH, CHP 2.7Adhesion Promoter Maleic Acid 2.6Free Radical Stabiliser Naphthoquinone 0.02Metal Chelator Stabiliser Na4GLDA / Na3MGDA 0Total 100Table 3* Made in sequential steps from the reaction of diols and carboxylic acids for form polyester diols, followed by reaction with toluene diisocyanate and finally capping with hydroxy propyl(meth)acrylate. See e.g. U.S. Patent Nos. 3425988 and 4309526.

[0100] A comparative formulation with Na4EDTA was also prepared basedon the stock anaerobically curable adhesive composition of Table 3 to givecomposition B1 set out in Table 4 below.

[0101] Na4GLDA, and Na3MGDA, were each converted to 3.5 weightpercent solutions in 1:3 volume ratio of water / propanediol. These were then mixed with the stock anaerobically curable adhesive composition of Table 3 to give the compositions in Table 4 below. Composition Stabiliser NumberComponent Stabiliser Amount(Comparative) B1 Na4EDTA 303 ppmB2 Na4GLDA 228 ppmB3 Na4GLDA 175 ppmB4 Na4GLDA 123 ppmB5 Na4GLDA 70 ppmB6 Na4GLDA 25 ppmB7 Na4GLDA 14 ppmB8 Na3MGDA 228 ppmB9 Na3MGDA 175 ppmB10 Na3MGDA 123 ppmB11 Na3MGDA 70 ppmB12 Na3MGDA 18 ppmTable 4

[0102] The two stabiliser component(s) were effective in the range ofabout 5 ppm to about 1000 ppm, such as from about 10 ppm to about 300 ppm, for example from about 15 ppm to about 100 ppm.

[0103] This repeat testing confirmed that Na4GLDA and Na3MGDA wereeffective metal ion chelators in anaerobic formulations at levels significantly lowerthan typically effective for Na4EDTA. See Table 5 below showing the range of concentrations tested for Na4GLDA and Na3MGDA and the results achieved for thermal stability and adhesive performance. 228 175 123 70 25 14 Control (Na4GLDA) ppm ppm ppm ppm ppm ppm 303 ppm (B2) (B3) (B4) (B5) (B6) (B7) Na4EDTA (B1) Thermal Stability at 55C15 d 10-13 d 10-13 d 8 d 8 d 4 d 9 d(days) Thermal Stability at 82>19 h5h 10h (h = hours, m =>19 h >19 h >19 h 14 h40m 50m minutes) Shear Strength 1 h on Mild Steel Pins and 11.0 15.8 18.6 19.7 20.9 19.42N.2 2 2 2 2 217 N.mm Collars ASTM mm N.mm N.mm N.mm N.mm N.mm D4562 Shear Strength 24 h on Mild Steel Pins and 25.5 27.2 25.6 26.8 29.4 27.6 29.5 N.mm2N2 2 2 2 2 2Collars ASTM .mm N.mm N.mm N.mm N.mm N.mm D4562 228 175 123 70 18 Control (Na3MGDA) ppm ppm ppm ppm Ppm 303 ppm (B8) (B9) (B10) (B11) (B12) Na4EDTA (B1) Thermal Stability at 55C15 d 15 d 10-13 d 15 d 9 d 9 d(days) Thermal Stability at 82>19h >19h >112h 10h (h = hours, m =9h 14h20m 50m minutes) Shear Strength 1 h on Mild Steel Pins and 6.228.9 17.4 20.5226 N.mm2 2 217 N.mm Collars ASTM N.mm N.mm N.mm N.mm D4562 Shear Strength 24 h on Mild Steel Pins and 22.7 19.3 22.9 25.5 26.0 29.5 N.mm2N.mm2N.mm2N.mm2 2 2Collars ASTM N.mm N.mm D4562 Table 5

[0104] The results confirmed that these stabiliser component(s) wereeffective in chelating metal ions and stabilising the adhesive formulations at much lower ppm levels than was required for the standard stabiliser, Na4EDTA.

[0105] The words “comprises / comprising” and the words “having / including”when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0106] It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

Claims

Claims 1. An anaerobically curable adhesive composition comprising:(a) an anaerobically curable component;(b) a cure inducing component; and(c) a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2- C6alkenyl, linear or branched C2-C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12heteroaralkyl, C6-C12(heteroalicyclyl)alkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6acyl, linear or branched C1-C6carboxylate, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+; nis an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2- C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12 aralkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1- C6 carboxylate, ester, or carbonyl; mis an integer selected from 3-n.

2. An anaerobically curable adhesive composition according to claim 1,wherein C(R1)(R2)-COOM is selected fromwherein M is a cation such as H+ or a metal cation; and R1and R2are each independently as defined above.

3. An anaerobically curable adhesive composition according to anypreceding claim, wherein the stabiliser component comprises one or both of thefollowing compounds: (i) glutamic acid diacetic acid tetrasodium salt (Na4GLDA) havingthe structure:(ii) methylglycine N,N-diacetic acid trisodium salt (Na3MGDA)having the structure:.

4. An anaerobically curable adhesive composition according to anypreceding claim, wherein the stabiliser component is present in the curable adhesive composition in an amount from about 10 ppm to 1000 ppm.

5. An anaerobically curable adhesive composition according to anypreceding claim, wherein the stabiliser component is present in the curable adhesive composition in an amount from about 10 ppm to 100 ppm.

6. An anaerobically curable adhesive composition according to anypreceding claim, wherein the stabiliser component functions as a metal ion chelator.

7. A method of anaerobically curing an anaerobically curable adhesivecomposition according to any of Claims 1 to 5, comprising the steps of: (A) providing an anaerobically curable adhesive composition comprising: (a) an anaerobically curable component;(b) a cure inducing component; and(c) a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1and R2are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9cycloalkynyl, C5-C9heteroaryl, C3-C9heteroalicyclyl, C6-C12aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ramay be selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C7-C12 aralkyl,C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate,ester, or carbonyl;m is an integer selected from 3-n;and (B) exposing the anaerobically curable adhesive composition to an anaerobic environment for a time sufficient to cure the composition.

8. The method of Claim 7, wherein the stabiliser component comprises oneor both of the following compounds: (i) glutamic acid diacetic acid tetrasodium salt (Na4GLDA)having the structure:(ii) methylglycine N,N-diacetic acid trisodium salt(Na3MGDA) having the structure:

9. The cure product formed by the curing of an anaerobically curableadhesive composition according to any of Claims 1 to 5.

10. A bonded assembly comprising a first substrate bonded to a secondsubstrate by the cure product formed by the curing of an anaerobically curable adhesive composition according to any of Claims 1 to 5.

11. Use of a stabiliser component of the structure:N–[C(R1)(R2)-COOM]n(Ra)mwherein R1 and R2 are each independently selected from H, OH, linear or branched C1-C6alkyl, linear or branched C1-C6alkoxy, linear or branched C2-C6alkenyl, linear or branched C2-C6alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12 heteroaralkyl, C6-C12 (heteroalicyclyl)alkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6acyl, linear or branched C1-C6carboxylate, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido; M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, or carbonyl;m is an integer selected from 3-n;as a stabiliser component for an anaerobically curable composition.

12. Use of Claim 11, wherein the stabiliser component is at least one of:(i) glutamic acid diacetic acid tetrasodium salt (Na4GLDA) havingthe structure:(ii) methylglycine N,N-diacetic acid trisodium salt (Na3MGDA)having the formula:

13. A method of stabilising an anaerobically curable adhesive composition byproviding an effective amount of a stabiliser component of the structure: N–[C(R1)(R2)-COOM]n(Ra)mwherein R1and R2are each independently selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9 aryl, C3-C9 cycloalkyl, C4-C9 cycloalkenyl, C4-C9 cycloalkynyl, C5-C9 heteroaryl, C3-C9 heteroalicyclyl, C6-C12 aralkyl, C6-C12heteroaralkyl, C6-C12(heteroalicyclyl)alkyl, C2-C6alkoxy, C5-C9aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N- carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, and trihalomethanesulfonamido;M is a cation such as H+ or a metal cation, for example Na+, Li+, or K+;n is an integer selected from 1, 2 or 3;Ra may be selected from H, OH, linear or branched C1-C6 alkyl, linear or branched C1-C6 alkoxy, linear or branched C2-C6 alkenyl, linear or branched C2-C6 alkynyl, C5-C9aryl, C3-C9cycloalkyl, C4-C9cycloalkenyl, C4-C9cycloalkynyl, C7-C12aralkyl, C2-C6 alkoxy, C5-C9 aryloxy, C2-C6 acyl, linear or branched C1-C6 carboxylate, ester, or carbonyl;m is an integer selected from 3-n.

14. The method of Claim 13, wherein the stabiliser component is at least oneof: (i) glutamic acid diacetic acid tetrasodium salt (Na4GLDA) havingthe structure:; or (ii) methylglycine N,N-diacetic acid trisodium salt (Na3MGDA)having the structure:as a component of the anaerobically curable composition.

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