CA1248664A - Structural adhesive compositions - Google Patents

Abstract

Abstract of the Disclosure A one-component adhesive for metal surfaces such as iron, zinc, copper, cadmium and their alloys will cure upon contact with the metal surface. The adhesive composition includes olefinically unsaturated monomer; reactive or non-reactive polymer; an acidic material; a compound containing sulfonyl halide group; and a compound containing a transition metal. The adhesive composition cures rapidly upon contact with a metal surface to form an adhesive bond betweeen the surfaces. The adhesive composition is especially useful as a thread lock adhesive, and as an adhesive for bonding structural components.

Description

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STRUCTU~AL AD~IESIVE FORMULATIONS

The present invention relates to structural adhesive composi-tions. More particularly, the invention relates to shelF-stable, one-package acrylic structural adhesive compositions which are curable at ambient temperature conditions~

Acrylic structura1 adhesives are well-known articles of commerce which are extensively used commercially for bonding metal and plastic materials. The acrylic adhesives typically comprise a mixture of one or more olefinically-unsaturated reactive monomers and curing agents, with cure or polymerization being effected through a free radical or ionic polymerization mechanism. The adhesives preferably contain one or more polymeric ~aterials which may or may not be reactive, that is, capable of being poly~erized per se or at least capable of interpolymerizing with the reactive monomers, such as grafting onto or crosslinking the growins poly0ers from the reactive monomer polymerization. In addition, the adhesives can contain other additives for improving adhesion to substrate materials, environmental resistance, impact strength, flexibility, heat resistance, and the like.

The polymerization (cure) of either type of acrylic structural adhesive can be initiated by free radical generators, such as peroxygen compounds, usually in combination with accelerators to increase the rate of free radical formation. It has been long recognized, in those applica-tiOIlS where at least one substrate was a metal surface, that at least certain metals, such as iron, copper, tin, aluminum9 silver and alloys of such metals, exhibited a catalyst effect upon the cure, which was not alwa~s positive, that is, in some instances, the metal substrate tended to poison the desired reaction.

There have been many attempts to utilize the catalytic effect of metals. For example, it has been proposed to pretreat non-catalytic surfaces with a catalytic salt solution, such as the resinates of iron, copper or cobalt, see Lees U.S.A. patent 3,658,254, column 1, lines 29-52.
The Lees patent itself is directed to two-package anaerobic acrylic 36~

adhesive cor,lpositions whose effectiveness was not inFluenced by the cata-lytic or non-catalytic character of the substrate. Skou1tchi, in U.S.A.
patents 3,880,956 and 3,957,561 discloses anaerobic acrylic adhesive compositions which are activated by contact with metal sur-Faces. The ~ompositions of Skoultchi U.S.A. patent 3,880,955 are single-packa~e anaerobic compositions containing diazonium salt catalysts which cure through a free radical polymerization mechanism when excluded From air or oxygen and in contact with certain metal surfaces such as iron, copper, tin, aluminum, silver, alloys of these metals and cadmium, chromium, nickel and zinc chromate platings. Skoultchi U.S.A. patent 3,957,561 discloses one-package anaerobic cor,lpositions utilizing a two-component catalyst system comprising at least one diazosulfone compound and o-sulfobenzimide which cure through a free radical polymerization mechanism when the adhesive is excluded from air or oxygen and in contact with active metal surfaces (the same surfaces described in Skoultchi '956). On the other hand, Skoultchi, in U.S.A. patent 4,052,244 utilized copper in the form of a copper salt of saccharin or p-toluenesulfonic acid to provide two-package anaerobic adhesives whose cure was otherwise not dependent on substra~e composition. In another development, Skoultchi, in U.S.A. patent 4,081,308 discloses two-package anaerobic adhesives which utilize, in one package, copper sacchrinate or saccharin in combination with a soluble copper salt, and, in the other package, an alpha-hydroxy sulfone, an alpha-aminosulfone or mixtures of such sulfones, as catalytic agents for the free radical curing of the anaerobic acrylic adhesive compositions. The cure of the Skoultchi 4,081,308 compositions is independent of substrate composition.

The present invention provides novel one-package acrylic adhe-sives which cure at ambient temperatures when brought into contact with certain metal surfaces, whether or not air or oxygen is excluded. In particular, the single-package adhesive compositions of this invention comprise, in admixture, ~A) at least one olefinically unsaturated monomer;
(B) at least one polymeric material selected from the group consisting of ~1) at least one olefinically unsaturated urethane reaction product of at least one isocyanate-functional prepolymer and at least one hydroxy-functional monomer having at least one unit of polymerizable olefinic unsaturation, such reaction product being characterized by the presence of at least two units of oleFinic unsaturation and the substantial absence of free isocyanate yroups;

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(2) at I east one butadlene-based elastomerlc polymerlc materlal selected from the group conslstlng of (a) homopolymer of butadlene; (b) copolymer of butadlene and at least one monomer copolymerlzable therewlth selected from the group conslstlng of styrene, acrylonltrlle, methacry I onltrlle and mlxtures thereo-f;
(c) modlfled elastomerlc polymerlc materlal selected from the group conslstlng of butadlene homopolymer and copolymer as prevl-ously deflned, such homopoIymer and copolymer havlng been modl-fled by copolymerlzatlon thereln by trace amounts up to 5 percent by welght, based on welght of modlfled elastomerlc materlal, of at least one functlonal monomer; and (d) mlxtures thereof;

(3) at least one homopolymer of copolyrner of at least one olefln I cally unsaturated monomer selected from the group con-slstlng of styrene and alkyi or hydroxyalkyl esters of acryllcand methacryllc acld, sald ester havlng one to 18 carbon atoms In the alkyl molety; and

(4) mlxtures of such polymerlc materlals;
(C) a Bronsted acld compound havlng at least one organlc or lnorganlc acld group and a pKa ln the range from 0.5 to 6;

(D) at least one comPound contalnlng at least one sul~
fonyl hallde group havlng the structure I

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5~2 X

whereln X ls selected from the group conslstlng of chlorlne, bromlne, or lodlne; and 35(E) at least one reduclble compound contalnlng at least one metal selected from the elements of classes Ib, ~ b, ~ b, ~2~

r~br Vb, Vlb, ~ b or VIIi on the perlodlc chart of the elements, wlth copper, zlnc, Iron, cobalt and nlc~el belng preferred, wlth copper being especlally preferred, sald metal belng most preferably In Its hlghest oxldatlon state.

In a preferred embodlment of the present Inventlon the amount of sald olefInlcally unsaturated monomer Is In the range from 10 to 90, preferably 17 to 87, percent by welght; the amount of sald oleflnlcally unsaturated urethane reactlon product Is In 10 the range from 10 to 90, preferably 13 to 83, percent by welght;
the amount of such butadlene-based elastomerlc polymerlc materlal Is In the range from 1 to 30, preferably 7 to 27, percent by welght; the amount of sald homopolymer or copolymer of at least one of styrene and esters of acryllc or substltuted acryllc aclds Is In the range from 2 to 60, preferably 5 to 60, percent by welght; the amount of sald acldlc compound Is In the range from 0.05 to 20, preferably 0.1 to 15, percent by welght; the amount of sald sulfonyl hallde-contalnlng compound Is In the range from 0.05 to 5, preferably 0.5 to 2, percent by welght; and the amount of sald transltlon r ~ 3~6~

metal compound is in the range from 0.05 to 5, preferably 0.5 to 2.5, percent by weight; said weight percents being based on the total weight of ingredients (A)-(E), ;nclusive.

The adhesive compositions of the invention can optionally contain up to 60~ preferably not more than 30, percent by weight, based on total weight of the adhesive composition, of at least one polymeric material having an intrinsic viscosity in the range from 0.1 to 1.3~ sueh polymeric material being obtained from the polymerization or copolymerization of at least one styrene monomer, acrylic monomer, substituted acrylic monomer, LO olefinically-unsaturated non-acrylic monomer, or mixtures thereof; up to 40, pr'eferably not more than 30, percent by weight, based'on total weight of the adhesive composition, of at least one elastomeric material having a second order glass transition temperature below 5 C; and up to 10 percent by ~eight of at least one unsaturated dicarboxylic acid ester. The latter recited optional ingredient is based also on the total weight of the adhesive composition.

Description of the Preferred Embodiments According to the present invention, an adheslve COr,lpOSitiOn -is provided which may be employed to bond metal surfaces together. The adhes;ve exhibits good bonding properties with zinc, copper, cadmium, iron, tin, aluminuln, silver, chromium, alloys of such metals metallic coatings or platings of such mPtals. The sur~aces of these metals, alloys and metallic platings can, for convenience be called "active surfaces" and this term is to be understood to include but not be limited to the mentioned metal specie. The adhesive exhibits good weathering characterist-ics. Adhesive composit-ions prepared according to this inven-tion are useful as a thread lock material to be applied to the threads of a threaded ~astener to form a tight hond between the fastener and its threaded receiving member, e.g., a bolt and nut. Other adhesive composi-tions prepared according to the invention are useful in the construction of building panels ~here the bonding of galvanized steel sheets to cjalvanized steel sheets is desired, as well as in bonding such galvanized sheets to other structural members. The use of structural fasteners avoids the need for unsightiy weld marks, exposed threaded fasteners, exposed riyets, etc. Structural adhesives may be substituted in part for other mechanica1 fasteners, for example, in the transportation industry where exterior panels are secured to frame members or to other panel members by means of exposed ~asteners, such as rivets, threaded fasteners, welding, etc. A number of the welds, rivets or threaded fasteners can be eliminated and their function can be performed by appropriate reliable structural adhesives in accordance with the present invention.

Monomeric liquid olefinically unsaturated compounds suitable for use in the adhesive compositionsl of the invention are characterized by the presence of at least one - C = C - group. The olefinically unsaturated group is preferably a vinyl group, more preferably terminally located, with acrylic and substituted acryl;c monomers being currently preferre~.
When olefinically unsaturated monomers ~Ihich do not contain acrylic or substituted acrylic groups are employed, they should be used in an amount not exceeding 50, preferably not more than 25, percent by weight, based upon the total weight of the adhesive composition. Representative olefinically unsaturated monomers include, without limitation, methyl methacrylate, butyl methacrylate, ethyl acrylatea diethylene glycol dimethacrylate, methacrylic acid, acrylic acid, acrylonitrile, methacrylo-nitrile, styrene9 vinyl styrene, vinyl acetate, chlorostyrene, glyci~yl methacrylate, itaconic acid, acrylamide9 methacrylamide, vinylidene chloride, 2,3-dichloro-1,3-butadiene, 2-chloro-1,3-butadiene~
methylstyrene and n-butylstyrene.

The isocyanate-functional prepolymers which are employed to form olefinically unsaturated urethane reaction products for use in the practice of the invention are uell known. Typically, such prepolymers are adducts or condensation products of polyisocyanate compounds having at least 2 free isocyanate groups and monomeric or polymeric polyols having at least t~o hydroxy groups, including mixtures of such polyols. The - reaction between the polyisocyanate and the polyols is effected employing an excess amount o~ polyisocyanate to ensure that the reaction product wil7 contain at least 2 free, unreacted isocyanate groups.

Polyols useful in preparing isocyanate-functional prepolymer used in the present invention preferably have an average molecular weight of 300 to 3,000. Suitable polyols include polyalkylene glycols such as poly-ethylene ylycols; polyetherpolyols such as those prepared by addition polymerization of ethylene oxide and a polyol such as trimethylol propane In a ratio to provide unreacted hydroxyl groups in the product; organic hydro~ylated elastomers exhibiting second order glass transition tempera-tures belo~ about 5 C such as poly(butadienestyrene) polyols and poly(butadiene) polyols; polyester polyols such as are prepared by polymerizing polyols, such as die-thylene glycol, trimethylol propane or 1,4-butanediol, with polycarboxylic acids, such as phthalic, terephthalic, adipic, maleic or succinic acids, ln a ratio to provide unreacted hydroxyl groups in the product; gly-ceride esters o~ hydroxylated fatty acids such as cas-tor oil, glycerol monoricinoleate, blown linseed oil and blown soya oil;
and polyesterpolyols such as are prepared by the polymerization of a lactone such as ~ caprolactone.

Polyisocyanates which can be reacted with polyols to form isocyanate-functional prepolymers for use in the present invention can be any monomeric; that is, non-polymeric, iso-cyanate compound having at least 2 free isocyanate groups, inclu-ding aliphatic, cycloaliphatic and aromatic com~ounds. Represen-tative polyisocyanates include, without limitation thereto, 2,4-tolylene diisocyanate, 2,~-tolylene diisocyanate, 4,4'-diphenyl-methane ~iisocyanate, m- and p-phenylene diisocyanate, polymethy-lene poly(phenyl isocyanate), hexamethylene diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), hexamethylene diisocyanate, 4,4'-methylene-bis(cyclohexyl isocyanate), isophorone diisocyan-ate, and other aliphatic cycloaliphatic and aromatic polyisocyan-ates, and including mixtures of such polyisocyanates. Currently, cycloaliphatic and aromatic polyisocyanates are preferred.

Hydroxy-functional compounds which can be employed to introduce oleiinic unsaturation into the isocyanate-~unctional prepolymer include, without limitation, hydroxyeth~l arcylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and allyl alcohol.

The butadiene-based elastomeric polymeric ma-terials which are suitable for use in the practice of this invention are also well-known and can be any elastomer derived from 1,3-buta-diene or its halogena-ted analogs which has a glass transition temperature below amb~ent temperature and pre~erably not above ~2g~

abou-t 5C. Sui-table elastomers include butadiene homopolymer, copolymers of butadiene with styrene, acrylonitrile and methacry-lonitrile, and such homopolymers and copolymers modified by cop-olymerization -therein of trace amounts (0.05 to 5%) of a func-tional comonomer, such as acrylic acid, methacrylic acid, maleicanhydride, fumaric acid, styrene and methyl me-thacrylate.

Elastomeric polymeric materials having second order glass transition temperatures below about 5C can be effective in modifying room tempera-ture flexibility of the adhesive bond.
Especially preferred of such elastomers are polychloroprene rub-ber, polybutadiene rubber; butadiene copolymer rubbers such as acrylonitrile-butadiene, carboxylated acrylonitrile-butadiene and styrene-butadiene rubbers; polyacrylate rubbers such as poly (ethyl acrylate) and poly(e-thyl acrylatehalogenated vinyl ether-acrylic acid) rubbers; and ethylene copolymers such as ethylene-vinyl acetate rubbers. Other elastomeric polymers having a glass transition temperature about 5C can be employed since, other than the low glass transition temperature, there are no other limitations on the identify of the elastomer except for the spe-cific requlrements of the particular adhesive being formulated, such as suitable molecular weight, viscosity characteristics and compatibility wi-th the other ingredients of the adhesive.

~L~ 4 Such elastomeric polymeric materials are particularly beneficial when incorporated in acrylic adhesives comprising at least one olefini-cally unsaturated polyurethane.

Polymeric materials having an intrinsic viscosity of 0.1 to about 1.3 which are suitable for use in the present invent70n can be obtained b~
the polymeriz~tion of 1 or more acrylic and nonacrylic monomers, including mix~ures thereof. Exemplary polymeric materials include poly(methyl methacrylate/n-butylacrylate/ethylacrylate) (90/5/5%); poly(n-butyl methacrylate/;sobutyl methacrylate) (50/50%); poly(n-butyl methacrylate) and poly(ethyl methacrylate). Preferably~ the viscosity will be about midway in the reclted range.

The use of polymeric materials having such intrinsic viscosities is especially beneficial in acrylic adhesives containing homopolymers and copolymers of l,3-butadiene.

15j The acidic compounds which are essential to the practice of this inventio~ can include .ubstant~ organic or inorganic acid having at least one acid group, and includes organic and inorganic partial esters of such acids. Suitable acidic compounds preferably have a PKa in the range from 0.5 to 6, most preferably in the range from 1.5 to 5. The acid;c co~pounds should also be reasonably soluble in the adhesive co~po-sitions of the invention to facilitate homogeneous distribution of the acid throughout the composition. The selection of the acidic component is a function of the substrate to be bonded, as well as the desired adhesive performance, and provides the adhesive chemist considerable latitude in formulating adhesive compositions specifically designed for any particular end use. For example, organic acids, as well as organic and inorganic partial esters of such acids are preferred for bonding ferrous metals and their alloys, but adhesives containing such organic acids can be prepared according to the Invention which are effective bond;ng agents for non-ferrous metals, such as galvanized steel. Conversely, the inorganic acids, and the organic and ;norgan;c partial esters of such acids, are preFerred for bonding non-ferrous metals and their alloys, but adhesives containing such inorganic acids can also be prepared which are useful for bonding ferrous metals and their alloys. In the general case, acidic compounds which contain both at least one acid group and at least one olefinically-unsaturated moiety are preferred.

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Representative acidic compounds ~Jhich are suitable for use in the practice of the invention include phosphoric acid, 2-hydroxyethyl methacrylate partial ester of phosphoric acid, 2-hydroxyethyl acrylate partial ester of phosphoric acid, phosphoric acid, benzenephosphonic acid, phosphorous acid, sulfuric acid, sulfurous acid, 2 ethylhexonic acid, formic acid, acetic acid, butyric acid, hexanoic acid, naphthenic acid, lauric acid, linoleic acid, valer;c acid, toluene sulfonic acid, nitrotoluene sulfonic acid, dichloroacetic acid, trichloroacetic acid, phenylacetic acid, sulfosalicylic acid, naphthalene disulfonic acid, acetoacetic acid, acrylic aGid, methacrylic acid, aminobenzosulfonic acid, ~aleic acid, malonic acid, phthalic acid, suberic acid, suddinic acid and vinyl acetic acid.

The inorganic acids and organic partial esters of inorganic acids are currently preferred ~or use with non-ferrous metals such as zinc, copper, codmium, tlleir alloys and platings, with olefinicially unsaturated partia1 esters of inorganic acids being currently preferred. Adhesive co~positions prepared in accordance with this invention which contain such inorganic acids typically provide better adhesion when bonding non-ferrous metals than is obtained from theuse of organic acids. Adhesive composi-tions containing the inorganic acids provide lower adhesion values with ferrous metal surfaces than is obtained from the use of organic acids;
ho~ever, the inorganic acid-containing adhesives are sufficiently effec-tive in bonding ferrous metals that they can be utilized in applications such as thread-locking of iron bolts and nuts.

As noted, the organic acids and inorganic partial esters of organic acids are currently preferred for structural bonding of ferrous metals, and can also be used for structural bonding of non-ferrous ~etals, although the adhesion provided by such adhesive compositions in this latter case is typically less than that provided by the use of inorganic acids.

In the general case, it has been noted that stronger aclds, as well as larger quantities of any acid, tend to increase the rate at which the adhesive compositions cure. The use of strong acids, e.g., those having PKa values of I or less, particularly in large amounts, can lead to corrosion problems and tends to deactivate the adhesives, possibly through chelate formation. The use of large amounts of any given acid also tends to give lower adhesion values; but it has been observed that such reductions in adhesion values is not as great when the acidic .

co~pound contains one or more polymerizable olefinically unsaturated groups. Thus some degree of expermentation may be required in selecting the acid and the amount of the acid, in order to achieve an acceptable compromise of properties. Currently, it is preferred-that the acidic compound be employed in amounts in the range from 0.05 to 20, preferably 0.1 to 15, percent by weight, based on the total weight of the adhesive components (A)-(E), inclusive, as recited, supra. In those cases where the acid does not contain polymerizable moities, the amount of the acid is preferable in the range from 0.05 to 5 percent by weight.

The sulfonyl halide-containing compounds are also essential to the practice of this invention and will be used in an amount in the range from 0.05 to 5, preferably 0.5 to 2, percent by weight, based on compo-nents (A)-(E), inclusive, of the compositions. As noted, the halide mo;ety can be chlorine, bromine or iodine with the sulfonyl chlorides being currently preferred. The sulfonyl halidea can be mono- or poly-functional and can be aliphatic sulfony halides having from one to lZ or more carbon atoms, aromatic sulfonyl halides having from l to 3 aromatic nuclei and containing from ~ to 24 carbon atoms. Representative sulfonyl halide containing compounds include biphenyl disulfonyl chloride, trich-lorobenzene sulfonyl chloride, p-toluene sulfonyl chlor;de, benzene sulfonyl chloride, hexadecane sulfonyl chloride9 diphenyl ether-4,4'-sulfonyl chloride, and the corresponding sulfonyl bromides and iodides.
Monomeric sulfonyl halides are currently preferred, with the aromatic sulfonyl halides9 particularly p-toluene sulfonic chloride, being especially preferred.

Equally as essential as are the compounds containing at least one sulfonyl group and the acidic compounds, both supra, are compounds con-taining at least one transition metal. As used herein, transition metals are those metals which have their valence electrons in a "d" subshell.
Such metals are found in classes Ib - VII b and VIII on the periodic chart of elements. The preferred metals are copper, zinc, cobalt, vanadium, iron and manganese. The metal should be in a higher oxidation state, with the highest oxidation state being preferred in all cases. The remainder of the compound does not appear to be critical. ~Ihether the transition metal is ionic or cationic in its ionized form also does not appear to be critical. ~lowever, wherl the transition metal forms part of the cation, e.g., meta~vanadate, it is preferred to employ the ammonium salt, e.g., arnmonium meta-vanadate. al;herwize, inorganic compounds containing the transition metals can be used, such as the metal salts exemplified by the _l I-- .

bromides, chlorides, phosphates, sul~ates, sulfides and oxides of the transition metals. Likewise, organic compounds containing the transition metals can be used, such as transition metal salts of organic mono- a~d poly-carboxylic acids and mono and poly-hydroxy compounds, such as cupric acetate, cupric maleate, cupric hexoate, iron naphthate, cobaltous and cobaltic naphthenate and the like. Particularly preferred organic deriva-tives are sulfimide and sulfonamide compounds which contain the transition metal, such as the currently preferred cupric sacchrinate. This is but a partial listing of suitable inorganic and inorganic salts; ho~ever, other useful salts will be readily obvious to those skilled in the art. The transition metal compounds ~Jill be employed in the adhesive compositions of this invention in a range from 0.05 to 5, preferab1y 0.5 to 2.5, percent by weight, based on total weight of adhesive components (A)-(E), inclusive.

The transition metal-containing organic compounds are typically more soluble in the adhesive compositions of this invention, and they are preferred compounds. It is important that the transition metal compound, be it organic or inorganic, has some degree of solubility, either in the adhesive composition itself or in an inert solvent which is preferably 2~ compatible with the adhesive compositions. Because of the limited solubility of at least some usable transition metal compounds, it can be advantageous to dissolve the compound in the adhesive or inert solvent and filter off the undissolved material.

The adhesive compositions may also contain stabilizers such as hydroquinone, T-butyl catechol and other well known stabilizers.

Thickeners such as fumed silica are includéd to thicken the compos~tion for handling and applicat10n. A preferred thickener is fumed silica comprising from 0.2 to 10.0 weight percent of the adhesive composition. Pigments also may be added if desired.

The adhesive compositions of the invention are readily prepared by combining the ingredients using any conventional mixing device to obtain a homogeneous mixture.

The adhesive coatings may be brushed, rolled, sprayed, dotted, knifed or otherwise applied to one substrate, but preferably to both substrates in a thickness not to exceed ~0 mils. The substrates may be clamped for firmness during cure in those installations where relative ~L~9~3~6~

movement of the two substrates might be expected. For example, to adhere metal surfaces, an adherent quantity of the adhesive composition is applied to one surface, preferably to both surfaces, and the surfaces are confronted w;th the adhesive composition therebetween. The adhesive should have a thickness less than 60 mils for optimum results. The smoothness of ~he surfaces and their clearance (e~g., in the case of nuts and bolts) will determine the required film thickness for optimum bonding.
The two metal surfaces and the interposed adhesive composition are maintained in engagement unt;l the said adhesive composition has cured sufficiently to bond the said surfacss.
Example I - Polymerizable Acrylic and ~lethacrylic Ingredients I-A. A polymer-in-monomer syrup comprises a low molecular weight ~ethyl methacrylate polymer in a methyl methacrylate monomer.
This material contains 38 weight percent polymer and is available from E~ I. duPont de Nemours Company under the trade name Elvacite 2008.
I-B. A carboxylated poly(l,3-butadiene/acrylonitrile) is carried in methyl methacrylate mono~er~ The composition contains 25 weight percent of the polymer.

I-C. A polycaprolactone triol (molecular weight 540~ is reacted with toluene diisocyanate in methyl methacrylate. The resulting polyiso-cyanate-functional prepolymer is capped with hydroxy ethyl methacrylate so that the resulting olefinically-unsaturated urethane polymer contains pendant methacrylate radicals and is substantially free of unreacted iso-cyanate radicals. This material corresponds to the product of Example l 2s described in U.S. Patent 3,~73,640, and contains 65 weight percent of the unsaturated urethane polymer in methyl methacrylate monomer.

Example II - Compositions Tested with Galvanized Steel Sheets Five typical adhesive compositions were prepared employing the polymerizable acrylic ingredients described in Example I-A and I-B. The compositions by weight are set forth in the following Table II (there is no Table I) along with the lap shear strength of a surface-to-surface bond after 24 hours. The lap shear test is carried out by using two galvanized steel coupons having a thic~ness of about 60 mils and a surface area of about l" x 311. The coupons are lapped ~or a distance of l" and a film of the adhesive composition is applied to each surface. The sur-faces are allowed to rest (without clamping pressure) for 24 hours before -the lap shear test is carried out. The lap shear test determines the tension ~measured in pounds per square inch) required to rupture the adhesive bond.

T~LE II

ADHESIVE COMPOSITIONS TESTED WITH GALVANIZED STEEL SHEETS

Adhesive II-A II-B II-C II-D
Inqredients_ _ Parts by Weiqht I-A Composition 100 --- --- ---15 I-B Composi-tion --- 100 100 100 p-toluene Sulfonyl Chloride 2 2 2 Methacrylic Acid 10 10 10 2 Copper Saccharinate 1 1 1 0.5 Zinc Saccharinate --- --- --- ---20 HEMA Phosphate* --- --- 10 Methyl Methacrylate --- --- --- 10 Results of 24 Hour Lap Shear Test lPSI) *~IEMA Phosphate is the beta-hydroxy-ethyl methacrylate monoester of phosphoric acid.

The data demonstrate the higher adhesion values which inorganic acids provide with non-ferrous metals such as galvani-zed steel. The data also demonstrate the suitability of employ-ing mixtures of inorganic and organic acidic compounds.

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The composit;ons are employed to bond solvent-wiped cold rolled steel and galvan;zed steel parts, following the procedure of Example II.
Lap shear testing is performed following the procedure set forth in Example II. The results are reported in Table III.

The data clearly show that the presence of the acidic compound, the sulfonyl chloride-containing compound and the reducible metal-containing compound is essential to the practice of the invention. Some degree of polymerization is seen with compositions III-C and III-F, which do not contain any reducible metal-containing compounds. As can be seen by the results obta;ned wlth compositions III-D and III-G, this low order o~ polymerization ~compositions III-C and III-F) is clearly outside the scope of the current invention, since these compositions do not provide acceptable levels of adhesion, even for thread-locking. However, the data from these formulations (compositions III-C and III-F) does demonstrate the contribution of active ~etal surfaces in accordance ~.ith the invention, particularly when taken in concert with the results of Example XI, infra.

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Composition IV-A is useful for bonding galvanized steel zinc phosphate treated metals and cadmium. It has particularly utility as a thread locking adhesive. iletal parts bonded with Composition IV-A are fully cu ed in seYeral hours. The composition has a viscosity of about 89000 CpS and a density of about 8.6 pounds per gallon.

A number of lap shear test specimens were prepared from G-90 galvanized steel coupons with adhesive IV-A. The coupons were exposed to various test environments for t~lo weeks. One set of coupons ~las main~
tained at room temperatures for the two-week period; a"other set was maintained in a salt spray cabinet for t~o weeks; another set was maintained at 100 percent relative humidity~ and another set ~as main-tained under water for the two-~eeks period. The results of the tests show a tensile failure strength as set ~orth belo~:

Environment Failure (psi) Room Temperature 2633 Salt Spray 1433 100 percent Relative ~u~idity 1600 Water Soak 19~0 The adhesive composition IV-A thus exhibits outstanding resistance to conventional degradation test environ~ents.

Co~position IV-B is useful for bonding galvanized steel and zinc phosphate treated metals. The composition also has utility as a thread locking adhesive. Full cure of the adhesive requires several hours. The composition has a viscosity of about 8 500 cps and a density of about 9.15 pounds per gallon.

Composition IV-D is useful for bonding steel surfaces but is particularly useful in bonding copper and brass. The adhesive develops hand1ing strength in about 25 minutes. The co~position is a viscous liquid having a density of about 8.8 pounds per gallon. Lap shear tests wlth cold-rolled steel coupons sho~ a strength exceeding 2000 psi.

Composition IV-E is useful as an adhesive for steel but may also be used with copper. Full cure requires several hours. The composition is a viscous black liquid because of the carbon black. The composition has a density of about 9.0 pounds per gallon.

~LZ~8~ 4~

Compositions IV-F, ~V-G and IV-H were subjected to a lap shear test (galvanized steel bonded to galvanized steel). Composition IV-F
developed a wiggle cure in seven minutes and an overnight shear strength of 2193 psi (average of four tests). the four hour strength of the composition was 500 psiO Composition IV-G developed a wiggle cure in ten minutes and an overnight strength of 2233 psi (average of four tests).
Co~position IV-G developed a four hour strength of 1900 psi. Composition IV-H developed a wiggle cure in one hour and an overnight strength of 2167 psi (average of four tests).

Example V - Thread-Lock Tests The adhesive composition of Example IV-A was applied as a thread locking adhesive with a zinc plated screw and bolt, a cadmium plated screw and bolt and a black iron screw and bolt. The zinc plated screw and bolt was 3/8" diameter. The cadmium plated bolt was 5/16" diameter. The blac~
iron bolt was 5/16" diameter and, as received and tested~ had a protective coating of surface oil. The bolts were coated with the composition IV-A
and the nuts were threaded onto the bolts to approximately the middle of the bolt. A ~iggle test was carried out to determine time required before the bolt and nut were initially secured and wou7d not move easil~. In addition a 24-hour torque test was carried out to determine the amount of torque required to turn the nut with respect to the bolt after Z4-hour set. The results of the test are presented in the following Table V.
.

TABLE V

THREAD LOCK TEST AND WIGGLE CURE TEST
_ _ _ _ .

. . .

- Wigg1e Cure 24-~lR Torque Time Inch-lbs . _ . _ _ _ .. . ..
Zinc plate bolt 10 minutes 45 3/8 inch Cadmium plate bolt 10 minutes 25 5/16 inch Blac~ iron bolt 4 hours 25 5/16 inch _19_ ~866fl~

Example VI - Lap Shear ~ests with Galvanized Steel A series of lap shear tests was carried out with galvanized steel coupons employing the adhesive composition of Exarnple IV-B. Each of the lap shear test specimens was exposed to a different environment for ten days and the shear failure was measured in pounds per square inch.
The first specimen was maintained at room temperature and failed at 2 473 psi. The second specimen was maintained under a salt spray exposure and fa;led at 2 407 psi. The third specimen was maintained in a lO0 percent relative humidity chamber and failed at 2 373 psi. The fourth specimen was maintained at 70C and fai1ed at 2 733 psi.

Example VII - Thread Lock Exposure Tests Zinc plated bolt~ 3/8 diameter were coated with the adhesive composition of Example IV-B and fitting nuts were threaded onto the coated bolts. The nuts and bolts were exposed to various environments for two weeks and thereafter the torque required to release the nuts was measured.
7~ Heat/Cold Test --- Jhe bolts were maintained at 70C for two and one-half hours and thereafter at -29C for two and one-half hours immediately prior to the torque test. This torque was ll foot pounds.

2. The nuts and bolts were maintained in boiling water for one hour prior to the torque test. The required torque was 11 foot pounds.
3. The nuts and bolts were maintained in a salt spray cabinet throughout the entire two weeks period. The torque was 12 foot pounds.

4. The nuts and bolts were mainta;ned at 100 percent relative humidity for two weeks. The torque was ll fôot pounds.

5. The nuts and bolts were soaked in water throughout the entire two week period. The torque was 11 foot pounds.

6. The nuts and bolts were maintained at 70C throughout the entlre two week period. The torque required was 22 foot poun~s.

7. The nuts and bolts were maintained at room temperature for the entire two week period. The torque was 12 foot pounds.

Example VIII - Lap Shear Tests Lap shear tests were carried out with various metal coupons includlng galvanized steel, brass, copper, magnesium, aluminum (2029-53 alloy) and steel. The adhesive was Composition II-A. ~he results of the lap shear tests are shown in the following Table VIII.

TABLE VIII

LAP SHEAR TESTS - COMPOSITIONS II-A

~letal Z 5 H ursFailU 24 hours _ Galvanized Steel 250 300 Brass 600 --*
Copper Magnesium o o Aluminum (2024-T5) o o Steel 200-300 * - Not lleasured Example IX - Lap Shear Tests The adhesive composition IV-C is an example oF a strong acid medium adhesive composition particularly useFul with zinc, copper and cadmium surFaces. This composition IV-E was applied to galvanized steel coupons (i.e., zinc surFaces) to carry out lap shear tests to illustrate the speed oF cure. The results oF the lap shear tests are set forth in the following Table IX.

~48~

TABLE IX

LAP SHEAR TESTS GA-L-vANIzED STEEL COMPOSITION IV-C

Time (Minutes) Failure - PSI

Example X - Lap Shear Tests The adhesive compositions IV-A, IV-B, IV-D, IV-E and IV-G were applied to galvanized steel, bare carbon steel, aluminum (6061-T6) alloy, cadmium plated metal, copper, brass coupons and a lap shear test was oarried out in accordance to ASTM 1002-79. All coupons were prepared by solvent wiping. The bonding area ~as a 1" overlap of t~lo strips with an adhesive thickness 0.005 inch. After 24 hours, the lap shear tests were carried out with the results set forth in the following Table X.
TABLE X
LAP SHEAR TESTS, 24 HOURS, P5I AT FAILURE
_ Adhesive Composition Metal Coupons IV-A IV-B IV-E IV-F ~ ~ IV-H
_ Galvanized Steel 2500 2470 200 213 2000 Bare Steel 200 20 2793 2467 *
A1uminum (6061-T6) 1100 * 733 * *
Aluminum (2024-T3) 107 * * * *
Cadmium Plate 1067 800 1833 2100 2250 Copper 867 1347 2833 767 900 Brass 433 1133 567 400 800 Galvaneal (Steel) 1233 1197 200 200 1153 30 * - Indicates no cure i4 Example XI - Plastic Sheet Tests In order to demonstrate that the present compositions are activated upon contact with an appropriate metal surface9 each of the adhesive compositions in Table II and Table III are applied between two plastic sheets (polyethylene terephthalate). The compositions remain fluid and did not cure.

Example XII

The adhesive compositions reported in Table XII are prepared.
The compositions are employed to bond cold rolled steel (CRS) and galvanized steel (GS) assemblies following the procedure of Example II.
Lap shear tests are performed according to the procedure of Example II
and the results are reported in Taoie XII.

TABLE XII

Adhesive XII-A XII-B XII-C XII-D XII-E
In~redients, parts by weight Part~ eight .
I-B Composition 3Q 30 30 50.2 50.
I-C Compositlon 30 30 30 50.2 50.
Methyl Methacrylate --- --- --- 29.8 ---Acetic acid ~ -- 6.8 ---Methacrylic acid --- -__ __ _ __ Phosphor1c acid --- --- ~ 5.0 HEMA Phosphate 3 3 3 __ __ p-to~uene sulfonyl chloride0.6 0.6 0.6 6.8 1.5 Saccharin 0.9 --- --- --- -__ Sodium succharin --- 0.9 --- -_- __ Cupric sacchrinate --- --- 0.9 0.7 - 1.5 Substrate GS GS GS GS GS
Lap shear, psi~ 24 hours353 760 2440 Adh Adh Failure CM CM Adh Adh Adh Cure conslstency Soft Soft Hard Hard Hard

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An ambient temperature-curable adhesive composition consisting essentially of, in admixture (A) at least one liquid olefinically unsaturated monomer; ( B ) at least one polymeric material selected from the group consisting of (1) at least one olefinically unsaturated urethane reaction product of at least one isocyanate functional prepolymer and at least one hydroxy-functional monomer having at least one unit of polymerizable olefinic unsaturation, such reaction product being characterized by the presence of at least two units of olefinic unsaturation and the substantial absence of free isocyanate groups; (2) at least one butadiene-based elastomeric polymeric material selected from the group consisting of (a) homopolymer of butadiene; (b) copolymer of butadiene and at least one monomer copolymerizable therewith selected from the group consisting of styrene, acry-lonitrile, methacrylonitrile and mixtures thereof; (c) modified elastomeric polymeric material selected from the group consisting of butadiene homopolymer and copolymer as previously defined, such homopolymer and copolymer having been modified by copolymer-ization therein by trace amounts up to 5 percent by weight, based on weight of modified elastomeric material, of at least one func-tional monomer; and (d) mixtures thereof; (3) at least one homopolymer of copolymer of at least olefinically unsaturated monomer selected from the group consisting of styrene and alkyl or hydroxyalkyl esters of acrylic and methacrylic acid, said ester having one to 18 carbon atoms in the alkyl moiety; and (4) mixtures of such polymeric materials; (C) a Bronsted acid com-pound having at least one organic or inorganic acid group and a pKa in the range from 0.5 to 6; (D) at least one compound con-taining at least one sulfonyl halide group having the structure wherein X is selected from the group consisting of chlorine, bromine, or iodine; and (E) at least one reducible compound con-taining at least one metal selected from the elements of classes Ib, IIb, IIIb, IVb, Vb, VIb, VIIb or VIII on the periodic chart of the elements.

2. An adhesive composition according to claim 1, wherein the amount of said olefinically unsaturated monomer (A) is in the range from 10 to 90 percent by weight; the amount of said olefinically unsaturated urethane reaction product (B)(1) is in the range form 10 to 90 percent by weight; the amount of said butadiene-based elastomeric polymeric material (B)(2) is in the range from 1 to 30 percent by weight; the amount of said homopolymer or copolymer of at least one of styrene and esters of acrylic or substituted acrylic acids (B)(3) is in the range from 2 to 60 percent by weight; the amount of said acidic compound (C) is in the range from 0.05 to 20 percent by weight; the amount of said sulfonyl halide-containing compound (D) is in the range from 0.05 to 5 percent by weight; and the amount of said metal com-pound (E) is in the range from 0.05 to 5 percent by weight; said weight percents being based on the total weight of ingredients (A)-(E), inclusive.

3. An adhesive composition according to claim 2, wherein said acidic compound is selected from the group consist-ing of inorganic acids and organic partial esters of inorganic acids.

4. An adhesive composition according to claim 2, wherein said acidic compound is selected from the group consist-ing of organic acids and organic partial esters of organic acids.