MXPA00007397A - Thiol-cured epoxy composition - Google Patents

Abstract

A composition that includes an epoxy compound, a thiol curing agent, a catalyst and a phosphorus-containing compound having at least one P-OH group and at least one organic moiety characterized by the presence of an ethylenically unsaturated group. The composition is particularly useful as a sealer for an adhesive joint.

Description

COMPOSITION OF EPOXY, CURED WITH TIOL BACKGROUND OF THE INVENTION The present invention relates to an epoxy composition, cured with thiol, which is particularly useful as a sealant for a joint between two substrates. The joints are often coated with a sealant to protect a joint against the penetration of water, oil, salt sprays or other potentially harmful liquids. A specific type of seal, which is preferably sealed, is the joint between two structural members, formed by welding or bonding with a structural adhesive. An example is the joint of a lightweight metal and plastic materials in the manufacture, repair and reconstruction of automobile and truck vehicle bodies and panels and component parts, such as doors and covers. A typical method for bonding these substrates, in the automotive industry, is described in U.S. Patent Nos. 5,487,803 and 5,470,416, both incorporated herein by reference. According to this method, an internal panel is placed inside an outer panel, with the edge of the outer panel extending beyond the edge of the inner panel. The edge of the outer panel is then bent or curled over the edge of the inner panel, in a process known as hemming, and the resulting structure is known as a hem flange. In order to permanently secure the inner panel with respect to the outer panel of the hem flange, a structural adhesive is applied between the surfaces of the panel or the two panels are welded together to form a permanent set of hem flange. A sealant is applied to cover and protect the adhesive or solder joint after this joint has been formed. A particular problem with the sealants used in connection with the adhesive seals is related to the cure temperature. Structural adhesives based on (meth) acrylics have become increasingly popular in the formation of hem flange joints. Structural adhesives based on (meth) acrylics are typically cured at temperatures below 121 ° C. Several plastisols, which only cure at temperatures higher than 149 ° C, are currently used as hem flange sealers. However, if the adhesive, based on (met) acrylic, previously applied, has not completely cured by itself, before being exposed during sealant cure at temperatures higher than 121 ° C, the (meth) acrylic-based adhesive tends to volatilize, thus losing your integrity In addition, induction healing has also become increasingly popular. Metallic substrates can warp when subjected to induction curing at the temperatures required for curing plastisol sealants. Sealants must also be able to be painted, be chemically compatible with the adhesive, exhibit good flow characteristics, adhere to the substrate and joint surfaces and exhibit flexibility to absorb the stresses caused by the movement of the joints. Adhesion to metal substrates can be especially problematic, due to the presence of die-cutting, milling and drawing oils on the surface, which are the result of the joint manufacturing process. A sealant, curable at low temperature, exhibiting good adhesion to metal substrates would thus be very convenient.

SUMMARY OF THE INVENTION In accordance with the present invention, a composition is delivered which cures at about the same temperature (in other words, within + 5 ° C or less, than the cure temperature of a (meth) acrylic base adhesive and exhibiting good adhesion to oil contaminated metal surfaces In particular, a sealing composition is provided which cures at <121 ° C. The composition includes an epoxy compound, a thiol curing agent, a catalyst or accelerator and an adhesion promoter compound, which contains phosphorus, which has at least one P-OH group and at least one organic part, characterized by the presence of an ethylenically unsaturated group. It has been found that the thiol-cured epoxy system provides the desired low cure temperature and is chemically compatible with a (meth) acrylic base adhesive. In addition, it has been discovered that the phosphorus-containing compound provides excellent adhesion for a thiol-cured epoxy system, particularly with respect to substrate surfaces that have been contaminated with oil.

Detailed Description of the Preferred Modes Unless otherwise indicated, the description of the components in the chemical nomenclature refers to the components, at the time of addition to any combination specified in the description, but does not necessarily prevent the chemical interactions between the components of a mixture, once mixed. The epoxy compound can be any compound that contains an epoxy group, which has the formula: O / \ - c The epoxy compound preferably has a viscosity of at least 50 to 50,000 centipoise at 25 ° C. Such materials, also known as epoxides, include the monomeric epoxy compounds and the epoxy of the polymeric type, and may be aliphatic, cycloaliphatic, aromatic or heterocyclic. These materials generally have, on average, at least 1.5, preferably at least 2, polymerizable epoxy groups per molecule. Polymer epoxies include linear polymers having epoxy groups (eg, a diglycidyl ether of a polyoxyalkylene glycol), oxirane units of polymer backbones (eg, polybutadiene polyepoxide), and polymers having epoxy groups slopes (such as the glycidyl methacrylate polymer or copolymer). The epoxies can be pure compounds, but they are generally mixtures containing one, two or more epoxy groups per molecule. The "average" number of epoxy groups per molecule is determined by dividing the total number of epoxy groups, in the epoxy-containing material, by the total number of epoxy molecules present. The molecular weight of the epoxy compound can vary from 130 to 4,000 or more. Mixtures of various epoxy compounds can also be used. The epoxy compounds may be cycloaliphatic or alicyclic epoxides. Examples of cycloaliphatic epoxides include diepoxides of cycloaliphatic esters of dicarboxylic acids, such as bis (3,4-epoxycyclohexylmethyl) oxalate, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexyl) -methyl) -adipate, bis (3, 4-epoxycyclohexyl-methyl) pimelate; vinylcyclohexene diepoxide; limonene diepoxide; dicyclopentadiene diepoxide; and similar. Other suitable diepoxides of cycloaliphatic esters of dicarboxylic acids are described, for example, in U.S. Patent No. 2,750,395, incorporated herein by reference. Other cycloaliphatic epoxides include the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylates, such as the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate; 3, 4-epoxy-1-methyl-cyclohexylmethyl-3, -epoxy-1-methylcyclohexane carboxylate; 6-methyl-3, 4-epoxycyclohexylmethylmethyl-6-methyl-3, 4-epoxy-cyclohexane carboxylate; 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate; 3, 4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexane carboxylate; 3,4-epoxy-5-methylcyclohexyl-methyl-3,4-epoxy-5-methylcyclohexane carboxylate, and the like. Other 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylates are described, for example, in U.S. Patent No. 2,890,194, incorporated herein by reference. Additional epoxy-containing materials, which are particularly useful, include those based on the glycidyl ether monomers of the formula: R '(OCH, CH-CH,). \ / O where R 'is alkyl or aryl and n is an integer of 1 to 6. Examples are the di- or polyglycidyl ethers of polyhydric phenols, obtained by the reaction of a polyhydric phenol with an excess of chlorohydrin, such as epichlorohydrin. Such polyhydric phenols include resorcinium, bis (4-hydroxyphenyl) methane (known as bisphenol F), 2,2-bis (4-hydroxyphenyl) propane (known as bisphenol A), 2,2-bis (4'-hydroxy). 3 ', 5' -dibromophenyl) propane, 1, 1, 2, 2-tetrakis (4'-hydroxy-phenyl) ethane or condensates of phenols with formaldehyde, such as those obtained under acidic conditions, such as phenol novolac and cresol novolac. Examples of this type are described in U.S. Patent No. 3,018,262 and in the "Handbook of Epoxy Resins" by Lee and Neville (McGraw-Hill Book Co. 1967), both incorporated by reference. Other examples include the di- or polyglycidyl ethers of polyhydric alcohols, such as 1,4-butanediol, or polyalkylene glycols, such as polypropylene glycol and the di- or polyglycidyl ethers of cycloaliphatic polyols, such as 2,2-bis (4-hydroxycyclohexyl) propane. Other examples are monofunctional resins, such as cresyl-glycidyl ether or butyl-glycyl ether. Another class of epoxy compounds are polyglycidyl esters and poly (β-methylglycidyl) esters of polyvalent carboxylic acids, such as phthalic acid, terephthalic acid, tetrahydrophthalic acid or hexahydrophthalic acid.

A further class of epoxy compounds are the N-glycidyl derivatives of amines, amides and heterocyclic nitrogen bases, such as N, N-diglycidyl-aniline, N, N-diglycidyl-toluidine, N, N, N ', N '-tetraglycidyl-bis (4-aminophenyl) methane, triglycidyl-isocyanurate, N, N'-diglycidyl-ethyl-urea, N, N'-diglycidyl-5,5-dimethylhydantoin and N, N'-diglycidyl-5-isopropylhydantoin . Still other epoxy-containing materials are the copolymers of glycidyl acrylic acid esters, such as glycidyl acrylate and glycidyl methacrylate, with one or more copolymerizable vinyl compounds. Examples of these copolymers are styrene-glycidylmethacrylate 1: 1, methyl-methacrylateglycidyl acrylate 1: 1 and methyl methacrylate-ethyl acrylate-glycidyl methacrylate 62.5: 24: 13.5. There are hosts of epoxy-containing materials, commercially available, commonly known as epoxy resins, which can be used as the epoxy compound. In particular, epoxy compounds that are readily available include octadecylene oxide, glycylmethrylate, diglycidyl ether of bisphenol A (such as those available under the tradenames EPON 828, EPON 1004 and EPON 1010, from Shell Chemical CO., DER. -331, DER-332 and DER-334, from Dow Chemical Co., and ARALDITE GY 6010 from Ciba-Geigy); vinylcyclohexene dioxide (such as that available under the tradename ERL-4106 from Union Carbide Corp.); 3, 4-epoxycyclohexylmethyl-33,4-epoxycyclohexane carboxylate (such as that available under the tradename ERL-4221 from Union Carbide Corp); the 3,4-epoxy-6-methylcyclohexyl-methyl-3,4-epoxy-6-methylcyclohexane carboxylate (such as that available under the tradename ARL-4201 from Union Carbide Corp.); bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate (such as that available under the tradename ERL-4289 from Union Carbide Corp.); bis (2,3-epoxycyclopentyl) ether (such as that available under the tradename ERL-0400 from Union Carbide Corp.); aliphatic epoxies modified with polypropylene glycol (such as those available from the trademarks ERL-4050 and ERL-4052 of Union Carbide Corp.); dipentene dioxide (such as that available under the trademark of ERL-4269 from Union Carbide Corp.); epoxidized polybutadiene (such as that available under the trade name of OXIRON 2001 from FMC Corp.); silicone resin containing epoxy functionality; epoxy resins that retard the flame (such as an epoxy resin of the brominated bisphenol type, available under the tradename DER-580 from Dow Chemical CO.); 1,4-butanediol diglycidyl ether of phenol formaldehyde novolac (such as those available under the trade names of DEN-431 and DEN-438 from Dow Chemical Co.); and resorcinol diglycidyl ether (such as that available under the tradename KOPOXITE from Koppers Company Ine.). Preferred epoxy compounds are the di- or polyglycidyl ethers of polyhydric phenols, particularly the diglycidyl ether of bisphenol A and the glycidyl ethers. Thiol curing agents for epoxy compounds are well known and are described, for example, in U.S. Patent No. 5,374,668. As used herein, the "thiol" also includes the curing agents of polythiol or polymercaptan. Exemplary thiols include aliphatic thiols, such as methanedithiol, propanedithiol, cyclohexanedithiol, 2-mercaptoethyl-2,3-dimerceptosuccinate, 2,3-dimercapto-1-propanol (2-mercapto-acetate), diethylene glycol-bis (2) -mercaptoacetate), 1,2-dimercaptopropyl methyl ether, bis (2-mer- absorethyl) ether, trimethylolpropane-tris (thioglycolate), pentaerythritol-tetra (mercaptopropionate), pentaerythritol-tetra) thioglycolate), ethylene glycol-dithioglycolate, trimethylolpropane-tris (β-thiopropionate), tris-mercapto derivative of the tri-glycidyl ether of propoxylated alkane and dipentaerythritol-poly (β-thiopropionate), halogen-substituted derivatives of the aliphatic thiols; aromatic thiols such as di-, tris- or tetra-mercaptobenzene, bis-, tris- or tetra- (mercaptoalkyl) benzene, dimercaptobiphenyl, toluenedithiol and naphthalenedithiol; halogen-substituted derivatives of aromatic thiols; thiols containing heterocyclic rings, such as amino-4,6-dithiol-sim-triazine, alkoxy-4,6-dithiol-sim-triazine, aryloxy-4,6-dithiol-simtriazine and 1, 3, 5-tris (3-mercaptopropyl) isocyanurate; halogen-substituted derivatives of thiols containing heterocyclic rings; thiol compounds having at least two mercapto groups and containing sulfur atoms in addition to mercapto groups, such as bis-, tris- or tetra (mercaptoalkylthio) benzene, bistris- or tetra (mercaptoalkylthio) alkane, bis (mercaptoalkyl) ) disulfide, hydroxyalkylsulfide-bis (mercaptopropionate), hydroxyalkylsulfide-bis (mercaptoacetate), mercaptoethyl ether-bis (mercaptopropionate, 1,4-dithian-2,5-diol-bis (mercaptoacetate), bis (mercaptoalkyl-ester) acid thiodiglycolic, bis (2-mercaptoalkyl ester) of thiodipropionic acid, bismutothiol and 2,5-dimercapto-1,3,4-thiadiazole The trio-mercaptan derivative of triglycidyl ether of the alkane is the preferred thiol curing agent propoxylated, commercially available from Henkel Corp. under the commercial designation CAPCURE 3-800 and having a generic structure, represented by: CH, OH R-1-O OífCCKHjCCBHOÍnCHiCHCHzSH where R is an alkyl group having from 1 to 5 carbon atoms and n is 1 or 2. The catalyst or accelerator can be a nucleophilic substance, such as an amine, a tertiary phosphine, a quaternary ammonium al with a nucleophilic anion, a salt of quaternary phosphonium with a nucleophilic anion, an imidazole,. a salt of tertiary arsenide, with a nucleophilic anion and a tertiary sulfonium salt with a nucleophilic anion. Possible amine catalysts include the primary, secondary and tertiary amines. Various mixtures of catalysts can be used. Tertiary amine catalysts are preferred and are described, for example, in U.S. Patent No. 5,385,990, incorporated herein by reference. Exemplary tertiary amines include methyldiethanolamine, triethanolamine, diethylaminopropylamine, benzyldimethylamine. m-xylylenedi (dimethylamine), N, N'-dimethylpiperazine, N-methylpyrrolidine, N-methyl-hydroxypiperidine, N, N, N '-N' -tetramethyldiaminoethane, N, N, N ', N', N '-pentamethyldiethylenetriamine, tributylamine, trimethylamine, diethyldecylamine, triethylene diamine, N-methyl-morpholine, N, N, N', N '-tetramethyl-propane-diamine, N-methyl -piperidine, N, N '-dimethyl-1, 3- (4-piperidino) propane, pyridine, and the like. Particularly preferred tertiary amines are 1,8-diazobicyclo [5.4.0] -undec-7-ene, 1,8-diazabicyclo [2.2.2] octane, 4-dimethylaminopyridine, 4- (N-pyrrolidino) pyridine, triethyl- amine and 2,4,6-tris (dimethylaminomethyl) phenol, with 1,8-diazobicyclo [5.4.0] undec-7-ene being especially preferred. The aliphatic polyamines which are modified by adduction with epoxy, acrylonitrile or (meth) acrylate resins can be used as amine catalysts. In addition, several Mannich bases can be employed as amine catalysts. The aromatic amines where the amine groups are attached directly to the aromatic ring can also be used. Exemplary quaternary ammonium salts with a nucleophilic anion include tetraethyl ammonium chloride, tetrapropyl ammonium acetate, hexyl trimethyl ammonium bromide, benzyl trimethyl ammonium cyanide, cetyl triethyl ammonium azide, N-cyanate. , N-dimethylpyrrolidinium, N-methyl pyridinium phenolate, N-methyl-o-chloropyridinium chloride, methyl viologen dichloride, and the like. The adhesion-promoting compound, which contains phosphorus, can be any phosphinic acid derivative, phosphonic acid or phosphoric acid, having at least one group of P-OH and at least one organic part, characterized by the presence of an unsaturated group ethylenically, which is terminally located in preferred form. The ethylenically unsaturated group must be reactive with the thiol curing agent by the anionic addition. A list of such phosphorus compounds is found in U.S. Patent No. 4,223,115, incorporated herein by reference. A preferred phosphorus-containing compound has a structure that can be represented by the formula: OR OH wherein R20 is selected from the group consisting of hydrogen, an alkyl group having from 1 to 8, preferably from 1 to 4 carbon atoms, and CH2 = CH-; R21 is selected from the group consisting of hydrogen, an alkyl group having from 1 to 8, preferably from 1 to 4 carbon atoms; A is selected from the group consisting of -R22 (O) OR220-, -R220- and (R230) n, where R22 is, independently, an alkylene, aliphatic or cycloaliphatic group, containing from 1 to 9, preferably from 2 to 6 carbon atoms; R23 is an alkylene group having from 1 to 7, preferably from 2 to 4 carbon atoms; n is an integer from 2 to 10, and m is 1 or 2, preferably 1. Phosphorus-containing compounds, which have a vinyl unsaturation, are preferred over the compounds having an allylic unsaturation, with the monoesters of phosphinic, phosphonic and phosphoric, which have an installation of a vinyl or allylic unit, especially vinyl, currently being preferred.

Representative phosphorus-containing compounds include, without limitation, 2-hydroxyethyl methacrylate phosphate; phosphate ester of 5-hydroxyhexanoyloxyethyl; bis- (2-methacryloyloxyethyl) phosphate; 2-acryloyloxyethyl phosphate; bis (2-acryloyloxyethyl) phosphate; methyl- (2-methacryloyloxyethyl) phosphate; ethyl-methacryloyloxyethyl phosphate; methyl acryloyloxyethyl phosphate; ethyl acryloyloxoethyl ethyl phosphate; compounds of the above formula, wherein R20 is hydrogen or methyl and R21 is propyl, isobutyl, ethylhexyl, halopropyl, haloisobutyl or haloethylhexyl; vinyl phosphonic acid; cyclohexen-3-phosphonic acid; alpha-hydroxybuten-2-phosphonic acid; 1-hydroxy-l-phenylmethane-1,1-diphosphonic acid; 1-hydroxy-l-methyl-1-diphosphonic acid; 1-amino-1-phenyl-1, 1-diphosphonic acid; 3-amino-1-hydroxypropan-1,1-diphosphonic acid; amino-tris acid (methylene phosphonic); gamma-amino-propylphosphonic acid; gamma-glycidoxypropylphosphonic acid; phosphoric acid mono-2-aminoethyl ester; allyl phosphonic acid; allyl phosphinic acid; ß-methacryloyloxyethyl acid; diallylphosphinic acid; ß-methacryloyloxyethyl-phosphinic acid and allyl-methacryloyloxyethyl-phosphinic acid. As used herein, the "essential ingredients" of the composition of the present invention refer to the epoxy compound, thiol curing agent, catalyst and phosphorus-containing adhesion promoting compound. The amount of the ingredients is defined herein in relation to the epoxy functionality, expressed as a ratio of equivalents. The thiol curing agent is present in an amount of 0.5 to 1.5, preferably 0.9 to 1.2. The catalyst is present in an amount of 0.01 to 0.30, preferably 0.02 to 0.10, and the phosphorus-containing compound is present in an amount of 0.005 to 0.200, preferably 0.02 to 0.10, provided that the catalyst is in excess with ratio to the amount of the adhesion-promoting compound, which contains phosphorus. Optionally, a rubber or elastomeric component can be included in the composition, to provide firmness and flexibility. The rubber component may be present as a dispersion of the rubber pre-laced in the epoxy compound, as is known in the art. Examples of previously crosslinked rubber compounds, available as dispersions in epoxy resins, include polyacrylates, polybutadienes, polyisoprenes and the like. The rubber component can also be a precursor, such as the acrylate-terminated butadienes, and the butadiene-acrylonitrile copolymers terminated in amine, acrylate or epoxy. The composition may also include additives and fillers, conventionally found in epoxy systems, such as silica, glass, talc, metal powders, titanium dioxide, wetting agents, pigments, coloring agents, and the like. The composition is preferably used as a two-part system, but one-part frozen systems can also be used. If used as a two-part system, the first part includes the epoxy compound and the second part includes the thiol curing agent, the phosphorus-containing compound and the catalyst. The ingredients of each part are mixed together by means known in the art. The phosphorus-containing compound is added to the part containing the thiol, with the other components, at the time of formulation. It does not previously react with the epoxy compound to form an epoxy that includes phosphate ester groups in its backbone structure. In the preferred two-part system, these two parts are dosed and mixed together for a predetermined time, before using in a volume ratio of the first to second part of 1:10 to 10: 1, preferably 1: 1. Preferably, the two parts are mixed together immediately before use, but the composition has an open time of 15, preferably 30 minutes. As used here, "open time" denotes the mixing time of the parts at the time in which the mixed composition cures to a point that can no longer be worked. As discussed above, this composition is particularly useful as a hem flange sealer, since it can be cured at about the same temperature (in other words, within ± 5 ° C) or less than the cure temperature of the adhesive based in (met) acrylic. In this case, the two parts of the composition are mixed together, the resulting mixture is applied to an adhesive or solder joint, between the two substrates, in order to substantially cover the joint and then the sealant is subjected to the heat having a temperature from the environment to 121 ° C, preferably from 75 to 121 ° C, from 0.25 to 1.0, preferably 0.25 to 0.50, minutes. The composition can be applied by any conventional method, such as a roller coating, brush, curtain coating or an automatic dispensing machine. Structural adhesives that are particularly useful in combination with sealant are described, for example, in U.S. Patent Nos. 5,641,834, 4,769,418m 4,467,071, 4,293,665 and 4,223,115, all incorporated herein by reference. In general, these adhesive compositions include at least one monomer and / or free radical polymerizable polymer, a polymeric material, which acts as a firmness rubber agent and a redox catalyst system. The free radical polymerizable monomer and / or polymer typically includes at least one (meth) acrylic based material. Sealing bonded substrates include metal and plastic substrates. Illustrative metal substrates include steel, iron, aluminum, brass, copper and the like. Examples of plastics include epoxy glass-filled resins, glass-filled polyesters, polyureas and polycarbonates. Common substrates particularly are steel and sheet molding compound ("SMC"). The present composition can also be useful as the adhesive itself to adhere these types of substrates.

Examples of the Invention and a Comparative Example are described below.

EXAMPLE 1 20 g of an epoxy diglycidyl ether of bisphenol A type (commercially available from Ciba-Geigy, under the trade designation of ARALDITE GY 6010), 5 g of cresyl glycidyl ether type epoxy (commercially available from Shell Chemical , under the trade designation of HELOXY 62), 9 g of glass sphere filler and 1 g of silica, were mixed together to form the first part. 25 g of the tris-mercaptan derivative of tri-glycidyl ether of the propoxylated alkane (commercially available from Henkel under the trade designation CAPCURE 3-800), 0.25 g of hydroxyethyl methacrylate phosphate (available from Lord Corp.), 0.34 g of 1,8-diazobicyclo [5.4.0] undec-7-ene (commercially available from Air Products under the trade designation POLYCAT SA-610-50), 3 g of glass sphere filler and 1 g of silica, they were mixed together to form the second part.

EXAMPLE 2 The first part was formulated as described in Example 1. 25 g of the tris-mercaptan derivative of the tri-glycidyl ether of the propoxylated alkane (commercially available from Henkel, under the trade designation CAPCURE 3-800) 0.30 g of phosphate ester of 6-hydroxyhexanoyloxyethyl acrylate (available from Nippon Kayaku Co., Ltd. under the trade designation KAYAMER PM-21), 0.40 g of 1,8-diazabicyclo [5.4.0] undec-7-ene (commercially available from Air Products under the trade designation POLYCAT SA-610-50), 3 g of glass sphere filler and 1 g of silica were mixed together to form the second part.

COMPARATIVE EXAMPLE 3 The first part was formulated as described in Example 1. 25 g of the tris-mercaptan derivative of the tri-glycidyl ether of the alkanopropoxylate (commercially available from Henkel under the trade designation of CAPCURE 3-800 =, 0.20 g of 1, 8-diazobicyclo [5.4.0] undec-7-ene (commercially available from Air Products under the trade designation POLICAT SA-610-50), 3 g of glass bead filler and 1 g of silica, they mixed together to form the second part.In contrast to Examples 1 and 2, Comparative Example 3 does not include an adhesion promoting compound, which contains phosphorus.

TEST The first and second parts of each example were mixed together in a volume ratio of 1: 1 and the resulting mixture was applied to a flat panel of electrogalvanized steel (EG) or hot dip steel (HD). Where indicated, the panels were coated with a water-based milling oil. Initial adhesion to the panel was tested after curing at 121 ° C and then cooled to room temperature. The adhesion after subjecting the panel to 204 ° C for one hour was also tested, in order to simulate the subsequent baking typically applied during the painting cycle to panels and parts of cars and trucks. The adhesion was tested by trying to remove the cured composition with a shaving blade. The results are shown in the following table. It is clear that the addition of the phosphorus-containing compound in Examples 1 and 2 provided superior adhesion relative to Comparative Example 3, particularly if there is oil on the substrate.

Claims (7)

1. CLAIMS 1. A composition comprising: a) an epoxy compound; b) a thiol curing agent; c) a catalyst; and d) a phosphorus-containing compound, which has at least one group of P-OH, and at least one part characterized by the presence of an ethylenically unsaturated group.
2. 2. A composition, according to claim 1, wherein the epoxy compound is a di- or polyglycidyl ether of a polyhydric phenol.
3. 3. A composition, according to claim 1, wherein the thiol curing agent is selected from the group consisting of an aliphatic thiol, an aromatic thiol, a thiol containing a heterocyclic ring and a thiol compound having at least two mercapto groups and containing sulfur atoms in addition to the mercapto groups.
4. 4. A composition, according to claim 1, wherein the catalyst is selected from the group consisting of an amine, a tertiary phosphine, a quaternary ammonium salt of a nucleophilic anion, a quaternary phosphonium salt of a nucleophilic anion and an imidazole .
5. 5. A composition, according to claim 1, wherein the phosphorus-containing compound has a structure, represented by the formula: OR OH where R20 is selected from the group consisting of hydrogen, an alkyl group having from 1 to 8 carbon atoms, and CH2 = CH-; R21 is selected from the group consisting of hydrogen, an alkyl group having from 1 to 8 carbon atoms; A is selected from the group consisting of -R22 (O) OR220-, -R220- and (R230) n, wherein R22 is, independently, an alkylene, aliphatic or cycloaliphatic group, containing from 1 to 9 carbon atoms; R23 is an alkylene group having 1 to 7 carbon atoms; n is an integer from 2 to 10, and m is 1 or 2.
6. 6. A composition, according to claim 1, wherein the thiol curing agent is present in an amount of 0.5 to 1.5, the catalyst is present in an amount of 0.01 to 0.30 and the phosphorus-containing compound is present in an amount from 0.005 to 0.200, all based on the ratio of equivalents to the amount of epoxy functionality, in the epoxy compound.
7. 7. A method for sealing a joint between two substrates, this method comprises applying a composition, according to claim 1, to a joint, between the two substrates, then subjecting the resulting assembly to an environment having a temperature from ambient to 121. ° C.