Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F4/00—Polymerisation catalysts
  • C08F4/40—Redox systems
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16

Definitions

• the invention relates generally to polymerizabie compositions, and more particularly to free radical polymerizabie compositions cured using redox catalysts.
• Redox catalyst systems are widely used to accelerate polymerization of unsaturated compounds in a variety of applications.
• Redox catalyst systems generally include an oxidizing agent and a reducing agent (also referred to as accelerators) which are co-reactive at room temperature to generate free radicals to initiate additional polymerization reactions.
• the oxidizing agent is an organic peroxide and the reducing agent is a tertiary amine.
• exemplary tertiary amines which are commercially available include N,N-diethanol-p-toluidine, N,N-dimethylaniline, and N,N-dimethyl-p- toluidine.
• air inhibition A common problem associated with polymerization of unsaturated compounds, such as acrylic adhesives, is referred to as "air inhibition.” Atmospheric oxygen is a powerful inhibitor of free radical reactions. In many applications, it is a practice to use a slight excess of adhesive to ensure complete coverage of the area to be bonded. This can result in some adhesive being squeezed out around the bond area and thus exposed to air, resulting in a layer of unreacted monomer remaining on the surface.
• compositions which include at least one free radical polymerizabie compound and a redox couple catalyst
• the redox catalyst includes at least one oxidizing agent and at least one reducing agent (or accelerator) which are co- reactive with one another to generate free radicals and to initiate and propagate polymerization of the polymerizabie compound.
• reducing agents of the invention have the following general structure according to Formula (I):
• each of R, and R 2 is independently selected from the group consisting of linear or branched, saturated or unsaturated, C1-C10 alky! and linear or branched, saturated or unsaturated, Cl -ClO hydroxyalkyl; each of R, and R 4 is independently selected from the group consisting of hydrogen and C1-C10 alkyl; and X is halogen.
• Exemplary accelerators in accordance to Formula I include N,N-d ⁇ sopropanol-p-chloroan ⁇ hne; N,N- dusopropanol-p-bromoaniline, N,N-d ⁇ sopropanol-p-bromo-m-methylan ⁇ l ⁇ ne; N,N- dimethyl-p-chloroanilme, N.N-dimethyl-p-bromoaniline, N.N-diethyl-p-chloroanihne; and N,N-d ⁇ ethyl-p-bromoanil ⁇ ne
• the halogenated compounds can be effective in reducing the air inhibition of the polymerizabie compositions even undei conditions of high humidity and temperature This can result in improved surface cuie. improved bond strength of the assembly, and can lower the perceived odor of the compositions
• the halogenated compounds can react more slowly than conventional tertiary amines, thus providing better open time for the composition
• the present invention also includes processes for bonding the compositions of the invention to the surface of a substrate
• compositions of the present invention include at least one free radical polymerizabie compound and a redox couple catalyst
• the redox catalyst includes at least one oxidizing agent and at least one reducing agent of Formula (I) above, which are co-reactive with one another to generate free radicals and to initiate and propagate polyme ⁇ zation of the polymerizabie compound.
• the reducing agents of the present invention have the following Formula (I)
• each of R, and R 2 which may be the same or different, is independently selected from the group consisting of linear or branched, saturated or unsaturated, C 1 -C 10 alkyl and linear or branched, saturated or unsaturated, C1-C10 hydroxyalkyl (I e , alk> 1 substituted by -OH), each of R, and R 4 is independently selected from the group consisting of hydrogen and linear or branched, saturated or unsaturated C1-C 10 alkyl, and
• each of R, and R. is independent! ) selected from the group consisting of C1 -C4 alkyl and C1-C4 hydroxyalkyl, and more preferably each of R, and R- are the same and are methyl or isopropanol, each of R, and R 4 is hydrogen, and X is fluorine, chlorine, bromine, or iodine, and more preferably chlorine or bromine.
• Exemplary reducing agents in accordance with the present invention include, but are not limited to, N,N-d ⁇ sopropanol-p-chloroan ⁇ lme, N,N-dnsopropanol-p- bromoamhne, N.N-d ⁇ sopropanol-p-bromo-m-methylaniline, N.N-dimethyl-p- chloroanihne, N,N-d ⁇ methyl-p-bromoanihne; N,N-d ⁇ ethyl-p-chloroan ⁇ hne, and N,N- diethyl-p-bromoanihne.
• the reducing agents of Formula (I) are typically present in the compositions of the invention in an amount from about 0.05 to about 10, preferably about 0.1 to about 6, weight percent based on the total weight of the composition
• oxidizing agents which can be used in conjunction with any oxidizing agents known in the art which is useful as a component of a redox catalyst system.
• exemplary oxidizing agents which can be used in accordance with the present invention include, but are not limited to, organic peroxides, such as hydrogen peroxide; ketone peroxides, such as a'- ⁇ tylacetone peroxide, methylethylketone peroxide, cyclohexanone peroxide and methyhsobutylketone peroxide; diacyl peroxides, such as benzoyl peroxide, lauroyl peroxide, isobutyryl peroxide, acetyl peroxide, 2,4- dichlorobenzoyl peroxide, succinic acid peroxide, decanoyl peroxide, diisononanoyl peroxide; hydroperoxides such as cumene hydroperoxide; peresters, such as tert
• the diacyl peroxides, and particularly benzoyl peroxide, are preferred initiators.
• the oxidizing agent can be present in the compositions of the invention in an amount from about 0.5 to about 50 percent by weight, based on the weight of the reducing agent.
• the reducing agents of the invention can be included in a variety of free radical polyme ⁇ zable or curable compositions, such as described in U.S Patent Nos. 2,981 ,650, 3,321,351 , 4,223, 1 15; 4,293,665; 4,467,071 ; 4,452,944, and 4,769.419, the entire disclosure of each of which is hereby inco ⁇ orated by reference.
• compositions of the invention include at least one free radical polyme ⁇ zable compound
• Representative monomers include, but are not limited to, methyl methacrylate, ethyl methacrylate, butyl methacrylate. methyl acrylate.
• styrene vinyl styrene, vinyl acetate, chlorostyrene, glycidyl methacrylate, itaconic acid, acrylamide, meth acrylamide, vinylidene chloride, 2,3-dichloro- 1.3-butadiene, 2-chloro- 1 ,3-butadiene, methylstyrene, p-tert-butyl styrene, esters of fumaric and maleic acid which are capable of free radical polymerization, and mixtures thereof.
• preferred monomers include methyl methacrylate and styrene.
• compositions of the invention typically include at least one free radical polymerizabie compound in an amount from about 10 to about 90, preferably about 20 to about 70, weight percent based on the total weight of the composition.
• the compositions of the invention advantageously also include at least one polymeric material which can act as a toughening agent to provide improved impact and shatter resistance to the resultant adhesive and to decrease the brittleness thereof.
• the polymeric material may or may not include an olefinically unsaturated structure that is capable of being polymerized per se or copolymerized with at least one of the free radical polymerizabie monomers described above.
• the polymeric material can be, for example, Neoprene as described in U.S. Patent No.
• Representative liquid olefinic-terminated elastomers include homopolymers of butadiene; copolymers of butadiene and at least one monomer copolymerizable therewith, for example, styrene, acrylonitrile, methacrylonitrile (e.g., poly(butadiene- (meth)acrylonitrile) or poly (butadiene-(meth)acrylonitrile-styrene) and mixtures thereof; as well as modified elastomeric polymeric materials, such as butadiene homopolymers and copolymers as noted above modified by copolymerization therewith of trace amounts of up to about 5 percent by weight of the elastomeric material of at least one lunctional monomer (such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, styrene, and methyl methacrylate, to give, for example, methacrylate-terminated polybutadiene homopolymers and/
• liquid butadiene-based elastomers can be reacted with an isocyanate to form a liquid urethane-modified butadiene elastomer.
• Representative urethane-modified butadiene-based elastomeric polymeric compounds and processing for preparing the same are described in U.S. Patent No. 4,769,419.
• Such liquid olefinic-terminated elastomers can be present in the compositions of the invention in amounts from about 10 to about 80, preferably about 20 to about 50, weight percent based on the total weight of the composition.
• Exemplary chlorosulfonated polyethylene rubbers are described in U.S. Patent No. 4,223,1 15 and include chlorosulfonated polyethylene and a mixture of sulfonyl chloride with chlorinated polyethylene. These compositions can have a chlo ⁇ ne content in the range of about 25 to about 67 weight percent and from 3 to about 160 mmols sulfonyl chloride moiety per 100 grams of polymer. Further, the polyethylene from which the chlorosulfonated polyethylene is made preferably has a melt index in the range from about 4 to about 500.
• olefinic urethane reaction products of isocyanate-functional prepolymers and hydroxy-functional monomers having at least one unit of polyme ⁇ zable unsaturation characterized by the presence of at least two units of unsaturation and the substantial absence of free isocyanate groups are also well-known
• prepolymers are adducts or condensation products of polyisocyanate compounds having at least two free isocyanate groups and monomeric or polymeric polyols having at least two hydroxy groups, including mixtures of such polyols.
• the reaction between the polyisocyanate and the polyols is effected employing an excess amount of polyisocyanate to ensure that the reaction product will contain at least two free, unreacted isocyanate groups.
• Such olefinic urethane reaction products can be present in the compositions of the invention in amounts from 0 to about 40, preferably about 1 to about 25. weight percent based on the total weight of the composition.
• the compositions of the present invention also include a phosphorus-containing compound having one or more olefinic group and no less than one P-OH group.
• Phosphorus-containing compounds which have been found to enhance metal adhesion, are selected from the group consisting of derivatives of phosphinic acid, phosphonic acid and phosphoric acid having at least one P-OH group and at least one organic moiety characterized by the presence of an olefinic group, which is preferably terminally located.
• a listing of such phosphorus-containing compounds is found in U.S . Patent No. 4,223,1 15, referenced above.
• Such phosphorus-containing compounds can be present in the compositions of the invention in amounts from about 0.1 to about 20, preferably about 2 to about 10, percent by weight, based on the total weight of the composition.
• a preferred group of phosphorus-containing compounds has the formula:
• R 6 is selected from the group consisting of H, Cl to C8, preferably Cl to C4, alkyl;
• A is selected from the group consisting of -R 7 O- and (R 8 O) n , wherein R 7 is an aliphatic or cycloaliphatic Cl to C9, preferably C2 to C6, alkylene group;
• R g is Cl to C7, preferably C2 to C4, alkylene group;
• n is an integer from 2 to 10 and m is 1 or 2, preferably 1.
• compositions of the invention can optionally contain up tc about 5 percent by weight based on the total weight of the composition of an unsaturated dicarboxylic acid ester which is not polymerizabie by free radical reaction mechanisms, in addition to any of the unsaturated dicarboxylic acid ester free radical polymerizabie monomers listed above.
• unsaturated dicarboxylic acid esters suitable for use in this regard are preferably alkyl esters with the alkyl moiety having from 1 to 18, preferably 1 to 8, carbon atoms, with fumaric and maleic being especially preferred.
• compositions of the invention can ateo optionally contain from zero to about 10 percent by weight based on the total weight of the composition of at least one unsaturated polyester resin.
• unsaturated polyester resins suitable for use in the adhesive systems described herein are well known in the art. Such resin esters are derived from polycarboxylic acids and polyhydric alcohols, preferably dicarboxylic acids and dihydric alcohols, at least one of the acid and alcohol components being unsaturated.
• the unsaturated polyester resin component will contain a relatively large number of double bonds and be derived from short chain aliphatic polyhydric polyols, such as ethylene glycol and 1 ,3-propylene glycol, and short chain unsaturated polybasic acids, such as fumaric acid and maleic acid.
• Such resins can contain quantities of longer chain polyols such as 1 ,6-hexanediol, a.s well as higher polybasic acids, such as adipic acid and phthalic acid.
• the compositions of the invention can optionally contain from zero to about 50 percent by weight based on the total weight of the adhesive composition of at least one polyvinyl alkyl ether.
• Polyvinyl alkyl ethers are well-known in the art. Such ethers will preferably contain 1 -8, more preferably 1-4, carbon atoms in the alkyl moiety of the ether. Likewise, styrene-acrylonitrile polymers which are suitable for use in the invention are also well known.
• compositions of the invention can also include up to about 60, preferably not more than about 30, percent by weight based on the total weight of the composition of a polymeric component in addition to the polymeric materials listed above having an intrinsic viscosity of 0.1 to 1.3 that can be obtained by the polymerization of at least one acrylic, styrene, substituted acrylic and non-acrylic olefinic monomers.
• Exemplary polymeric materials include poly(methyl methacrylate/n-butylacry!ate/ethyl acrylate) (90/5/5); poly (n- butyl methacrylate/isobutyl methacrylate) (50/50); poly(n-butyl methacrylate) and poly (ethyl methacrylate).
• Epoxy compounds can also be included in the adhesive compositions of the invention in amounts from 0 to about 40, preferably 0 to about 20, weight based on the total weight of the composition.
• the addition of an epoxy compound can impart heat resistance to the compositions.
• Epoxy compounds which are suitable for use in the invention are described in U.S. Patent No. 4,467,071, referenced above, and can be any monomeric or polymeric compound or mixture of compounds having an average of greater than one 1 ,2-epoxy groups per molecule.
• the polymeric epoxide compounds can have a number average molecular weight from about 300 to about 10,000. Epoxy compounds are well-known, see for example, U.S. Pat. Nos.
• Useful epoxy compounds include the polyglycidyl ethers of polyhydric alcohols, such as ethylene glycol, triethylene glycol, 1 ,2-propylene glycol, 1 ,5- pentanediol, 1 ,2,6-hexanetriol, glycerol and 2,2-bis(4-hydroxy-cyclohexyl)propane; the polyglycidyl esters of aliphatic or aromatic polycarboxylic acids, such as oxalic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid and dimerized linolenic acid; and the polyglycidyl ethers of polyphenols, such as Bisphenol A, l , l-bis(4-hydroxyphenyI)ethane, l ,l-bis(hydroxypheny
• Another optional component is about 0.01 to about 10, preferably about 0.5 to about 5, percent by weight based on the total weight of the composition of tertiary amines having the formula * wherein Z is methylene; Y is selected from the group consisting of hydrogen, hydroxy, amino, Cl to C8, preferably Cl to C4, alkyl, and Cl to C8, preferably Cl to C4, alkoxy, a is zero or 1 ; and b is 1 or 2.
• This tertiary amine is advantageous in accelerating the cure of such compositions containing the unsaturated organophosphorus compounds described above.
• Especially preferred tertiary amines are N,N-dimethyl aniline and N,N- dimethylaminomethylphenol.
• the environmental resistance of the compositions of the invention can be improved by the optional addition of about 0.005 to about 15, preferably about 0.1 to about 10, percent by weight based on total weight of composition of a mixture of a metal molybdate such as zinc molybdate, calcium molybdate, barium molybdate, strontium molybdate and mixtures thereof, and an inert filler such as zinc phosphate, calcium phosphate, magnesium phosphate, calcium carbonate and mixtures thereof, said metal molybdate being present on a volume concentration basis of from about 0.5 to about 3 parts per part of said inert filler.
• a metal molybdate such as zinc molybdate, calcium molybdate, barium molybdate, strontium molybdate and mixtures thereof
• an inert filler such as zinc phosphate, calcium phosphate, magnesium phosphate, calcium carbonate and mixtures thereof, said metal molybdate being present on a volume concentration basis of from about 0.5 to about 3 parts per part of said
• compositions can also optionally include polybasic lead salts of phosphorous acid and saturated and unsaturated organic dicarboxylic acids and acid anhydrides, particularly dibasic lead phthalate, monohydrous tribasic lead maleate, tetrabasic lead fumarate, dibasic lead phosphite and mixtures thereof; and zinc oxide, in an amount of about 0.1 to about 15, preferably about 1 to about 10, percent by weight, based on the total weight of the composition. These compounds can be effective in improving environmental resistance. Small quantities of various waxy materials as described in U.S. Patent No.
• 3,321 ,351 are also advantageously present in the adhesive compositions of the invention.
• Such materials include, but are not limited to, paraffin, montan wax, beeswax, ceresine wax, spermaceti (natural and synthetic), and the like.
• the preferred quantity of such waxy materials is about 0.1 to about 3.0 percent by weight based on the total weight of the composition.
• compositions of the invention can also include other additives as known in the art, for example, coloring agents, fillers, pigments such as titanium dioxide and carbon black, extenders such as calcium carbonate, WoUastonite, and talc, viscosity controlling agents, and the like.
• coloring agents for example, coloring agents, fillers, pigments such as titanium dioxide and carbon black, extenders such as calcium carbonate, WoUastonite, and talc, viscosity controlling agents, and the like.
• a preferred composition of the invention is an ambient temperature-curable adhesive composition that includes: (a) about 10 to about 90, preferably about 20 to about 70, weight percent of at least one free radical polymerizabie monomer as described above;
• At least one oxidizing agent which is co-reactive with the reducing agent in an amount effective to generate free radicals and to initiate and propagate polymerization of at least one free radical polymerizabie monomer, wherein the weight percents are based on the total weight of components (a) - (e).
• compositions of the invention are normally provided as two-package adhesive systems, with the packages being mixed at the time of use to provide a free radical curable adhesive.
• the first package includes at least one free radical polymerizabie compound and at least one reducing agent.
• the second package includes at least one oxidizing agent, and is referred to generally in the art as a bonding accelerator package.
• the bonding activators which are employed in the adhesive systems of this invention advantageously include (1 ) from about 0.5 to about 50 percent by weight based on total weight of bonding activator of at least one oxidizing agent as described above; and (2) from about 30 to about 99.5 percent by weight based on total weight of bonding accelerator, of a carrier vehicle.
• the carrier vehicles which are suitable for use in the bonding activators of the present invention can be a simple inert solvent or diluent such as methylene chloride, or butyl benzyl phthalate, including mixtures of such solvents or diluents.
• the carrier vehicle should contain not more than 5 percent by weight of any moiety which is reactive with the oxidizing agent at room temperature.
• the carrier vehicle can be a more complex mixture including at least one film-forming binder in addition to inert solvent or diluent.
• the film-forming binder is preferably substantially inert with respect to the oxidant which is present in the accelerator composition.
• a particularly preferred carrier vehicle comprising at least one film-forming binder is an admixture comprising from about 0.05 to about 50 percent by weight of (1) at least one saturated organic polymeric film-forming binder having a glass transition temperature in the range from about 0°C to about 150°C or
• polymeric film-forming binder materials which can be employed in the carrier vehicle are, without limitation, polyalkylacrylates and methacrylates and copolymers thereof, polystyrene and copolymers thereof, vinyl polymers and copolymers, polyesters, polyketones, polysulfones, phenolic resins, polyvinyl acetals and butyrals, and polycarbonates.
• the carrier vehicle can contain, in addition to solvent or solvent and film-forming binder, additives such as external plasticizers, flexibilizers, suspenders, and stabilizers, providing that any such additives do not unacceptably adversely affect the stability of the activator compositions.
• additives such as external plasticizers, flexibilizers, suspenders, and stabilizers, providing that any such additives do not unacceptably adversely affect the stability of the activator compositions.
• compositions of the invention comprising: a bonding activator containing an oxidizing agent of a redox couple catalyst system, the oxidizing agent being reactive at room temperature with agent (d) when the first and second packages are mixed to produce free radicals which are capable of initiating and propagating free radical polymerizations, the amount of the oxidizing agent being sufficient to interact with agent (d), preferably about 0.5 to about 50 percent by weight of the reducing agent, * wherein the weight percents are based on the total weight of the first package.
• the composition systems include the first and second packages in conventional amounts, for example, in a volume ratio of about 24: 1 to about 1: 1, preferably about 10: 1 to about 1 : 1 , first package: second package ratio.
• one pack will contain the unsaturated organophosphorus partial ester and the other pack will contain the epoxy resin.
• the epoxy resin will be inco ⁇ orated into the bonding accelerator which contains the oxidant of the redox couple catalyst system, with the organophosphorus compound being inco ⁇ orated into the pack containing the polymerizabie adhesive composition.
• the bonding accelerator can contain the reductant of the redox couple catalyst system and the epoxy resin with the oxidant and polymerization inhibitors being inco ⁇ orated into the pack containing the polymerizabie adhesive mass, they are less preferable with respect to shelf stability.
• the adhesive systems of the invention may be used to bond metal surfaces, such as steel, aluminum and copper, to a variety of substrates, including metal, plastics, and other polymers, reinforced plastics, fibers, glass, ceramics, wood and the like. It is a feature of the present invention that the herein-described adhesive compositions can be employed to bond metal substrates such as steel, aluminum and copper with little, if any, pretreatment of the metal surface prior to application of the adhesive. Thus, bonding can be effected even to oily metal surfaces which are otherwise clean without an extensive pretreatment as is usually required with the vast majority of currently available primers and adhesives.
• the adhesive systems of this invention provide effective bonding at room temperature, thus heat is not required either for applying the adhesive systems to the substrates or for curing. They can also be employed on porous substrates, unlike the anaerobic adhesives which require the exclusive of air and thus cannot be used on surfaces containing air in their pores.
• Methacrylated polybutadiene rubber 35.5 Methyl methacrylate 34.0
• the methacrylated polybutadiene rubber is a methacrylate terminated acrylonitrile butadiene rubber as described in U.S. Patent No. 4,769,419, referenced above, and is added as a toughening agent for the acrylic adhesive to decrease the brittleness thereof.
• WoUastonite pigment 325 mesh, available from Nyco Co ⁇ oration, is a known extender pigment added to provide some degree of structural reinforcement in the adhesive and to lower cost. Fumed silica available from Cabot Co ⁇ . as Cabot HS-5 was added as a viscosity control agent.
• Synthetic spermecetti wax available from Witco, although not required, is added to also lower air inhibition, as described in U.S. Patent No. 3,321,351.
• This composition was mixed in a 4:1 volume ratio with Accelerator 19, a benzoyl peroxide initiator in carrier commercially available from Lord Co ⁇ oration.
• the adhesive was applied to the surface of two 0.063" x 1" x 4" cold rolled steel coupons (Q-Panel
• Example 1 After an overnight cure at room temperature, lap shear tests were performed on the assemblies according to ASTM 1002-94. The lap shear test determines the tension (measured in pounds per square inch, or psi) required to rupture the adhesive bond. Five samples were used, and the results averaged. The adhesive composition of Example 1 gave a strength of 2400 psi (pounds per square inch) vs. 1610 psi for a control using N,N-diisopropanol-p-toIuidine in identical concentration to N,N-diisopropanol-p-chloraniline.
• Both of the adhesive compositions were applied to an aluminum panel in a 50 mil thickness using an eight-path drawdown blade to simulate "squeeze out" of adhesive typically seen in the use of acrylic adhesives in manufacturing applications and to evaluate surface cure of the compositions.
• the samples were allowed to cure at room temperature for two hours, then scraped with the sha ⁇ edge of a wooden tongue blade that was broken in half.
• the sample cured with N,N-diisopropanol-p-toluidine had an uncured layer of about 25 mils thickness at the surface
• the sample cured with N,N-dnsopropanol-p- chloroanihne has an uncured layer of 2-3 mils thickness
• Example 2 A composition similar to Example 1 was prepared, except using N,N- dnsopropanol-p-bromoanihne in place of N,N-dusopropanol-p-chloroan ⁇ hne The bond strength and surface cure of this composition was evaluated as described in Example 1 The lap shear strength was 2120 psi, and the sample had an uncured layer of 8- 10 mils thickness
• Example 3 A composition similar to Example 1 was prepared except using N,N- diisopropanol-p-bromo-m-methylanihne in place of N,N-diisopropanol-p-chloroa ⁇ l ⁇ ne This compositions gave a lap shear strength of 2380 psi, and an uncured layer of 1-2 mils thickness.
• Example 4 A composition similar to Example 1 was prepared, except using N.N-dimethyl-p- bromoaniline in place of N,N-d ⁇ sopropanol-p-chloroaniline. This composition gave a lap shear strength of 2480 psi, and an uncured layer of 0-2 mils thickness
• Example 5 The composition of Example 1 was applied to a 0.063" x 1" x 4" 2024-T3 aluminum coupon (Q Panel Company, stock number AR-14), rather than steel coupons The bond strength of the structure was evaluated as desc ⁇ bed above and gave a lap shear strength of 2470 psi
• Example 6 A composition similar to Example 1 was prepared, except using 3% N,N- dnsopropanol-p-chloroanihne, with the difference made up with less meth ⁇ l methacrylate This composition gave a lap shear strength on steel coupons of 2480 psi
• Example 7 A composition similar to Example 1 was prepared, except using 0 2% N,N- dnsopropanol-p-chloroanihne, with the difference made up with more meth ⁇ 1 methacrylate This composition gave a lap shear strength on steel coupons of 1950 psi
• Example 8
• Example 2 A composition similar to Example 1 was prepared, except using N.N-diethyl-p- bromoaniline in place of N,N-diisopropanol-p-chloroaniline. This composition gave a lap shear strength of 2391 psi, and an uncured layer of 35-40 mils thickness. It is believed that the poor surface cure is a result, at least in part, of impurities in the amine, which is supported by theoretical considerations. In the generally accepted mechanism of redox initiation, the tertiary amine is converted to a free radical centered on the alkyl carbon adjacent the nitrogen atom (via the nitrogen centered radial cation). Differences between the radicals generated by various R groups on the nitrogen atom should be relatively minor.
• this composition When drawn onto an aluminum panel, this composition cured to a tack free surface. When five lap shear samples were tested, the average strength was 490 psi. This indicates that these amines are effective in the cure of systems containing monomers other than acrylates.
• Example 10 Comparative A composition similar to Example 1 was prepared, except with N,N-dimethyl-m- chloroaniline in place of N,N-diisopropanol-p-chloroaniline. This composition gave a lap shear strength of 2202 psi, and an uncured layer of 35-40 mils thickness.
• Example 1 1 Comparative A composition similar to Example 1 was prepared, except with N,N-diethanol-m- chloroaniline in place of N,N-diisopropanol-p-chloroaniline. This composition gave a lap shear strength of 2075 psi and an uncured layer of 50 mils thickness. Comparative examples 10 and 1 1 illustrate that the para-position of the halogen atom of the accelerators of the invention is important to piovide good surface cure When the aniline compounds are substituted at the meta position, the resultant adhesive compositions exhibit poor air inhibition as evidenced by the high level of uncured monomei remaining on the surface (35 to 50 mils thick, as compared to 10 mils, and less, for the accelerators of the present invention)
• Example 12 Compositions prepared as described in Example 1 above were evaluated with regard to the effect of the amine initiator on salt spray resistance of the resultant acrylic bond, according to ASTM Bl 17-90. The compositions were applied to the surface of two 1" x 4" aluminum coupons, and the coupons were lapped for a distance a half inch.

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