WO2018081032A1 - Adhésif époxyde présentant une résistance aux chocs à basse température améliorée - Google Patents

Adhésif époxyde présentant une résistance aux chocs à basse température améliorée Download PDF

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Publication number
WO2018081032A1
WO2018081032A1 PCT/US2017/057951 US2017057951W WO2018081032A1 WO 2018081032 A1 WO2018081032 A1 WO 2018081032A1 US 2017057951 W US2017057951 W US 2017057951W WO 2018081032 A1 WO2018081032 A1 WO 2018081032A1
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WIPO (PCT)
Prior art keywords
adhesive
amino
epoxy
polyepoxide
bisphenol
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PCT/US2017/057951
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English (en)
Inventor
Tyler AUVIL
Gary L. Jialanella
Bindu KRISHNAN
Felix Koch
Eric E. Cole
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Dow Global Technologies Llc
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Publication of WO2018081032A1 publication Critical patent/WO2018081032A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/14—Polycondensates modified by chemical after-treatment
    • C08G59/1433—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds
    • C08G59/1438—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds containing oxygen
    • C08G59/1444—Monoalcohols
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/14—Polycondensates modified by chemical after-treatment
    • C08G59/1433—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds
    • C08G59/1477—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
    • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
    • C08G59/4014—Nitrogen containing compounds
    • C08G59/4021—Ureas; Thioureas; Guanidines; Dicyandiamides

Definitions

  • the invention is related to a thermosetting epoxy resin having improved low-temperature impact resistance while still maintaining a high elastic (Young's) modulus.
  • Epoxy resin based adhesives are used to bond a variety of different substrates together. In certain applications, the adhesive must maintain good bonding to the substrate and good impact resistance over a very wide temperature range.
  • epoxy resin adhesives are used in the automotive industry metal-metal bonding in frame and other structures. Adhesive bonding can reduce the number of welds that are needed to construct the frame, and for that reason the use of these adhesives can reduce assembly costs.
  • the cured adhesive will be subjected to a very wide range of temperatures during subsequent manufacturing processes and during the lifetime of the vehicle. These temperatures may be as high as 80° C. Automobiles that are used in cold climates may be exposed to temperatures as low as -40 0 C.
  • Structural adhesives potentially offer similar advantages in aerospace manufacturing as they do in the automotive sector-reduced vehicle weight and reduced manufacturing costs.
  • Rubber tougheners are elastomeric polymers having alkene double bonds in the repeating units of the polymer and do not include aromatic double bonds that are reacted into the epoxy.
  • a common rubber toughener is a carboxylic acid terminated butadiene acrylonitrile (CTBN) copolymer.
  • WO/2017/108958 amphiphilic block copolymers were described as tougheners for improving the impact resistance at less than -40° C, which may be terminated with hydroxyl or carboxylic acid groups. These tougheners, however, may cause reduced shelf life of the adhesive and only somewhat improved low temperature properties.
  • WO 2005/007720 and US 2007/0066721 an adhesive system is described which contains a polytetrahydrofuran-based toughener based on polytetrahydrofuran (PTHF, also known as polytetramethylene glycol, PTMEG, polytetramethylene oxide, and PTMO).
  • PTHF polytetrahydrofuran
  • PTMEG polytetrahydrofuran
  • PTMO polytetrahydrofuran
  • Embodiments of the present invention comprise a one component adhesive composition that may help overcome one or more of the foregoing discussed problems.
  • embodiments of the invention provide an epoxy adhesive composition having improved impact resistance at low temperatures, such as minus 40° C or less while still having a sufficient shelf life.
  • a composite structure prepared with the adhesive has an impact peel strength of at least 15 N/mm at a temperature of minus 40° C, wherein the impact peel strength is measure in accordance with ISO 11343 wedge impact method.
  • Sufficient shelf life means that the adhesive composition has a shelf life that is at least 3 months and desirably equal to or more than 6, 12 or 18 months.
  • the shelf life generally is taken as being when the initial viscosity of the adhesive composition has increased by 50% when maintained at room temperature ( ⁇ 23 0 C+5°C) in a sealed container.
  • the viscosity may be determined using a Brookfield viscometer using a number 5 spindle.
  • the prepolymer preferably exhibits a viscosity, which facilitates formulation of a pumpable adhesive which has good green strength.
  • the viscosity of the prepolymer is about 100,000 centipoise (100 Pa s) or less and more preferably about 50,000 centipoise (50 Pa s) or less, and most preferably about 30,000 centipoise (30 Pa s) or less to about 1,000 centipoise (1 Pa s) or greater.
  • the viscosity of the adhesive can be adjusted with fillers, although the fillers generally do not improve the green strength of the final adhesive. Below about 1,000 centipoise (1 Pa s), the adhesive prepared from the prepolymer may exhibit poor green strength. Above about 100,000 centipoise (100 Pa s), the prepolymer may be unstable and hard to dispense.
  • composite structures prepared with the inventive adhesive may have impact peel strengths of at least 15 N/mm at a temperature of -40° C, wherein the impact peel strength is measure in accordance with ISO 11343 wedge impact method, and preferably at least 17 N/mm, and more preferably, at least 20 N/mm, while still having an elastic modulus of at least 2000 MPa.
  • a first aspect of the invention is a one component adhesive composition adhesive composition
  • an epoxy resin comprising: an epoxy resin; a polyurethane based toughener; an epoxy curing agent; and an epoxy capped prepolymer comprised of the reaction product of a polyepoxide and an alkanolamine having the following formula:
  • Ri is a hydrocarbon radical having from 1 to 10 carbons and at least one hydroxyl group.
  • the epoxy resin includes at least one diglycidyl ether of a bisphenol.
  • the amount of epoxy resin may be from about 30 to 60 weight percent, based on the total weight of the adhesive composition.
  • the polyurethane based toughener includes aliphatic diisocyanate groups that are blocked or capped with one or more of Bisphenol A or diisopropyl amine.
  • the polyurethane based toughener is a reaction product of an aliphatic diisocyanate and a polyol having a molecular weight ranging between 2,000 and 12,000 Daltons.
  • the amount of polyurethane may range from about 10 to 25 weight percent, based on the total weight of the adhesive composition.
  • the polyepoxide of the epoxy capped prepolymer is a diglycidyl ether of bisphenol and in particular bisphenol A, F or mixture thereof.
  • the amount of epoxy capped prepolymer may range from about 1 to 15 weight percent, based on the total weight of the adhesive composition.
  • the adhesive may comprise at least one filler, such as mineral fillers, glass particles, and fumed silica.
  • the adhesive may also include curing promoting and accelerating agents.
  • a second aspect of the invention is directed to a composite structure comprising a first substrate, a second substrate, and a cured adhesive composition of the first aspect of the present invention that adhesively bonds the first and second substrates together.
  • the substrates may be the same material or comprise materials that are different from each other.
  • the first and second substrates may both be metal.
  • one of the first and second substrates is metal, and the other substrate is plastic.
  • aspects of the invention are also directed to methods of joining materials.
  • a method comprising applying the inventive adhesive to surfaces of two substrates, and curing the adhesive to form an adhesive bond.
  • Another aspect of the invention is a method of forming an epoxy capped prepolymer comprising;
  • Ri is a hydrocarbon radical having from 1 to 10 carbons and at least one hydroxyl group at a stoichiometric excess of polyepoxide
  • the adhesive contains at least one epoxy resin. All or part of the epoxy resin may be present in the form of a rubber-modified epoxy resin, as discussed below, but generally this is not necessary and it is preferred that the epoxy resin is not so modified.
  • a wide range of epoxy resins can be used, including those described at column 2 line 66 to column 4 line 24 of U.S. Pat. No. 4,734,332, incorporated herein by reference.
  • Suitable epoxy resins include the diglycidyl ethers of polyhydric phenol compounds such as resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (l,l-bis(4- hydroxylphenyl)-l -phenyl ethane), bisphenol F, bisphenol K, bisphenol M, tetramethylbiphenol, diglycidyl ethers of aliphatic glycols and polyether glycols such as the diglycidyl ethers of C2-24 alkylene glycols and poly(ethylene oxide) or poly(propylene oxide) glycols; polyglycidyl ethers of phenol-formaldehyde novolac resins, alkyl substituted phenol-formaldehyde resins (epoxy novalac resins), phenol-hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins and dicyclopenta
  • Suitable diglycidyl ethers include diglycidyl ethers of bisphenol A resins such as are sold by Olin Corporation under the tradenames D.E.R. 330, D.E.R. 331, D.E.R..RTM. 332, D.E.R. 383, D.E.R. 661 and D.E.R. 662 resins.
  • diglycidyl ethers of polyglycols include those sold as D.E.R. 732 and D.E.R. 736 by Olin Corporation.
  • Epoxy novolac resins may also be used. Such resins are available commercially as D.E.N. 354, D.E.N. 431, D.E.N. 438 and D.E.N. 439 from Olin Corporation.
  • a cycloaliphatic epoxide includes a saturated carbon ring having an epoxy oxygen bonded to two vicinal atoms in the carbon ring, as illustrated by the following structure I:
  • R is an aliphatic, cycloaliphatic and/or aromatic group and n is a number from 1 to 10, preferably from 2 to 4.
  • n is 1, the cycloaliphatic epoxide is a monoepoxide.
  • Di- or epoxy resins are formed when n is 2 or more. Mixtures of mono-, di- and/or epoxy resins can be used. Cycloaliphatic epoxy resins as described in U.S. Pat. No. 3,686,359 may be used in embodiments of the present invention.
  • Cycloaliphatic epoxy resins of particular interest are (3,4- epoxycyclohexyl-methyl)-3,4-epoxy-cyclohexane carboxylate, bis-(3,4-epoxycyclohexyl) adipate, vinylcyclohexene monoxide and mixtures thereof.
  • Suitable epoxy resins may include oxazolidone-containing compounds as described in U.S. Pat. No. 5,112,932.
  • an advanced epoxy-isocyanate copolymer such as those sold commercially as D.E.R. 592 and D.E.R. 6508 (Olin Corporation) may be used.
  • the epoxy resin preferably is a bisphenol-type epoxy resin or mixture thereof with up to 10 percent by weight of another type of epoxy resin.
  • the bisphenol type epoxy resin is a liquid epoxy resin or a mixture of a solid epoxy resin dispersed in a liquid epoxy resin.
  • the most preferred epoxy resins are bisphenol-A based epoxy resins and bisphenol-F based epoxy resins.
  • An especially preferred epoxy resin is a mixture of a diglycidyl ether of at least one polyhydric phenol, preferably bisphenol-A or bisphenol-F, having an epoxy equivalent weight of from 170 to 299, especially from 170 to 225, and at least one second diglycidyl ether of a polyhydric phenol, again preferably bisphenol-A or bisphenol-F, this one having an epoxy equivalent weight of at least 300, preferably from 310 to 600.
  • the proportions of the two types of resins are preferably such that the mixture of the two resins has an average epoxy equivalent weight of from 225 to 400.
  • the mixture optionally may also contain up to 20%, preferably up to 10%, of one or more other epoxy resin.
  • the epoxy resin may make up at least about 10 weight percent, of the weight of the adhesive composition, preferably at least about 15 weight percent, and most preferably at least about 20 weight percent of the weight of the adhesive composition. In some embodiments, the epoxy resin preferably comprises up to about 70 weight percent of the adhesive composition, more preferably up to about 60 weight percent, and most preferably up to about 50 weight percent, of the weight of the adhesive composition.
  • the epoxy capped prepolymer comprises the reaction product of a polyepoxide and an alkanolamine.
  • the polyepoxide may be any epoxy resin where the epoxy resin has two or more epoxides. Generally, any one of the epoxy resins described above may be used as the polyepoxide having 2 or more epoxide groups. Preferably the polyepoxide has two expoxide groups.
  • Particularly useful polyepoxides include a diglycidyl ether of a bisphenol such as diglycidyl ether of bisphenol A, F, or mixture thereof.
  • the alkanolamine may be any primary amine that has at least one hydroxyl group.
  • the hydroxyl group may be primary, secondary, or any combination thereof if more than one is present.
  • the alkanolamine may be represented by the following formula:
  • Ri is a hydrocarbon radical having from 1 to 10 carbons and at least one hydroxyl group.
  • Ri may be alkyl, cyclic alkyl, aromatic. Ri may contain carbon-carbon double or triple bond.
  • Ri is an alkyl or aromatic group having one or more hydroxyls substituents.
  • Ri has from 1 to 6 carbons and from 1 to 5 hydroxyls.
  • alkanolamines include 2-amino-2-ethyl-l-pentanol, 2-amino-2-methyl-l- heptanol, 2-amino-2-propyl- 1 -pentanol, 2-amino-2-heptyl- 1 ,3 -propanediol,
  • 2-amino-2-ethyl-l-heptanol 2-amino-2-propyl-l-hexanol, 2-amino-2- methyl- 1-nonanol, 2-amino-2-ethyl-l-octanol, 2-amino-2-propyl-l-heptanol, 2-amino-2-nonyl-l,3-propanediol, 2- amino-2-methyl- 1 -decanol, 2-amino-2-ethyl- 1 -nonanol, 2-amino-2-propyl- 1 -octanol,
  • 2-amino-2-butyl- 1 -heptanol 2-amino-2-methyl- 1 -undecanol, 2-amino-2-ethyl- 1 -decanol, 2-amino-2-propyl- 1-nonanol, 2-amino-2-butyl-l -octanol, 2-amino-2- pentyl-1 -heptanol,
  • 2-amino-2-heptyl- 1 -nonanol 2-amino-2-methyl- 1 -hexadecanol, 2-amino-2-ethyl- 1 - pentadecanol, 2-amino-2-propyl-l-tetradecanol, 2-amino-2-butyl-l-tridecanol, 2-amino-2-pentyl-
  • 2- amino-2-ethyl- 1 -heptadecanol 2-amino-2-propyl- 1 -hexadecanol, 2-amino-2-butyl- 1 - pentadecanol, 2-amino-2-pentyl-l-tetradecanol, 2-amino-2-hexyl-l-tridecanol, 2-amino-2- heptyl- 1 -dodecanol, 2-amino-2-octyl-l -undecanol and mixtures thereof.
  • Preferred alkanolamines include ethanolamines, propanolamines, butanolamines, aminophenols, tris(hydroxymethyl)aminomethane, or mixture thereof. More preferably the alkanolamine is 2,2-amino-l-butanol, 2-amino-2-methyl-l-propanol, 2-amino-2-ethyl-l,3- propanediol, 2-amino- 1-ethanol, l-amino-2-propanol, tris(hydroxymethyl)aminomethane, 2- amino-2-methyl-l,3-propanediol, a monophenolamine (e.g., 4-aminophenol and 2-aminophenol), or mixture thereof.
  • a monophenolamine e.g., 4-aminophenol and 2-aminophenol
  • the amount of epoxy capped prepolymer may vary over a wide range, but typically is from about 1 to 15 weight percent, based on the total weight of the adhesive composition. The amount may be 2 or 3 to 14 or 12 weight percent.
  • the preparation of the epoxy capped prepolymer may be formed by reacting the alkanolamine with the polyepoxide at reaction conditions such that amino hydrogens react with the epoxide groups of the polyepoxide preferentially. This generally means that alkanolamines are reacted with a substantial excess of epoxide groups. Illustratively, if the polyepoxide has 2 epoxides, the amount of polyepoxide to amine is reacted at an excess from about 2: 1 to 12: 1 amine:polyepoxide.
  • the ratio of the epoxide groups of the polyepoxide to the amino hydrogens of the alkanolamine is equal to or greater than 2 to 1.
  • the epoxide/amino hydrogen ratio is 4 to 12 or 6 to 10.
  • the reaction can be performed in the range of 25°C to 150°C. Generally, the reaction is performed at temperatures from about 40°C to 80°C for a sufficient time (e.g., 10 minutes to 2, 3, 5 or 10 hours) but not too high a temperature or too long a time where the hydroxyls from the alkanolamines, or that result from the reaction of the amino groups with the epoxide, react to any great extent.
  • the epoxides react with the amino groups without reacting with the hydroxyls means that less than about 5 to 10% of the hydroxyls are consumed. Preferably, less than 1% of the hydroxyls are consumed and more preferably only trace amounts of the hydroxyls are consumed.
  • the reaction is conducted without solvent by adding the aminoalcohol to an excess of polyepoxide, under an atmosphere of nitrogen, and while agitating.
  • the reaction mixture can then be raised to the appropriate temperature.
  • the reaction is immediately cooled after complete consumption of the alkamolamine, as judged by a variety of analytical techniques.
  • Exemplary analytical techniques include NMR or FTIR spectroscopy, liquid or gas
  • the epoxy capped prepolymer generally has an epoxy equivalent weight (EEW), which illustratively is desirably from about 180 to 500 g/equivalent.
  • EW epoxy equivalent weight
  • the epoxy capped prepolymer generally contains a substantial amount of free epoxy molecules, which may vary over a wide range. Typically, there is about 2% or 5% to 20% or 25% by weight of the epoxy capped prepolymer with the remainder being free polyepoxide.
  • the polyurethane based toughener comprises a polyurethane polymer that is a reaction product of a polyol and an aliphatic diisocyanate, such as 1,6 hexane diisocyanate and isophorone diisocyanate.
  • polyurethane based tougheners in accordance with the present invention include end groups that are either reactive toward the epoxy curatives, or are removed so that the isocyanate groups are available to react with the epoxy curatives.
  • diisocyanates that may be used in the preparation of the polyurethane polymer include aromatic diisocyantes, toluene diisocyanate (TDI) and methylene diphenyl diisocyanate, MDI, aliphatic and cycloaliphatic isocyanates , such as 1,6-hexamethylene diisocyanate (HDI), l-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), and 4,4'-diisocyanato dicyclohexylmethane, (H12MDI or hydrogenated MDI).
  • HDI 1,6-hexamethylene diisocyanate
  • IPDI isophorone diisocyanate
  • H12MDI 4,4'-diisocyanato dicyclohexylmethane
  • the polyol component may comprise polyether polyols, which are made by the reaction of epoxides with an active hydrogen containing starter compounds, or polyester polyols, which are made by the polycondensation of multifunctional carboxylic acids and hydroxyl compounds.
  • the isocyanate groups of the polyurethane-based toughener may be capped or blocked with an end group, such as a phenolic compound, an aminophenolic compound, carboxylic acid group, or hydroxyl group.
  • Preferred capping groups include phenolic compounds, such as bisphenol-A, or diallyl bisphenol-A and diisopropylamine.
  • the polyurethane toughener comprise a polyol component having good flexibility.
  • polyol components having relatively high molecular weights may provide improved flexibility.
  • the polyol may have a molecular weight ranging between 2,000 and 12,000 Daltons, and in particular, between 3,000 and 10,000.
  • the polyol comprises a polyether chain having from 4-12 consecutive carbon atoms between each pair of ether groups, and preferably having from 4-8 consecutive carbon atoms between each pair of ether groups.
  • the polyol component of the polyurethane based toughener may range from about 70 to 90 weight percent, based on the total weight of the polyurethane based toughener.
  • the polyol component of the polyurethane based toughener is from about 72 to 88 weight percent, and more preferably, from about 75 to 85 weight percent, based on the total weight of the polyurethane based toughener.
  • Some exemplary tougheners include bis-phenol blocked PU such as RAM 1087, RAM 965 an isocyanate- terminated polyurethane prepolymer prepared from a polyether polyol and an aliphatic diisocyanate, in which the isocyanate groups are capped with ⁇ , ⁇ -diallyl bisphenol A, and is made as described in Example 13 of EP 308 664, an isocyanate-terminated polyurethane prepolymer prepared from a polyether polyol and an aliphatic diisocyanate, in which the isocyanate groups are capped with bisphenol A, further described as Toughener B in U.S.
  • bis-phenol blocked PU such as RAM 1087, RAM 965 an isocyanate- terminated polyurethane prepolymer prepared from a polyether polyol and an aliphatic diisocyanate, in which the isocyanate groups are capped with ⁇ , ⁇ -diallyl bisphenol A, and is made as described in Example 13 of EP 308
  • the amount of the polyurethane based toughener generally ranges from about 10 to 25 weight percent, based on the total weight of the adhesive composition, and in particular, from about 10 to 20, and more particularly, from about 14 to 18 weight percent, based on the total weight of the adhesive composition.
  • the adhesive may include up to about 25, up to about 20, up to about 18, up to about 16, or up to about 14 weight percent, of the polyurethane based toughener, based on the total weight of the adhesive composition.
  • the adhesive further contains a curing agent.
  • the curing agent is a causes the adhesive to cure (cross-link) when heated to a temperature of at least 80° C, preferably at least 100° C or greater, but does not cause the adhesive to cure or the adhesive cures very slowly at room temperature (about 22° C.) or even at temperatures up to at least 50° C.
  • Suitable curing agents include boron trichloride/amine and boron trifluoride/amine complexes, dicyandiamide, melamine, diallylmelamine, guanamines such as acetoguanamine and benzoguanamine, aminotriazoles such as 3-amino-l,2,4-triazole, hydrazides such as adipic dihydrazide, stearic dihydrazide, isophthalic dihydrazide, semicarbazide, cyanoacetamide, and aromatic polyamines such as diaminodiphenylsulphones.
  • dicyandiamide, isophthalic acid dihydrazide, adipic acid dihydrazide and 4,4'-diaminodiphenylsulphone is particularly preferred.
  • the curing agent is used in sufficient amount to cure the adhesive.
  • the curing agent typically constitutes at least about 1.5 weight percent of the one component adhesive
  • the composition may be at least about 2.5 weight percent.
  • the curing agent desirably constitutes up to about 15 weight percent of the adhesive, more preferably up to about 10 weight percent, and most preferably up to about 6 weight percent.
  • the one component adhesive may contain a catalyst for accelerating the cure of the adhesive.
  • the catalyst is latent in the same way as the curing agent in that it catalyzes the adhesive cure upon heating as described above.
  • preferred epoxy catalysts are ureas such as p-chlorophenyl-N,N-dimethylurea (Monuron), 3 -phenyl- 1,1 -dimethylurea (Phenuron), 3,4-dichlorophenyl-N,N-dimethylurea (Diuron), N-(3-chloro-4-methylphenyl)- ⁇ ', ⁇ '-dimethylurea (Chlortoluron), tert-acryl- or alkylene amines like benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, piperidine or derivates thereof, imidazole derivatives, in general C.sub.
  • a preferred catalyst is 2,4,6- tris(dimethylaminomethyl)phenol integrated into a poly(p-vinylphenol) matrix (as described in European patent EP 0 197 892).
  • the catalyst may be encapsulated or otherwise be a latent type which becomes active only upon exposure to elevated temperatures.
  • the catalyst is present in the adhesive composition in the amount of at least about 0.1 weight percent of the adhesive composition, and most preferably about 0.2 weight percent.
  • the epoxy curing catalyst is present in an amount of up to about 2 weight percent of the adhesive composition, more preferably up to about 1.0 weight percent, and most preferably about
  • the adhesive of the invention may contain various other optional components.
  • fillers, rheology modifiers or pigments, one or more additional epoxy resins and other tougheners such as rubber tougheners such as such as carboxyl-terminated butadiene- acrylonitrile copolymers commonly referred to as CTBN rubber tougheners.
  • a filler, rheology modifier and/or pigment are typically useful in the adhesive composition. These can perform several functions, such as (1) modifying the rheology of the adhesive in a desirable way, (2) reducing overall cost, (3) absorbing moisture or oils from the adhesive or from a substrate to which it is applied, and/or (4) promoting cohesive, rather than adhesive, failure.
  • these materials include calcium carbonate, calcium oxide, talc, coal tar, carbon black, textile fibers, glass particles or fibers, aramid pulp, boron fibers, carbon fibers, mineral silicates, mica, powdered quartz, hydrated aluminum oxide, bentonite, wollastonite, kaolin, fumed silica, silica aerogel or metal powders such as aluminum powder or iron powder.
  • calcium carbonate, talc, calcium oxide, fumed silica and wollastonite are preferred, either singly or in some combination, as these often promote the desired cohesive failure mode.
  • the adhesive composition can further contain other additives such as diluents, plasticizers, extenders, pigments and dyes, fire -retarding agents, thixotropic agents, flow control agents, thickeners such as thermoplastic polyesters, gelling agents such as polyvinylbutyral, adhesion promoters and antioxidants.
  • additives such as diluents, plasticizers, extenders, pigments and dyes, fire -retarding agents, thixotropic agents, flow control agents, thickeners such as thermoplastic polyesters, gelling agents such as polyvinylbutyral, adhesion promoters and antioxidants.
  • Fillers, rheology modifiers, gelling agents, thickeners and pigments preferably are used in an aggregate amount of about 5 weight percent, based on the total weight of the adhesive composition or greater, more preferably about 10 weight percent of the adhesive composition or greater. In one embodiment, such components may preferably be present in an amount of up to about 25 weight percent of the adhesive, more preferably up to about 20 weight percent.
  • Another optional component is a bisphenol compound that has two or more, preferably two, phenolic hydroxyl groups per molecule.
  • suitable bisphenol compounds include, for example, resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (l,l-bis(4-hydroxylphenyl)-l -phenyl ethane), bisphenol F, bisphenol K, tetramethylbiphenol and the like.
  • the bisphenol component can be dissolved into the adhesive composition or present in the form of finely divided particles.
  • the bisphenol component is pre-reacted with an epoxy resin (which may include a rubber-modified epoxy resin, if present) to advance the resin somewhat.
  • the bisphenol component is preferably used in an amount from about 3 to about 35 parts by weight per 100 parts by weight of the rubber component. A preferred amount is from about 5 to about 25 parts by weight per 100 parts by weight of the rubber component.
  • the bisphenol component When added directly into the adhesive composition, it usually constitutes from 0.25 to 2 weight percent, especially 0.4 to 1.5 weight percent, of the adhesive.
  • the adhesive composition may be applied by any convenient technique. It may be applied cold or be applied warm if desired. It may be applied by extruding it from a robot into bead form on the substrate, it may be applied using manual application methods such as a caulking gun, or any other manual application means.
  • the adhesive composition may also be applied using jet spraying methods such as a steaming method or a swirl technique.
  • the swirl technique is applied using an apparatus well known to one skilled in the art such as pumps, control systems, dosing gun assemblies, remote dosing devices and application guns.
  • the adhesive may be applied to the substrate using a streaming process. Generally, the adhesive is applied to one or both substrates. The substrates are contacted such that the adhesive is located between the substrates to be bonded together.
  • the adhesive may be cured by heating to a temperature at which the curing agent initiates cure of the epoxy resin composition.
  • this temperature is about 80° C or above, preferably 100° C or above.
  • the temperature is about 220° C or less, and more preferably about 180° C or less.
  • the adhesive of the invention can be used to bond a variety of substrates together including wood, metal, coated metal, aluminum, a variety of plastic and filled plastic substrates, fiberglass and the like.
  • the adhesive is used to bond parts of automobiles together or parts to automobiles.
  • Such parts can be steel, coated steel, galvanized steel, aluminum, coated aluminum, plastic, fiber composites (e.g., carbon or glass fiber impregnated with epoxy resin composites) and filled plastic substrates.
  • the frame components are often metals such as cold rolled steel, galvanized metals, or aluminum.
  • the components that are to be bonded to the frame components can also be metals as just described, or can be other metals, plastics, composite materials, and the like.
  • Adhesion to brittle metals such as steel coated with galvanneal is of particular interest in the automotive industry. Galvanneal tends to have a zinc-iron surface that is somewhat rich in iron content and is brittle for that reason.
  • a particular advantage of this invention is that the cured adhesive bonds well to metals with a brittle coating, such as galvanneal.
  • Another application of particular interest is the bonding of aerospace components, particularly exterior metal components or other metal components that are exposed to ambient atmospheric conditions during flight.
  • the adhesive composition once cured preferably has a Young's modulus or elastic modulus of at least 1000 MPa as measured according to DIN EN ISO 527-1. More preferably, the Young's modulus is about 1200, 1500 or 2000 MPa or greater.
  • the cured adhesive demonstrates a tensile strength of about 25 MPa or greater, more preferably about 30 MPa or greater, and most preferably about 35 MPa or greater.
  • the lap shear strength of a 0.25 mm thick cured adhesive layer is about 15 MPa or greater, more preferably about 20 MPa or greater, and most preferably about 25 MPa or greater measured according to DIN EN 1465 at room temperature ( ⁇ 23 0 C ⁇ 5°C).
  • EP-MPA Epoxy capped monoisopropanolamine
  • Epoxy capped monoisopropanolamine (15 wt% in D.E.R. TM 383) was prepared as follows and is referred to herein as EP-monoisopropanolamine (EP-MPA).
  • EP-MPA EP-monoisopropanolamine
  • 450 grams of DER383 and 11.94 grams of monoisopropanolamine were added to a 1 L flask equipped with a thermocouple and overhead stirrer and then placed under an atmosphere of nitrogen. Stirring was initiated and an initial aliquot of material was taken for EEW titration. The temperature was then increased to 60 °C by heating mantle, and a slight exotherm was observed, carrying the reaction temperature to approximately 70-75 °C.
  • reaction temperature cooled to 60 °C and this temperature was maintained for the duration of the reaction.
  • the reaction progress was monitored by EEW titration and the prepolymer synthesis was considered to have reached completion after reaching a target equivalent weight of 212.1 g/equivalents coinciding where minimal alcohol would have been reacted.
  • the hot resin was poured into a dry glass jar and stored under an atmosphere of nitrogen.
  • EP-MEA Epoxy capped monoethanolamine
  • Epoxy capped monoethanolamine (15 wt% in D.E.R. TM 383) was prepared as follows and is referred to herein as EP-monoethanolamine (EP-MEA). 450 grams of DER383 and
  • Epoxy capped aminophenol (10 wt% in D.E.R. TM 383) was prepared as follows and is referred to herein as EP- aminophenol (EP-4AP). 195.25 grams of DER383 and 4.75 grams of aminophenol were added to a 500 mL flask equipped with a thermocouple and overhead stirrer and then placed under an atmosphere of nitrogen. Stirring was initiated and an initial aliquot of material was taken for EEW titration. The temperature was then increased to 70 °C by heating mantle for two hours, and then the temperature was raised to 80 °C for three additional hours. The reaction progress was monitored by EEW titration and the prepolymer synthesis was considered to have reached completion after reaching a target equivalent weight of
  • SilquestTM and CarduraTM are a trademarks of Momentive Performance Materials Inc.
  • D.E.R.TM is a trademark of Olin Corporation.
  • AralditeTM is a trademark of Huntsman Advanced Materials.
  • Amicure ® is a registered trademark of Air Products and Chemicals, Inc.
  • Atomite ® is a registered trademark of Imerys Group.
  • Cab-O-Sil ® is a registered trademark of Cabot Corporation.
  • OmicureTM is a trademark of Emerald Performance Materials, LLC.
  • Quicklime CaO, Atomite®, and Cab-O-Sil® TS-720 were added to the mixing cup and mixed at 800 rpm for 30 seconds, followed by 2100 rpm for 2 min. Heat was generated during the mixing process, and the temperature was measured by IR thermometer to ensure that the mixture did not exceed 65 °C. After the mixture had cooled below 45 °C, EP796 was added and mixed at 2100 rpm for 1 min.
  • EP-MPA (15 wt%) - 6.67 13.34 26.68 53.36
  • NC-700 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
  • a mold geometry of a 7" x 7" x 3 mm was filled with the adhesive formulation and placed between two steel plates. The mold was wrapped in aluminum foil and the adhesive formulations were cured by compression molding for 30 min in a pneumatic press at 170 °C.
  • the ASTM D-638 tensile bar geometries were prepared from the cured plaques by a water-jet cutter and the tensile properties were measured with an INSTRON 4505 with a test speed of 0.2 in/min.
  • DMTA data were obtained over the temperature range of -90 °C to 250 °C employing a TA Instruments RSA III analyzer operating at a frequency of 1 Hz and a heating rate of 3
  • Impact Peel specimens were prepared and tested according to the ISO Standard ISO 11343.
  • the substrate used was 0.8 mm thick GMC-5E cold rolled steel supplied by ACT Laboratories, Inc. Test coupons were cut into 20mm x 100mm strips. 10 mil thick Teflon tape was applied to the end and middle of one coupon marking off the bonding area of
  • Impact testing was performed with an Instron Dynatup Crush Tower. The specimens were placed inverted on a fixed wedge. The crosshead with the load cell and 501b weight attached was dropped from a fixed height at a velocity of 6.7 ft/s. The cleavage force was measured and converted to N/mm of bond line. Specimens tested at -40°C were condition for 1 hour in a freezer set to -43 °C and then immediately tested at room temperature.
  • Lap shear specimens were prepared and tested according to the ISO Standard ISO 4587.
  • the substrate used was 1.6 mm thick GMC-5E cold rolled steel supplied by ACT Laboratories, Inc.
  • Test coupons were cut into 1 in. X 4 in. strips.
  • the 1 ⁇ 2 in. bonding overlap section of each coupon was cleaned with acetone.
  • the adhesive was applied to the bonding section of the coupon, and 10 mil glass bead spacers were applied on top to control the bond gap.
  • Another coupon was laid on top, and the specimen was assembled in a fixture yielding a 1 ⁇ 2 in. overlap.
  • the edges of the assembly were scraped clean using a spatula and held together with clips while curing for a 30 minute 170°C bake cycle in a programmable Blue M Electric Oven programmed with repeatable heat up and cool down cycles.
  • the loads to failure of the lap shears were measured using an Instron® 5500R Materials Testing System (Instron Corporation). Mechanical grips were used to hold the lap shear samples in place. The distance between the grips was seven inches. The crosshead speed was 0.5 in./min. The computer measured the load as a function of crosshead displacement and loads were converted to pounds of force per square inch of bond area. After each lap shear was tested to failure, a failure mode was assigned by visual evaluation. Failure modes were classified as either adhesive failure or cohesive failure and a percentage was assigned.
  • Comparative Example 1 lacking the epoxy capped prepolymer, while maintaining if not improving the tensile modulus.
  • the modulus and impact peel results are comparable to the Comparative Example 1, but Inventive Example 1 has a significantly improved (higher) tensile strength.
  • Table 5 show the results of varying the amount of epoxy capped prepolymer that was capped with monoisopropanolamine.
  • the results show (Inventive Example 4) that even at low concentrations of the epoxy capped prepolymer (-1% by weight of the adhesive composition), the properties are improved over an adhesive composition (Comparative Example 2) having the same components other than the capped prepolymer.
  • the results also show that increasing the amount of the epoxy capped prepolymer further improves the properties and in particular the minus 40°C impact peel without sacrificing tensile modulus while even improving the modulus.

Abstract

La présente invention concerne une composition adhésive époxyde monoconstituant qui est constituée d'une résine époxyde, d'un durcisseur à base de polyuréthane, d'un agent de durcissement époxyde, et d'un prépolymère coiffé par des époxydes constitué du produit de réaction d'un polyépoxyde et d'une alcanolamine dans laquelle l'amine est une amine primaire. Le prépolymère coiffé par des époxydes peut être obtenu en mélangeant et en faisant réagir une alcanolamine avec un polyépoxyde à un excès stœchiométrique du polyépoxyde par rapport à l'alcanolamine, ledit excès stœchiométrique ayant un rapport en groupes époxydes/amino d'au moins 2 sur 1 de sorte que les groupes amino réagissent tandis que les hydroxyles présents dans l'alcanolamine ne réagissent pas. La composition adhésive peut conférer une résistance au pelage par impact améliorée tout en ne réduisant sensiblement pas le module élastique. L'adhésif peut être utilisé pour relier des composants métalliques dans des cadres d'automobiles et analogues.
PCT/US2017/057951 2016-10-25 2017-10-24 Adhésif époxyde présentant une résistance aux chocs à basse température améliorée WO2018081032A1 (fr)

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CN106010135A (zh) * 2016-08-07 2016-10-12 薛常刚 一种阴极电泳涂料

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