Storage stable heat activated quaternary ammonium catalysts for epoxy cure

Abstract

The present invention relates to a catalyst composition for curing epoxy group containing compounds comprising a base and a quaternary ammonium salt, of Formula (I): ##STR00001##
with R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, Y, A and X being as defined herein. Also encompassed are adhesive compositions containing said catalyst composition and the use of the catalyst composition.

Claims

1. Catalyst composition comprising: (a) a base; and (b) a quaternary ammonium salt represented by Formula (I): ##STR00005## wherein R.sup.1, R.sup.2 and R.sup.3 are independently from each other selected from the group consisting of linear or branched, substituted or unsubstituted alkyl with 1 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkenyl with 3 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkoxy with 1 to 20 carbon atoms and substituted or unsubstituted aryl with 6 to 20 carbon atoms; two of R.sup.1, R.sup.2 and R.sup.3 may combine to form together with the nitrogen atom to which they are attached a substituted or unsubstituted 5-to 10-membered ring; R.sup.4 is selected from the group consisting of hydrogen, linear or branched, substituted or unsubstituted alkyl with 1 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkenyl with 3 to 20 carbon atoms and substituted or unsubstituted aryl with 6 to 20 carbon atoms; Y is C or N.sup.+, provided that if Y is N.sup.+, A is O and R.sup.5 is O.sup.; A is O or CR.sup.6R.sup.7; R.sup.5 is selected from the group consisting of hydrogen, OH, linear or branched, substituted or unsubstituted alkyl with 1 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkenyl with 3 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkoxy with 1 to 20 carbon atoms, and substituted or unsubstituted aryl with 6 to 20 carbon atoms, or, if Y is N.sup.+ and A is O, R.sup.5 is O.sup.; R.sup.6 and R.sup.7 are independently from each other selected from the group consisting of hydrogen, halogen, nitro, NRR, cyano, C(O)R, C(O)OR, (CO)NRR, NRC(O)R, OC(O)R, linear or branched, substituted or unsubstituted alkyl with 1 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkenyl with 3 to 20 carbon atoms, linear or branched, substituted or unsubstituted alkoxy with 1 to 20 carbon atoms, and substituted or unsubstituted aryl with 6 to 20 carbon atoms; or R.sup.5 and R.sup.6 may combine to form together with the carbon atoms to which they are attached a substituted or unsubstituted 5- to 10-membered cycloalkenyl, heteroalicyclic or heteroaryl ring; R and R are independently selected from H, alkyl with 1 to 20 carbon atoms, alkenyl with 2 to 20 carbon atoms, alkynyl with 2 to 20 carbon atoms, aryl with 6 to 14 carbon atoms, cycloalk(en)yl with 3 to 8 carbon atoms, 5- to 14-membered heteroaryl, comprising 1 to 4 heteroatoms selected from N, O, and S, and 5- to 14-membered heterocycloalk(en)yl, comprising 1 to 4 heteroatoms selected from N, O, and S; and X is an anion.

2. The catalyst composition according to claim 1, wherein the quaternary ammonium salt is represented by Formula (II) ##STR00006## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.5, R.sup.6, R.sup.7 and X are as defined in claim 1.

3. The catalyst composition according to claim 1, wherein the quaternary ammonium salt is represented by Formula (III): ##STR00007## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.5 and X are as defined above.

4. The catalyst composition according to claim 1, wherein R.sup.1, R.sup.2 and/or R.sup.3 are methyl or ethyl.

5. The catalyst composition according to claim 1, wherein the anion X is selected from the group consisting of dicyandiamide-anion, F.sup., Cl.sup., Br.sup., I.sup.,OH.sup., HSO.sub.3.sup., SO.sub.3.sup.2 , SO.sub.4.sup.2, NO.sub.2.sup., NO.sub.3.sup., PO.sub.4.sup.3, BF.sub.4.sup., SbF.sub.6.sup., PF.sub.6.sup., ClO.sub.4.sup., acetate, citrate, formate, glutarate, lactate, maleate, malonate, oxalate, pyruvate, and tartrate.

6. The catalyst composition according to claim 2 or 3, wherein (a) the ammonium compound is a compound represented by Formula (II) wherein R.sup.5, R.sup.6 and R.sup.7 are hydrogen, or R.sup.5 and R.sup.7 are hydrogen and R.sup.6 is C(O)OR, with R being C.sub.1-C.sub.20 alkyl; (b) the ammonium compound is a compound represented by Formula (III) and R.sup.5 is independently selected from the group consisting of substituted or unsubstituted phenyl or C.sub.1-20 alkoxy; or (c) the ammonium compound is selected from the group consisting triethylallyl ammonium, triethyl (4-crotonic acid ethyl ester)ammonium, triethyl (2-phenylethan-2-one) ammonium, triethyl (4-nitro-2-phenylethan-2-one) ammonium, triethyl (4-chloro-2-phenylethan-2-one) ammonium, and triethyl (2-acetic acid ethyl ester)ammonium, with X being an anion.

7. The catalyst composition according to claim 1, wherein the base is a liquid base and is selected from the group consisting of metal alkoxides, aqueous NaOH, KOH, Ca(OH).sub.2, Na.sub.2CO.sub.3, Na.sub.3PO.sub.4 and combinations thereof.

8. The catalyst composition according to claim 1, wherein a combination of base and ammonium compound is selected from the group consisting of: triethylallyl ammonium bromide and titanium tetrabutoxide; triethylallyl ammonium bromide and titanium tetraisopropoxide; triethylallyl ammonium bromide and Na methoxylate; triethyl-(2-phenylethan-2-one) ammonium bromide and titanium tetraisopropoxide; triethyl-(4-chloro-2-phenylethan-2-one) ammonium bromide and titanium tetraisopropoxide; triethylallyl ammonium hexafluoroantimonate and titanium tetraisopropoxide; triethyl-(4-chloro-2-phenylethan-2-one) ammonium hexafluoroantimonate and titanium tetraisopropoxide; triethyl-(4-nitro-2-phenylethan-2-one) ammonium hexafluoroantimonate and titanium tetraisopropoxide; triethyl (2-acetic acid ethyl ester)ammonium bromide and titanium tetraisopropoxide; triethyl (2-acetic acid ethyl ester)ammonium hexafluoroantimonate and titanium tetraisopropoxide; triethyl (4-crotonic acid ethyl ester) ammonium bromide and titanium tetraisopropoxide; and triethyl (4-crotonic acid ethyl ester)ammonium hexafluoroantimonate and titanium tetraisopropoxide.

9. The catalyst composition according to claim 1, wherein the catalyst composition further comprises a second curing agent.

10. The catalyst composition according to claim 9, wherein the catalyst composition further comprises an accelerator selected from the group consisting of urea derivatives, imidazole derivatives, and mixtures thereof.

11. A method of curing epoxy resins comprising curing epoxy resins with the catalyst composition according to claim 1, wherein the epoxy resins are selected from the group consisting of diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (1,1-bis(4-hydroxylphenyl)-1-phenyl ethane), bisphenol F, bisphenol K, bisphenol M, bisphenol S, tetramethylbiphenol; diglycidyl ethers of alkylene glycols with 2 to 20 carbon atoms 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 dicyclopentadiene-substituted phenol resins, and any combination thereof.

12. The method of curing epoxy resins according to claim 11, wherein the epoxy resins are cured at a temperature from about 50 to about 180 C.

13. Adhesive composition comprising the catalyst composition according to claim 1 and at least one epoxy resin, wherein the at least one epoxy resin is selected from the group consisting of diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (1,1-bis(4-hydroxylphenyl)-1-phenyl ethane), bisphenol F, bisphenol K, bisphenol M, bisphenol S, tetramethylbiphenol; diglycidyl ethers of alkylene glycols with 2 to 20 carbon atoms 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 dicyclopentadiene-substituted phenol resins, and any combination thereof.

Description

EXAMPLES

(1) Stability Test as Accelerator for Dicyandiamide

(2) To a suspension of 20 g of a Bisphenol-A-diglycidylether (DER 331 from Dow), 1.4 g of dicyandiamide (Dyhard 100SH from Alz Chem) and 0.06 g of the tested ammonium salt, an amount of titanium tetraisopropoxide (Alfa Aesar) equimolar to the ammonium salt was added. The compositions were mixed in a vacuum speed mixer (Thinky AVR 310) for one minute at 2000 rpm and a vacuum below 50 mbar. For the comparative examples 20 g of a Bisphenol-A-diglycidylether (DER 331 from Dow), 1.4 g of dicyandiamide (Dyhard 100SH from Alz Chem) and 0.06 g of the tested urea accelerators (UR300 or UR 700 from Alz Chem) are mixed in the speed mixer as described above.

(3) 2 g of the described mixtures were put into aluminium cups so that the resulting level of liquid in below 5 mm to prevent overheating due to reaction exotherm. The cups were placed in convection oven and the mixtures were cured for 30 minutes at 180 C. After cooling to room temperature all mixtures are manually evaluated.

(4) To check the stability of the formulation the uncured mixtures were stored in a convection oven at 50 C. Samples were taken from the mixtures on a regular basis and the viscosity was measured using a plate rheometer in oscillation mode at 25 C. A three fold increase in viscosity compared to the result measured before the storage was rated as the limit of shelf life at 50 C.

(5) TABLE-US-00001 Storage time at 50 C. until Accelerator triple initial viscosity Dyhard UR 300 8 days Dyhard UR 700 20 days Triethylallylammoniumbromide >30 days

(6) Test of Curing Behavior as Sole Hardener

(7) To a suspension of 9 g of a Bisphenol-A-diglycidyether (DER 331 from Dow), 1 g mineral filler (Casiflux A25 from Ankerport n.v.) and 0.5 g of the tested ammonium salt an amount of titanium tetraisopropoxide (Alfa Aesar) equimolar to the ammonium salt was added. The composition was mixed in a vacuum speed mixer (Thinky AVR 310) for one minute at 2000 rpm and a vacuum below 50 mbar.

(8) The reaction exotherm of the mixture was measured via DSC. Multiple portions of the reaction mixtures were cured at various temperatures for 30 minutes each in a convection oven. The resulting exotherm of these samples is again measured via DSC. The percentage of the difference between the total reaction exotherm and the residual exotherm after oven cure compared to the total reaction exotherm is calculated as the degree of cure in percent.

(9) TABLE-US-00002 Degree of cure after 30 Minutes at the given temperature in C. in % 180 170 160 150 140 130 120 110 Triethylallylammoniumbromide 100 100 100 100 100 70.6 68.7 38.3 Triethylbenzylammoniumbromide 100 100 100 100 100 91.4 90.5 72.5 Triethyl-(2-phenylethan-2- 100 100 100 100 100 95.6 93.4 93.7 on)ammoniumbromide Triethyl-(4-nitro-2-phenylethan- 100 100 100 12.5 2-on)ammoniumbromide Triethyl-(4-chloro-2-phenylethan-2- 100 100 100 97 82 75 on)ammoniumbromide Triethyl-4- 100 100 100 100 82 bromobenzylammniumbromide Triethyl-4- 100 100 100 95 80 nitrobenzylammoniumbromide Triethyl-(4-crotonic-ethyl- 100 100 100 100 100 100 100 ester)ammoniumbromide Triethyl-(2-acetic-ethyl- 100 100 100 100 91 80 ester)ammoniumbromide Triethylbenzylammonuimhexafluoroantimonate 100 94 Triethylallylammoniumhexafluoroantimonate 100 92 Triethyl-(4-nitro-2-phenylethan-2- 100 on)ammoniumhexafluoroantimonate Triethyl-(4-chloro-2-phenylethan-2- 100 71 on)ammoniumhexafluoroantimonate Triethyl-4- 100 98.2 bromobenzylammoniumbromide hexafluoroantimonate