AMIDINE CATALYST FOR CURABLE COMPOSITIONS

Abstract

The present invention relates to an amidine of the formula (I) and its use as a catalyst for crosslinking a curable composition. The amidine of the formula (I) contains at least one aliphatic amidine group. It is substantially odorless and nonvolatile at room temperature and accelerates the crosslinking of curable compositions very efficiently, without impairing the storage stability of the compositions. It is particularly suitable for compositions based on polymers containing silane groups, with which it is compatible, as a result of which such compositions do not have a tendency to separation or migration or evaporation of the catalyst.

Claims

1. An amidine of the formula (I) ##STR00032## wherein p is 1 and r is 0, L is a monovalent hydrocarbyl radical having 1 to 6 carbon atoms and containing an alkoxysilane group, Q is a glycidoxy group, Q is a divalent connecting unit formed from the reaction of a reactive Q group with HZ, and Z is an aliphatic amidine group bonded via a nitrogen atom.

2. An amidine as claimed in claim 1, wherein Q is ##STR00033##

3. An amidine as claimed in claim 1, wherein said amidine is of formula (I): ##STR00034## wherein E.sup.5 is an alkylene radical having 1 to 6 carbon atoms, E.sup.6 is an alkyl radical having 1 to 4 carbon atoms, u is 0 or 1, and v is 2 or 3, with the proviso that (u+v) equals 3, and Z is an aliphatic amidine group bonded via a nitrogen atom.

4. An amidine as claimed in claim 1, wherein L is triethoxysilylpropyl or trimethoxysilylpropyl.

5. An amidine as claimed in claim 1, wherein Z is ##STR00035## wherein R.sup.1 is a hydrogen radical or an alkyl or cycloalkyl or aralkyl radical having 1 to 8 carbon atoms or together with R.sup.2 is R.sup.4, R.sup.2 is a hydrogen radical or an alkyl, cycloalkyl or aralkyl radical which has 1 to 18 carbon atoms and optionally contains ether oxygen or tertiary amine nitrogen, or together with R.sup.1 is R.sup.4, R.sup.3 is a hydrogen radical or an alkyl or cycloalkyl or aralkyl radical having 1 to 12 carbon atoms, wherein R.sup.4 is an optionally substituted 1,2-ethylene, 1,3-propylene or 1,4-butylene radical having 2 to 12 carbon atoms, and wherein R.sup.2 and R.sup.3 together may also be an alkylene radical having 3 to 6 carbon atoms.

6. An amidine as claimed in claim 5 wherein R.sup.1 and R.sup.2 together are R.sup.4.

7. A process for preparing the amidine of the formula (I) as claimed in claim 1, wherein at least one amidine of the formula HZ is reacted with at least one functional compound of the formula LQ].sub.(p+r) wherein p is 1 and r is 0, L is a monovalent hydrocarbyl radical having 1 to 6 carbon atoms and containing an alkoxysilane group, and Q is a glycidoxy group.

8. The process as claimed in claim 7, wherein the amidine of the formula HZ has the formula ##STR00036##

9. A method comprising applying as catalyst for the crosslinking of a curable composition the amidine of the formula (I) as claimed in claim 1.

10. A method as claimed in claim 9, wherein the curable composition is an epoxy resin composition or a polyurethane composition or an epoxy resin/polyurethane composition or a cyanate ester resin composition or a composition containing silane groups.

11. A method as claimed claim 10, wherein the curable composition is a composition based on polymers containing silane groups selected from the group consisting of polyorganosiloxanes having terminal silane groups and organic polymers containing silane groups.

12. A curable composition comprising at least one amidine of the formula (I) as claimed in claim 1.

13. The composition as claimed in claim 12, wherein it further comprises at least one polymer containing silane groups.

14. The composition as claimed in claim 12, wherein it is an adhesive or a sealant or a coating.

15. A method as claimed in claim 9, wherein the curable composition is a polyurethane composition or a composition containing silane groups.

Description

EXAMPLES

[0310] Adduced hereinafter are working examples which are intended to elucidate the invention described in detail. It will be appreciated that the invention is not restricted to these described working examples.

[0311] Standard climatic conditions refer to a temperature of 231 C. and a relative air humidity of 505%.

[0312] EEW stands for epoxy equivalent weight.

[0313] .sup.1H NMR spectra were measured on a spectrometer of the Bruker Ascend 400 type at 400.14 MHz; the chemical shifts b are reported in ppm relative to tetramethylsilane (TMS). Coupling constants J are reported in Hz. No distinction was made between true coupling and pseudo-coupling patterns. Infrared spectra (FT-IR) were measured on a Nicolet iS5 FT-IR instrument from Thermo Scientific equipped with a horizontal ATR measurement unit with a diamond crystal. Liquid samples were applied undiluted as films; solid samples were dissolved in CH.sub.2Cl.sub.2. The absorption bands are reported in wavenumbers (cm.sup.1) (measurement window: 4000-650 cm.sup.1).

[0314] The skin time (ST) was determined by applying a few grams of the composition to cardboard in a layer thickness of about 2 mm and measuring, under standard climatic conditions, the time until, when the surface of the composition was gently tapped by means of an LDPE pipette, there were for the first time no residues remaining any longer on the pipette.

[0315] The characteristics of the surface were tested by touch.

[0316] The mechanical properties of tensile strength, elongation at break and modulus of elasticity (at 0-5% and at 0-50% or 0-100% elongation) were measured in accordance with DIN EN 53504 at a pulling speed of 200 mm/min.

[0317] Functional Compounds Used: [0318] PGE phenyl glycidyl ether (from Sigma-Aldrich) [0319] GLYEO 3-glycidoxypropyltriethoxysilane (Dynasylan GLYEO, from Evonik) [0320] TBA tert-butyl acrylate (from Sigma-Aldrich) [0321] THFMA tetrahydrofurfuryl methacrylate (from Sigma-Aldrich) [0322] TMPTA 1,1,1-trimethylolpropane triacrylate (SR-351, from Sartomer) [0323] Y-9936 3-methacryloyloxypropyltriethoxysilane (Silquest Y-9936, from Momentive) [0324] NAM 4-acryloylmorpholine (from Sigma-Aldrich) [0325] DEM diethyl maleate (from Sigma-Aldrich)

Preparation of Amidines of the Formula HZ

Amidine HZ-1: 2-Methyl-1 1,4,5,6-tetrahydropyrimidine

[0326] In a round-bottom flask, 7.58 g of propane-1,3-diamine, 16.37 g of trimethyl orthoacetate and 0.60 g of lanthanum(III) trifluoromethanesulfonate were mixed and the mixture was heated to 100 C. while stirring for 24 hours. Thereafter, the reaction mixture was freed of the volatile constituents under reduced pressure.

[0327] This gave 5.97 g of a white solid.

[0328] .sup.1H NMR (CDCl.sub.3): 1.75 (quint, 2H, J=5.8, NCH.sub.2CH.sub.2CH.sub.2N), 1.83 (s, 3H, CH.sub.3), 3.30 (t, 4H, J=5.8, NCH.sub.2).

[0329] FT-IR: 3214, 3177, 2996, 2925, 2843, 1630, 1542, 1475, 1438, 1380, 1360, 1322, 1294, 1273, 1204, 1191, 1139, 1114, 1095, 1035, 1009, 977, 915, 875, 839, 731.

Preparation of Amidines of the Formula (I)

Amidine K-1: 1-(2-Hydroxy-3-phenoxyprop-1-yl)-2-methyl-1,4,5,6-tetrahydropyrimidine

[0330] In a round-bottom flask, 1.26 g of amidine HZ-1 were mixed with 1.93 g of PGE and heated to 80 C. for 3 hours. This gave an odorless, yellow oil of high viscosity.

[0331] FT-IR: 3060, 2925, 2852, 2714, 1598, 1586, 1494, 1430, 1379, 1359, 1316, 1299, 1241, 1172, 1153, 1077, 1036, 1020, 951, 918, 881, 814, 751, 690.

Amidine K-2: 1-(2-Hydroxy-3-(3-triethoxysilylpropoxy)prop-1-yl)-2-methyl-1,4,5,6-tetrahydropyrimidine

[0332] In a round-bottom flask, 1.55 g of amidine HZ-1 were mixed with 4.21 g of GLYEO and heated to 100 C. until, after 3.5 hours, no GLYEO was detectable any longer by means of gas chromatography. This gave an odorless yellow oil. .sup.1H NMR (CDCl.sub.3): 0.62 (br m, 2H, CH.sub.2Si), 1.20 (t, 9H, J=6.8, CH.sub.2CH.sub.3), 1.6-1.75 (m, 2H, CH.sub.2CH.sub.2Si), 1.77-1.85 (m, 2H, NCH.sub.2CH.sub.2CH.sub.2N), 1.99 (s, 3H, NCCH.sub.3), 3.22-3.3 (m, 6H, CH.sub.2N), 3.3-3.5 und 3.65 (m, 4H, CH.sub.2OCH.sub.2), 3.81 (q, 6H, J=6.9, SiOCH.sub.2), 4.16 (br m, 1H, CHOH).

[0333] FT-IR: 2971, 2925, 2882, 2863, 1615, 1550, 1482, 1433, 1379, 1318, 1294, 1261, 1194, 1164, 1100, 1074, 1031, 951, 880, 850, 772, 655.

Amidine K-3: tert-Butyl 3-(2-methyl-1,4,5,6-tetrahydropyrimidin-1-yl)propionate

[0334] In a round-bottom flask, 2.20 g of amidine HZ-1 were mixed with 2.72 g of TBA and heated to 100 C. until, after 5 hours, no TBA was detectable any longer by means of gas chromatography. Thereafter, the reaction mixture was freed of the volatile constituents under reduced pressure. This gave an odorless yellow oil.

[0335] .sup.1H NMR (CDCl.sub.3): 1.47 (s, 9H, C(CH.sub.3).sub.3), 1.81 (t, 2H, J=5.8, NCH.sub.2CH.sub.2CH.sub.2N), 1.99 (s, 3H, NCCH.sub.3), 2.44 (t, 2H, J=7.3, CH.sub.2CO), 3.17 (t, 2H, J=5.9, NCH.sub.2.sup.Cy), 3.27-3.32 (m, 2H, NCH.sub.2.sup.Cy), 3.45 (t, 2H, J=7.2, NCH.sub.2CH.sub.2CO).

[0336] FT-IR: 3220, 2974, 2929, 2848, 1723, 1669, 1618, 1551, 1422, 1366, 1316, 1281, 1253, 1211, 1150, 1119, 1083, 1046, 1008, 988, 953, 922, 882, 845, 753, 695.

Amidine K-4: Tetrahydrofurfuryl 3-(2-methyl-1,4,5,6-tetrahydropyrimidin-1-yl)-2-methylpropionate

[0337] In a round-bottom flask, 2.03 g of amidine HZ-1 were mixed with 3.36 g of THFMA and heated to 100 C. until, after 5 hours, no THFMA was detectable any longer by means of gas chromatography. Thereafter, the reaction mixture was freed of the volatile constituents under reduced pressure. This gave an odorless orange oil.

[0338] FT-IR: 3292, 2930, 2860, 1732, 1696, 1638, 1615, 1564, 1496, 1440, 1377, 1361, 1319, 1287, 1259, 1208, 1173, 1140, 1068, 1031, 986, 952, 919, 885, 841, 814, 724, 688.

Amidine K-5: Reaction mixture comprising 1,1,1-trimethylolpropane bis(3-(2-methyl-1 1,4,5,6-tetrahydropyrimidin-1-yl)propionate) acrylate

[0339] In a round-bottom flask, 2.45 g of amidine HZ-1, 3.56 g of TMPTA and 10 mL of tetrahydrofuran were mixed and heated to 80 C. until, after 24 hours, no TMPTA was detectable any longer by means of gas chromatography. Thereafter, the reaction mixture was freed of the volatile constituents under reduced pressure. This gave an odorless, yellow oil of high viscosity.

[0340] FT-IR: 3258, 2928, 2853, 1729, 2696, 1637, 1613, 1554, 1494, 1443, 1382, 1319, 1284, 1206, 1171, 1119, 1048, 1030, 992, 949, 914, 885, 852, 841, 778, 713, 686.

Amidine K-6: 3-Triethoxysilylpropyl 3-(2-methyl-1,4,5,6-tetrahydropyrimidin-1-yl)-2-methylpropionate

[0341] In a round-bottom flask, 1.97 g of amidine HZ-1, 5.15 g of Y-9936 and 8 ml of tetrahydrofuran were mixed and heated to 90 C. for 6 hours. Thereafter, the reaction mixture was freed of the volatile constituents under reduced pressure.

[0342] This gave an odorless yellow oil.

[0343] FT-IR: 3180, 2971, 2927, 2883, 1731, 1720, 1637, 1619, 1566, 1497, 1440, 1383, 1319, 1295, 1254, 1166, 1075, 1018, 951, 886, 841, 765, 690.

Amidine K-7: 3-(2-Methyl-1,4,5,6-tetrahydropyrimidin-1-yl)-1-morpholinopropan-1-one

[0344] In a round-bottom flask, 1.16 g of amidine HZ-1 and 1.68 g of NAM were mixed and heated to 80 C. for 4 hours. This gave an odorless yellow oil which solidified when left to stand at room temperature.

[0345] .sup.1H NMR (CDCl.sub.3): 1.80-1.87 (m, 2H, NCH.sub.2CH.sub.2CH.sub.2N), 2.01 (s, 3H, CH.sub.3), 2.53 (t, 2H, J=7.3, CH.sub.2CO), 3.16-3.32 and 3.27-3.34 (2m, 22 H, NCH.sub.2CH.sub.2CH.sub.2N), 3.44-3.5 (m, 2H, CH.sub.2N.sup.morpholine), 3.53 (t, 2H, J=7.5, NCH.sub.2CH.sub.2CO), 3.6-3.65 (m, 2H, CH.sub.2N.sup.morpholine), 3.66-3.7 (m, 4H, CH.sub.2O).

[0346] FT-IR: 3177, 2924, 2851, 1611, 1424, 1380, 1358, 1316, 1298, 1270, 1230, 1214, 1113, 1085, 1068, 1025, 1008, 982, 845, 915, 882, 847, 790, 720.

Amidine K-8: Diethyl 2-(2-methyl-1,4,5,6-tetrahydropyrimidin-1-yl)succinate

[0347] In a round-bottom flask, 1.84 g of amidine HZ-1 and 3.28 g of DEM were mixed and heated to 60 C. until, after 1 hour, no DEM was detectable any longer by means of thin-layer chromatography. This gave an odorless orange oil.

[0348] FT-IR: 3221, 2979, 2933, 2853, 1729, 1674, 1625, 1568, 1502, 1475, 1442, 1414, 1393, 1361, 1295, 1269, 1156, 1096, 1026, 974, 957, 882, 824, 792, 777, 735, 690.

Preparation of Polyethers Containing Silane Groups

Polymer STP-1

[0349] With exclusion of moisture, 1000 g of Acclaim 12200 polyol (polyoxypropylenediol having a low level of unsaturation, from Bayer; OH number 11.0 mg KOH/g), 43.6 g of isophorone diisocyanate (IPDI; Vestanat IPDI, from Evonik), 126.4 g of diisodecyl phthalate (DIDP) and 0.1 g of bismuth tris(neodecanoate) (10% by weight in DIDP) were heated up to 90 C. while stirring constantly and left at this temperature until the content of free isocyanate groups determined by titrimetry had reached a stable value of 0.63% by weight. Subsequently, 63.0 g of diethyl N-(3-trimethoxysilylpropyl)-aminosuccinate (adduct formed from 3-aminopropyltrimethoxysilane and diethyl maleate; prepared according to the details in U.S. Pat. No. 5,364,955) were mixed in and the mixture was stirred at 90 C. until it was no longer possible to detect any free isocyanate by means of FT-IR spectroscopy. The polyether containing trimethoxysilane groups thus obtained, having a silane equivalent weight of about 6880 g/eq (calculated from the amounts used), was cooled down to room temperature and stored with exclusion of moisture.

[0350] Commercial Catalysts Used:

[0351] DBU 1,8-diazabicyclo[5.4.0]undec-7-ene (Lupragen N 700, from BASF)

[0352] TMG 1,1,3,3-tetramethylguanidine (from Sigma-Aldrich)

[0353] Compositions Based on Polymers Containing Silane Groups:

[0354] Comparative examples in tables 1 to 4 are indicated by (Ref).

[0355] Compositions Z1 to Z10:

[0356] A composition composed of 96.5 g of polymer STP-1, 0.5 g of vinyltrimethoxysilane and 3.0 g of 3-aminopropyltrimethoxysilane was blended with various catalysts in the amount specified according to table 1, and the mixture was tested for viscosity and skin time (ST) under standard climatic conditions, before and after storage. The skin time serves as a measure of the activity of the catalyst in relation to the crosslinking reaction of the silane groups, i.e. of the crosslinking rate; the change in viscosity and the skin time after storage are a measure of storage stability. In addition, the mixture applied, after 24 hours under standard climatic conditions, was tested as to whether the surface was dry as desired or whether a greasy film had formed, which is a sign of the exudation of the catalyst owing to poor compatibility with the cured polymer, and/or whether the surface was tacky, which is a sign of incomplete curing. In addition, the mixture was used to produce a film of thickness 2 mm, which was left to cure under standard climatic conditions for 7 days and tested for mechanical properties. The results are shown in tables 1 and 2. Comp. stands for composition.

TABLE-US-00001 TABLE 1 Viscosity [Pa .Math. s] ST Comp. Catalyst Amount Concentration.sup.1 fresh stored.sup.2 increase fresh stored.sup.2 Z1 Amidine K-1.sup.3 0.46 g 1.9 29.2 30.5 4% 20 24 Z2 Amidine K-2 0.69 g 1.9 22.0 28.3 29% 27 29 Z3 Amidine K-3 0.41 g 1.9 21.3 25.5 20% 29 32 Z4 Amidine K-4 0.49 g 1.9 21.9 29.1 33% 30 42 Z5 Amidine K-5 0.48 g 1.9 30.6 35.4 16% 53 54 Z6 Amidine K-6 0.71 g 1.9 29.3 32.1 10% 28 29 Z7 Amidine K-7.sup.3 0.44 g 1.9 30.0 38.0 27% 25 21 Z8 Amidine K-8 0.50 g 1.9 30.3 34.5 14% 29 30 Z9 (ref.) DBU 0.28 g 1.9 27.2 36.9 36% 25 29 Z10 (ref.) TMG 0.21 g 1.9 22.3 24.6 10% 65 75 .sup.1mmol of amidine or guanidine groups per 100 g of polyether containing silane groups. .sup.2for 7 days at 60 C. in a closed container. .sup.3as a solution (30% by wt.) in N-ethylpyrrolidone.

TABLE-US-00002 TABLE 2 Surface Tensile Elongation Modulus of elasticity Comp. after 24 h strength at break 0-5% 0-50% Z1 dry 0.67 MPa 89% 1.29 MPa 0.82 MPa Z2 almost dry 0.71 MPa 100% 1.23 MPa 0.82 MPa Z3 almost dry 0.68 MPa 95% 1.25 MPa 0.80 MPa Z4 almost dry 0.73 MPa 110% 1.25 MPa 0.79 MPa Z5 dry 0.78 MPa 126% 1.21 MPa 0.79 MPa Z6 dry 0.82 MPa 99% 1.26 MPa 0.83 MPa Z7 dry 0.69 MPa 88% 1.22 MPa 0.81 MPa Z8 dry 0.70 MPa 95% 1.17 MPa 0.82 MPa Z9 (ref.) greasy 0.58 MPa 72% 1.16 MPa 0.77 MPa Z10 (ref.) tacky 0.62 MPa 90% 1.19 MPa 0.75 MPa

[0357] Compositions Z11 and Z12

[0358] In a round-bottom flask, 71.1 g of an OH-terminated linear polydimethylsiloxane having a viscosity of about 50,000 mPas at 23 C. (Wacker Silicone Rubber Polymer FD 50, from Wacker) were blended with 2.6 g of vinyltris(methylethylketoximo)silane and mixed under reduced pressure for 15 minutes. 26.3 g of trimethylsilyl-terminated polydimethylsiloxane (Wacker AK 100 silicone oil, from Wacker) were stirred into the polydimethylsiloxane having vinylbis(methylethylketoximo)silyl end groups that was obtained in this way. This mixture was blended with various catalysts according to table 3 below and, as described for composition Z1, tested for viscosity, skin time (ST), surface characteristics and mechanical properties. The results are shown in tables 3 and 4. Comp. stands for composition.

TABLE-US-00003 TABLE 3 Viscosity [Pa .Math. s] ST Comp. Catalyst Amount Concentration.sup.1 fresh stored.sup.2 increase fresh stored.sup.2 Z11 Amidine K-2 0.15 g 0.6 13.1 9.6 27% 23 27 Z12 (ref.) DBU 0.06 g 0.6 13.0 10.2 22% 13 14 .sup.1mmol of amidine groups per 100 g of ketoximato-polydimethylsiloxane polymer. .sup.2for 7 days at 70 C. in a closed container.

TABLE-US-00004 TABLE 4 Surface Tensile Elongation Modulus of elasticity Comp. after 24 h strength at break 0-5% 0-50% Z11 dry 0.18 MPa 240% 0.20 MPa 0.11 MPa Z12 (ref.) almost dry 0.25 MPa 289% 0.22 MPa 0.16 MPa