AMINE FOR LOW-EMISSION EPOXY RESIN COMPOSITIONS

Abstract

The use of an amine of formula (I) as a component of a hardener for epoxy resins, hardeners for epoxy resins containing the amine of formula (I), and resultant epoxy resin compositions which can particularly be used as low-emission room-temperature-curing epoxy-resin coatings with high hardness and surface quality. The amine of formula (I) is low-odour and a very successful diluent for epoxy resin compositions. It is particularly obtained by reductive alkylation from 1,2-ethylenediamine or 1,2-propylenediamine and an aldehyde or ketone.

Claims

1. An epoxy resin composition comprising a resin component comprising at least one epoxy resin and a hardener component comprising at least one amine of the formula (I), ##STR00004## where X is 1,2-ethylene or 1,2-propylene, R is a hydrogen radical or is a hydrocarbon radical having 1 to 6 carbon atoms, A is a five-, six- or seven-membered cycloalkyl radical having 4 to 7 carbon atoms and in the ring contains an oxygen, sulfur or nitrogen atom, Y is identical or different radicals selected from the group consisting of alkyl, alkoxy and dialkylamino having 1 to 18 carbon atoms, and n is 0 or 1 or 2 or 3.

2. The epoxy resin composition as claimed in claim 1, wherein X is 1,2-ethylene.

3. The epoxy resin composition as claimed in claim 1, wherein R is a hydrogen radical.

4. The epoxy resin composition as claimed in claim 1, wherein A is a five- or six-membered cycloalkyl radical having 4 to 6 carbon atoms and the ring contains an oxygen atom.

5. The epoxy resin composition as claimed in claim 1, wherein R is a hydrogen radical and n is 0.

6. The epoxy resin composition as claimed in claim 1, wherein A is a five-membered cycloalkyl radical having 4 carbon atoms and one oxygen atom.

7. The epoxy resin composition as claimed in claim 1, wherein A is a tetrahydrofuran-2-yl or a tetrahydrofuran-3-yl radical.

8. The epoxy resin composition as claimed in claim 1, wherein the amine of the formula (I) is obtained from the reductive alkylation of 1,2-ethylenediamine or 1,2-propylenediamine with at least one aldehyde or ketone of the formula (II) and hydrogen, ##STR00005## where G is A or an unsaturated radical which can be hydrogenated to A.

9. The epoxy resin composition as claimed in claim 8, wherein 1,2-ethylenediamine or 1,2-propylenediamine is used in a stoichiometric excess over the carbonyl groups and the excess is removed distillatively after the reduction.

10. A hardener for epoxy resins, comprising at least one amine of the formula (I), ##STR00006## where X is 1,2-ethylene or 1,2-propylene, R is a hydrogen radical or is a hydrocarbon radical having 1 to 6 carbon atoms, A is a five-, six- or seven-membered cycloalkyl radical having 4 to 7 carbon atoms and in the ring contains an oxygen, sulfur or nitrogen atom, Y is identical or different radicals selected from the group consisting of alkyl, alkoxy and dialkylamino having 1 to 18 carbon atoms, and n is 0 or 1 or 2 or 3, and at least one further amine not corresponding to the formula (I), and/or at least one accelerator.

11. The hardener as claimed in claim 10, wherein the further amine is selected from the group consisting of 2,2(4),4-trimethylhexamethylenediamine, 1,2-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 2(4)-methyl-1,3-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(amino-methyl)cyclohexane, 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,3-bis(aminomethyl)benzene, 1,4-bis(aminomethyl)benzene, polyoxyalky-lenediamines, polyoxyalkylenetriamines, bis(hexamethylene)triamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, N,N′-bis(3-aminopropyl)ethylenediamine, N-benzyl-1,3-bis(aminomethyl)-benzene, N,N′-dibenzyl-1,3-bis(aminomethyl)benzene, N-2-ethylhexyl-1,3-bis(aminomethyl)benzene, N,N′-bis(2-ethylhexyl)-1,3-bis(aminome-thyl)benzene, N-benzyl-1,2-propanediamine, N-benzyl-1,2-ethanediamine and adducts of polyamines with epoxides.

12. The hardener as claimed in claim 10, wherein the further amine is an adduct, containing at least three amine hydrogens, of at least one polyamine having 2 to 12 carbon atoms and at least one epoxide.

13. The hardener as claimed in claim 10, wherein the hardener contains 5 to 65 weight % of the amine of the formula (I) based on the reactive constituents of the hardener.

14. A cured composition obtained from the curing of the epoxy resin composition as claimed in claim 1.

15. The epoxy resin composition as claimed in claim 1, which contains not more than 5 weight % of a diluent.

Description

EXAMPLES

[0198] Set out below are working examples which are intended to elucidate in more detail the invention described. The invention is of course not confined to these working examples described.

[0199] “AHEW” stands for the amine hydrogen equivalent weight.

[0200] “EEW” stands for the epoxide equivalent weight.

[0201] “Standard conditions” refer to a temperature of 23±1° C. and a relative atmospheric humidity of 50±5%. “SC” stands for “standard conditions”.

[0202] Description of Measurement Methods:

[0203] Infrared spectra (FT-IR) were measured as undiluted films on an FT-IR instrument 1600 from Perkin-Elmer equipped with a horizontal ATR measurement unit with ZnSe crystal; the absorption bands are reported in wavenumbers (cm.sup.−1); (measuring window: 4000-650 cm.sup.−1).

[0204] .sup.1H-NMR spectra were measured on a Bruker Ascend 400 spectrometer at 400.14 MHz; the chemical shifts 5 are reported in ppm relative to tetramethylsilane (TMS). No distinction is made between true and pseudo-coupling patterns.

[0205] Gas chromatograms (GC) were measured in the temperature range from 60 to 320° C. at a heating rate of 15° C./min and 10 min dwell time at 320° C. The injector temperature was 250° C. A Zebron ZB-5 column was used (L=30 m, ID=0.25 mm, dj=0.5 μm) with a gas flow rate of 1.5 ml/min. Detection took place by means of flame ionization (FID).

[0206] The viscosity of samples with relatively high viscosity (above 150 mPa.Math.s) was measured on a thermostated cone/plate viscometer, Rheotec RC30 (cone diameter 50 mm, cone angle 1°, cone tip/plate distance 0.05 mm, shear rate s.sup.−1).

[0207] The viscosity of low-viscosity samples (below 150 mPa.Math.s) was measured on a thermostated cone/plate rheometer, Anton Paar Physica MCR 300 (cone diameter 25 mm, cone angle 2°, cone tip/plate distance 0.05 mm, shear rate 100 s.sup.−1).

[0208] The amine number was determined by titration (with 0.1 N HClO.sub.4 in acetic acid against crystal violet).

[0209] Substances Used: [0210] Cyclohexane—technical, ≥90% (Sigma-Aldrich) [0211] carbaldehyde: [0212] Tetrahydrofuran-3—solution 50% by weight in water (98%) (Sigma Aldrich) [0213] carbaldehyde: [0214] Araldite® GY 250: bisphenol A diglycidyl ether, EEW about 187.5 g/eq (from Huntsman) [0215] Araldite® DY-E: monoglycidyl ether of C.sub.12 to C.sub.14 alcohols, EEW about 290 g/eq (from Huntsman) [0216] EP adduct 1: reaction product of 1,2-propylenediamine and Araldite® DY-K, as described below; AHEW about 90.0 g/eq; viscosity (20° C.) 23 000 mPa.Math.s [0217] Araldite® DY-K: cresyl glycidyl ether, EEW about 182 g/eq (from Huntsman) [0218] Gaskamine® 240: styrenized 1,3-bis(aminomethyl)benzene; AHEW 103 g/eq; viscosity (20° C.) 165 mPa.Math.s (from Mitsubishi Gas Chemical)

[0219] EP adduct 1 was prepared by initially introducing 4.15 kg of 1,2-propylenediamine under a nitrogen atmosphere, heating this initial charge to 70° C. and then slowly adding 2.93 kg of Araldite® DY-K with thorough stirring, the temperature of the reaction mixture being 70 to 80° C. After 1 hour at 80° C., the reaction mixture was cooled and the volatile constituents were removed by distillation using a thin-film evaporator (0.5-1 mbar, jacket temperature 115° C.).

[0220] Preparation of Amines:

Amine 1: Mixture of N′-cyclohexyl-1,2-propanediamine and N.SUP.2.-cyclohexyl-1-2-propanediamine

[0221] A round-bottomed flask was charged at room temperature with 68.2 g (0.92 mol) of 1,2-propylenediamine under a nitrogen atmosphere. With thorough stirring, a solution of 25.0 g (0.23 mol) of cyclohexanecarbaldehyde in 500 ml of isopropanol was added slowly dropwise, followed by stirring for 2 hours more. Thereafter the reaction mixture was hydrogenated under a hydrogen pressure of 90 bar, at a temperature of 80° C. and with a flow rate of 5 ml/min, on a continuous hydrogenation apparatus with Pd/C fixed-bed catalyst. To monitor the reaction, IR spectroscopy was used to verify whether the imine band at about 1665 cm.sup.−1 had disappeared. At that point the hydrogenated solution was concentrated on a rotary evaporator at 65° C., with unreacted 1,2-propylenediamine and isopropanol being removed. The resulting reaction mixture was a clear, slightly yellowish liquid.

[0222] 28.1 g of this reaction mixture were distilled under reduced pressure at 80° C., and 12.5 g of distillate were collected at a vapor temperature of 57 to 59° C. and 0.035 bar. This gave a colorless liquid having a viscosity of 11.5 mPa.Math.s at 20° C., an amine number of 635.1 mg KOH/g and a purity as determined by GC of >90% (retention time 8.45-8.50 min), which was used hereinafter as amine 1.

[0223] .sup.1H-NMR (CDCl.sub.3): 2.96-2.70 (m, 1H, CHCH.sub.3), 2.60-2.29 (m, 4H, 2×CH.sub.2—N), 1.82-0.84 (m, 11H, Cy-H), 1.35 (br s, 3H, NH and NH.sub.2), 1.06 (d, 3H, CH.sub.3). FT-IR: 3295, 2925, 2807, 1592, 1447, 1372, 1344, 1308, 1262, 1128, 1091, 955, 842, 821, 793.

Amine 2: Mixture of N′-(3-tetrahydrofurylmethyl)-1,2-propanediamine and N.SUP.2.-(3-tetrahydrofurylmethyl)-1-2-propanediamine

[0224] A round-bottomed flask was charged at room temperature with 74.1 g (1 mol) of 1,2-propylenediamine under a nitrogen atmosphere. With thorough stirring, a mixture of 50.0 g (0.25 mol) of a solution of 50 weight % of tetrahydrofuran-3-carbaldehyde in water and 500 ml of isopropanol was added slowly dropwise, followed by stirring for 2 hours more. Thereafter the reaction mixture was hydrogenated under a hydrogen pressure of 90 bar, at a temperature of 80° C. and with a flow rate of 5 ml/min, on a continuous hydrogenation apparatus with Pd/C fixed-bed catalyst. To monitor the reaction, IR spectroscopy was used to verify whether the imine band at about 1665 cm.sup.−1 had disappeared. At that point the hydrogenated solution was concentrated on a rotary evaporator at 65° C., with unreacted 1,2-propylenediamine, water and isopropanol being removed. The resulting reaction mixture was a clear, yellowish liquid having an amine number of 523 mg KOH/g.

[0225] 30 g of this reaction mixture were distilled under reduced pressure at 95° C., and 17.2 g of distillate were collected at a vapor temperature of 64 to 74° C. and 0.028 bar. This gave a colorless liquid having a viscosity of 10.5 mPa.Math.s at 20° C., an amine number of 693 mg KOH/g and a purity as determined by GC of >95% (retention time 8.16-8.21 min), which was used hereinafter as amine 2.

[0226] .sup.1H-NMR (CDCl.sub.3): 3.90-3.48 (m, 4H, CH.sub.2—O—CH.sub.2), 2.95 (m, 1H, CHCH.sub.3), 2.75-2.42 (m, 4H, 2×CH.sub.2N), 2.35-1.59 (m, 2H, OCH.sub.2CH.sub.2), 2.02 (m, 1H, CHCH.sub.2N), 1.26 (br s, 3H, NH and NH.sub.2), 1.03 (d, 3H, CH.sub.3). FT-IR: 3301, 2956, 2925, 2884, 1590, 1452, 1372, 1345, 1129, 1071, 1046, 945, 828.

[0227] Production of Hardeners and Epoxy Resin Compositions

[0228] For each example, the ingredients specified in table 1 were mixed in the stated quantities (in parts by weight) of the hardener component using a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and the mixtures were stored in the absence of moisture.

[0229] Similarly, the ingredients of the resin component as specified in table 1 were processed and stored.

[0230] Thereafter the two components of each composition were processed to a homogeneous liquid using the centrifugal mixer, and this liquid was tested immediately as follows:

[0231] 10 minutes after mixing, the viscosity at 20° C. was ascertained (“viscosity (10′)”).

[0232] A first film was drawn down in a film thickness of 500 μm onto a glass plate, which was stored/cured under standard conditions. Determined on this film was the König hardness (pendulum hardness as König, measured to DIN EN ISO 1522) after 1 day (“König hardness (1 d SC)”), after 2 days (“König hardness (2 d SC)”), after 4 days (“König hardness (4 d SC)”), after 7 days (“König hardness (7 d SC)”), and after 14 days (“König hardness (14 d SC)”). After 14 days, the appearance of the film was assessed (identified in the table as “appearance (SC)”. A film identified as “attractive” there was clear and had a glossy and nonsticky surface without structure. “Structure” here refers to any kind of marking or pattern on the surface.

[0233] A second film was drawn down onto a glass plate in a film thickness of 500 μm, and this film immediately after application was stored, or cured, at 8° C. and at 80% relative humidity for 7 days and subsequently under standard conditions (SC) for 3 weeks. 24 hours after application, a polypropylene bottle cap was placed onto the film, with a moist sponge placed beneath the cap. After a further 24 hours, the sponge and the cap were removed and were placed on a new site on the film, where, after 24 hours, they were removed again and placed anew, a total of 4 times. Thereafter the appearance of this film was assessed (identified in the tables as “appearance (8°/80%)”), in the same way as described for the appearance (SC). Also reported here in each case is the number of marks visible in the film as a result of the wet sponge and/or the applied cap. On the films cured in this way, the König hardness was again determined, in each case after 7 days at 8° C. and 80% relative humidity (“König hardness (7 d 8°/80%)”), then after a further 2 days under SC (“König hardness (+2 d SC)”), 7 days under SC (“König hardness (+7 d SC)”), and 14 d under SC (“König hardness (+14 d SC)”).

[0234] A further measure used for the yellowing was the color change after exposure in a weathering tester. For this purpose, a further film was drawn down in a film thickness of 500 μm onto a glass plate and was stored, or cured, under standard conditions for 2 weeks and subsequently exposed in a Q-Sun Xenon Xe-1 weathering tester with Q-SUN Daylight-Q optical filter and with a xenon lamp, with a luminous intensity of 0.51 W/m.sup.2 at 340 nm and at a temperature of 65° C. for 72 hours (Q-Sun (72 h)). Thereafter the color difference ΔE of the film thus exposed was determined in comparison to the corresponding unexposed film, using an NH310 colorimeter from Shenzen 3NH Technology Co. LTD, equipped with Silicon Photoelectric Diode Detector, Light Source A, Color Space Measurement Interface CIE L*a*b*C*H*. AE values of 0.5 to 1.5 here represent a small color difference, 1.5 to 3 a marked color difference, 3 to 6 a distinctly visible color difference, and more than 6 a large color difference.

[0235] The results are reported in table 1.

[0236] The epoxy resin compositions EZ-1 to EZ-4 are inventive examples. The epoxy resin compositions Ref-1 and Ref-2 are comparative examples.

TABLE-US-00001 TABLE 1 Composition and properties of EZ-1 to EZ-4 and Ref-1 to Ref-2. EZ-1 EZ-2 EZ-3 EZ-4 Ref-1 Ref-2 Example NV-2410 NV-2411 NV-2412 NV-2413 NV-2309 NV-2352 Resin component: Araldite ® GY-250 167.2 167.2 167.2 167.2 167.2 167.2 Araldite ® DY-E 31.8 31.8 31.8 31.8 31.8 31.8 Hardener component: Amine 1 1 2 2 56.8 28.4 52.8 26.4 — — EP adduct 1 — 45.0 — 45.0 — 45.0 Gaskamine ® 240 — — — — 103.0 51.5 Viscosity (10′) [Pa .Math. s] 0.36 1.36 0.34 1.19 0.60 1.66 König hardness [s] (1 d SC) 19 56 9 42 29 43 (2 d SC) 83 119 77 113 77 87 (4 d SC) 143 172 158 165 113 134 (7 d SC) 181 188 176 190 132 148 (14 d SC) 182 202 171 195 143 175 Appearance (SC) attractive attractive attractive attractive attractive attractive Q-Sun (72 h) ΔE 2.5 2.1 1.4 0.9 17.3 5.0 König hardness [s] (7 d 8°/80%) 10 46 n.m. 24 36 14 (+2 d SC) 13 134 n.m. 76 85 119 (+7 d SC) 52 168 n.m. 84 116 157 (+14 d SC) 70 186 n.m. 99 126 176 Appearance (8°/80%) slightly matt attractive sticky slightly matt attractive attractive Number of marks 2 1 n.m. 4 1 1 “n.m.” stands for “not measurable” (sticky)