LOW-EMISSION EPOXY RESIN COMPOSITION

Abstract

An epoxy resin composition, the curing components of which contain at least one amine of formula (I) and optionally at least one amine A which is, in particular, an adduct of a polyamine and an epoxide. The amine for formula (I) is used in particular in the form of a reaction product of the reductive alkylation of 1,2-ethylenediamine and an aldehyde or ketone. The epoxy resin composition is used in particular as a low-emission, room-temperature-curing epoxy-resin coating. It is characterised by good processibility, quick curing, high hardness, a nice surface and a low tendency to yellowing.

Claims

1. A process for producing an amine of formula (I), ##STR00005## where n is 0 or 1 or 2 or 3, R is a hydrogen radical or is a hydrocarbon radical having 1 to 6 carbon atoms, and X is identical or different radicals selected from the group consisting of alkyl and alkoxy having in each case 1 to 18 carbon atoms, the method comprising: (i) performing reductive alkylation of a stoichiometric excess of 1,2-ethylenediamine with an aldehyde or ketone of the formula (II) ##STR00006## and hydrogen, wherein a ratio between the number of 1,2-ethylenediamine molecules and the number of carbonyl groups is at least 2/1; and (ii) then removing unreacted 1,2-ethylenediamine to obtain a reaction product.

2. The process as claimed in claim 1, wherein R is a hydrogen radical or is methyl.

3. The process as claimed in claim 1, wherein R is a hydrogen radical and n is 0.

4. The process as claimed in claim 1, wherein R is a hydrogen radical, n is 1, and X is methoxy in para position.

5. The process as claimed in claim 1, wherein the ratio between the number of 1,2-ethylenediamine molecules and the number of carbonyl groups is at least 3/1.

6. The process as claimed in claim 1, wherein the unreacted 1,2-ethylenediamine is removed by distillation to a content of less than 1 weight % based on the total reaction product.

7. The process as claimed in claim 6, wherein the reaction product is further purified by distillation.

8. The reaction product obtained from the process as claimed in claim 1.

9. A method comprising curing an epoxy resin with the reaction product of claim 8.

10. A hardener for curing an epoxy resin comprising the reaction product as claimed in claim 8, wherein the hardener contains 1 to 90 weight % of the amine of the formula (I) based on the total weight of the hardener.

11. The hardener as claimed in claim 10, wherein the hardener further contains at least one amine A having at least three amine hydrogens and a molecular weight of at least 200 g/mol which does not correspond to formula (I).

12. The hardener as claimed in claim 11, wherein the amine A is selected from adducts of polyamines with epoxides, polyamidoamines, phenalkamines and polyoxyalkylene diamines and triamines having an average molecular weight in the range from 200 to 500 g/mol.

13. An epoxy resin composition comprising a resin component comprising at least one epoxy resin, and a hardener component comprising the reaction product as claimed in claim 8.

14. A cured composition obtained from curing the epoxy resin composition as claimed in claim 13.

15. A coating comprising the epoxy resin composition as claimed in claim 13 or the cured composition as claimed in claim 14.

Description

EXAMPLES

[0189] 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.

[0190] “AHEW” stands for the amine hydrogen equivalent weight.

[0191] “EEW” stands for the epoxide equivalent weight.

[0192] “Standard conditions” refer to a temperature of 23±1° C. and a relative atmospheric humidity of 50±5%. “SC” stands for “standard conditions”.

Description of Measurement Methods:

[0193] 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).

[0194] .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.

[0195] 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).

[0196] 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 10 s.sup.−1).

[0197] 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).

[0198] The amine number was determined by titration (with 0.1N HCIO.sub.4 in acetic acid against crystal violet).

Substances Used:

[0199] Araldite® GY 250: bisphenol A diglycidyl ether, EEW about 187.5 g/eq (from Huntsman) [0200] Araldite® DY-E: monoglycidyl ether of C.sub.12 to C.sub.14 alcohols, EEW about 290 g/eq (from Huntsman) [0201] EP adduct 2: reaction product of 1,5-diamino-2-methylpentane and Araldite® DY-K, as described below; AHEW about 106.5 g/eq; viscosity (20° C.) 13 000 mPa.Math.s [0202] EP adduct 3: 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 [0203] Araldite® DY-K: cresyl glycidyl ether, EEW about 182 g/eq (from Huntsman) [0204] Gaskamine® 240: styrenized 1,3-bis(aminomethyl)benzene; AHEW 103 g/eq; viscosity (20° C.) 165 mPa.Math.s (from Mitsubishi Gas Chemical) [0205] Jeffamine® D-230: polyoxypropylenediamine with average molecular weight of about 240 g/mol, AHEW about 60 g/eq (from Huntsman) [0206] Ancamine® K 54: 2,4,6-tris(dimethylaminomethyl)phenol (from Air Products)

[0207] EP adduct 2 was prepared by initially introducing 4.65 kg of 1,5-diamino-2-methylpentane (Dytek® A from Invista) under a nitrogen atmosphere, heating this initial charge to 70° C. and then slowly adding 1.83 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 160° C.).

[0208] EP adduct 3 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.).

Preparation of Amines:

Amine 1: N-benzyl-1,2-ethanediamine

[0209] A round-bottomed flask was charged at room temperature with 120.2 g (2 mol) of 1,2-ethylenediamine under a nitrogen atmosphere. With thorough stirring, a solution of 42.4 g (0.4 mol) of benzaldehyde in 800 ml of isopropanol was added slowly dropwise, followed by stirring for 2 hours more. The reaction mixture was subsequently hydrogenated under a hydrogen pressure of 90 bar, at a temperature of 90° 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 removal of unreacted 1,2-ethylenediamine and isopropanol. The reaction mixture thus obtained was a clear, slightly yellowish liquid having an amine number of 668.4 mg KOH/g.

[0210] 50 g of this reaction mixture were distilled under reduced pressure at 80° C., and 31.3 g of distillate were collected at a vapor temperature of 60 to 65° C. under 0.06 bar. The product was a colorless liquid having a viscosity of 8.3 mPa.Math.s at 20° C., an amine number of 749.6 mg KOH/g and a purity as determined by GC of >97% (retention time 8.47-8.57 min), which was used below as amine 1.

[0211] .sup.1H-NMR (CDCl.sub.3): 7.36-7.32 (m, 5H, Ar—H), 3.79 (s, 2H, Ar—CH.sub.2), 2.80 (t, 2H, CH.sub.2NH.sub.2), 2.68 (t, 2H, NHCH.sub.2CH.sub.2), 1.28 (br s, 3H NH and NH.sub.2) FT-IR: 3365, 3285, 3025, 2913, 2814, 1601, 1493, 1451, 1199, 1067, 1027, 801, 731.

Amine 2: N-(4-methoxybenzyl)-1,2-ethanediamine

[0212] A round-bottomed flask was charged at room temperature with 120.2 g (2 mol) of 1,2-ethylenediamine under a nitrogen atmosphere. With thorough stirring, a solution of 54.4 g (0.4 mol) of 4-methoxybenzaldehyde (=anisaldehyde) in 800 ml of isopropanol was added slowly dropwise with stirring continued for 2 hours thereafter. The reaction mixture was subsequently hydrogenated under a hydrogen pressure of 90 bar at a temperature of 85° C. and with a flow rate of 5 ml/min on a continuous hydrogenation apparatus with Pd/C fixed-bed catalyst. For reaction monitoring, 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 at 65° C. on a rotary evaporator, with removal of unreacted 1,2-ethylenediamine and isopropanol. The reaction mixture thus obtained was a clear, yellowish liquid. 62.7 g of this reaction mixture were distilled under reduced pressure at 110° C., and 48.9 g of distillate with a vapor temperature of 90 to 92° C. at 0.024 bar were collected. This gave a colorless liquid having a viscosity of 22 mPa.Math.s at 20° C., an amine number of 615.1 mg KOH/g and a purity as determined by GC of >97% (retention time 10.69 min), which was used hereinafter as amine 2.

[0213] .sup.1H-NMR (CDCl.sub.3): 7.22 (d, 2H, Ar—H), 6.85 (d, 2H, Ar—H), 3.78 (s, 3H, OCH.sub.3), 3.72 (d, 2H, Ar—CH.sub.2NH), 2.79 (t, 2H, CH.sub.2NH.sub.2), 2.66 (t, 2H, NHCH.sub.2CH.sub.2), 1.29 (br s, 3H NH and NH.sub.2).

[0214] FT-IR: 3285, 2931, 2832, 1610, 1584, 1509, 1461, 1441, 1299, 1248, 1173, 1106, 1031, 808.

Amine 3: N-benzyl-1,3-propanediamine (Comparative)

[0215] A round-bottomed flask was charged at room temperature with 148.3 g (2 mol) of 1,3-propanediamine under a nitrogen atmosphere. With thorough stirring, a solution of 42.4 g (0.4 mol) of benzaldehyde in 800 ml of isopropanol was added slowly dropwise, followed by stirring for 2 hours more. The reaction mixture was subsequently hydrogenated under a hydrogen pressure of 90 bar, at a temperature of 90° 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 removal of unreacted 1,3-propanediamine and isopropanol. The reaction mixture thus obtained was a clear, slightly yellowish liquid having an amine number of 569 mg KOH/g. 50 g of this reaction mixture were distilled under reduced pressure at 90° C., and 33.8 g of distillate with a vapor temperature of 68 to 73° C. at 0.06 bar were collected. This gave a colorless liquid having a viscosity of 10.8 mPa.Math.s at 20° C., an amine number of 682 mg KOH/g and a purity as determined by GC of >97% (retention time 9.39-9.46 min), which was used hereinafter as amine 3 for comparison purposes.

Production of Hardeners and Epoxy Resin Compositions

[0216] For each example, the ingredients specified in tables 1 to 2 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.

[0217] Similarly, the ingredients of the resin component as specified in tables 1 to 2 were processed and stored.

[0218] 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:

[0219] 10 minutes after mixing, the viscosity at 20° C. was ascertained (“viscosity (10′)”).

[0220] 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.

[0221] 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 (“Konig hardness (+14 d SC)”).

[0222] 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. The results are reported in tables 1 to 2.

[0223] The epoxy resin compositions EZ-1 to EZ-7 are inventive examples. The epoxy resin compositions Ref-1 to Ref-5 are comparative examples.

TABLE-US-00001 TABLE 1 Composition and properties of EZ-1 to EZ-4 and Ref-1 and Ref-2. Example EZ-1 EZ-2 EZ-3 EZ-4 Ref-1 Ref-2 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 1 2 3 — 25.0 25.0 25.0 30.9 27.4 Gaskamine ® 240 — — — — — 51.5 EP adduct 2 53.3 53.3 — — — — EP adduct 3 — — 45.0 45.0 45.0 45.0 Jeffamine ® D-230 — — — — — — Salicylic acid 1.3 — — — — — Ancamine ® K 54 1.3 — — — — — Viscosity (10′) [Pa .Math. s] 1.53 1.39 1.33 2.16 1.39 1.66 König (1 d SC) 101 83 74 91 62 43 hardness (2 d SC) 144 125 134 140 109 87 [s] (4 d SC) 168 151 170 171 147 134 (7 d SC) 177 170 188 188 171 148 (14 d SC) 178 170 195 197 187 175 Appearance (SC) attrac- attrac- attrac- attrac- attrac- attrac- tive tive tive tive tive tive Q-Sun (72 h) ΔE 10.3 4.3 2.6 3.8 3.7 5.0 König (7 d 8°/80%) 26 27 38 73 43 14 hardness (+2 d SC) 59 92 153 161 132 119 [s] (+7 d SC) 167 98 174 172 173 157 (+14 d SC) 172 170 193 200 186 176 Appearance (8°/80%) attrac- attrac- attrac- attrac- attrac- attrac- tive tive tive tive tive tive Number of marks 1 1 1 1 3 1

TABLE-US-00002 TABLE 2 Composition and properties of EZ-5 to EZ-7 and Ref-3 and Ref-5. Example EZ-5 EZ-6 Ref-3 Ref-4 EZ-7 Ref-5 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 3 1 2 3 45.1 40.1 43.8 50.1 61.8 54.7 Jeffamine ® D-230 6.0 12.0 12.0 — — — Viscosity (10′) [Pa .Math. s] 0.29 0.30 0.30 0.33 0.45 0.36 König (1 d SC) 56 43 25 34 88 38 hardness (2 d SC) 71 109 52 79 123 53 [s] (4 d SC) 100 147 99 136 137 70 (7 d SC) 136 154 99 163 145 85 (14 d SC) 144 166 119 167 146 101 Appearance (SC) attrac- attrac- very attrac- attrac- very tive tive hazy tive tive hazy Q-Sun (72 h) ΔE 3.2 3.0 12.6 3.4 9.3 13.2 König (7 d 8°/80%) 18 24 24 35 54 27 hardness (+2 d SC) 119 67 63 110 106 63 [s] (+7 d SC) 153 76 88 143 116 106 (+14 d SC) 160 78 106 151 123 109 Appearance (8°/80%) attrac- attrac- very slightly attrac- very tive tive hazy hazy tive hazy Number of marks 1 1 2 1 none 2