AMINE FOR LOW-EMISSION EPOXY RESIN COMPOSITIONS

Abstract

An amine of the formula (I) and a process for its preparation by reductive alkylation of 1,2-propylenediamine with a di- or trifunctional carbonyl compound and hydrogen. The amine of the formula (I) is low in viscosity and in odour, high in reactivity towards epoxides and outstanding in its compatibility with other amines and with epoxy resins. The amine of the formula (I) allows access to low-emission epoxy resin compositions which have good processing qualities, cure rapidly even at low temperatures and form high-quality, high-hardness plastics having an attractive surface.

Claims

1. An amine of the formula (I) ##STR00008## where n is 2 or 3, R is a hydrogen radical or is methyl or phenyl, and A is an n-valent hydrocarbon radical having 5 to 20 C atoms which optionally contains oxygen or sulfur or nitrogen atoms and which comprises at least one cycloaliphatic or aromatic ring.

2. The amine of the formula (I) as claimed in claim 1, wherein n is 2.

3. The amine of the formula (I) as claimed in claim 1, wherein R is a hydrogen radical.

4. The amine of the formula (I) as claimed in claim 1, wherein A is an optionally substituted phenylene or cyclohexylene or dicycloheptylene or tricyclodecylene or pentacyclopentadecylene or furandiyl or tetrahydrofurandiyl or thiophenediyl or tetrahydrothiophenediyl or N,N′-piperazine-bis(2,2-dimethylpropane)diyl radical.

5. The amine of the formula (I) as claimed in claim 1, wherein it is 1,4-bis(2-aminopropylaminomethyl)benzene or 1,4-bis(2-aminopropylaminomethyl)cyclohexane.

6. A process for preparing an amine of the formula (I) as claimed in claim 1, wherein 1,2-propylenediamine is subjected to reductive alkylation with at least one di- or trifunctional carbonyl compound of the formula (III) and hydrogen. ##STR00009##

7. The process as claimed in claim 6, wherein 1,2-propylenediamine is used in stoichiometric excess over the carbonyl groups of the carbonyl compound of the formula (III).

8. A method, comprising: hardening epoxy resins with an amine of the formula (I) as claimed in claim 1.

9. A hardener for epoxy resins, comprising at least one amine of the formula (I) as claimed in claim 1 and at least one further amine and/or at least one accelerator.

10. The hardener as claimed in claim 9, wherein the accelerator is salicylic acid or 2,4,6-tris(dimethylaminomethyl)phenol or a combination thereof.

11. The hardener as claimed in claim 9, wherein the further amine comprises 1-(2-aminopropylaminomethyl)-4-(1-aminoprop-2-ylaminomethyl)benzene or 1,4-bis(1-aminoprop-2-ylaminomethyl)benzene or 1-(2-aminopropylaminomethyl)-4-(1-aminoprop-2-ylaminomethyl)cyclohexane or 1,4-bis(1-aminoprop-2-ylaminomethyl)cyclohexane.

12. The hardener as claimed in claim 9, wherein the further amine comprises a partially styrenized polyamine or a product of the reductive alkylation of primary aliphatic polyamines with monofunctional aldehydes or ketones.

13. The hardener as claimed in claim 9, wherein it contains not more than 10 weight % of unincorporable diluents.

14. 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) as claimed in claim 1.

15. A method comprising, applying an epoxy resin composition as claimed in claim 14 as fiber composite matrix for fiber composite materials or as adhesive or as coating, covering or finish.

Description

EXAMPLES

[0154] 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.

[0155] “AHEW” stands for the amine hydrogen equivalent weight.

[0156] “EEW” stands for the epoxide equivalent weight.

[0157] “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:

[0158] 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).

[0159] The viscosity 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).

[0160] The amine number was determined by titration (with 0.1N HClO.sub.4 in acetic acid against crystal violet).

Substances Used:

[0161] Araldite® GY 250: bisphenol A diglycidyl ether, EEW about 187.5 g/eq (from Huntsman) [0162] Araldite® DY-E: monoglycidyl ether of C.sub.12 to C.sub.14 alcohols, EEW about 290 g/eq (from Huntsman) [0163] Ancamine® K 54: 2,4,6-tris(dimethylaminomethyl)phenol (from Air Products) [0164] EP adduct 1: reaction product of 116.0 g 1,5-diamino-2-methylpentane with 200.2 g of Araldite® DY-K; [0165] AHEW about 109.5 g/eq; viscosity (20° C.) about 13.1 Pa.Math.s [0166] Araldite® DY-K: cresyl glycidyl ether, EEW about 182 g/eq (from Huntsman) [0167] Jeffamine® D-230: polyoxypropylenediamine with average molecular weight of about 240 g/mol, AHEW about 60 g/eq (from Huntsman) [0168] Gaskamine® 240: styrenized 1,3-bis(aminomethyl)benzene; AHEW 103 g/eq; viscosity (20° C.) 165 mPa.Math.s (from Mitsubishi Gas Chemical) [0169] N-Benzyl-1,2-propanediamine: reaction mixture prepared as described below

N-Benzyl-1,2-propanediamine

[0170] A round-bottomed flask was charged at room temperature with 444.8 g (6 mol) of 1,2-propanediamine under a nitrogen atmosphere. With thorough stirring, a solution of 212.2 g (2 mol) of benzaldehyde in 1500 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-propanediamine and isopropanol. This gave a clear, slightly yellowish liquid. Of this, 300 g were distilled under reduced pressure at 80° C., and 237.5 g of distillate with a vapor temperature of 60 to 63° C. at 0.08 to 0.09 bar were collected. This gave a colorless liquid having a viscosity of 8.5 mPa.Math.s at 20° C. and an amine number of 682 mg KOH/g, which, according to .sup.1H-NMR, gave a mixture of N.sup.1-benzyl-1,2-propanediamine and N.sup.2-benzyl-1,2-propanediamine in a ratio of about 2/1.

Preparation of Amines of Formula (I)

Amine 1: reaction mixture comprising 1,4-bis(aminopropylaminomethyl)benzene

[0171] A round-bottomed flask was charged at room temperature with 74.1 g (1.0 mol) of 1,2-propanediamine under a nitrogen atmosphere. With thorough stirring, a solution of 26.8 g (0.2 mol) of terephthalic aldehyde in 500 ml of dioxane was added slowly dropwise, followed by stirring for 30 minutes more. The reaction mixture was hydrogenated under a hydrogen pressure of 85 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. 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 excess 1,2-propylenediamine and the solvent were removed on a rotary evaporator at 65° C. and 1 mbar. This gave a clear, yellowish liquid having a viscosity of 4.13 Pa.Math.s at 20° C. and an amine number of 768.8 mg KOH/g.

[0172] FT-IR: 2959, 2913, 2890, 2852, 1454, 1366, 1288, 1254, 1117, 1082, 1048, 890, 870.

Amine 2: reaction mixture comprising 1,4-bis(aminopropylaminomethyl)benzene

[0173] A round-bottomed flask was charged at room temperature with 111.2 g (1.5 mol) of 1,2-propanediamine under a nitrogen atmosphere. With thorough stirring, a solution of 26.8 g (0.2 mol) of terephthalic aldehyde in 600 ml of dioxane, heated to 50° C., was added slowly dropwise, followed by stirring for 30 minutes more. The reaction mixture was 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 excess 1,2-propylenediamine and the solvent were removed on a rotary evaporator at 65° C. and 1 mbar. This gave a clear, pale yellow liquid having a viscosity of 0.24 Pa.Math.s at 20° C. and an amine number of 849.2 mg KOH/g.

[0174] FT-IR: 2959, 2800, 1567, 1500, 1440, 1367, 1100, 1010, 1048, 810.

Production of Hardeners and Epoxy Resin Compositions

[0175] For each example, the ingredients specified in table 1 or 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.

[0176] Similarly, the ingredients of the resin component as specified in table 1 or 2 were processed and stored.

[0177] 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:

[0178] 10 minutes after mixing, the viscosity at 20° C. was ascertained (“viscosity (10′)”).

[0179] 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.

[0180] 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 standard conditions (“König hardness (+2 d SC)”), 7 days under standard conditions (“König hardness (+7 d SC)”), and after 2 weeks under standard conditions (“König hardness (+14 d SC)”).

[0181] The results are reported in table 1 or 2.

[0182] The epoxy resin compositions EZ-1 to EZ-8 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. Example EZ-1 EZ-2 EZ-3 EZ-4 Ref-1 Ref-2 Resin comp.: 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 comp.: Amine 1 39.4 41.7 54.3 — — — Amine 2 — — — 41.7 — — EP adduct 1 — — — — 109.5 109.5 Ancamine ® K 54 4.8 — — — 6.2 — Viscosity (10′) [Pa .Math. s] 2.4 2.3 2.6 1.6 4.6 4.6 König (1 d SC) 91 39 109 109 108 63 hardness [s] (2 d SC) 134 71 140 140 147 85 (4 d SC) 167 94 155 144 168 105 (7 d SC) 188 104 157 161 176 121 (14 d SC) 203 111 161 n.d. 185 140 Appearance (SC) attractive attractive attractive attractive attractive attractive König (7 d 8°/80%) 42 21 46 11 53 37 hardness [s] (+2 d SC) 59 28 64 15 129 94 (+7 d SC) 76 34 77 n.d. 161 113 (+14 d SC) 125 34 80 n.d. 183 125 Appearance (8°/80%) slightly slightly slightly attractive slightly slightly matt matt matt matt matt Number of marks 1 1 1 none 2 2 “n.d.” stands for “not determined”

TABLE-US-00002 TABLE 2 Composition and properties of EZ-5 to EZ-8. Example EZ-5 EZ-6 EZ-7 EZ-8 Resin comp.: Araldite ® GY-250 167.2 167.2 167.2 167.2 Araldite ® DY-E 31.8 31.8 31.8 31.8 Hardener comp.: Amine 1 29.2 20.9 20.9 — Amine 2 — — — 25.0 Jeffamine ® D-230 18.0 — — — Gaskamine ® 240 — 51.5 — — N-Benzyl-1,2- — — 27.4 27.4 propanediamine Viscosity (10′) [Pa .Math. s] 1.11 0.93 0.71 0.58 König (1 d SC) 15 55 50 109 hardness [s] (2 d SC) 80 123 136 155 (4 d SC) 97 144 153 176 (7 d SC) 106 157 158 185 (14 d SC) 132 178 170 n.d. Appearance (NK) attrac- attrac- attrac- attrac- tive tive tive tive König (7 d 8°/80%) 3 24 25 38 hardness [s] (+2 d SC) 4 50 40 50 (+7 d SC) 6 66 55 n.d. (+14 d SC) 8 85 55 n.d. Appearance (8°/80%) tacky slightly slightly attrac- matt matt tive Number of marks 1 1 1 none “n.d.” stands for “not determined”