Amine for low-emission epoxy resin products

Abstract

The present invention relates to an amine of the formula (I) which is an adduct of 1,2-propylenediamine with an aryl monoglycidyl ether, to the use thereof as part of a hardener for epoxy resins, and to epoxy resin compositions obtained therewith. The amine of the formula (I) is preparable in a simple process in high purity, is of very low viscosity and is especially suitable for the curing of epoxy resins. It allows low-emission epoxy resin compositions which have good workability and which cure even under cold and damp conditions, quickly and without blushing effects, to form very hard products of high surface quality that display virtually no yellowing on exposure to light.

Claims

1. An amine of the formula (I), ##STR00003## where R is an alkyl, cycloalkyl, aralkyl or alkoxy radical having 1 to 22 carbon atoms which optionally comprises unsaturated fractions; and n is 0 or 1 or 2 or 3.

2. The amine as claimed in claim 1, wherein n is 1.

3. The amine as claimed in claim 1, wherein R is methyl.

4. A process for preparing an amine as claimed in claim 1 comprising reacting 1,2-propylenediamine with an aryl glycidyl ether in a 1,2-propylenediamine/aryl glycidyl ether molar ratio in a range from 1.1 to 5, and subsequent distillative removal of unreacted 1,2-propylenediamine.

5. A method of hardening epoxy resins by mixing a hardener comprising the amine of formula (I) as claimed in claim 1 with at least one epoxy resin.

6. The method as claimed in claim 5, wherein the hardener comprises the amine of formula (I) in an amount such that 5 to 100% of the amine hydrogens in the hardener that are reactive toward epoxide groups originate from the amine of the formula (I).

7. The method as claimed in claim 5, wherein the hardener comprises at least one further polyamine having at least two amine hydrogens that are active toward epoxide groups.

8. The method as claimed in claim 7, wherein the further polyamine is a primary diamine selected from the group consisting of 2,2,4- and 2,4,4-trimethylhexamethylenediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 1,3-bis(aminomethyl)benzene, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclohexyl)methane, 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0.sup.2,6]decane, and polyamines containing ether groups and having an average molecular weight of up to 500 g/mol.

9. The method as claimed in claim 7, wherein the further polyamine is a polyamine having at least one secondary amino group, selected from the group consisting of N-monoalkylated 1,6-hexanediamine, N,N-dialkylated 1,6-hexanediamine, N-monoalkylated 1,5-diamino-2-methylpentane, N,N-dialkylated 1,5-diamino-2-methylpentane, N-monoalkylated 1,3-bis(aminomethyl)cyclohexane, N,N-dialkylated 1,3-bis(aminomethyl)cyclohexane, N-monoalkylated 1,4-bis(aminomethyl)cyclohexane, N,N-dialkylated 1,4-bis(aminomethyl)cyclohexane, N-monoalkylated 1,3-bis(aminomethyl)benzene, N,N-dialkylated 1,3-bis(aminomethyl)benzene, N-monoalkylated bis(hexamethylene)triamine, N,N-dialkylated bis(hexamethylene)triamine, N-monoalkylated diethylenetriamine, N,N-dialkylated diethylenetriamine, N-monoalkylated triethylenetetramine, N,N-dialkylated triethylenetetramine, N monoalkylated tetraethylenepentamine, N,N-dialkylated tetraethylenepentamine, N-monoalkylated dipropylenetriamine, N,N-dialkylated dipropylenetriamine, N-monoalkylated N-(2-aminoethyl)-1,3-propanediamine, N,N-dialkylated N-(2-aminoethyl)-1,3-propanediamine, N-monoalkylated N,N-bis(aminopropyl)-1,4-diaminobutane and N,N-dialkylated N,N-bis(aminopropyl)-1,4-diaminobutane, the alkyl groups being selected in each case from the group consisting of benzyl, 2-phenylethyl, isobutyl, hexyl, and 2-ethylhexyl.

10. The method as claimed in claim 7, wherein the further polyamine is a diamine containing ether groups.

11. The method as claimed in claim 5, wherein the hardener contains less than 25 weight % of unincorporable diluents.

12. An epoxy resin composition comprising at least one epoxy resin and a hardener as described in claim 5.

13. The epoxy resin composition as claimed in claim 12, wherein it is a two-pack composition consisting of (i) a resin component comprising at least one epoxy resin, and (ii) a hardener component comprising the hardener.

14. A cured composition obtained from the curing of an epoxy resin composition as claimed in claim 12.

15. An article comprising a cured composition as claimed in claim 14.

16. The amine as claimed in claim 1, wherein R is methyl or tert-butyl.

Description

EXAMPLES

(1) 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 that are described.

(2) AHEW stands for the amine hydrogen equivalent weight.

(3) EEW stands for the epoxide equivalent weight.

1. Description of Measurement Methods

(4) 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).

(5) 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).

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

(7) The melting point was determined by means of DMTA measurement in the temperature range from 50 C. to 25 C., at 5 K/min and 10 Hz.

2. Commercial Substances Used

(8) Araldite DY-K: (from Huntsman), 2-cresyl glycidyl ether, EEW about 183 g/eq Araldite DY-P: (from Huntsman), p-tert-butylphenyl glycidyl ether, EEW about 225 g/eq Cardolite LITE (from Cardolite), glycidyl ether of cardanol, EEW about 2513HP: 415 g/eq Araldite GY 250: (from Huntsman), bisphenol A diglycidyl ether, EEW about 187.5 g/eq Araldite DY-E: (from Huntsman), monoglycidyl ether of C.sub.12 to C.sub.14 alcohols, EEW about 290 g/eq Ancamine K 54: (from Air Products), 2,4,6-tris(dimethylaminomethyl)phenol Dytek A: (from Invista), 1,5-diamino-2-nnethylpentane, AHEW MXDA: (from Mitsubishi Gas Chemical), 1,3-bis(aminomethyl)-benzene Gaskamine 240: (from Mitsubishi Gas Chemical), styrenized 1,3-bis(aminomethyl)benzene, AHEW about 103 g/eq Jeffamine D-230: (from Huntsman), polyoxypropylenediamine with average molecular weight of about 240 g/mol, AHEW 60 g/eq Jeffamine RFD-270: (from Huntsman), cycloaliphatic diamine containing ether groups, from the propoxylation and subsequent amination of 1,4-dimethylolcyclohexane, average molecular weight about 270 g/mol, AHEW 67 g/eq Vestamin TMD: (from Evonik), 2,2,4- and 2,4,4-trimethylhexamethylenediamine, AHEW 39.6 g/eq 1,3-BAC: (from Mitsubishi Gas Chemical), 1,3-bis(aminomethyl)cyclohexane, AHEW 35.5 g/eq

3. Preparation of Amines

Amine A-1: 1-((2-Aminopropyl)amino)-3-(2-methylphenoxy)propan-2-ol

(9) 4.15 kg (56 mol) of 1,2-propylenediamine were introduced under a nitrogen atmosphere and heated to 70 C., and slowly 2.93 kg (16 mol) of Araldite DY-K were added, accompanied by thorough stirring, the temperature of the reaction mixture being held by cooling at between 70 and 80 C. The reaction mixture was left at 80 C. for an hour, then cooled and freed of its volatile constituents on a thin-film evaporator (0.5-1 mbar, jacket temperature 115 C.). This gave a clear, slightly yellowish liquid having a viscosity at 20 C. of 3.3 Pa.Math.s, an amine number of 478.7 mg KOH/g, a purity of 91.5% (determined by gas chromatography, 8.5% 1,3-bis(2-methylphenoxy)propan-2-ol from Araldite DY-K), a melting point of 25 C., and a theoretical AHEW of about 85.7 g/eq. FT-IR: 3025, 2955, 2918, 1601, 1590, 1494, 1456, 1377, 1307, 1288, 1242, 1191, 1120, 1050, 1035, 926, 837, 748, 713.

Amine A-2: 1-((2-Aminopropyl)amino)-3-(4-tert-butylphenoxy)propan-2-ol

(10) 77.4 g (1.04 mol) of 1,2-propylenediamine were introduced under a nitrogen atmosphere and heated to 70 C., and slowly 67.5 g (0.3 mol) of Araldite DY-P were added, accompanied by thorough stirring. The reaction mixture was left at 80 C. for 2 hours. The volatile constituents were then removed on a rotary evaporator at 65 C. and 1 mbar over 3 hours. This gave a clear, slightly yellowish liquid having a viscosity of 105 Pa.Math.s, an amine number of 374.9 mg KOH/g, and a theoretical AHEW of about 99.7 g/eq.

Amine A-3

(11) As described for amine A-2, 51.9 g (0.7 mol) of 1,2-propylenediamine were reacted with 83.0 g (0.2 mol) of Cardolite LITE 2513HP. This gave a clear, slightly yellowish liquid having a viscosity of 1.93 Pas, an amine number of 204.3 mg KOH/g, and a theoretical AHEW of about 163.0 g/eq.

Amine A-4: (Comparative)

(12) As described for amine A-1, 4.65 kg (40 mol) of Dytek A were reacted with 1.83 kg (10 mol) of Araldite DY-K, the jacket temperature of the thin-film evaporator being 160 C. This gave a clear, slightly yellowish liquid having a viscosity at 20 C. of 6.5 Pa's, an amine number of 367.1 mg KOH/g, and a theoretical AHEW of about 99.7 g/eq.

Amine A-5: (Comparative)

(13) As described for amine A-2, 96.2 g (1.6 mol) of ethylenediamine were reacted with 73.2 g (0.4 mol) of Araldite DY-K. This gave a clear, slightly yellowish liquid having a viscosity of 8.26 Pas, an amine number of 484.9 mg KOH/g, and a theoretical AHEW of about 81.0 g/eq.

(14) Amines A-1 to A-3 are amines of the formula (I); the amines A-4 and A-5 serve for comparison.

4. Preparation of Alkylated Amines

Benzylated MXDA

(15) In a round-bottomed flask, 17.0 g (0.16 mol) of benzaldehyde and 13.6 g (0.10 mol) of MXDA were dissolved under a nitrogen atmosphere in a sufficient quantity of isopropanol. The solution was stirred at 23 C. for 30 minutes and then subjected to hydrogenation under a hydrogen pressure of 80 bar at a temperature of 80 C. with a flow rate of 3 ml/min on a continuously operating 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. Thereupon, the solution was concentrated under reduced pressure at 80 C. This gave a clear, yellowish oil having a viscosity of 0.1 Pas at 20 C., an amine number of 416.8 mg KOH/g, and a theoretical AHEW of about 115.5 g/eq.

Ethylhexylated MXDA

(16) In the same way as described for the benzylated MXDA, 25.6 g (0.20 mol) of 2-ethylhexanal and 13.6 g (0.10 mol) of MXDA were reacted. This gave a clear, slightly yellowish liquid having a viscosity of 140 mPa.Math.s at 20 C., an amine number of 308.6 mg KOH/g, and a theoretical AHEW of about 180.3 g/eq.

5. Production of Hardeners and Epoxy Resin Compositions

(17) For each example, the ingredients specified in Tables 1 to 4 were mixed in the specified amounts (in parts by weight) of the hardener component by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) and stored in the absence of moisture.

(18) Similarly, the ingredients of the resin component as specified in Tables 1 to 4 were processed and stored.

(19) Subsequently the two components of each composition were processed to a homogeneous liquid using the centrifugal mixer, and this liquid was immediately tested as follows:

(20) 10 minutes after mixing, the viscosity at 20 C. was ascertained (viscosity (10)).

(21) A first film was drawn down in a thickness of 500 m onto a glass plate, which was stored at 231 C. and 505% relative humidity (i.e., standard conditions, abbreviated below to SC), and cured. The Knig hardness (pendulum hardness by Knig method, measured according to DIN EN ISO 1522) of this film was ascertained after 2 days (Knig hardness (SC) (2d)), after 4 days (Knig hardness (SC) (4d)), after 7 days (Knig hardness (SC) (7d)), and after 14 days (Knig hardness (SC) (14 d)). After 14 days, the aspect of the film was assessed (designated in the table as aspect (SC)). A film designated attractive was clear and had a glossy and nonsticky surface without structure. Structure in this context is any kind of marking or pattern on the surface.

(22) A second film was drawn down in a thickness of 500 m onto a glass plate, which, immediately after application, was stored for 7 days at 8 C. and 80% relative humidity and then for 3 weeks under SC, and cured. 24 hours after application, a polypropylene bottle cap was placed on the film, with a moist piece of sponge placed beneath it. After a further 24 hours, the sponge and the cap were removed, and were placed at a new site on the film, then removed again after 24 hours and placed at a new site, a total of 4 times. Subsequently the aspect of this film was assessed (identified in the tables as aspect (8/80%)), in the same way as described for the aspect (SC). In this case each time the number of markings was also indicated that were visible in the film as a result of the moist sponge and/or the applied cap. Once again, the Knig hardness of the films cured in this way was ascertained, in each case after 7 days at 8 C. and 80% relative humidity (Knig h. (7 d 8/80%)), then after a further 2 days under SC (Knig h. (+2 d SC)), 7 days under SC (Knig h. (+7 d SC)), and after 14 days under SC (Knig h. (+14 d SC)).

(23) The results are recorded in Tables 1 to 4.

(24) The epoxy resin compositions EZ-1 to EZ-16 are inventive examples. The epoxy resin compositions Ref-1 to Ref-9 are comparative examples.

(25) TABLE-US-00001 TABLE 1 Composition and properties of EZ-1 to EZ-4 and Ref-1 to Ref-3. Example EZ-1 EZ-2 EZ-3 EZ-4 Ref-1 Ref-2 Ref-3 Resin comp.: Araldite GY-250 167.2 167.2 167.2 167.2 167.2 167.2 167.2 Araldite DY-E 31.8 31.8 31.8 31.8 31.8 31.8 31.8 Hardener comp.: Amine A-1 A-1 A-2 A-3 A-4 A-4 A-5 85.7 85.7 99.7 163.0 99.7 99.7 81.0 Ancamine K 54 2.8 2.9 2.9 2.9 2.8 Viscosity (10) [Pa .Math. s] 2.19 2.24 6.05 1.81 3.49 3.63 8.51 Knig (1 d SC) 105 137 119 n.m. 64 101 151 hardness (2 d SC) 165 186 175 9 98 139 176 [s] (4 d SC) 199 210 204 18 125 166 195 (7 d SC) 214 221 220 27 148 182 200 (14 d SC) 218 220 221 38 171 180 204 Aspect (SC) attrac- attrac- attrac- attrac- attrac- attrac- milky tive tive tive tive tive tive Knig (7 d 8/80%) 59 81 83 n.m. 35 52 87 h. (+2 d SC) 175 183 181 n.m. 88 126 172 [s] (+7 d SC) 206 198 221 n.m. 125 168 196 (+14 d SC) 205 203 220 n.m. 151 175 198 Aspect (8/80%) attrac- attrac- attrac- sticky attrac- attrac- milky 3 Number of marks tive 1 tive 1 tive 2 n.d. tive 1 tive 1 n.m. stands for not measurable. n.d. stands for not determined.

(26) TABLE-US-00002 TABLE 2 Composition and properties of EZ-5 to EZ-11. Example EZ-5 EZ-6 EZ-7 EZ-8 EZ-9 EZ-10 EZ-11 Resin comp.: Araldite GY-250 167.2 167.2 167.2 167.2 167.2 167.2 167.2 Araldite DY-E 31.8 31.8 31.8 31.8 31.8 31.8 31.8 Hardener comp.: Amine A-1 A-1 A-1 A-1 A-1 A-1 A-2 51.4 34.3 42.9 42.9 42.9 42.9 59.8 Jeffamine D-230 24.0 24.0 18.0 21.0 21.0 24.0 Jeffamine RFD-270 20.1 Gaskamine 240 20.6 Ethylhexylated MXDA 36.0 Benzylated MXDA 23.1 1,3-BAC 5.3 VestaminTMD 5.9 Ancamine K 54 2.7 2.8 3.0 2.8 2.7 2.7 2.8 Viscosity (10) [Pa .Math. s] 1.07 0.79 0.56 0.91 0.97 0.94 1.73 Knig (1 d SC) 74 75 33 74 84 46 60 hardness (2 d SC) 160 148 81 153 122 104 143 [s] (4 d SC) 185 186 110 190 170 181 198 (7 d SC) 206 200 133 203 171 206 219 (14 d SC) 207 218 143 213 179 214 218 Aspect (SC) attrac- attrac- attrac- attrac- sl. attrac- attrac- tive tive tive tive structure tive tive Knig (7 d 8/80%) 50 47 25 47 33 24 53 h. (+2 d SC) 151 160 77 167 104 81 165 [s] (+7 d SC) 165 206 111 203 151 116 193 (+14 d SC) 168 205 115 204 153 121 198 Aspect (8/80%) attrac- attrac- attrac- attrac- attrac- attrac- attrac- Number of marks tive 1 tive 1 tive none tive 1 tive 2 tive 2 tive 2 sl. stands for slight

(27) TABLE-US-00003 TABLE 3 Composition and properties of Ref-4 to Ref-9. Example Ref-4 Ref-5 Ref-6 Ref-7 Ref-8 Ref-9 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 A-4 A-4 A-4 A-5 A-5 A-5 59.8 39.9 49.9 48.6 32.4 40.5 Jeffamine D-230 24.0 24.0 21.0 24.0 24.0 21.0 Gaskamine 240 20.6 20.6 1,3-BAC 5.3 5.3 Ancamine K 54 2.8 2.8 2.7 2.7 2.8 2.7 Viscosity (10') [Pa .Math. s] 1.21 0.93 1.13 2.13 0.97 1.24 Knig (1 d SC) 50 42 75 89 63 108 hardness (2 d SC) 112 102 148 141 123 158 [s] (4 d SC) 155 155 186 181 166 190 (7 d SC) 183 173 195 191 183 202 (14 d SC) 200 192 203 204 197 213 Aspect (SC) attrac- attrac- attrac- sl. attrac- attrac- tive tive tive milky tive tive Knig (7 d 8/80%) 35 25 26 47 32 29 h. (+2 d SC) 132 111 46 151 109 91 [s] (+7 d SC) 175 169 77 182 160 119 (+14 d SC) 188 176 79 185 164 122 Aspect (8/80%) attrac- attrac- sl. sl. attrac- attrac- Number of marks tive 1 tive 1 sticky 2 milky 1 tive 1 tive 2 sl. stands for slightly

(28) TABLE-US-00004 TABLE 4 Composition and properties of EZ-12 to EZ-16. Example EZ-12 EZ-13 EZ-14 EZ-15 EZ-16 Resin comp.: Araldite GY-250 167.2 167.2 167.2 167.2 167.2 Araldite DY-E 31.8 31.8 31.8 31.8 31.8 Hardener comp.: Amine A-1 A-1 A-1 A-1 A-1 79.5 89.9 47.7 54.0 31.8 Jeffamine D-230 24.0 24.0 24.0 Gaskamine 240 20.6 Salicylic acid.sup.1 1.6 4.8 1.0 2.9 1.6 Ancamine K 54 0.8 1.9 0.7 1.2 0.8 Viscosity (10) [Pa .Math. s] 2.86 11.10 1.16 2.40 0.92 Knig hardness (1 d SC) 115 83 56 45 43 [s] (2 d SC) 171 150 146 126 111 (4 d SC) 200 185 188 178 169 (7 d SC) 219 197 209 197 189 (14 d SC) 219 217 211 213 201 Aspect (SC) attractive attractive attractive attractive attractive Knig h. (7 d 8/80%) 68 59 42 36 36 [s] (+2 d SC) 175 171 161 148 148 (+7 d SC) 219 199 185 192 175 (+14 d SC) 216 218 203 207 188 Aspect (8/80%) attractive 1 attractive 1 attractive 1 attractive attractive 1 Number of marks none .sup.1dissolved in the premixed amines