Curing agents for low-emission epoxy resin products

Abstract

The present invention relates to curing agents for epoxy resins, containing at least one adduct of trimethylhexamethylenediamine and cresyl glycidyl ether. The curing agent has a low viscosity and cures quickly together with epoxy resins even in moist, cold conditions and without blushing to form films with a high hardness and surface quality, which scarcely undergo yellowing upon exposure to light. It is particularly suited for low-emission room temperature-curing coatings.

Claims

1. A curing agent, suitable for curing epoxy resins, comprising: at least one adduct of trimethylhexamethylenediamine and cresyl glycidyl ether, wherein the adduct is a reaction product of trimethylhexamethylenediamine and cresyl glycidyl ether in a trimethylhexamethylenediamine molecules/cresyl glycidyl ether molecules ratio in a range of 0.9 to 2.0.

2. The curing agent according to claim 1, wherein the trimethylhexamethylenediamine is 2,2,4-trimethyl-1,6-hexanediamine or 2,4,4-trimethyl-1,6-hexanediamine or a mixture of these isomers.

3. The curing agent according to claim 2, wherein the cresyl glycidyl ether is ortho-cresyl glycidyl ether.

4. The curing agent of claim 3, wherein the adduct is a reaction product of trimethylhexamethylenediamine and cresyl glycidyl ether in a trimethylhexamethylenediamine molecules/cresyl glycidyl ether molecules ratio in the range of 0.9 to 2.0.

5. The curing agent according to claim 4, wherein in addition to the adduct, additionally at least one further polyamine with at least two amine hydrogens reactive toward epoxide groups is present.

6. The curing agent according to claim 1, wherein the cresyl glycidyl ether is ortho-cresyl glycidyl ether.

7. The curing agent according to claim 1, wherein in addition to the adduct, additionally at least one further polyamine with at least two amine hydrogens reactive toward epoxide groups is present.

8. The curing agent according to claim 7, wherein the additional polyamine is a polyamine with at least two primary aliphatic amine groups.

9. The curing agent according to claim 8, wherein the polyamine with at least two primary aliphatic amine groups is selected from the group consisting of: isophorone diamine, 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(amino-methyl)bicyclo[2.2.1]heptane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0.sup.2,6]decane, 1,3-bis(aminomethyl)benzene and ether group-containing polyamines with an average molecular weight of up to 500 g/mol.

10. The curing agent according to claim 7, wherein the additional polyamine is a polyamine with at least one secondary amino group.

11. The curing agent according to claim 10, wherein the polyamine with at least one secondary amino group is selected from the group consisting of N-monoalkylated and N,N′-dialkylated 1,6-hexanediamine, 1,5-diamino-2-methylpentane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)benzene, bis(hexamethylene)triamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, N-(2-aminoethyl)-1,3-propanediamine and N,N′-bis(3-aminopropyl)ethylenediamine, with the alkyl groups benzyl, 2-phenyl ethyl, isobutyl, hexyl or 2-ethylhexyl.

12. The curing agent according to claim 11, wherein 5 to 90% of the amine hydrogens reactive toward epoxide groups in the curing agent originate from the adduct.

13. The curing agent according to claim 12, wherein a content of non-reactive diluents is less than 25 wt.-%.

14. The curing agent according to claim 7, wherein 5 to 90% of the amine hydrogens reactive toward epoxide groups in the curing agent originate from the adduct.

15. The curing agent according to claim 1, wherein a content of non-reactive diluents is less than 25 wt.-%.

16. An epoxy resin composition containing at least one epoxy resin and a curing agent according to claim 1.

17. The epoxy resin composition according to claim 16, wherein it is a two-component composition consisting of: a resin component containing at least one epoxy resin; and (ii) a curing agent component containing the curing agent.

18. A cured composition obtained from curing a composition according to claim 16.

19. An article containing a cured composition according to claim 18.

Description

EXAMPLES

(1) Exemplary embodiments are shown below, which are intended to illustrate the invention described in more detail. Of course, the invention is not limited to the exemplary embodiments described.

(2) “ANEW” stands for the amine hydrogen equivalent weight.

(3) “EEW” stands for the epoxide equivalent weight.

(4) 1. Description of the Measurement Methods

(5) The viscosity was measured on a Rheotec RC30 cone-plate viscometer with thermostat (cone diameter 50 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.−1).

(6) 2. Commercial Substances Used:

(7) TABLE-US-00001 Araldite ® DY-K (from Huntsman), cresyl glycidyl ether, EEW approx. 182 g/Eq Araldite ® GY 250 (from Huntsman), bisphenol A diglycidyl ether, EEW approx. 187.5 g/Eq Araldite ® DY-E (from Huntsman), monoglycidyl ether of C.sub.12 to C.sub.14 alcohols, EEW approx. 290 g/Eq Ancamine ® K 54 (from Air Products), 2,4,6-tris(dimethylaminomethyl)phenol Vestamin ® TMD (from Evonik), 2,2,4- and 2,4,4-trimethylhexamethylene- diamine, AHEW 39.6 g/Eq Dytek ® A (from Invista), 1,5-diamino-2-methylpentane, AHEW 29.0 g/Eq Vestamin ® IPD (from Evonik), 3-aminomethyl-3,5,5-trimethyl- cyclohexyldiamine (isophorone diamine), AHEW 42.6 g/Eq 1,3-BAC (from Mitsubishi Gas Chemical), 1,3-bis(aminomethyl)cyclo- hexane, AHEW 35.5 g/Eq MXDA (from Mitsubishi Gas Chemical), 1,3-bis(aminomethyl)- benzene Gaskamine ® 240 (from Mitsubishi Gas Chemical), styrenated 1,3-bis(amino- methyl)benzene, AHEW approx. 103 g/Eq Jeffamine ® D-230 (from Huntsman), polyoxypropylenediamine with average molecular weight of approx. 240 g/mol, AHEW 60 g/Eq Jeffamine ® RFD- (from Huntsman), cycloaliphatic ether group-containing 270 diamine from the propoxylation and subsequent amination of 1,4-dimethylol-cyclohexane, average molecular weight approx. 270 g/mol, AHEW 67 g/Eq
3. Preparation of Adducts:
Adduct A-1:

(8) 165.7 g (1.05 mol) Vestamin® TMD were placed in a vessel and heated. Under a nitrogen atmosphere and good stirring, at a temperature of 80° C. over a period of 2 hours, 182.0 g (1.00 mol) Araldite® DY-K were added slowly, making sure that the temperature of the reaction mixture did not rise above 85° C. The reaction mixture was allowed to stand for 2 hours at 80° C., then cooled to 23° C., closed, and stored. A clear, slightly yellowish liquid with a viscosity of 9.7 Pa.Math.s, an amine number of 341.5 mg KOH/g and a theoretical AHEW of approx. 109.1 g/Eq was obtained.

(9) Adduct A-2:

(10) As described for adduct A-1, 186.1 g (1.18 mol) Vestamin® TMD were reacted with 182.0 g (1.00 mol) Araldite® DY-K. A clear, slightly yellowish liquid with a viscosity of 4.8 Pa.Math.s, an amine number of 361.8 mg KOH/g and a theoretical AHEW of approx. 99.4 g/Eq was obtained.

(11) Adduct A-3:

(12) As described for adduct A-1, 186.1 g (1.10 mol) Vestamin® TMD were reacted with 182.0 g (1.00 mol) Araldite® DY-K. A clear, slightly yellowish liquid with a viscosity of 6.9 Pa.Math.s, an amine number of 351.3 mg KOH/g and a theoretical AHEW of approx. 104.2 g/Eq was obtained.

(13) Adduct A-4: (Comparison)

(14) As described for adduct A-1, 116.0 g (1.00 mol) Dytek® A were reacted with 200.2 g (1.10 mol) Araldite® DY-K. A clear, slightly yellowish liquid with a viscosity of 13.1 Pa.Math.s, an amine number of 355 mg KOH/g and a theoretical AHEW of approx. 109.1 g/Eq was obtained.

(15) Adduct A-5: (Comparison)

(16) As described for adduct A-1, 116.0 g (1.00 mol) Dytek® A was reacted with 182.0 g (1.00 mol) Araldite® DY-K. A clear, slightly yellowish liquid with a viscosity of 5.8 Pa.Math.s, an amine number of 377 mg KOH/g and a theoretical AHEW of approx. 99.4 g/Eq was obtained.

(17) Adduct A-6: (Comparison)

(18) As described for adduct A-1, 127.6 g (1.10 mol) Dytek® A was reacted with 182.0 g (1.00 mol) Araldite® DY-K. A clear, slightly yellowish liquid with a viscosity of 3.1 Pa.Math.s, an amine number of 401 mg KOH/g and a theoretical AHEW of approx. 91.1 g/Eq was obtained.

(19) Adduct A-7: (Comparison)

(20) As described for adduct A-1, 187.4 g (1.10 mol) Vestamin® IPD was reacted with 182.0 g (1.00 mol) Araldite® DY-K. A clear, slightly yellowish, highly viscous liquid with a viscosity, measured at 40° C., of 17.5 Pa.Math.s, an amine number of 340 mg KOH/g and a theoretical AHEW of approx. 108.7 g/Eq was obtained.

(21) Adduct A-8: (Comparison)

(22) As described for adduct A-1, 156.4 g (1.10 mol) 1,3-BAC was reacted with 182.0 g (1.00 mol) Araldite® DY-K. A clear, slightly yellowish liquid with a viscosity of 59.4 Pa.Math.s, an amine number of 369 mg KOH/g and a theoretical AHEW of approx. 99.5 g/Eq was obtained.

(23) 4. Preparation of Hydrogenated Amines

(24) Benzylated MXDA:

(25) In a round-bottom flask, 17.0 g (0.16 mol) benzaldehyde and 13.6 g (0.10 mol) MXDA were dissolved under a nitrogen atmosphere in a sufficient quantity of isopropanol. The solution was stirred for 30 minutes at 23° C. and then hydrogenated at a hydrogen pressure of 80 bar, a temperature of 80° C. and a flow rate of 3 ml/min on a continuously operating hydrogenation apparatus with Pd/C-fixed-bed catalyst. To follow the progress of the reaction, IR spectroscopy was used to check whether the imine band at approx. 1665 cm.sup.−1 had disappeared. Then the solution was concentrated under vacuum at 80° C. The product obtained was a clear, yellowish oil with a viscosity of 0.1 Pa.Math.s at 20° C., an amine number of 416.8 mg KOH/g and a theoretical AHEW of approx. 115.5 g/Eq.

(26) Ethylhexylated MXDA:

(27) In the same manner as for the benzylated MXDA, 25.6 g (0.20 mol) 2-ethylhexanal and 13.6 g (0.10 mol) MXDA were reacted. A clear, slightly yellowish liquid with a viscosity of 140 mPa.Math.s at 20° C., an amine number of 308.6 mg KOH/g and a theoretical AHEW of approx. 180.3 g/Eq was obtained.

(28) 5. Preparation of Curing Agents and Epoxy Resin Compositions

(29) For each example, the constituents shown in Tables 1 to 4 were mixed in the indicated quantities (in parts by weight) of the curing agent component using a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and stored with exclusion of moisture.

(30) Similarly, the constituents of the resin component shown in Tables 1 to 4 were processed and stored.

(31) Then the two components of each composition were processed using the centrifugal mixer into a homogenous liquid which was tested immediately thereafter as follows:

(32) 10 minutes after mixing, the viscosity was determined at 20° C. (“viscosity (10′)”).

(33) A first film was drawn in a layer thickness of 500 μm on a glass plate and held at 23±1° C. and 50±5% relative humidity (=standard climate, abbreviated as “SC” in the following), or cured. The König hardness (pendulum hardness according to König, measured according to DIN EN ISO 1522) of this film was determined after 2 days (“König hardness (SC) (2d)”), after 4 days (“Kónig hardness (SC) (4d)”), after 7 days (“König hardness (SC) (7d)”) and either after 4 weeks (“König hardness (SC) (4w)”) or after 14 days (“König hardness (SC) (14d)”). After 14 days the appearance of the film was assessed (designated in the table as “Appearance (SC)”). The designation “good” was applied to a film that was clear and had a glossy, non-sticky, non-structured surface. The term “structure” is applied to any kind of marking or pattern on the surface.

(34) A second film was drawn at a layer thickness of 500 μm on a glass plate, and this was stored immediately after application for 7 days at 8° C. and 80% relative humidity and then for 3 weeks under SC, or cured. 24 hours after the application, a polypropylene bottle cap was placed on the film, and a damp sponge piece was placed under the cap. After an additional 24 hours, the sponge piece and the cap were removed and placed at a new location on the film, from which it was removed after 24 hours and moved to a new place, for a total of 4 times. Then the appearance of this film was assessed (designated in the tables as “Appearance (8°/80%)”), in the manner described for the appearance (SC). Here also the number of marks visible on the film due to the damp sponge piece and/or the covering cap was reported. Again, the Konig hardness was determined for the films thus cured, in each case after 7 days at 8° C. and 80% relative humidity (“Kónig hardness (7d 8°/80%)”), then after an additional 2 days under SC (“König hardness (+2d SC)”), 7 days under SC (“König hardness (+7d SC)”) and in some instances also after 3 weeks under SC (“König hardness (+3w SC)”).

(35) The results are given in Tables 1 to 4.

(36) The epoxy resin compositions EZ-1 to EZ-13 are examples according to the invention. The epoxy resin compositions Ref-1 to Ref-11 are comparison examples.

(37) TABLE-US-00002 TABLE 1 Composition and properties of EZ-1 to EZ-3 and Ref-1 to Ref-3. Example EZ-1 Ref-1 EZ-2 Ref-2 EZ-3 Ref-3 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 curing agent-comp. adduct A-1 A-4 A-1 A-4 A-1 A-4 109.1 109.1 65.5 65.5 65.5 65.5 Jeffamine ® D-230 — — 24.0 24.0 — — Jeffamine ® RFD-270 — — — — 26.8 26.8 Ancamine ® K 54 6.2 6.2 5.8 5.8 5.8 5.8 Viscosity (10′) [Pa .Math. s] 3.5 4.1 1.2 1.4 1.7 2.2 König (2 d SC) 158 172 154 131 186 179 hardness (4 d SC) 179 192 189 143 206 192 [s] (7 d SC) 185 202 204 192 218 209 (4 w SC) 208 209 213 210 217 215 Appearance (SC) good, sl. good, sl. good, good, high schlie- high struc- high high gloss ren, gloss ture, gloss gloss poor little gloss gloss König (7 d 8°/80%) 62 68 49 55 73 78 hardness (+2 d SC) 160 165 164 150 180 175 [s] (+7 d SC) 183 192 204 189 210 189 (+3 w SC) 203 206 208 201 212 204 Appearance (8°/80%) good, sl. good, sl. good, sl. No. of markings high dull, high struc- high dull, gloss; little gloss; ture, gloss; little none gloss; 1 little none gloss; 1 gloss; 1 1 “sl.” stands for “slight(ly)”

(38) TABLE-US-00003 TABLE 2 Composition and properties of EZ-4 to EZ-6 and Ref-4 to Ref-6. Example EZ-4 Ref-4 EZ-5 Ref-5 EZ-6 Ref-6 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 curing agent-comp. adduct A-2 A-5 A-2 A-5 A-2 A-5 99.4 99.4 59.6 59.6 59.6 59.6 Jeffamine ® D-230 — — 24.0 24.0 — — Jeffamine ® RFD-270 — — — — 26.8 26.8 Ancamine ® K 54 6.0 6.0 5.7 5.7 5.7 5.7 Viscosity (10′) [Pa .Math. s] 2.7 3.1 1.1 1.1 1.6 1.6 König (2 d SC) 164 186 161 150 186 182 hardness (4 d SC) 176 199 189 163 206 202 [s] (7 d SC) 186 209 201 189 215 212 (4 w SC) 203 215 209 210 216 214 Appearance (SC) good, slightly good, slight good, sl. cloudy, high dull little high structure, high little gloss gloss gloss little gloss gloss gloss König (7 d 8°/80%) 64 73 52 49 67 76 hardness (+2 d SC) 155 161 158 148 178 167 [s] (+7 d SC) 197 180 186 172 196 189 (+3 w SC) 201 202 201 199 204 209 Appearance (8°/80%) slightly slightly good, slightly good, slightly No. of markings dull little dull little high dull little high dull little gloss; gloss; gloss; gloss; gloss; gloss; 1 1 1 1 none none “sl.” stands for “slight(ly)”

(39) TABLE-US-00004 TABLE 3 Composition and properties of EZ-7 to EZ-12 and Ref-7 and Ref-8. Example EZ-7 Ref-7 EZ-8 Ref-8 EZ-9 EZ-10 EZ-11 EZ-12 Resin comp.: Araldite ® GY-250 167.2 167.2 167.2 167.2 167.2 167.2 167.2 167.2 Araldite ® DY-E 31.8 31.8 31.8 31.8 31.8 31.8 31.8 31.8 Curing agent-comp.: Adduct A-2 A-5 A-2 A-5 A-1 A-1 A-1 A-1 59.6 59.6 59.6 59.6 65.5 65.5 43.6 54.6 Gaskamine ® 240 36.1 36.1 — — 36.1 — 20.6 — benzylated MXDA — — 40.4 40.4 — 40.4 — — ethylhexylated MXDA — — — — — — — 21.6 Jeffamine ® D-230 — — — — — — 24.0 — Jeffamine ® RFD-270 — — — — — — — 25.5 Ancamine ® K 54 5.9 5.9 6.0 6.0 6.1 6.2 5.7 6.0 Viscosity (10′) [Pa .Math. s] 1.4 1.6 1.0 1.3 1.7 1.3 0.97 0.87 König (2 d SC) 141 132 171 140 151 162 136 126 hardness (4 d SC) 165 176 192 164 176 183 180 157 [s] (7 d SC) 189 196 204 193 195 195 203 176 (4 w SC) 211 207 214 210 203 209 215 193 Appearance (SC) good, sl. cloudy, good, good, good, good, good, good, high little high high high high high high gloss gloss gloss gloss gloss gloss gloss gloss König (7 d 8°/80%) 56 66 64 69 59 62 47 51 h. (+2 d SC) 146 162 162 169 153 158 152 130 [s] (+7 d SC) 190 189 197 195 187 192 193 168 (+3 w SC) 203 201 207 205 204 204 202 182 Appearance (8°/80%) good, sl. cloudy, good, sl. cloudy, good, good, good, good, No. of markings high little high little high high high high gloss; gloss; gloss; gloss; gloss; gloss; gloss; gloss; none none none none none none none none “sl.” stands for “slight(ly)”; “ethylhexylated” stands for “ethyl-hexylated”

(40) TABLE-US-00005 TABLE 4 Composition and properties of EZ-13 and Ref-9 to Ref-11. Example EZ-13 Ref-9 Ref-10 Ref-11 Resin comp.: Araldite ® GY-250 167.2 167.2 167.2 167.2 Araldite ® DY-E 31.8 31.8 31.8 31.8 Curing agent-comp. Adduct A-3 A-6 A-7 A-8 62.5 54.7 65.2 59.7 Jeffamine ® D-230 24.0 24.0 24.0 24.0 Ancamine ® K 54 5.7 5.6 5.8 5.7 Viscosity (10′) [Pa .Math. s] 1.2 1.0 2.7 1.8 König (2 d SC) 148 130 174 181 hardness (4 d SC) 189 171 214 192 [s] (7 d SC) 195 192 225 219 (14 d SC) 209 197 227 220 Appearance (SC) good, dull, fine good, slight high gloss bubbles high gloss structure, dull König (7 d 8°/80%) 42 32 62 76 hardness (+2 d SC) 157 106 197 155 [s] (+7 d SC) 189 157 220 193 Appearance (8°/80%) good, dull/ good, dull; No. of markings high gloss; cloudy; high gloss; 1 1 2 1