CURING AGENTS FOR EPOXY RESIN COATINGS

Abstract

A curing agent for epoxy resins, including 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzyl-1,2-ethandiamine in an amount for the ratio of the number of its amine hydrogens to be in the range of 90/10 to 20/80. The curing agent permits suitable epoxy resin compositions that have excellent workability and that cure particularly rapidly in cold and damp conditions, without blushing-induced surface defects, thus achieving coatings of in particular high hardness, high glass transition temperature and surprisingly little tendency to yellowing.

Claims

1. A curing agent for epoxy resins, comprising 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzylethane-1,2-diamine in such an amount that the ratio of the number of amine hydrogens therein is within a range from 90/10 to 20/80.

2. The curing agent as claimed in claim 1, wherein less than 10% by weight, weight of 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane adducted with epoxy resin is present.

3. The curing agent as claimed in claim 1, wherein N-benzylethane-1,2-diamine has a purity of at least 80% by weight.

4. The curing agent as claimed in claim 1, wherein less than 10% by weight of N-benzylethane-1,2-diamine adducted with epoxy resin is present.

5. The curing agent as claimed in claim 1, wherein the ratio of the number of amine hydrogens from 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzylethane-1,2-diamine is within a range from 80/20 to 25/75.

6. The curing agent as claimed in claim 1, wherein at least one further constituent selected from the group consisting of further amines, accelerators, and thinners is present.

7. The curing agent as claimed in claim 1, wherein at least 30% of all the amine hydrogens present in the curing agent originate from 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and N-benzylethane-1,2-diamine.

8. The curing agent as claimed in claim 1, wherein it contains salicylic acid.

9. An epoxy resin composition comprising a resin component comprising at least one epoxy resin and a curing agent component comprising the curing agent as claimed in claim 1.

10. The epoxy resin composition as claimed in claim 9, wherein, 10 minutes after the resin component and curing agent component have been mixed, it has a viscosity at 20° C. within a range from 100 to 4000 mPa.Math.s, measured using a cone-plate viscometer at a shear rate of 10 s.sup.−1.

11. The epoxy resin composition as claimed in claim 9, wherein after the components have been mixed and after a curing time of 14 days at room temperature, it has a glass transition temperature during the first heating (first run) of at least 45° C., and during the second heating (second run) of at least 60° C., determined by DSC with a measurement program of (1) −10° C. for 2 min, (2) −10 to 200° C. at a heating rate of 10 K/min (=first run), (3) 200 to −10° C. at a cooling rate of −50 K/min, (4) −10° C. for 2 min, (5) −10 to 180° C. at a heating rate of 10 K/min (=second run).

12. A method comprising: applying the epoxy resin composition as claimed in claim 9 to a substrate, wherein the epoxy resin composition is applied to the substrate as a coating, primer, adhesive, sealant, potting compound, casting resin, impregnating resin or as matrix.

13. A method for coating, comprising the steps of (i) mixing the components of the epoxy resin composition as claimed in claim 9, (ii) applying the mixed composition to a substrate within the pot life, followed by the curing of the mixed composition.

14. A method for bonding, comprising the steps of (i) mixing the components of the epoxy resin composition as claimed in claim 9, (ii) applying the mixed composition within the pot life, either to at least one of the substrates to be bonded and joining the substrates to form a bond within the open time, or into a cavity or gap between two or more substrates and optionally inserting an anchor into the cavity or gap within the open time, followed by the curing of the mixed composition.

15. An article obtained from the method as claimed in claim 12.

16. An article obtained from the method as claimed in claim 13.

17. An article obtained from the method as claimed in claim 14.

Description

EXAMPLES

[0145] Working examples are adduced hereinafter, which are intended to further elucidate the invention described. The invention is of course not limited to these described working examples.

[0146] “AHEW” stands for amine hydrogen equivalent weight.

[0147] “EEW” stands for epoxy equivalent weight.

[0148] “Standard climatic conditions” (“SCC”) refers to a temperature of 23±1° C. and a relative air humidity of 50±5%.

[0149] The chemicals used were unless otherwise stated from Sigma-Aldrich Chemie GmbH.

[0150] Description of the Measurement Methods:

[0151] The viscosity was measured on a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.−1).

[0152] The amine value was determined by titration (with 0.1N HClO.sub.4 in acetic acid against crystal violet).

[0153] Substances and Abbreviations Used: [0154] Araldite® GY 250: Bisphenol A diglycidyl ether, EEW 187 g/equiv. (from Huntsman) [0155] Araldite® DY-E: Monoglycidyl ethers of C.sub.12 to C.sub.14 alcohols, EEW approx. 290 g/equiv. (from Huntsman) [0156] IPDA: 1-Amino-3-aminomethyl-3,5,5-trimethylcyclohexane, AHEW 42.6 g/equiv. (Vestamin® IPD from Evonik) [0157] B-EDA: N-Benzylethane-1,2-diamine, prepared as described below, 150.2 g/mol, AHEW 50 g/equiv. [0158] BAC 1,3-Bis(aminomethyl)cyclohexane, AHEW 35.5 g/equiv. (from Mitsubishi Gas Chemical) [0159] MXDA 1,3-Bis(aminomethyl)benzene, AHEW 34 g/equiv. (from Mitsubishi Gas Chemical) [0160] TMD 2,2(4),4-Trimethylhexamethylenediamine, AHEW 39.6 g/equiv. (Vestamin® TMD from Evonik) [0161] TEPA Tetraethylenepentamine, AHEW about 30 g/equiv. (technical grade, from Huntsman) [0162] Ancamine® K54 2,4,6-Tris(dimethylaminomethyl)phenol (from Air Products)

[0163] N-Benzylethane-1,2-Diamine (B-EDA):

[0164] A round-bottomed flask was charged with 180.3 g (3 mol) of ethane-1,2-diamine under a nitrogen atmosphere at room temperature. A solution of 106.0 g (1 mol) of benzaldehyde in 1200 ml of isopropanol was slowly added dropwise while stirring well and stirring was continued for a further 2 hours. The reaction mixture was then hydrogenated in a continuous hydrogenation apparatus with a Pd/C fixed-bed catalyst at a hydrogen pressure of 80 bar, a temperature of 80° C., and a flow rate of 5 ml/min. To monitor the reaction, IR spectroscopy was used to check whether the imine band at approx. 1665 cm.sup.−1 had disappeared. The hydrogenated solution was then concentrated on a rotary evaporator at 65° C., removing unreacted ethane-1,2-diamine, water, and isopropanol. The reaction mixture thus obtained was a clear, pale yellowish liquid having an amine value of 678 mg KOH/g and containing approx. 85% by weight of N-benzylethane-1,2-diamine (retention time 8.47-8.57 min), as determined by GC.

[0165] 120 g of this reaction mixture was purified by distillation at 80° C. under reduced pressure, resulting in 75.1 g of distillate (N-benzylethane-1,2-diamine) being collected at a vapor temperature of 60 to 65° C. and 0.06 mbar. A colorless liquid having a viscosity of 8 mPa.Math.s at 20° C., an amine value of 750 mg KOH/g and a purity, determined by GC, of >97% was obtained. This was used for the further examples.

[0166] Preparation of Curing Agents and Epoxy Resin Compositions:

Examples 1 to 18

[0167] For each example, the ingredients of the resin component specified in Tables 1 to 3 were mixed in the specified amounts (in parts by weight) using a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and stored with the exclusion of moisture.

[0168] The ingredients of the curing agent component specified in Tables 1 to 3 were likewise processed and stored.

[0169] The two components of each composition were then processed using the centrifugal mixer into a homogeneous liquid and this was tested immediately as follows:

[0170] 10 minutes after mixing, the viscosity was measured at 20° C. (“Viscosity (10′)”). The gel time was determined in standard climatic conditions by agitating the mixed composition (25 g) with a spatula from time to time until it began to gel.

[0171] For determination of Shore D hardness in accordance with DIN 53505, two cylindrical test specimens (diameter 20 mm, thickness 5 mm) were in each case produced. One was stored under standard climatic conditions and the hardness measured after 1 day and after 2 days (1d SCC and 2d SCC); the other was stored at 8° C. and 80% relative humidity and the hardness measured after 1 day and after 2 days in the cold state (1d 8°/80% and 2d 8°/80%).

[0172] A first film coating was applied to a glass plate in a layer thickness of 500 μm, and this was stored/cured under standard climatic conditions. The König hardness (König pendulum hardness, measured in accordance with DIN EN ISO 1522) was determined on this film after 1 day (“König hardness (1d SCC)”), after 2 days (“König hardness (2d SCC)”), after 4 days (“König hardness (4d SCC)”), after 7 days (“König hardness (7d SCC)”), and after 14 days (“König hardness (14d SCC)”). After 14 days, the appearance of the film was assessed (designated “Appearance (SCC)” in the table). A film was described as “nice” if it had a glossy and nontacky surface with no structure. “Structure” refers to any kind of marking or pattern on the surface. A film with reduced gloss was referred to as “dull”.

[0173] A second film coating was applied to a glass plate in a layer thickness of 500 μm and this was immediately after application stored/cured for 7 days at 8° C. and 80% relative humidity and then for 2 weeks under standard climatic conditions. 24 hours after application, a polypropylene bottle top beneath which a damp sponge had been positioned was placed on the film. After a further 24 hours, the sponge and the bottle top were removed and positioned at a new point on the film, from which it was removed and repositioned after 24 hours, this being done a total of 4 times. The appearance of this film was then assessed (designated “Appearance (8°/80%)” in the tables) in the same way as described for Appearance (SCC). Also reported in each case here was the number and nature of visible marks that had formed in the film as a result of the damp sponge or the bottle top on top. The number of white discolored spots was reported as “blushing”. A faint white discolored spot was designated as “(1)”. A clear white discolored spot was designated as “1”. The designation “ring” was reported if a ring-shaped imprint was present due to sinking of the first bottle top placed 24 hours after application. Such a ring-shaped imprint indicates that the coating was not ready to be walked on. A very minimal ring-shaped imprint was designated as “(yes)”. A clear ring-shaped imprint was designated as “yes”. The König hardness was again determined on the films thus cured, in each case after 7 days at 8° C. and 80% relative humidity (“König hardness (7d 8°/80%)”) and then after a further 2 days under SCC (“König hardness (+2d SCC)”), 7 days under SCC (“König hardness (+7d SCC)”), and 14 d under SCC (“König hardness (+14d SCC)”).

[0174] The Tg (glass transition temperature) was determined by DSC on cured samples that had been stored under standard climatic conditions for 14 days using a Mettler Toledo DSC 3+ 700 instrument and the following measurement program: (1) −10° C. for 2 min, (2) −10 to 200° C. at a heating rate of 10 K/min (=1st run), (3) 200 to −10° C. at a cooling rate of −50 K/min, (4) −10° C. for 2 min, (5) −10 to 180° C. at a heating rate of 10 K/min (=2nd run).

[0175] As a measure of yellowing, the change in color after stressing in a weathering tester was determined. For this, a further film coating was applied to a glass plate in a layer thickness of 500 μm and this was stored/cured under standard climatic conditions for 2 weeks and then stressed for 72 hours at a temperature of 65° C. in a model Q-Sun Xenon Xe-1 weathering tester having a Q-SUN Daylight-Q optical filter and a xenon lamp having a light intensity of 0.51 W/m.sup.2 at 340 nm (Q-Sun (72 h)). The difference in color ΔE of the stressed film versus the corresponding unstressed film was then determined 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*.

[0176] The results are reported in Tables 1 to 3.

[0177] The examples designated “(Ref.)” are comparative examples.

TABLE-US-00001 TABLE 1 Composition and properties of examples 1 to 7. Example 1 (Ref.) 2 3 4 5 6 (Ref.) 7 (Ref.) 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 Curing agent comp.: IPDA 42.6 34.1 25.6 21.3 12.8 6.4 — B-EDA — 10.0 20.0 25.0 35.0 42.5 50.0 Benzyl alcohol 25.0 25.0 25.0 25.0 25.0 25.0 25.0 Salicylic acid 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Ancamine ® K54 2.0 2.0 2.0 2.0 2.0 2.0 2.0 IPDA/B-EDA.sup.1 100/0 80/20 60/40 50/50 30/70 15/85 0/100 Viscosity (10′) [Pa .Math. s] 0.79 0.56 0.49 0.45 0.44 0.40 0.30 Gel time (h:min) 4:00 4:05 4:00 4:00 4:10 3:51 3:53 Shore D (1 d SCC) 69 59 58 61 56 58 51 (2 d SCC) 75 72 72 71 66 68 56 Shore D (1 d 8°/80%) 9 8 11 13 14 15 18 (2 d 8°/80%) 63 45 59 65 66 62 66 König h. (1 d SC 74 46 34 27 29 21 14 [s] (2 d SC 140 115 91 73 48 36 24 (4 d SC 167 148 137 120 81 64 28 (7 d SC 175 161 151 139 101 77 31 (14 d SC 177 165 160 157 116 83 31 Appearance (SCC) nice nice nice nice nice nice nice Tg 1st/2nd run [° C.] 57/87 54/79 50/73 47/66 46/60 42/53 40/50 Q-Sun (72 h) ΔE 16.8 12.7 9.7 10.7 11.4 13.0 12.9 König h. (7 d 8°/80 70 46 25 25 11 10 8 [s] (+2 d SC 150 134 123 88 57 32 22 (+7 d SC 171 157 155 109 69 67 41 (+14 d SC 172 175 161 139 88 68 41 Appearance dull nice nice nice nice nice nice (8°/80%) (1) (1) (1) (1) (1) (1) (1) Blushing Ring yes (yes) none none none none none .sup.1Ratio of amine hydrogen equivalents from IPDA and B-EDA indicates data missing or illegible when filed

TABLE-US-00002 TABLE 2 Composition and properties of examples 8 to 11. Example 8 (Ref.) 9 (Ref.) 10 (Ref.) 11 (Ref.) 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.: Further amine BAC MXDA TMD TEPA 17.8 17.0 19.9 15.0 B-EDA 25.0 25.0 25.0 25.0 Benzyl alcohol 25.0 25.0 25.0 25.0 Salicylic acid 2.0 2.0 2.0 2.0 Ancamine ® K54 2.0 2.0 2.0 2.0 Viscosity (10′) [Pa.Math.s] 0.42 0.36 0.35 0.48 Gel time (h:min) 3:00 3:30 3:30 3:35 Shore D (1 d SCC) 70 70 63 68 (2 d SCC) 72 74 71 75 Shore D (1 d 8°/80%) 48 44 28 27 (2 d 8°/80%) 74 77 72 76 König h. (1 d SC  38 16 12 13 [s] (2 d SC  73 36 35 28 (7 d SC  99 62 76 63 (14 d SC  123 94 85 84 Appearance (SCC) nice slight nice slight structure structure Tg 1st/2nd run [° C.] 41/60 41/51 40/57 44/51 Q-Sun (72 h) ΔE 14.2 13.4 13.6 16.9 König h. (7 d 8°/80  14 10 8 4 [s] (+2 d SC  56 24 38 7 (+7 d SC  83 45 52 18 (+14 d SC  n.d. n.d. n.d. n.d. Appearance (8°/80%) slight haze haze, structure nice haze, tacky Blushing 0 4 0 4 Ring none none (yes) yes indicates data missing or illegible when filed

TABLE-US-00003 TABLE 3 Composition and properties of examples 12 to 18. Example 12 13 14 15 16 17 18 Resin component: 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 Curing agent component: IPDA 21.3 21.3 21.3 21.3 21.3 21.3 25.6 B-EDA 25.0 25.0 25.0 25.0 25.0 25.0 20.0 Benzyl alcohol 25.0 25.0 25.0 25.0 25.0 25.0 25.0 Salicylic acid 2.0 — 2.0 — 4.0 4.0 2.0 Ancamine ® K54 2.0 2.0 — 4.0 — 4.0 4.0 IPDA/B-EDA.sup.1 50/50 50/50 50/50 50/50 50/50 50/50 60/40 Viscosity (10′) [Pa .Math. s] 0.39 0.26 0.34 0.23 0.49 0.59 0.49 Gel time (h:min) 4:00 4:30 3:30 3:50 3:00 2:25 3:20 Shore D (1 d SCC) 68 69 58 74 62 72 68 (2 d SCC) 75 78 73 79 73 77 71 Shore D (1 d 8°/80%) 17 10 14 24 30 41 37 (2 d 8°/80%) 61 61 20 39 65 63 70 König h. (1 d SC 36 32 25 53 22 52 63 [s] (2 d SC 77 84 63 108 59 94 116 (7 d SC 137 129 111 153 119 146 162 (14 d SC 155 151 146 167 143 160 169 Appearance (SCC) nice nice nice nice nice nice nice König h. (7 d 8°/80 25 25 13 34 17 29 41 [s] (+2 d SC 66 84 39 78 77 105 114 (+7 d SC 132 132 87 146 105 141 167 (+14 d SC 133 144 127 150 140 147 168 Appearance nice nice nice slight haze nice nice nice (8°/80%) (1) 1 (1) 1 (1) (1) (1) Blushing Ring none none yes none yes none none .sup.1Ratio of amine hydrogen equivalents from IPDA and B-EDA indicates data missing or illegible when filed

Examples 19 to 21

[0178] For these examples, a filled, commercial resin component was used in the amount shown in Table 4: Sikafloor®-264N component A RAL 5005 (from Sika).

[0179] The ingredients of the curing agent component shown in Table 4 were processed and stored as described above. The two components were then processed as described above into a homogeneous liquid and tested as specified for example 1. The results are reported in Table 4.

TABLE-US-00004 TABLE 4 Composition and properties of examples 19 to 21. Example 19 20 21 Resin component: Sikafloor ®-264N 436.0 436.0 436.0 Component A Curing agent component: IPDA 25.6 29.8 29.8 B-EDA 20.0 15.0 10.0 BAC — — 7.1 Benzyl alcohol 25.0 35.0 35.0 Salicylic acid 2.0 2.0 2.0 Ancamine ® K54 4.0 4.0 4.0 IPDA/B-EDA.sup.1 60/40 70/30 75/25 Viscosity (10′) [Pa.Math.s] 2.7 2.4 3.0 Gel time (h:min) 2:50 3:15 2:45 Shore D (1 d SCC) 68 59 66 (2 d SCC) 73 69 73 Shore D (1 d 8°/80%) 48 24 40 (2 d 8°/80%) 74 62 65 König h. (1 d SCC) 52 25 34 [s] (2 d SCC) 97 57 69 (7 d SCC) 148 120 119 (14 d SCC) 148 133 125 Appearance (SCC) nice nice nice Q-Sun (72 h) ΔE 6.0 7.3 5.6 König h. (7 d 8°/80%) 11 17 24 [s] (+2 d SCC) 83 62 64 (+7 d SCC) 98 81 83 (+14 d SCC) 111 88 92 Appearance (8°/80%) nice nice nice Blushing (1) (1) 3 Ring none none none .sup.1Ratio of amine hydrogen equivalents from IPDA and B-EDA