AMINE EPOXY RESIN ADDUCT

Abstract

An amine-functional adduct from the reaction of an amine mixture containing at least one diamine of formula (I) and at least one diamine of formula (II) in a weight ratio ranging from 65/35 to 95/5 with at least one diepoxide in a stoichiometric ratio of at least 1. 2 moles of diamine of the formula (I) to 1 mole equivalent of epoxide groups. The adduct is liquid at room temperature without diluent even in the presence of a small excess of diamine and is surprisingly low in viscosity. In addition, it is particularly cost-effective, as it is available from an amine mixture that is technically easy to produce. The adduct enables low-emission or emission-free epoxy resin coatings with surprisingly good workability at surprisingly fast curing, which have a high hardness and low tendency to yellowing, and which hardly tend to blushing-related defects even in cold and humid conditions.

Claims

1. An amine-functional adduct from the reaction of (i) an amine mixture comprising at least one diamine of formula (I) and at least one diamine of formula (II) in a weight ratio within a range from 65/35 to 95/5, ##STR00006## where A is an alkylene radical, cycloalkylene radical or arylalkylene radical having 2 to 12 carbon atoms, and R is an alkyl radical, cycloalkyl radical or arylalkyl radical having 1 to 12 carbon atoms, wherein the two nitrogen atoms in the diamine of formula (I) and (II) are in each case separated from one another by at least two carbon atoms and the diamine of formula (I) has a total of 8 to 15 carbon atoms, (ii) with at least one diepoxide in a stoichiometric ratio of at least 1.2 moles of diamine of formula (I) to 1 mole equivalent of epoxy groups.

2. The adduct as claimed in claim 1, wherein the amine mixture used for production of the adduct has a content of diamine of formula H.sub.2N-A-NH.sub.2 of not more than 5% by weight.

3. The adduct as claimed in claim 1, wherein the radicals A and R in the diamines of formulas (I) and (II) are identical radicals.

4. The adduct as claimed in claim 1, wherein the diamine of formula (I) is N-benzylethane-1,2-diamine and the diamine of formula (II) is N,N′-dibenzylethane-1,2-diamine.

5. The adduct as claimed in claim 1, wherein the weight ratio between the diamine of formula (I) and the diamine of formula (II) is within a range from 70/30 to 95/5.

6. The adduct as claimed in claim 1, wherein the amine mixture is a reaction product from the reductive alkylation of at least one amine of formula H.sub.2N-A-NH.sub.2 with at least one aldehyde or ketone and hydrogen.

7. The adduct as claimed in claim 1, wherein the diepoxide is an aromatic diepoxide.

8. The adduct as claimed in claim 1, wherein the stoichiometric ratio is within a range from 1.3 to 2, moles of diamine of formula (I) to 1 molar equivalent of epoxy groups of the diepoxide.

9. The adduct as claimed in claim 8, wherein it contains 2:1 adducts and higher adducts in a weight ratio within a range from 30/70 to 80/20.

10. The adduct as claimed in claim 1, wherein it contains less than 1% by weight of thinner or water.

11. A curing agent for epoxy resins comprising the adduct as claimed in claim 1 and at least one further constituent selected from the group consisting of further amines, accelerators, and thinners.

12. The curing agent for epoxy resins as claimed in claim 11, wherein at least one further amine having aliphatic amino groups and at least three amine hydrogens is present that was not present during the preparation of the adduct.

13. The curing agent for epoxy resins as claimed claim 1, wherein the further amine is selected from the group consisting of N-benzylethane-1,2-diamine, 2,2(4),4-trimethylhexane-1,6-diamine, 1,2-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 2(4)-methyl-1,3-diaminocyclohexane, 1,3-bis(aminomethyl)benzene, polyoxypropylene diamines having an average molecular weight M.sub.n within a range from 200 to 500 g/mol, and polyoxypropylene triamines having an average molecular weight M.sub.n within a range from 300 to 500 g/mol is present.

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

15. A coating, primer, adhesive, sealant, potting compound, casting resin, impregnating resin, or matrix for fiber composites, comprising the epoxy resin composition as claimed in claim 14.

16. An article obtained from claim 15.

Description

EXAMPLES

[0183] 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.

[0184] “ANEW” stands for amine hydrogen equivalent weight.

[0185] “EEW” stands for epoxy equivalent weight.

[0186] “Standard climatic conditions” (“SCC”) refer to a temperature of 23±1° C. and a relative air humidity of 50±5%.

[0187] The chemicals used were unless otherwise stated from Sigma-Aldrich Chemie GmbH.

Description of the Measurement Methods:

[0188] 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).

[0189] The amine value was determined by titration (with 0.1N HClO.sub.4 in acetic acid against crystal violet).

[0190] Liquid chromatography (UHPLC) was carried out for quantitative determination of N-benzylethane-1,2-diamine after derivatization with phenyl isocyanate against external calibration.

[0191] Gel-permeation chromatography (GPC) was carried out for determination of the weight ratios between 2:1 adduct, 3:2 adduct and >3:2 adduct against polystyrene as a standard.

Substances and Abbreviations Used:

[0192] Araldite® GY 250: Bisphenol A diglycidyl ether, EEW 187 g/equiv. (from Huntsman)

[0193] Araldite® DY-E: Monoglycidyl ethers of C.sub.12 to C.sub.14 alcohols, EEW approx. 290 g/equiv. (from Huntsman)

[0194] B-EDA mix Amine mixture containing approx. 85% by weight of N-benzylethane-1,2-diamine and approx. 14% by weight of N,N′-dibenzylethane-1,2-diamine, prepared as described below, AHEW 55 g/equiv.

[0195] B-EDA pure Purified N-benzylethane-1,2-diamine, prepared as described below, 150.2 g/mol, AHEW 50 g/equiv.

[0196] DB-EDA N,N′-Dibenzylethane-1,2-diamine, 240.4 g/mol, AHEW 120.2 g/equiv. (from Sigma Aldrich)

[0197] IPDA 3-Aminomethyl-3,5,5-trimethylcyclohexylamine, AHEW 42.6 g/equiv. (Vestamin® IPD from Evonik)

Preparation of Diamines of Formula (I) and (II):

[0198] Amine mixture containing N-benzylethane-1,2-diamine and N,N′-dibenzylethane-1,2-diamine (B-EDA mix):

[0199] 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 106.1 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) and approx. 14% by weight of N,N′-dibenzylethane-1,2-diamine (retention time 14.27 min), as determined by GC. This corresponds to a weight ratio between N-benzylethane-1,2-diamine and N,N′-dibenzylethane-1,2-diamine of 86/14.

[0200] N-Benzylethane-1,2-diamine (purified, B-EDA pure): 50 g of the amine mixture comprising N-benzylethane-1,2-diamine and N,N′-dibenzylethane-1,2-diamine (B-EDA-mix) prepared as described was distilled under reduced pressure at 80° C., resulting in 31.3 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.

Preparation of Adducts:

Adduct A1: (Inventive Example)

[0201] 53.0 g of the amine mixture B-EDA-mix (containing 0.3 mol of N-benzylethane-1,2-diamine and 0.03 mol of N,N′-dibenzylethane-1,2-diamine), prepared as described above, was initially charged under a nitrogen atmosphere and heated to 80° C. To this was slowly added 36.8 g (0.2 mol of epoxy groups) of Araldite® GY 250 while stirring well, with the temperature of the reaction mixture maintained between 70 and 90° C. by cooling. The reaction mixture was held within this temperature range for one hour and then cooled. A clear, slightly yellowish liquid having a viscosity at 20° C. of 74 Pa.s and a calculated AHEW of 117 g/equiv. was obtained. The adduct A1 contained 27.8% by weight of N-benzylethane-1,2-diamine according to UHPLC, the adduct molecules being in the weight ratio 2:1 adducts/3:2 adducts/>3:2 adducts=46.5/27.2/26.3 according to GPC.

Adduct A2: (Inventive Example)

[0202] 45.0 g (0.3 mol) of purified N-benzylethane-1,2-diamine (B-EDA pure) prepared as described above and 11.3 g (0.05 mol) of N,N′-dibenzylethane-1,2-diamine (DB-EDA) were initially charged under a nitrogen atmosphere, mixed, and heated to 80° C. To this was slowly added 36.8 g (0.2 mol of epoxy groups) of Araldite® GY 250 while stirring well, with the temperature of the reaction mixture maintained between 70 and 90° C. by cooling. The reaction mixture was held within this temperature range for one hour and then cooled. A clear, slightly yellowish liquid having a viscosity at 20° C. of 47 Pa.s and a calculated AHEW of 117.3 g/equiv. was obtained.

Adduct A3: (Inventive Example)

[0203] 45.0 g (0.3 mol) of purified N-benzylethane-1,2-diamine (B-EDA pure) prepared as described above and 19.3 g (0.08 mol) of N,N′-dibenzylethane-1,2-diamine (DB-EDA) were initially charged under a nitrogen atmosphere, mixed, and heated to 80° C. To this was slowly added 36.8 g (0.2 mol of epoxy groups) of Araldite® GY 250 while stirring well, with the temperature of the reaction mixture maintained between 70 and 90° C. by cooling. The reaction mixture was held within this temperature range for one hour and then cooled. A clear, slightly yellowish liquid having a viscosity at 20° C. of 19 Pa.s and a calculated AHEW of 117.5 g/equiv. was obtained.

Adduct A4: (Comparative Example)

[0204] 45.0 g (0.3 mol) of purified N-benzylethane-1,2-diamine (B-EDA pure) prepared as described above was initially charged under a nitrogen atmosphere and heated to 80° C. To this was slowly added 36.8 g (0.2 mol of epoxy groups) of Araldite® GY 250 while stirring well, with the temperature of the reaction mixture maintained between 70 and 90° C. by cooling. The reaction mixture was held within this temperature range for one hour and then cooled. A clear, slightly yellowish liquid having a viscosity at 20° C. of 262 Pa.s and a calculated AHEW of 116.3 g/equiv. was obtained.

[0205] The adduct A4 contained 24.2% by weight of N-benzylethane-1,2-diamine according to UHPLC, the adduct molecules being in the weight ratio 2:1 adducts /3:2 adducts/>3:2 adducts=42.5/27.0/30.5 according to GPC.

Preparation of Curing Agents and Epoxy Resin Compositions:

Examples 1 to 12

[0206] 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.

[0207] The ingredients of the curing agent component specified in Tables 1 to 3 were likewise processed and stored.

[0208] The two components of each composition were then processed using the centrifugal mixer into a homogeneous liquid and this was tested immediately as follows:

[0209] 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. 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 (1 d 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%).

[0210] A first film 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 (1 d 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)”). Once values of more than 200 s had been attained, the König hardness was not determined again. 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.

[0211] A second film 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 in turn 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 and/or the bottle top on top. The number of white-colored spots was reported as “blushing”. A faint 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 applied 24 hours after application. Such a ring-shaped impression indicates that the coating was not ready to be walked on. 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%)”), 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)”). Once values of more than 190 s had been attained, the König hardness was not determined again.

[0212] As a measure of yellowing, the change in color after stressing in a weathering tester was also determined. For this, a further film 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*. AE values up to 5 represent slight yellowing.

[0213] The results are reported in Tables 1 to 3.

[0214] The examples designated “(Ref.)” are comparative examples.

TABLE-US-00001 TABLE 1 Composition and properties of examples 1 to 4. 4 Example 1 2 3 (Ref.) Resin component: Araldite ® GY 250: 167.2 167.2 167.2 167.2 Araldite ® DY-E: 31.8 31.8 31.8 31.8 Curing agent component: Adduct A1 117.0 — — — Adduct A2 — 117.3 — — Adduct A3 — — 117.5 — Adduct A4 — — — 116.3 Viscosity (10′) [Pa .Math. s] 7.8 7.6 5.4 13.3 Gel time (h:min) 3:15 3:15 3:30 2:50 Shore D (1 d SCC) 75 74 77 78 (2 d SCC) 76 79 77 78 Shore D (1 d 8°/80%) 72 60 60 73 (2 d 8°/80%) 78 78 74 79 König h. (1 d SCC) 174 176 161 182 [s] (2 d SCC) 203 200 190 207 (7 d SCC) 209 Appearance (SCC) nice nice nice nice Q-Sun (72 h) ΔE 2.9 n.d. n.d. 3.1 König h. (7 d 8°/80%) 95 88 71 97 [s] (+2d SCC) 192 190 185 195 Appearance (8°/80%) nice nice nice nice Blushing (1) (1) 0 (1) Ring none none none none “n.d.” stands for “not determined”

TABLE-US-00002 TABLE 2 Composition and properties of examples 5 to 8. 8 Example 5 6 7 (Ref.) Resin component: Araldite ® GY 250: 167.2 167.2 167.2 167.2 Araldite ® DY-E: 31.8 31.8 31.8 31.8 Curing agent component: Adduct A1 64.4 — — — Adduct A2 — 64.5 — Adduct A3 — 64.6 Adduct A4 — — — 64.0 B-EDA pure 22.6 22.6 22.6 22.6 Viscosity (10′) [Pa .Math. s] 1.59 1.54 1.38 2.20 Gel time (h:min) 3:30 3:45 4:05 3:25 Shore D (1 d SCC) 78 78 77 78 (2 d SCC) 79 80 77 78 Shore D (1 d 8°/80%) 65 60 60 64 (2 d 8°/80%) 78 78 65 77 König h. (1 d SCC) 154 158 147 165 [s] (2 d SCC) 189 183 185 195 (7 d SCC) 206 205 203 206 Appearance (SCC) nice nice nice nice Q-Sun (72 h) ΔE 3.5 n.d. n.d. 3.6 König h. (7 d 8°/80%) 87 70 64 98 [s]  (+2 d SCC) 162 172 172 179  (+7 d SCC) 178 193 186 196 (+14 d SCC) 193 203 195 201 Appearance (8°/80%) nice nice nice nice Blushing (1) 0 0 (1) Ring none none none none “n.d.” stands for “not determined”

TABLE-US-00003 TABLE 3 Composition and properties of examples 9 to 12. 12 Example 9 10 11 (Ref.) Resin component: Araldite ® GY 250: 167.2 167.2 167.2 167.2 Araldite ® DY-E: 31.8 31.8 31.8 31.8 Curing agent component: Adduct A1 58.5 — — — Adduct A2 — 58.7 — — Adduct A3 — — 58.8 — Adduct A4 — — — 58.2 IPDA 21.3 21.3 21.3 21.3 Benzyl alcohol 20.0 20.0 20.0 20.0 Viscosity (10′) [Pa .Math. s] 2.00 1.65 1.57 2.41 Gel time (h:min) 3:25 3:40 4:00 3:15 Shore D  (1 d SCC) 68 74 68 70  (2 d SCC) 74 76 72 73 Shore D (1 d 8°/80%) 39 40 21 41 (2 d 8°/80%) 72 72 59 73 König h.  (1 d SCC) 55 62 56 57 [s]  (2 d SCC) 102 104 92 104  (7 d SCC) 162 156 123 164 (14 d SCC) 168 167 168 174 Appearance (SCC) nice nice nice nice Q-Sun (72 h) ΔE 3.5 n.d. n.d. 2.9 König h. (7 d 8°/80%) 41 34 31 48 [s]  (+2 d SCC) 123 115 108 132  (+7 d SCC) 161 154 146 155 (+14 d SCC) 164 174 168 168 Appearance (8°/80%) nice nice nice nice Blushing (1) (1) (1) (1) Ring none yes yes none “n.d.” stands for “not determined”