HARDENER FOR EPOXY RESINS

Abstract

A curing agent for epoxy resins, including at least one amine A1 of the formula (I) and at least one amine A2 which is a polyalkyleneamine or polyethyleneimine, where the weight ratio between amine A1 and amine A2 is in the range from 20/1 to 1/2. The curing agent of the invention enables inexpensive and low-emission epoxy resin products having good processability, long pot life, surprisingly rapid curing, especially also under cold conditions, high strength, high bond strengths, high glass transition temperature and a low tendency to yellowing, with formation of surprisingly nice surfaces having barely any blushing-related defects even in the case of two-dimensional application and under moist and cold conditions. Such epoxy resin products are advantageously usable as coating, especially for floors, or as adhesive.

Claims

1. A curing agent for epoxy resins comprising at least one amine A1 of the formula (I) ##STR00003## where m is 0 or 1, n is 1 or 2 and (m+n) is 2, A is 1,2-ethylene or 1,2-propylene, R is H or an alkyl radical having 1 to 12 carbon atoms, and Y is an optionally substituted aromatic or cycloaliphatic radical having 6 to 20 carbon atoms, and at least one amine A2 which is a polyalkyleneamine or polyethyleneimine, where the weight ratio between amine A1 and amine A2 is in the range from 20/1 to 1/2.

2. The curing agent as claimed in claim 1, wherein Y is a phenyl radical.

3. The curing agent as claimed in claim 1, wherein m and n are each 1.

4. The curing agent as claimed in claim 1, wherein the amine A1 of the formula (I) is N-benzylethane-1,2-diamine.

5. The curing agent as claimed in claim 1, wherein the amine A2 is a polyalkyleneamine of the formula (II) ##STR00004## where x is an integer from 1 to 6, and B is independently an alkylene radical having 2 to 6 carbon atoms.

6. The curing agent as claimed in claim 1, wherein the weight ratio between amine A1 and amine A2 is in the range from 15/1 to 1/1.

7. The curing agent as claimed in claim 1, wherein the weight ratio between amine A1 and amine A2 is in the range from 10/1 to 1/2.

8. The curing agent as claimed in claim 1, wherein it comprises at least one further amine selected from the group consisting of 2,2(4),4-trimethylhexane-1,6-diamine, 1,2-, 1,3- or 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 2(4)-methyl-1,3-diaminocyclohexane, 1,3-bis(aminomethyl)benzene, polyoxypropylenediamines having an average molecular weight M.sub.n in the range from 200 to 500 g/mol, 3-(3-(dimethylamino)propylamino)propylamine, adducts of these or further polyamines with mono- or diepoxides, and Mannich bases.

9. The curing agent as claimed in claim 1, wherein the further amine present is 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane.

10. The curing agent as claimed in claim 1, wherein the further amine present is 3-(3-(dimethylamino)propylamino)propylamine.

11. 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.

12. The epoxy resin composition as claimed in claim 11, wherein it comprises at least one further constituent selected from the group consisting of thinners, accelerators and fillers.

13. A method of coating, comprising the steps of (i) mixing the components of the epoxy resin composition as claimed in claim 11, (ii) applying the mixed composition to a substrate within the pot life, followed by the curing of the mixed composition.

14. A method of bonding, comprising the steps of (i) mixing the components of the epoxy resin composition as claimed in claim 11, (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 a method as claimed in claim 13.

Description

EXAMPLES

[0166] Working examples are adduced hereinafter, which are intended to elucidate the invention described. The invention is of course not limited to these described working examples.

[0167] “AHEW” stands for amine hydrogen equivalent weight.

[0168] “EEW” stands for epoxy equivalent weight.

[0169] “Standard climatic conditions” refer to a temperature of 23±1° C. and a relative air humidity of 50±5%.

Description of the Measurement Methods:

[0170] 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).

[0171] Amine value was determined by means of titration (with 0.1N HClO.sub.4 in acetic acid versus crystal violet).

Substances and Abbreviations Used:

[0172] Sikafloor®-264N (A) Sikafloor®-264N component A (RAL 5005), filled pigmented resin component of an epoxy resin floor coating, EEW 450 g/eq (from Sika) [0173] Sikadur®-30 (A) Sikadur®-30 component A, quartz-filled resin component of a structural epoxy resin adhesive, containing bisphenol A diglycidyl ether and butane-1,4-diol diglycidyl ether, EEW about 700 g/eq (from Sika) [0174] B-EDA N-benzylethane-1,2-diamine, prepared as described below, AHEW 50.1 g/eq [0175] B-PDA N-benzylpropane-1,2-diamine, prepared as described below, AHEW 54.8 g/eq [0176] TEPA tetraethylenepentamine, AHEW about 30 g/eq (technical grade, from Huntsman) [0177] BHMT bis(6-aminohexyl)amine, AHEW about 43 g/eq (Dytek® BHMT-HP, from Invista) [0178] BHMT-50 technical grade quality of bis(6-aminohexyl)amine with a purity in the range from 50% to 78% by weight, AHEW about 48 g/eq (Dytek® BHMT Amine (50-78%), from Invista) [0179] PEI polyethyleneimine, average molecular weight about 800 g/mol, AHEW about 38 g/eq (Lupasol® FG, from BASF) [0180] IPDA 3-aminomethyl-3,5,5-trimethylcyclohexylamine, AHEW 42.6 g/eq (Vestamin® IPD, from Evonik) [0181] BAC 1,3-bis(aminomethyl)cyclohexane, AHEW 35.5 g/eq (from Mitsubishi Gas Chemical) [0182] TMD 2,2(4),4-trimethylhexamethylenediamine, AHEW 39.6 g/eq (Vestamin® TMD from Evonik) [0183] MPMD 1,5-diamino-2-methylpentane, AHEW 29.0 g/eq (Dytek® A, from Invista) [0184] Adduct-1 adduct of propylene-1,2-diamine and technical grade o-cresyl glycidyl ether, prepared as described below, AHEW 90 g/eq [0185] DMAPAPA 3-(3-(dimethylamino)propylamino)propylamine, AHEW 53 g/eq (DMAPAPA, from Arkema). [0186] Ca nitrate solution 50% by weight of calcium nitrate tetrahydrate in water [0187] Ancamine® K54 2,4,6-tris(dimethylaminomethyl)phenol (from Air Products) [0188] Quartz flour grain size 0 to 75 μm [0189] Quartz sand grain size 0.1 to 0.3 mm [0190] Precipitated chalk stearate-coated precipitated chalk (Socal® U1S2, from Solvay) [0191] B-EDA and B-PDA are amines A1. TEPA, BHMT, BHMT-50 and PEI are amines A2.

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

[0192] A round-bottom flask was initially charged with 180.3 g (3 mol) of ethylene-1,2-diamine under a nitrogen atmosphere at room temperature. With good stirring, a solution of 106.0 g (1 mol) of benzaldehyde in 1200 ml of isopropanol was slowly added dropwise, and the mixture was stirred for 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 about 1665 cm.sup.−1 had disappeared. Thereafter, the hydrogenated solution was concentrated on a rotary evaporator at 65° C., removing unreacted ethylene-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. 50 g of this were distilled at 80° C. under reduced pressure, with collection of 31.3 g of distillate at a vapor temperature of 60 to 65° C. and 0.06 mbar. What was obtained was a colorless liquid having a viscosity of 8.3 mPa.Math.s at 20° C., an amine value of 750 mg KOH/g and a purity, determined by GC, of >97%.

N-Benzylpropane-1,2-Diamine (B-PDA):

[0193] A round-bottom flask was initially charged with 444.8 g (6 mol) of propane-1,2-diamine under a nitrogen atmosphere at room temperature. With good stirring, a solution of 212.2 g (2 mol) of benzaldehyde in 1500 ml of isopropanol was slowly added dropwise, and the mixture was stirred for 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 90 bar, a temperature of 85° C. and a flow rate of 5 ml/min. To monitor the reaction, IR spectroscopy was used to check whether the imine band at about 1665 cm.sup.−1 had disappeared. Thereafter, the hydrogenated solution was concentrated on a rotary evaporator at 65° C., removing unreacted propane-1,2-diamine, isopropanol and water. A clear, pale yellowish liquid was obtained. 300 g of this were distilled at 80° C. under reduced pressure, with collection of 237.5 g of distillate at a vapor temperature of 60 to 65° C. and 0.08 mbar. A colorless liquid having an amine value of 682 mg KOH/g was obtained, which, by .sup.1H NMR, was a mixture of N.sup.1-benzylpropane-1,2-diamine and N.sup.2-benzylpropane-1,2-diamine in a ratio of about 2/1 and had a GC purity of >97%.

Adduct-1:

[0194] An initial charge of 4.15 kg of propylene-1,2-diamine under a nitrogen atmosphere was heated to 70° C. and then, with good stirring, 2.93 kg of Araldite® DY-K (o-cresyl glycidyl ether, technical grade, from Huntsman) was added gradually, with the temperature of the reaction mixture being from 70 to 80° C. After 1 hour at 80° C., the reaction mixture was cooled down and the volatile constituents were removed by distillation by means of a thin-film evaporator (0.5-1 mbar, jacket temperature 115° C.).

Production of Epoxy Resin Compositions:

Examples 1 to 13: Coatings

[0195] For each example, the ingredients of the curing agent component indicated in tables 1 to 2 were mixed in the indicated amounts (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and stored with the exclusion of moisture.

[0196] The resin component used was Sikafloor®-264N comp. A (blue) (from Sika) in the amount specified in tables 1 to 2 (in parts by weight).

[0197] The two components of each composition were then processed by means of the centrifugal mixer to give a homogeneous liquid and this was tested immediately as follows: [0198] 10 minutes after mixing, the viscosity was measured at 20° C. (“Viscosity (10′)”).

[0199] For the determination of Shore D hardness to DIN 53505, two cylindrical test specimens (diameter 20 mm, thickness 5 mm) in each case were produced. One was stored under standard climatic conditions and hardness was measured after 1 day and after 2 days (1 d SCC and 2 d SCC); the other was stored at 8° C. and 80% relative humidity and hardness was measured after 1 day and after 2 days in the cold state (1 d 8°/80% and 2 d 8°/80%).

[0200] 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. König hardness (König pendulum hardness, measured according to DIN EN ISO 1522) was determined on this film after 1 day (“König hardness (1 d SCC)”), after 2 days (“König hardness (2 d SCC)”), after 4 days (“König hardness (4 d SCC)”), after 7 days (“König hardness (7 d SCC)”) and after 14 days (“König hardness (14 d 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 a nontacky surface without structure and with reduced gloss was described as “matt”.

[0201] A second film was applied to a glass plate in a layer thickness of 500 μm and immediately after application this was 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 bottletop beneath which a damp sponge had been positioned was placed onto the film. After a further 24 hours, the sponge and the bottletop were removed and positioned at a new point on the film, from which it was in turn removed and repositioned after 24 hours, and this was 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 kind of visible marks that had formed in the film as a result of the damp sponge and/or the bottletop on top. The number of white-colored spots was reported as “blushing”. The intensity of any ring-shaped impression formed by sinking of the first bottletop applied 24 h after application was reported as “ring”. Such a ring-shaped impression indicates that the coating is not ready to be walked upon. 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 (7 d 8°/80%)”) and then after a further 2 days under SCC (“König hardness (+2 d SCC)”), 7 days under SCC (“König hardness (+7 d SCC)”), and 14 d under SCC (“König hardness (+14 d SCC)”).

[0202] As a measure of yellowing, the change in color after stressing in a weathering tester was furthermore 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 (Q-Sun (72 h)) 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. The color difference ΔE of the thus 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*. ΔE values up to 5 represent slight yellowing.

[0203] The results are reported in tables 1 to 2.

[0204] The examples labeled “(Ref.)” are comparative examples.

TABLE-US-00001 TABLE 1 Composition and properties of examples 1 to 7. 1 6 Example (Ref.) 2 3 4 5 (Ref.) 7 Resin comp.: Sikafloor ®-264N (A) 450.0 450.0 450.0 450.0 450.0 450.0 450.0 Curing agent comp.: B-EDA 50.1 45.9 42.6 37.6 30.6 — B-PDA — — — — — 27.4 21.9 TEPA — 3.0 4.5 7.5 12.0 — 6.0 Adduct-1 — — — — — 45.0 36.0 Benzyl alcohol 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Ca nitrate solution 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 A1/A2 ratio.sup.1 — 15.3/1 9.5/1 5/1 2.6/1 — 3.7/1 Viscosity (10′) [Pa .Math. s] 1.6 1.7 1.8 2.1 2.7 3.2 3.4 Shore D (1 d SC 63 71 73 75 76 67 75 (2 d SC 67 75 75 75 78 73 80 Shore D (1 d 8°/80° 17 49 51 53 60 n.m. 9 (2 d 8°/80° 64 69 71 75 77 55 57 König hardness (1 d S 43 50 52 53 50 32 59 [s] (2 d SC 56 74 76 77 80 104 113 (4 d SC 78 87 92 95 97 141 150 (7 d SC 94 94 99 105 119 168 168 (14 d SC 109 111 120 129 126 168 169 Appearance (SCC) nice nice nice nice nice nice nice Q-Sun (72 h) ΔE 5.3 4.8 4.4 3.4 4.9 3.5 3.8 König h. (7 d 8°/80° 9 16 17 21 28 38 41 [s] (+2 d SC 20 38 37 45 80 130 122 (+7 d SC 29 54 56 71 99 132 125 (+14 d SC 46 70 77 94 129 144 139 Appearance (8°/80%) nice 1 nice 1 nice 1 nice 1 matt 1 matt 1 matt 1 Blushing Ring slight none none none none strong slight .sup.1Weight ratio between amine A1 and amine A2 “n.m.” means “not measurable” (too soft) indicates data missing or illegible when filed

TABLE-US-00002 TABLE 2 Composition and properties of examples 8 to 13. 10 11 12 13 Example 8 9 (Ref.) (Ref.) (Ref.) (Ref.) Resin comp.: Sikafloor ®-264N (A) 450.0 450.0 450.0 450.0 450.0 450.0 Curing agent comp.: B-EDA 42.6 42.6 42.6 42.6 42.6 42.6 Amine BHMT .sup.2 PEI IPDA BAC TMD MPMD 6.5 5.7 6.4 5.3 5.9 4.4 Benzyl alcohol 10.0 10.0 10.0 10.0 10.0 10.0 Ca nitrate solution 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 A1/A2 ratio.sup.1 6.6/1 7.5/1 — — — — Viscosity (10′) [Pa .Math. s] 2.05 2.15 2.33 2.17 2.34 2.28 Shore D (1 d SCC) 70 75 71 44 72 72 (2 d SCC) 71 73 76 63 76 76 Shore D (1 d 8°/80%) 53 48 45 53 50 48 (2 d 8°/80%) 70 72 68 70 69 68 König hardness (1 d SCC 39 53 41 43 38 31 [s] (2 d SCC) 60 78 78 71 70 59 (4 d SCC) 74 94 97 83 83 71 (7 d SCC) 85 99 106 90 92 77 (14 d SCC) 104 122 125 140 105 97 Appearance (SCC) nice nice nice nice nice nice Q-Sun (72 h) ΔE 6.6 5.6 5.6 5.5 5.8 5.7 König h. (7 d 8°/80%) 14 17 13 14 10 13 [s] (+2 d SCC) 34 36 42 33 33 25 (+7 d SCC) 59 55 60 43 50 36 (+14 d SCC) 83 73 76 59 71 57 Appearance (8°/80%) nice 1 matt 1 matt/ matt/ matt/ matt/ tacky 1 tacky 3 tacky 3 tacky 1 Blushing Ring none none none none none none .sup.1Weight ratio between amine A1 and amine A2 .sup.2 dissolved in B-EDA indicates data missing or illegible when filed

[0205] Examples 14 to 20: (Adhesives) For each example, the ingredients of the curing agent component specified in table 3 were mixed in the specified amounts (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) and stored with exclusion of moisture.

[0206] The resin component used was Sikadur®-30 component A (from Sika) in the amount specified in table 3 (in parts by weight).

[0207] For each example, the resin component and the curing agent component were then processed by means of the centrifugal mixer to give a homogeneous paste and this was immediately tested as follows:

[0208] Pot life was determined under standard climatic conditions by moving the mixed adhesive by means of a spatula every 5 min until the adhesive had thickened to such an extent that it was no longer processable.

[0209] The mechanical properties were determined by applying and curing the mixed adhesive under standard climatic conditions to a silicone mold to give dumbbell-shaped specimens having a thickness of 10 mm and a length of 150 mm with a gage length of 80 mm and a gage width of 10 mm. The tensile specimens were removed from the mold after a curing time of 7 days, and these were used to measure tensile strength (“TS”) and elongation at break (“EaB”) to EN ISO 527 at a strain rate of 1 mm/min.

[0210] The characteristics of the surface were assessed on the dumbbell-shaped specimens to determine the mechanical properties on the side exposed to the air in the course of curing. A nontacky surface was referred to as “smooth”.

[0211] Lap shear strength on steel (LSS steel) was measured by producing multiple adhesive bonds, wherein the mixed adhesive was applied between two heptane-degreased steel sheets in a layer thickness of 0.5 mm with an overlapping bonding area of 10×25 mm. After a storage time of 7 days under standard climatic conditions, lap shear strength was determined to DIN EN 1465 at a strain rate of 10 mm/min.

[0212] Lap shear strength on carbon fiber composite (CRP) (LSS CRP) was measured by producing multiple adhesive bonds, wherein the mixed adhesive was applied between two heptane-degreased Sika® CarboDur® S512 lamellas in a layer thickness of 0.5 mm with an overlapping bonding area of 10×50 mm. After a storage time of 7 days under standard climatic conditions, lap shear strength was determined as described.

[0213] Compressive strength (“CS”) was determined by applying the mixed adhesive under standard climatic conditions in a silicone mold to give cuboids of dimensions 12.7×12.7×25.4 mm and curing them under standard climatic conditions. After 7 days, several such cuboids were removed from the mold and compressed to destruction as per ASTM D695 at a testing speed of 1.3 mm/min, reading off the compressive strength value at the maximum force in each case.

[0214] Tg (glass transition temperature) was determined by means of DSC on cured adhesive samples that had been stored under standard climatic conditions for 14 days with 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).

[0215] The results are reported in table 3.

[0216] The examples labeled “(Ref.)” are comparative examples.

TABLE-US-00003 TABLE 3 Composition and properties of examples 14 to 20. 14 15 Example (Ref.) (Ref.) 16 17 18 19 20 Resin comp.: Sikadur ®-30 (A) 300.0 300.0 300.0 300.0 300.0 300.0 300.0 Curing agent comp.: B-EDA 21.5 15.8 13.6 10.8 10.8 7.1 5.6 TEPA — 1.5 3.0 3.0 3.0 BHMT-50 — — — — 4.8 3.5 5.0 DMAPAPA — 6.0 6.0 6.0 6.0 6.0 6.0 Quartz flour 35.3 35.2 35.2 36.5 34.7 36.6 36.6 Quartz sand 28.2 28.0 28.7 28.7 28.7 28.8 28.8 Precipitated chalk 15.0 15.0 15.0 15.0 15.0 15.0 15.0 A1/A2 ratio.sup.1 — — 9.7/1   3.6/1   2.3/1   1.1/1     1/1.4 Pot life 2:00 1:30 1:20 1:15 1:30 1:30 1:30 TS 34 35 36 31 40 37 35 EaB 0.3 0.3 0.3 0.2 0.3 0.3 0.3 Surface smooth smooth smooth smooth smooth smooth smooth LSS steel 6.2 11.2 10.6 10.8 12.5 13.7 15.2 LSS CRP 8.3 8.5 9.0 10.0 12.1 10.2 10.0 CS 90 109 111 107 111 109 110 Tg 1st/2nd run 48/57 58/60 58/68 59/68 57/63 61/64 61/69 .sup.1Weight ratio between amine A1 and amine A2 indicates data missing or illegible when filed