Hardener for cold hardening epoxy resin adhesives having fast hardening

Abstract

An adduct AD obtained from the reaction of at least one novolak glycidyl ether containing an average of 2.5 to 4 epoxy groups per molecule with an amine mixture including bis(6-aminohexyl)amine and at least one amine A1 other than bis(6-aminohexyl)amine that has at least one primary amino group. Preferably, the amine mixture is a technical grade quality of bis(6-aminohexyl)amine that contains 25% to 82% by weight of bis(6-aminohexyl)amine. The adduct AD is preparable in a simple manner and without the use of solvents, and enables low-odor, low-toxicity and low-viscosity hardeners that can be processed and stored even under cold conditions. Epoxy resin compositions cured therewith very rapidly build up high binding forces and high strengths under ambient outdoor temperatures, even on substrates that are difficult to bond.

Claims

1. An epoxy resin composition comprising: at least 50% by weight of inorganic fillers, a resin component comprising at least one epoxy resin, and a hardener component comprising an adduct AD that is obtained from a reaction of at least one novolak glycidyl ether containing an average of 2.5 to 4 epoxy groups per molecule with an amine mixture comprising bis(6-aminohexyl)amine and at least one amine A1 other than bis(6-aminohexyl)amine, the at least one amine A1 having at least one primary amino group.

2. The epoxy resin composition as claimed in claim 1, wherein the at least one novolak glycidyl ether is a phenol novolak glycidyl ether.

3. The epoxy resin composition as claimed in claim 1, wherein the amine mixture contains from 25% to 82% by weight of bis(6-aminohexyl)amine and from 15% to 75% by weight of the at least one amine A1.

4. The epoxy resin composition as claimed in claim 3, wherein the amine mixture contains from 50% to 78% by weight of bis(6-aminohexyl)amine.

5. The epoxy resin composition as claimed in claim 3, wherein the amine mixture contains from 20% to 50% by weight of the at least one amine A1.

6. The epoxy resin composition as claimed in claim 1, wherein the at least one amine A1 is selected from the group consisting of hexamethylene-1,6-diamine, higher oligomers of hexamethylene-1,6-diamine, 6-aminocapronitrile, and 6-aminocaproamide.

7. The epoxy resin composition as claimed in claim 1, wherein, in the reaction, the primary amino groups of the amine mixture are present in a stoichiometric excess over the epoxy groups of the at least one novolak glycidyl ether.

8. The epoxy resin composition as claimed in claim 1, wherein the amine mixture is initially charged and the at least one novolak glycidyl ether is mixed in, where the reaction is conducted at a temperature in a range of from 60 to 140 C. and without solvent or thinner.

9. The epoxy resin composition as claimed in claim 1, wherein the hardener further comprises at least one further amine A2 other than bis(6-aminohexyl)amine, the at least one further amine A2 having at least two amine hydrogens reactive toward epoxy groups per molecule.

10. The epoxy resin composition as claimed in claim 9, wherein the at least one further amine A2 is selected from the group consisting of 2,2(4),4-trimethylhexamethylenediamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, N,N-bis(3-aminopropyl)ethylenediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)benzene, polyoxyalkylenedi- and -triamines having an average molecular weight in the range from 200 to 500 g/mol and and 3-(3-(dimethylamino)propylamino)propylamine.

11. The epoxy resin composition as claimed in claim 9, wherein a content of the adduct AD in hardener is in a range of from 20% to 80% by weight based on the compounds reactive with epoxy groups that are present in the hardener.

12. The epoxy resin composition as claimed in claim 11, wherein a content of the at least one further amine A2 in hardener is in a range of from 10% to 70% by weight based on the compounds reactive with epoxy groups that are present in the hardener.

13. The epoxy resin composition as claimed in claim 9, wherein the at least one further amine A2 includes 3-(3-(dimethylamino)propylamino)propylamine.

14. A cured epoxy resin composition obtained by: mixing the components of the epoxy resin composition as claimed in claim 1, and curing thereof.

15. A method comprising applying the epoxy resin composition as claimed in claim 1 in a method of adhesive bonding, comprising mixing the components by a suitable method and either applying the mixed composition to at least one of the substrates to be bonded, joining the substrates to give an adhesive bond within the open time of the mixed composition, or applying the mixed composition to a cavity or gap between two substrates, optionally inserting an anchor into the cavity or gap within the open time of the mixed composition, followed by curing the mixed composition.

16. An adhesive-bonded article obtained from the method as claimed in claim 15.

17. The epoxy resin composition as claimed in claim 1, wherein the inorganic fillers are present in both the resin component and the hardener component.

18. The epoxy resin composition as claimed in claim 1, comprising from 50% to 90% by weight of the inorganic fillers.

19. The epoxy resin composition as claimed in claim 1, wherein the inorganic fillers include at least one selected from the group consisting of quartz flour, quartz sand, silicon carbide, wollastonite, mica, a precipitated, fatty acid-coated calcium carbonate, and fumed silica.

Description

EXAMPLES

(1) Working examples are adduced hereinafter, which are intended to elucidate the invention described in detail. It will be appreciated that the invention is not restricted to these described working examples.

(2) AHEW stands for amine hydrogen equivalent weight.

(3) EEW stands for epoxy equivalent weight.

(4) Standard conditions refer to a temperature of 231 C. and a relative air humidity of 505%. SC stands for standard conditions.

(5) Viscosity was measured with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1, cone tip-plate distance 0.05 mm) at a shear rate of 10 s.sup.1.

(6) Commercial Substances Used: BA-DGE: bisphenol A diglycidyl ether, EEW about 190 g/eq (Araldite GY 250, from Huntsman). BuD-DGE: butane-1,4-diol diglycidyl ether, EEW about 122 g/eq (Araldite DY-D, from Huntsman). D.E.N. 438: epoxy novolak resin (phenol novolak glycidyl ether), EEW about 180 g/eq, functionality 3.6 (from Olin) Solvesso: solvent based on aromatic hydrocarbons (Solvesso 150 ND, from ExxonMobil). BHMT-HP: bis(6-aminohexyl)amine with a purity in the region of about 98% by weight, AHEW about 43 g/eq (Dytek BHMT-HP from Invista) BHMT-(50-78%): 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) DMAPAPA: 3-(3-(dimethylamino)propylamino)propylamine, AHEW 53 g/eq (DMAPAPA, from Arkema). TETA: triethylenetetramine, AHEW about 27 g/eq (technical grade, from Huntsman) Quartz flour: grain size 0 to 75 m Quartz sand: grain size 0.1 to 0.3 mm

(7) Preparation of Adducts:

(8) Adduct A-1:

(9) An initial charge of 77.5 g of BHMT-(50-78%) under a nitrogen atmosphere was heated to 80 C. While stirring, 22.5 g of D.E.N. 438 preheated to 100 C. were added gradually, while keeping the temperature of the reaction mixture between 80 and 100 C. by cooling. The reaction mixture was then left at 80 to 100 C. for 1 hour and then cooled down to room temperature. A dark-colored liquid having a viscosity at 25 C. of 19.8 Pa.Math.s and a theoretical AHEW of 67.1 g/eq was obtained.

(10) Adduct A-2 (Ref.):

(11) An initial charge of 76.3 g of BHMT-HP under a nitrogen atmosphere was heated to 80 C. While stirring, 22.5 g of D.E.N. 438 preheated to 100 C. were added gradually, while keeping the temperature of the reaction mixture between 80 and 100 C. by cooling. The reaction mixture was then left at 80 to 100 C. for 1 hour and then cooled down to room temperature. A clear, yellowish liquid having a viscosity at 25 C. of 1.4 Pa.Math.s and a theoretical AHEW of 60.8 g/eq was obtained.

(12) Adduct A-3 (Ref.):

(13) An initial charge of 69.4 g of TETA under a nitrogen atmosphere was heated to 80 C. While stirring, 30.6 g of D.E.N. 438 preheated to 100 C. were added gradually, while keeping the temperature of the reaction mixture between 80 and 100 C. by cooling. The reaction mixture was then left at 70 to 90 C. for 1 hour and then cooled down to room temperature. A clear, yellowish liquid having a viscosity at 25 C. of 6.9 Pa.Math.s and a theoretical AHEW of 41.7 g/eq was obtained.

(14) Adduct A-4 (Ref.):

(15) An initial charge of 77.5 g of BHMT-(50-78%) under a nitrogen atmosphere was heated to 80 C. While stirring, 22.5 g of BA-DGE preheated to 60 C. were added gradually, while keeping the temperature of the reaction mixture between 60 and 90 C. by cooling. The reaction mixture was then left at 70 to 90 C. for 1 hour and then cooled down to room temperature. A dark-colored liquid having a viscosity at 25 C. of 8.8 Pa.Math.s and a theoretical AHEW of 67.1 g/eq was obtained.

(16) Adduct A-1 is an inventive adduct AD. Adducts A-2, A-3 and A-4 are comparative examples and are labeled (Ref.).

(17) Preparation of Hardeners:

(18) Hardener H-1 to H-7

(19) For each hardener, the adduct specified in table 1 and the ingredients specified in table 1 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.

(20) The storage stability of each hardener at 5 C. and the viscosity at 25 C. were determined.

(21) Storage stability at 5 C. was determined by storing the hardener in a closed glass container at 5 C. for 14 days and then making a visual assessment. If the hardener consisted of a homogeneous liquid, storage stability was answered yes, otherwise no. In the case of the unstable hardeners tested, complete or partial solidification was observed in each case.

(22) The calculated AHEW, the viscosity and the storage stability at 5 C. of the hardeners prepared are reported in table 1.

(23) The hardeners labeled (Ref.) are comparative examples.

(24) TABLE-US-00001 TABLE 1 Composition, AHEW and viscosity of the hardeners H-1 to H-7. Hardener H-2 H-3 H-4 H-6 H-7 H-1 (Ref.) (Ref.) (Ref.) H-5 (Ref.) (Ref.) Adduct A-1 A-2 A-3 A-4 A-1 A-2 A-3 70.0 70.0 65.0 70 80.0 80.0 80.0 DMAPAPA 30.0 30.0 35.0 30.0 TETA 20.0 20.0 20.0 AHEW [g/eq] 62.1 58.3 45.1 62.0 51.7 48.7 37.6 Viscosity (25 C.) 0.57 0.20 0.36 0.37 1.47 0.53 1.75 [Pa .Math. s] Storage stability yes yes yes yes yes no.sup.1 yes at 5 C. .sup.1partly solid

(25) Production of Epoxy Resin Adhesives:

Examples 1 to 8

(26) For each example, a resin component (Resin comp.) was produced by mixing the ingredients of the resin component specified in table 2 in the specified amounts (in parts by weight) by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) and storing it with exclusion of moisture.

(27) In addition, for each example, a hardener component (Hardener comp.) was prepared by mixing the adducts specified in table 2 and the further ingredients of the hardener component in the amounts specified (in parts by weight) by means of the centrifugal mixer and storing it with exclusion of moisture. For each example, the resin and the hardener component were then processed by means of the centrifugal mixer to give a homogeneous paste and this was immediately tested as follows:

(28) Mechanical properties were tested 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. Some tensile specimens were removed from the mold after a curing time of 2 days and further tensile specimens after 7 days, and these were used to determine tensile strength and elongation at break (2d SCC) and (7d SCC) to EN ISO 527 at a strain rate of 1 mm/min. Further such tensile specimens were produced by cooling the components to 5 C. prior to the mixing, then mixing them, applying them to give tensile specimens and curing them at 5 and about 70% relative air humidity. After 3 days, the tensile specimens were removed from the mold and tested as described for tensile strength and elongation at break (3d 5 C.). Compressive strength (2d SCC; 7d SCC) was determined by applying the mixed adhesive under standard climatic conditions to a silicone mold to give cuboids of dimensions 12.712.725.4 mm and allowing them to cure under standard climatic conditions. After 2 and after 7 days, several cuboids in each case 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. Further such cuboids were produced by cooling the components to 5 C. prior to the mixing, then mixing them, applying them to cuboids and curing them at 5 C. and about 70% relative air humidity. After 7 days, some of the cuboids were removed from the mold and tested as described for compressive strength (7d 5 C.), while further cuboids were additionally stored under standard climatic conditions for 7 days and only then removed from the mold and tested as described for compressive strength (7d 5 C.+7d SCC). A great deviation between the value after 7d 5 C.+7d SCC and the value after 7d SCC is a sign of curing defects under cold conditions.

(29) 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 1025 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.

(30) 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 1050 mm. After a storage time of 7 days under standard climatic conditions, lap shear strength was determined as described.

(31) To measure adhesive bond strength between concrete and steel (Bond strength), multiple adhesive bonds were produced by applying a few grams of the mixed adhesive in each case to a concrete plate that has been cleaned by means of a steel brush and bonding an acetone-clean steel cylinder having a diameter of 20 mm above its base area, with a thickness of the adhesive bond of 2 mm. The bonds were stored under standard climatic conditions. After 7 days, they were pulled apart until fracture in accordance with DIN EN 4624 at a testing speed of 2 mm/min in order to determine the strength of the adhesive bond at the maximum force.

(32) Tg (glass transition temperature) was determined by means of DSC on cured adhesive samples that had been stored under standard climatic conditions for 7 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).

(33) The results are reported in table 2.

(34) The examples labeled (Ref.) are comparative examples.

(35) TABLE-US-00002 TABLE 2 Composition and properties of examples 1 to 8. Example 2 3 4 5 7 8 1 (Ref.) (Ref.) (Ref.) (Ref.) 6 (Ref.) (Ref.) Resin comp. BA-DGE 59.9 60.8 64.3 59.9 52.4 62.5 63.3 66.5 D.E.N. 438 7.5 BuD-DGE 11.2 11.4 12.1 11.2 11.2 11.7 11.9 12.5 Solvesso 3.8 3.8 4.0 3.8 3.8 3.9 4.0 4.1 Quartz flour 130.0 130.0 130.0 130.0 130.0 130.0 130.0 130.0 Quartz 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 sand Hardener comp. Adduct A1 A2 A3 A4 A4 A1 A2 A3 17.6 16.8 12.7 17.6 17.6 17.5 16.6 13.5 DMAPAPA 7.5 7.2 6.9 7.5 7.5 TETA 4.4 4.2 3.4 Quartz flour 20.0 20.0 20.0 20.0 20.0 20.0 20.0 20.0 Quartz 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 sand Tensile strength: (2 d SCC) [MPa] 31 27 n.d. 23 19 32 28 24 (7 d SCC) [MPa] 34 28 24 24 26 32 29 26 (3 d 5 C.) [MPa] 26 25 n.d. 13 18 n.d. n.d. n.d. Elongation at break: (2 d SCC) 0.2% 0.2% n.d. 0.2% 0.2% 0.2% 0.2% 0.2% (7 d SCC) 0.2% 0.2% 0.2% 0.2% 0.2% 0.2% 0.2% 0.2% (3 d 5 C.) 0.3% 0.5% n.d. 0.2% 0.2% n.d. n.d. n.d. Compressive strength [MPa] (2 d SCC) 131 121 131 n.d. n.d. 104 103 n.d. (7 d SCC) 138 134 134 n.d. n.d. 116 109 n.d. (7 d 5 C.) 115 101 101 n.d. n.d. n.d. n.d. n.d. (7 d 5 C. + 7 d 133 112 118 n.d. n.d. n.d. n.d. n.d. SCC) LSS steel [MPa] 10.1 8.1 9.3 8.6 9.4 4.8 2.8 4.0 LSS CRP [MPa] 10.6 15.3 7.6 9.5 7.7 n.d. n.d. n.d. Bond strength 24.1 17.7 n.d. 18.1 22.8 14.4 11.4 12.0 [MPa] Tg 1st/2nd run [ C.] 58/73 59/93 63/79 54/67 55/69 51/73 52/74 53/91 n.d. stands for not determined