Heat-curing epoxy resin adhesives
A heat-curing epoxy resin compositions which can in particular be used as bodyshell adhesives for motor vehicle construction. The heat-curing epoxy resin compositions contain a curing agent which can be activated through elevated temperature and has a first component K 1 containing at least one epoxy resin and a second component K 2 containing at least one tertiary amine and also a primary amine. These compositions, after short-term heating of 30 to 120 seconds at a temperature of 90° C. to 130° C., exhibit sufficient strength and adhesion to withstand transport-induced mechanical strains.
1. A heat-curing epoxy resin composition comprising:
at least one curing agent B for epoxy resins, the at least one curing agent B is configured to be activated by elevated temperature;
a first component K 1 containing:
at least one epoxy resin A with, on average, more than one epoxy group per molecule, wherein a proportion of the at least one epoxy resin A is in a range of 10 to 50% by weight, based on a total weight of the heat-curing epoxy resin composition;
a second component K 2 containing:
at least one tertiary amine tAM represented by formula (I):
in which R 1 is an alkylene group with 1-20 carbon atoms, which is optionally substituted and optionally contains heteroatoms, and n is a value of 1-3;
at least one primary amine pAM chosen from the list consisting of 1,3-xylylenediamine (MXDA), 1,4-xylylenediamine (PXDA), and 1,3,5-tris(aminomethyl)benzene, wherein:
a ratio of a proportion of the at least one tertiary amine tAM in grams per mole of epoxy groups of the at least one epoxy resin A is in a range of 2.4-19.6 g/mol of epoxy groups, and
a ratio of a proportion of the at least one primary amine pAM in grams per mole of epoxy groups of the at least one epoxy resin A is in a range of 6-31 g/mol of epoxy groups.
2. The heat-curing epoxy resin composition as claimed in claim 1 , wherein the ratio of the proportion of the at least one tertiary amine tAM in grams per mol of epoxy groups of the at least one epoxy resin A is in a range of 2.4-13.7 g/mol of epoxy groups.
3. The heat-curing epoxy resin composition as claimed in claim 1 , wherein the ratio of the proportion of the at least one tertiary amine tAM in grams per mol of epoxy groups of the at least one epoxy resin A is in a range of 4.7-13.7 g/mol of epoxy groups.
4. The heat-curing epoxy resin composition as claimed in claim 1 , wherein
R 1 is CH 2 or —CH 2 —NH—C 3 H 6 and
n=1-3.
5. The heat-curing epoxy resin composition as claimed in claim 1 , wherein the at least one tertiary amine tAM is chosen from the group consisting of 2-(dimethylaminomethyl)phenol, 2,6-bis(dimethylaminomethyl)phenol, 2,4-bis(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, and 2,4,6-tris(((3-(dimethylamino)propyl)amino)methyl) phenol.
6. The heat-curing epoxy resin composition as claimed in claim 1 , wherein the ratio of the proportion of the at least one primary amine pAM in grams per mol of epoxy groups of the at least one epoxy resin A is in a range of 6-27 g/mol of epoxy groups.
7. The heat-curing epoxy resin composition as claimed in claim 1 , wherein
the at least one curing agent B is dicyandiamide, and
a ratio of a proportion of the dicyandiamide in grams per mole of epoxy groups of the at least one epoxy resin A is 10-20 g/mol of epoxy groups.
8. The heat-curing epoxy resin composition as claimed in claim 1 , wherein the heat-curing epoxy resin composition exhibits, immediately after the mixing at 25° C., a viscosity that is in a range of 500-4000 Pa·s.
9. A process for the adhesive bonding of heat-stable substrates, comprising:
a) applying the heat-curing epoxy resin composition as claimed in claim 1 to the surface of a heat-stable substrate S 1 ;
b) bringing the heat-curing epoxy resin composition applied into contact with the surface of a further heat-stable substrate S 2 ;
c) heating the heat-curing epoxy resin composition at a temperature that is in a range of 90-130° C.;
d) curing the heat-curing epoxy resin composition at a temperature that is in a range from 100 to 220° C.;
in which the substrate S 2 consists of the same material as or a different material from the substrate S 1 .
10. The process as claimed in claim 9 , wherein the heating in c) includes leaving the heat-curing epoxy resin composition at the temperature that is in a range of 90-130° C. for 10 s-300 s.
11. The process as claimed in claim 9 , wherein the curing in d) includes leaving the heat-curing epoxy resin composition at the temperature that is in a range from 100 to 220° C. for 10 min-6 h.
12. The process as claimed in claim 9 , wherein between c) and d), the process further comprising bringing the heat-curing epoxy resin composition to a temperature that is in a range of 0-50° C.
13. An adhesive-bonded article obtained from the process as claimed in claim 9 .
14. A method comprising applying the heat-curing epoxy resin composition as claimed in claim 1 as a heat-curing adhesive.
15. A method comprising partially curing the heat-curing epoxy resin composition as claimed in claim 1 by mixing the second component K 2 , the first component K 1 , and the at least one curing agent B.
16. The heat-curing epoxy resin composition as claimed in claim 1 , wherein the more than one epoxy group is a glycidyl ether group.
17. The heat-curing epoxy resin composition as claimed in claim 1 , further comprising at least one filler F, a total proportion of the at least one filler F being in a range of 10 to 50% by weight, based on a total weight of the heat-curing epoxy resin composition.