Structural Two-Component Adhesive

Abstract

The present invention relates to a structural two-component adhesive composition comprising a latent catalyst mixture as well as a method for producing the same. Further, the present invention relates to a method for bonding substrates using the structural two-component adhesive composition.

Claims

1. A two-component adhesive composition comprising a first component A and a second component B, wherein component A comprises: a) at least one polyether polyol having a molecular weight of 1000 to 12000 g/mol and a functionality of 1.5 to 2.5; b) at least one chain extender having a molecular weight of 60 to 600 g/mol and a functionality of 1.5 to 2.5; c) a latent catalyst mixture, the mixture comprising: c-1) a metal chelate complex, the metal being selected from the group consisting of Ti, Zr, Fe, Zn, Al and Bi; c-2) at least one amidine salt and/or tertiary amine salt; and c-3) at least one co-catalyst capable of accelerating the trimerization of isocyanates; and component B comprises at least one NCO-terminated compound.

2. The two-component adhesive composition according to claim 1, wherein the mixing ratio by volume of component A and component B is 10:1 to 1:2.

3. The two-component adhesive composition according to claim 1, wherein the at least one polyether polyol is present in an amount of at least 40 wt.-%, based on the total weight of component A.

4. The two-component adhesive composition according to claim 1, wherein the at least one chain extender is present in an amount of 4 to 15 wt.-%, based on the total weight of component A.

5. The two-component adhesive composition according to claim 1, wherein the hydroxyl-equivalent ratio of the at least one chain extender and the least one polyether polyol is in the range of 2 to 11.

6. The two-component adhesive composition according to claim 1, wherein the metal chelate complex is a Ti(IV) metal-organic compound, a Zr(IV) metal-organic compound or both a Ti(IV) metal-organic compound and a Zr(IV) metal-organic compound.

7. The two-component adhesive composition according to claim 1, wherein the amidine salt and/or tertiary amine salt is an organic acid salt.

8. The two-component adhesive composition according to claim 1, wherein the amidine salt and/or tertiary amine salt is an organic acid salt of 1,8-diaza-bicyclo(5.4.0)undec-7-ene (DBU).

9. The two-component adhesive composition according to claim 1, wherein the co-catalyst is an aliphatic amine or polyamine.

10. The two-component adhesive composition according to claim 1, wherein the latent catalyst mixture is present in an amount of 0.01 to 5 wt.-%, based on the total weight of component A.

11. The two-component adhesive composition according to claim 1, wherein component B comprises monomeric diisocyanate and/or monomeric triisocyanate.

12. The two-component adhesive composition according to claim 1, wherein component B comprises an NCO-terminated prepolymer reaction product of at least one isocyanate-reactive compound and at least one polyisocyanate.

13. Cured reaction products of a mixture of the component A and component B of according to claim 1.

14. An article comprising a mixture of the two-component adhesive composition according to claim 1.

15. A method for bonding a first substrate surface to a second substrate surface with the two-component adhesive composition of claim 1, comprising: providing the component A of claim 1; providing the component B of claim 1; mixing components A and B to obtain a mixed adhesive composition; applying the mixed adhesive composition to at least one of the substrate surfaces to be bonded; and disposing the first substrate surface adjacent the second substrate surface with the mixed adhesive composition between the substrates and in contact with both the first substrate surface and the second substrate surface.

16. The method for bonding a first substrate surface to a second substrate surface of claim 15, comprising the step of curing the applied adhesive composition.

17. An article obtained by the method for bonding a first substrate surface to a second substrate surface of claim 15.

Description

EXAMPLES

[0066] The following compounds were used as catalysts:
(c-1) Chelate metal complex: Ti(IV) chelate
(c-2) Amidine salt and/or tertiary amine salt:
c-2-1: mixture of DBU and butenoic acid in 50 weight % diethylene glycol
c-2-2: carboxylic acid salt of 1,8-Diazabicyclo[5.4.0]undec-7-en
c-2-3: 2-ethylhexanoic acid salt of 1,8-Diazabicyclo[5.4.0]undec-7-en
(c-3) Co-catalyst: N,N,N,N,N,N-hexamethyl-1,3,5-triazine-1,3,5(2H,4H,6H)-tripropanamine
DABCO: 33% 1,4-diazabicyclo[2.2.2]octane in dipropylene glycol
DBTDL: dibutyltin dilaurate
The content of the individual components is given in weight-%.

TABLE-US-00001 TABLE 1 Component A Ex 1 Ex 2 Ex 3 Polyether diol 74 74 74 (M.sub.n 4000 g/mol) butanediol 6 6 6 Fumed silica 3.5 3.5 3.5 Carbon black 10 10 10 zeolite 5.4 5.4 5.4 c-1/c-3 1 1 1 in reactive diluent c-2-1 0.13 c-2-2 0.15 c-2-3 0.12 Total 100 100 100
As component B an MDI-based diisocyanate component was used. Each of the Examples had an NCO index of 1.05.
As comparative examples, the following compositions were prepared, with the contents given in weight-%.

TABLE-US-00002 TABLE 2 Component A Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 Ex 9 Polyether diol 74 74 74 74 74 74 (M.sub.n 4000 g/mol) Chain 6 6 6 6 6 6 extender Fumed silica 3.5 3.5 3.5 3.5 3.5 3.5 Carbon black 10 10 10 10 10 10 zeolite 5.4 5.4 5.4 5.4 5.4 5.4 c-1/c-3 in 1 1.4 reactive diluent c-2-1 0.13 0.48 DABCO 0.1 DBTDL 0.02 Total 100 100 100 100 100 100
As component B an MDI-based diisocyanate component was used. Each of the Examples had an NCO index of 1.05.
The following tests were conducted:
A) Lap shear strength was determined after 24 h (A-1) and 7 days (A-2) after curing by room temperature, 1.5 mm gap, Wevo e-coated steel (45 mm100 mm2.5 mm)
B) Heat activation 180 s 120 C. IR radiation cure, 1.5 mm gap, PU CFRP (LOCTITE MAX 3 resin) (45 mm100 mm2.5 mm)
C) Open time limit, 1010 mm adhesive bead squeezability test, manual mixing of 20 g for 30 s at room temperature, point in time of solidification is given
D-1) Tensile test I: 7 d, 23 C./50% rh cure, 4 mm 1BA; 10 mm/min; E-modulus determination with 10 mm/min and regression line
D-2) Tensile test II: 3 d, 80 C. cure, 4 mm 1BA; 10 mm/min; E-modulus determination with 10 mm/min and regression line
The results are summarized in Table 3:

TABLE-US-00003 Test Ex 1 Ex 2 Ex 3 Ex 4* Ex 5* Ex 6* Ex 7* Ex 8* Ex 9* A-1 3.6 3.2 3.8 3.2 1.2 3.6 5.6 0.4 1.6 [MPa] A-2 7.9 10.4 9.8 6.4 2.7 8.9 11.4 1.4 2.3 [MPa] B 1.58 2.2 2.1 0.03 fail 0.15 0.44 1.26 1.41 [MPa] C [min] 5 5 5 4 5 7.5 5 >90 7 D-1 E.sub.t 33.5 25.5 31.9 19.2 16.7 25.3 24.6 16.9 28.7 [MPa] m 7.9 8.9 9.7 3.6 3.4 9.5 8.8 2.1 5.8 [MPa] .sub.m [%] 160 250 260 80 100 240 170 29 140 .sub.b [%] 170 290 240 80 110 210 170 150 D-2 Et 15 17.1 15.6 18.4 11.7 17.9 [MPa] m 6.8 10 10.5 10.4 10.1 5.3 [MPa] .sub.m [%] 270 260 280 240 250 160 .sub.b [%] 260 250 290 230 250 180 *not according to the invention
The examples according to the invention show excellent mechanical properties as well as excellent heat activation and fast cure at low temperature (23 C.) while maintaining a good workability (open time).
As can be seen from the data presented above, the compositions according to invention show excellent performance in all respective fields. In contrast thereto, the comparative composition lacking the inventive catalyst system, failed in at least one aspect of performance. In particular, the inventive composition showed an excellent heat activation behavior, resulting in a high bonding strength even after a short activation time, which could not be matched by the comparative compositions.