Adhesive for filling joints and gaps in rotor blades for wind power plants

Abstract

The present invention relates to two-component polyurethane compositions which on the one hand have a long open time and, even after extended exposure to a climate with high atmospheric humidity (e.g., 70% relative humidity), even after 40 minutes and in particular even after 60 minutes, can still be glued and cured to form polymers having high mechanical strength. The composition comprises castor oil, at least one polyol having 5-8 hydroxyl groups, a mixture of two different polyether alcohols and/or polyester polyols on the basis of castor oil or soybean oil and at least one polyisocyanate. The two-component polyurethane compositions are suitable in particular for non-positive filling joints or gaps that are joined by large-surface area structural gluing, in particular of vane half shells of rotor blades for wind power plants.

Claims

1. A two-component polyurethane composition consisting of a polyol component and a polyisocyanate component; wherein the polyol component comprises: 10-15 wt-% of castor oil, 1-10 wt-% of at least one polyol having 5-8 hydroxyl groups, 1-40 wt-% of at least one polyether and/or polyester polyol on the basis of castor oil or soybean oil having an OH number of 150 to 200 mg KOH/g, and 1-30 wt-% of at least one polyether and/or polyester polyol based on castor oil or soybean oil with an OH number of 210-300 mg KOH/g; and the polyisocyanate component comprises at least one polyisocyanate.

2. The two-component polyurethane composition according to claim 1, wherein the polyol having 5 to 8 hydroxyl groups is a polyol having exclusively secondary hydroxyl groups.

3. The two-component polyurethane composition according to claim 1, wherein the polyol having 5-8 hydroxyl groups is a polyether polyol on the basis of sorbitol.

4. The two-component polyurethane composition according to claim 1, wherein the polyisocyanate is an aromatic polyisocyanate.

5. The two-component polyurethane composition according to claim 1, wherein the polyol component further contains a polyamine in an amount of 0.5 to 5 wt-%.

6. A method for non-positive filling joints and gaps in a substrate, comprising the steps of a) mixing said polyol component and said polyisocyanate component of a two-component polyurethane composition according to claim 1, b) applying said mixed polyurethane composition in the joint to be bridged between two substrates, or in the gap to be filled at the surface of a substrate, c) curing the polyurethane composition in the joint or gap.

7. A method of gluing, comprising the steps of a) mixing the polyol component and the polyisocyanate component of a two-component polyurethane composition according to claim 1, b) applying the mixed polyurethane composition to at least one surface of the substrates to be glued, c) joining within the open time, d) curing the polyurethane composition.

8. The method according to claim 6, wherein substrate forming the gap to be bridged is plastic.

9. An item, which was obtained by a method according to claim 6.

10. The item according to claim 9, wherein the item is a rotor blade for wind power plants.

11. A method comprising: adhering a structure with the two-component polyurethane composition according to claim 1.

12. A method comprising: non-positively filling joints or gaps with a two-component polyurethane composition according to claim 1.

13. The method according to claim 11, wherein the two-component polyurethane composition is a force-transmitting structural element in the construction of rotor blades for wind power plants.

14. The method according to claim 6, wherein the substrate forming the gap to be bridged is fiber-reinforced plastic.

15. The two-component polyurethane composition according to claim 1, wherein a volume ratio of the polyol component to the polyisocyanate component is between 1:3 and 3:1.

16. The two-component polyurethane composition according to claim 1, wherein a volume ratio of the polyol component to the polyisocyanate component is between 1:2 and 2:1.

17. The method according to claim 6, wherein a volume ratio of the polyol component to the polyisocyanate component is between 1:3 and 3:1.

18. The method according to claim 6, wherein a volume ratio of the polyol component to the polyisocyanate component is between 1:2 and 2:1.

19. The method according to claim 7, wherein a volume ratio of the polyol component to the polyisocyanate component is between 1:3 and 3:1.

20. The method according to claim 7, wherein a volume ratio of the polyol component to the polyisocyanate component is between 1:2 and 2:1.

Description

EXAMPLES

(1) The following examples are intended to illustrate the present invention: However, the examples should not be considered as limiting the invention.

(2) The compositions 1 exemplified in Table 1, and Ref. 1 to Ref. 4 as reference examples all have the same component K2.

(3) For the preparation of the components K1, the polyol mixture was charged into a vacuum dissolver and following the addition of catalyst and desiccant stirred for 20 minutes at 25 C. with exclusion of moisture. Subsequently, these polypol components K1 were filled in air- and moisture-tight cartridges.

(4) For component K2, the polyisocyanate component B1 was filled into an air- and moisture-tight cartridge.

(5) Components K1 and K2, at the weight ratio K1:K2 as indicated in Table 1, were mixed by means of a static mixer (corresponding to an NCO/OH ratio of 1.1).

(6) Measurements

(7) Modulus of Elasticity, Tensile Strength and Elongation at Break

(8) The mixed components K1 and K2 were mixed, and immediately after mixing dumbbells according to ISO 527, part 2, 1B (ISO 527-2) were prepared; they were cured for 24 h at 25 C. and then for 72 h at 60 C. After a conditioning time of 24 h at 25 C., tensile strength, modulus of elasticity and elongation at break of the specimens thus prepared were measured in accordance with ISO 527-2 on a Zwick Z020 tensile tester at a test temperature of 20 C. and a test speed of 2 mm/min.

(9) Tensile Shear Strength

(10) The mixed components K1 and K2 were mixed and applied on the first plate of glass fiber-reinforced epoxy (GRE). This was followed immediately or after 40 or 60 minutes after exposure (t.sub.exp) at 25 C. and 70% relative humidity further with the production of the tensile shear strength specimen (contacting with a second glass glass fiber-reinforced epoxy plate, pressing, adhesive thickness 2 mm). The adhesive was then cured for 24 h at 25 C. and then for 72 h at 60 C., and the tensile shear strength was determined in accordance with ISO 527 following a conditioning time of 24 h at 25 C.

(11) TABLE-US-00001 TABLE 1 Compositions and measuring results. Examples 1 Ref. 1 Ref. 2 Ref. 3 Ref. 4 A1 Ref. A1 Ref. A2 Ref. A3 Ref. A4 (pbw.sup.3) (pbw.sup.3) (pbw.sup.3) (pbw.sup.3) (pbw.sup.3) Component K1 Castor oil A0 16 16 16 16 Polyether polyol A1 8 8 8 8 on the basis of sorbitol having 6 hydroxyl groups (hydroxyl number 490 mg KOH/g) Sovermol 805 A2-1 31.1 31.3 31.3 31.3 Polyol.sup.2 A2-2 13 13 13 13 Zeolite 6 6 6 6 6 (desiccant) Chalk 22 22 22 22 22 Pyrogenic silica 1.5 1.5 1.5 1.5 1.5 4,4-Methylene- PA 2.2 2.2 2.2 2.2 2.2 bis-(2,6- diethylaniline) 100 87 92 68.7 84 Component K2 Desmodur B1 100 100 100 100 100 VKS20F Mixing ratio 100/ 100/ 100/ 100/ 100/ K1/K2 (wt/wt) 40 36.4 32.1 37.3 39.5 Tensile strength 21.5 28.2 12.2 25.6 30.8 [MPa] Elongation at 12.6 9.6 49.8 3.4 4.3 break [%] Modulus of 764 1321 50 1069 1242 elasticity [MPa] t.sub.exp: 0 min (25 C., 70% rel. hum.sup.1) Tensile shear 18.1 12.8 13.2 14.8 15.5 strength [MPa] t.sub.exp: 40 min (25 C., 70% rel. hum.sup.1) Tensile shear 15.2 7.8 12.3 7.6 6.5 strength [MPa] t.sub.exp: 60 min (25 C., 70% rel. hum.sup.1) Tensile shear 12.0 1.2 11.9 0.6 1.3 strength [MPa] .sup.1rel. hum = relative humidity .sup.2Polyester/polyether on the basis of castor oil with OH number of 220-260 mg KOH/g, functionality: 2.8 .sup.3pbw = parts by weight

(12) The comparison of Example 1 and Ref. 2 shows that the absence of the polyol having 5 to 8 hydroxyl groups leads to an unduly strong reduction of the tensile strength and a significant increase in elongation at break. Surprisingly, the tensile shear strength also deteriorated significantly.

(13) The comparison of Example 1 and Ref. 1 shows the importance of the simultaneously present polyether and/or polyester polyol on the basis of castor oil or soybean oil (A2-1) and (A2-2). In the absence of said polyether and/or polyester polyol on the basis of castor oil having a high hydroxyl number, the tensile shear strength deteriorates unexpectedly dramatic after extended open times, in particular after 60 minutes in humid air.

(14) Also in Ref. 3 and Ref. 4, the tensile shear strength deteriorates unexpectedly dramatic after extended open times, in particular after 60 minutes in humid air.

(15) Example 1 shows that using the composition of the invention on the one hand, a good balance between the elongation at break and tensile strength necessary for fillers can be achieved, and on the other hand, that even after extended exposure of the applied polyurethane composition in moist air, a reliable formation of adhesion and thus non-positive tight fit at the interface between filler and the substrate can be achieved.