Curing agent for moisture-curing compositions

Abstract

The present invention relates to a curing agent for moisture-curing compositions which includes at least one aqueous emulsion of at least one epoxy resin. Curing agents according to the invention are especially used for the accelerated curing of moisture-curing compositions which are based on polyurethane polymers that have isocyanate groups or of silane-functional polymers.

Claims

1. A method of adhesive bonding, sealing, or coating a substrate, comprising: mixing a component A and a component B of a two-component composition together to obtain a curable composition; applying the curable composition to the substrate; and curing the curable composition applied to the substrate, wherein: component A, at a time of mixing, comprises, in a nonaqueous system, (i) at least one moisture-curing composition comprising at least one polyurethane polymer including isocyanate groups, and (ii) at least one curing agent or accelerator for curing an epoxy resin; component B, at a time of mixing, comprises at least one curing agent comprising at least one aqueous emulsion of at least one epoxy resin; and the weight ratio of component A to component B is 100:0.5 to 100:20.

2. The method according to claim 1, wherein the two-component composition is a moisture-curing adhesive, sealing agent or a moisture-curing coating.

3. The method according to claim 1, wherein the aqueous emulsion of at least one epoxy resin contains 10 to 40 wt % water.

4. The method according to claim 1, wherein the aqueous emulsion of at least one epoxy resin contains 10 to 30 wt % water.

5. The method according to claim 1, wherein the epoxy resin has an average particle size in the range of 0.05 to 10 μm.

6. The method according to claim 1, wherein the emulsion has a particle size distribution in which the size ratio of the largest particles to the smallest particles has a value in the range of <25.

7. The method according to claim 1, wherein 90% of the particles in the emulsion are smaller than 6 μm.

8. The method according to claim 1, wherein the at least one curing agent or accelerator for curing the epoxy resin is 0.5 to 15 wt % based on component A.

9. The method according to claim 1, wherein at least 50% of reactive groups of the at least one polyurethane polymer are reacted with water present in component B.

10. A method of adhesive bonding, sealing, or coating a substrate, comprising: mixing a component A and a component B of a two-component composition together to obtain a curable composition; applying the curable composition to the substrate; and curing the curable composition applied to the substrate, wherein: component A, at a time of mixing, comprises, in a nonaqueous system, (i) at least one moisture-curing composition comprising at least one silane-functional polymer, and (ii) at least one curing agent or accelerator for curing an epoxy resin; component B, at a time of mixing, comprises at least one curing agent comprising at least one aqueous emulsion including epoxy resin particles and an emulsifier formed by emulsifying at least one liquid epoxy resin in the presence of the emulsifier and water; and the weight ratio of component A to component B is 100:0.5 to 100:20.

11. The method according to claim 10, wherein the silane-functional polymer is a silane-terminated polyether or a silane-terminated poly(meth)acrylate.

12. The method according to claim 10, wherein the aqueous emulsion of at least one epoxy resin contains 10 to 40 wt % water.

13. The method according to claim 10, wherein the aqueous emulsion of at least one epoxy resin contains 10 to 30 wt % water.

14. The method according to claim 10, wherein the epoxy resin has an average particle size in the range of 0.05 to 10 μm.

15. The method according to claim 10, wherein the emulsion has a particle size distribution in which the size ratio of the largest particles to the smallest particles has a value in the range of <25.

16. The method according to claim 10, wherein 90% of the particles in the emulsion are smaller than 6 μm.

17. The method according to claim 10, wherein the at least one curing agent or accelerator for curing the epoxy resin is 0.5 to 15 wt % based on component A.

18. The method according to claim 10, wherein at least 50% of reactive groups of the at least one silane-functional polymer are reacted with water present in component B.

Description

EXAMPLES

(1) Exemplary embodiments, which illustrate the invention described here in greater detail, are presented below. The invention is of course not limited to the exemplary embodiments described here.

(2) Description of the Measurement Methods

(3) The viscosity was measured on a thermostatically regulated cone-plate viscometer Physica UM (cone diameter 20 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 to 1000 s.sup.−1).

(4) The average particle size was measured by laser diffraction on a Sympatec instrument with a HELOS laser diffraction sensor.

(5) The standard strength and the threads at the nozzle were used as a measure of the application properties of the composition. To determine the stability, the composition was observed by means of a wooden spatula applied vertically to a piece of cardboard and observing the runoff behavior. The stability was evaluated as “good” if the composition would easily flow down within one minute; the result was evaluated as “very good” if the composition did not move at all. The threads at the nozzle were assessed qualitatively by applying the composition to a piece of cardboard attached to the wall by using a cartridge gun, then removing the cartridge gun by rapidly retracting it at the end of application and measuring the length of the thread remaining at the pull-away location.

(6) To measure the tack-free time (skin-forming time), a small part of the composition at room temperature was applied to cardboard in a layer approx. 3 mm thick and then the time until no more residue would remain on the pipette when the surface of the composition was touched lightly by a pipette made of LDPE in a standard climate (“NK”; 23±1° C., 50±5% relative atmospheric humidity) was determined. The tensile strength, elongation at break and modulus of elasticity (E modulus) were determined in accordance with DIN EN 53504 (tensile speed 200 mm/min) on dumbbells 75 mm long with a web length of 30 mm and a web width of 4 mm, produced by punching out of films approx. 3 mm thick made of the composition cured in a standard climate. To test the early strength, the tensile shear strength was measured by means of the following method: For each measurement 2 KTL-lacquered steel plates 0.75 mm thick, 45 mm wide and 100 mm long (obtainable from Rocholl GmbH, Schönbrunn, Germany) degreased with isohexane were used for each measurement. After an airing time of 10 minutes, the plates were arranged with the help of a suitable PTFE mold at a vertical spacing of 2 mm from one another, so that they would overlap by 15 mm at the head ends. The overlap region between the plates was filled with adhesive, so that the adhesive came to lie on the degreased sides of the plates. The plates which were glued to one another in this way were stored at 23° C. and 50% relative atmospheric humidity, pulled apart after 2 and/or 4 and/or 24 hours with the help of a tensile testing machine (Zwick) at a constant transverse yoke rate of 10 mm/min in accordance with DIN EN 1465 until a break occurred, and then the breaking strength was measured in MPa (N/mm.sup.2). The values given are averages of two measurements.

(7) Moisture-Curing Compositions

(8) Composition Z1: Sikaflex® 265 polyurethane glazing adhesive (obtainable from Sika Schweiz AG).

(9) Composition Z2: component A of the mounting adhesive Sikaflex® 553 based on silane-terminated polymer (obtainable from Sika Schweiz AG).

(10) Production of Curing Agents

(11) Curing agent H1: 68.5 parts by weight bisphenol A liquid resin (Araldite® GY-250 from Huntsman) were mixed with 10 parts by weight reactive diluent (Araldite® DY-E from Huntsman) and 1.5 parts by weight emulsifier (Disponil® 23 from Cognis) at 50° C. and then emulsified continuously with 20 parts by weight water using a stator-rotor mixer at a rotational speed of 22 m/s. The resulting white emulsion had a creamy consistency, a viscosity of approx. 1100 mPa.Math.s at 20° C., an epoxy group content of 4.08 mEq/g and an average particle size of approx. 1.6 μm, with 90% of the particles being smaller than 2.7 μm, and it remained unchanged for more than 1 year when stored at room temperature.

(12) Curing agent H2: 68.5 parts by weight bisphenol A liquid resin (Araldite® GY-250 from Huntsman) and 10 parts by weight bisphenol F liquid resin (D.E.R.™ 354 from Dow Chemical) were mixed with 1.5 parts by weight emulsifier (Disponil® 23 from Cognis) at 50° C. and then emulsified continuously with 20 parts by weight water using a stator-rotor mixer at a rotational speed of 22 m/s. The resulting white emulsion had a creamy consistency, a viscosity of approx. 1500 mPa.Math.s at 20° C., an epoxy group content of 4.28 mEq/g and an average particle size of approx. 1.5 μm, with 90% of the particles being smaller than 2.6 μm, and it remained unchanged for more than 1 year when stored at room temperature.

(13) Curing agent H3: Accelerator paste Sika® Booster (obtainable from Sika Schweiz AG).

(14) Curing agent H4: Component B (version L30) of the mounting adhesive Sikaflex® 553 (obtainable from Sika Schweiz AG).

(15) Production of Accelerated Curing Compositions

Examples 1 to 4 and Ref 1 and Ref 2

(16) For each example, a moisture-curing composition as component A was combined with a curing agent as component B in the weight ratio indicated according to Table 1 by means of a dynamic mixer, then applied directly and cured in a standard climate.

(17) TABLE-US-00001 TABLE 1 Accelerated curing compositions (amounts in parts by weight) Example Ref 1 1 Ref 2 2 3 4 Component A: Composition Z1 100 100 — — — — Composition Z2 — — 100 100 100 100 Component B: Curing agent H1 — — — 2.5 — — Curing agent H2 —  2 — — 2.5  10

(18) The resulting compositions were tested for stability, threads at nozzle, tack-free time and mechanical properties after 7 days of curing in a standard climate plus an additional 7 days of storage at 70° C.

(19) Table 2 summarizes the results of these tests.

(20) TABLE-US-00002 TABLE 2 Properties of the compositions. Example Ref 1 1 Ref 2 2 3 4 Stability good very good very very very good good good good Thread pull 7 3 6 3 3 2 (mm) Freedom from 60 38 30 30 32 41 tackiness.sup.a Mechanical properties (7 days in standard climate) Tensile 8.4 7.0 2.4 2.5 2.5 3.1 strength (MPa) Elongation at 500 450 270 280 260 500 break (%) E modulus 2.0.sup.b 2.4.sup.b 1.5.sup.c 1.5.sup.c 1.6.sup.c 1.0.sup.c (MPa) Mechanical properties (7 days at standard climate + 7 days at 70° C.) Tensile 8.9 8.3 2.5 2.7 2.7 3.3 strength (MPa) Elongation at 560 610 230 260 220 380 break (%) E modulus 2.0.sup.b 2.2.sup.b 1.6.sup.c 1.6.sup.c 1.7.sup.c 1.5.sup.c (MPa) .sup.aTack-free time; .sup.bat 0.5 to 5% elongation; .sup.cat 0.5 to 50% elongation

Examples 5 and 6 as Well as Ref 3 to Ref 6

(21) For each example, a moisture-curing composition as component A was mixed with a curing agent as component B in the stated weight ratio using a dynamic mixer in a standard climate according to Table 3, then applied immediately and cured in a standard climate.

(22) TABLE-US-00003 TABLE 3 Accelerated curing compositions (amounts in parts by weight) Example Ref 3 Ref 4 5 Ref 5 Ref 6 6 Component A: Composition Z1 100 100 100 — — — Composition Z2 — — — 100 100 100 Component B: Curing agent H2 — —  2 — —  10 Curing agent H3 —  2 — — — — Curing agent H4 — — — —  10 —

(23) The resulting compositions were tested for early strength. The results of these tests are listed in Table 4.

(24) TABLE-US-00004 TABLE 4 Early strength (in MPa) of the compositions (amounts in parts by weight); n.d. = not determined. Example Ref 3 Ref 4 5 Ref 5 Ref 6 6 Early strength after 2 hours n.d. 1.2 0.8 n.d. 0.3 0.2 Early strength after 4 hours n.d. 3.5 2.8 n.d. 0.8 0.5 Early strength after 24 hours 1.4 4.9 4.1 0.3 1.8 1.5