ISOCYANATE-TERMINATED PREPOLYMERS BASED ON POLYOXYMETHYLENE-POLYOXYALKYLENE BLOCK COPOLYMERS, PROCESS FOR THE PREPARATION AND USE THEREOF

Abstract

The present invention relates to isocyanate-terminated prepolymers based on polyoxymethylene-polyoxyalkylene block copolymers, to a process for their preparation, and to the use of these isocyanate-terminated prepolymers as isocyanate components in 1- and 2-component systems for coatings, adhesives and sealants.

Claims

1. A process for preparing an isocyanate-terminated prepolymer comprising reacting A. at least one aliphatic, cycloaliphatic, araliphatic and/or aromatic polyisocyanate, wherein component A has an NCO content according to DIN EN ISO 11909:2007-05 of 15% to 60% by weight, B. at least one polyoxymethylene-polyoxyalkylene block copolymer having a hydroxyl number according to DIN 53240-2:2007-11 of 15 mg KOH/g to 200 mg KOH/g, C. i) at least one amino-containing polyether based on propylene oxide having a hydroxyl number according to DIN 53240-2:2007-11 of 40 to 80 mg KOH/g, an OH functionality of 4.0 and an amine content according to DIN EN 9702:1998 in the range from 0.5% to 1.0% by weight, ii) optionally at least one amino-containing polyether based on based on ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide having an NH.sub.2-functionality of 2 or 3, with the exception of amino-containing polyethers of component Ci, and D. optionally auxiliaries containing protic acids (D2) and/or auxiliaries which are not protic acids of D2 (D1).

2. The process as claimed in claim 1, characterized in that component B consists of a polyoxymethylene-polypropylene oxide block copolymer or a polyoxymethylene-polyoxyalkylene carbonate block copolymer.

3. The process as claimed in claim 1, wherein at least component B has been prepared in the presence of a double metal cyanide catalyst, and component B contains at least some of the double metal cyanide catalyst, wherein the content of double metal cyanide catalyst based on the total amount of components B and C is 10 to 5000 ppm determined using the amount of metal content from the double metal cyanide catalyst determined according to DIN ISO 17025 (August 2005).

4. The process as claimed in claim 1, wherein the at least one polyoxymethylene-polyoxyalkylene block copolymer of component B has a hydroxyl number according to DIN 53240-2:2007-11 of 15 mg KOH/g to 150 mg KOH/g.

5. The process as claimed in claim 1, wherein the at least one amino-containing polyether of component Ci has a hydroxyl number according to DIN 53240-2:2007-11 of 45 to 75 mg KOH/g.

6. The process as claimed in claim 1, wherein the at least one amino-containing polyether of component Ci has an amine content according to DIN EN 9702:1998 of 0.56% to 0.94% by weight.

7. The process as claimed in claim 1, wherein component A comprises at least one aromatic polyisocyanate.

8. The process as claimed in claim 1, wherein the isocyanate-terminated prepolymer is a reaction product of a composition comprising: 50% to 70% by weight of component A, 15% to 30% by weight of component B, 10% to 30% by weight of component Ci, 0% to 15% by weight of component Cii, 0.10% to 0.20% by weight of component D1, and 0% to 0.50% by weight of component D2, wherein the % by weight values are based on the sum of all components of the composition.

9. An isocyanate-terminated prepolymer obtained by the process as claimed in claim 1.

10. (canceled)

11. A paint, adhesive or sealant system containing at least one isocyanate-terminated prepolymer as claimed in claim 17.

12. The paint, adhesive or sealant system as claimed in claim 11, wherein the system is a 1-component moisture-curable system which comprises no isocyanate-reactive components in addition to the at least one isocyanate-terminated prepolymer.

13. The paint, adhesive or sealant system as claimed in claim 11, wherein the system is a 2-component moisture-curable system which comprises at least one isocyanate-reactive component in addition to the at least one isocyanate-terminated prepolymer.

14. A substrate coated or bonded with paint, adhesive or sealant systems as claimed in claim 11.

15. The process as claimed in claim 2, wherein the block copolymer comprises two terminal polyoxyalkylene blocks.

16. The process as claimed in claim 7 wherein the at least one aromatic polyisocyanate comprises 1,5-naphthalene diisocyanate, diisocyanatodiphenylmethane, poly(methylene phenyl isocyanate), diisocyanatomethylbenzene, or a mixture thereof.

17. An isocyanate-terminated prepolymer comprising a reaction product of a composition comprising: A. at least one aliphatic, cycloaliphatic, araliphatic and/or aromatic polyisocyanate, wherein component A has an NCO content according to DIN EN ISO 11909:2007-05 of 15% to 60% by weight, B. at least one polyoxymethylene-polyoxyalkylene block copolymer having a hydroxyl number according to DIN 53240-2:2007-11 of 15 mg KOH/g to 200 mg KOH/g, C. i) at least one amino-containing polyether based on propylene oxide having a hydroxyl number according to DIN 53240-2:2007-11 of 40 to 80 mg KOH/g, an OH functionality of 4.0 and an amine content according to DIN EN 9702:1998 in the range from 0.5% to 1.0% by weight, ii) optionally at least one amino-containing polyether based on based on ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide having an NH.sub.2-functionality of 2 or 3, with the exception of amino-containing polyethers of component Ci, and D. optionally auxiliaries containing protic acids (D2) and/or auxiliaries which are not protic acids of D2 (D1).

18. The isocyanate-terminated prepolymer of claim 17, wherein the isocyanate-terminated prepolymer is a reaction product of a composition comprising: 50% to 70% by weight of component A, 15% to 30% by weight of component B, 10% to 30% by weight of component Ci, 0% to 15% by weight of component Cii, 0.10% to 0.20% by weight of component D1, and 0% to 0.50% by weight of component D2, wherein the % by weight values are based on the sum of all components of the composition.

Description

EXAMPLES

[0077] Materials [0078] Isocyanate 1: aromatic polyisocyanate based on diphenylmethane diisocyanate (MDI) having an NCO content of 31.5% (31.8), a content of 2,2′-MDI of 2.3% (0.1), a content of 2,4′-MDI of 12.6% (12.7) and a content of 4,4′-MDI of 42.4% (54.4)) as well as a viscosity of 90 (100) mPas at 25° C. [0079] Polyol 1: polyoxymethylene-polypropylene oxide block copolymer having an OH number of 112 mg KOH/g, prepared under double metal cyanide catalysis, the double metal cyanide catalyst having been prepared according to example 6 of WO 01/80994 A1 [0080] Polyol 2: polyoxymethylene-polypropylene oxide block copolymer having an OH number of 56 mg KOH/g, prepared under double metal cyanide catalysis, the double metal cyanide catalyst having been prepared according to example 6 of WO 01/80994 A1 [0081] Polyol 3: polyoxymethylene-polypropylene oxide block copolymer having an OH number of 18 mg KOH/g, prepared under double metal cyanide catalysis, the double metal cyanide catalyst having been prepared according to example 6 of WO 01/80994 A1 [0082] Polyol 4: polypropylene oxide polyether based on 1,2-propylene glycol having an OH number of 112 mg KOH/g [0083] Polyol 5: polypropylene oxide polyether based on 1,2-propylene glycol having an OH number of 56 mg KOH/g [0084] Polyol 6: polypropylene oxide polyether based on 1,2-propylene glycol having an OH number of 14 mg KOH/g [0085] Polyol 7: polypropylene oxide polyether based on 1,2-diaminoethane having an OH number of 60 mg KOH/g and an amine content of 0.7% by weight

[0086] Methods

[0087] OH numbers were determined titrimetrically on the basis of DIN 53240-2:2007-11.

[0088] Amine content was determined titrimetrically according to DIN EN ISO 9702:1998.

[0089] NCO contents were determined titrimetrically according to DIN EN ISO 11909:2007-05.

[0090] All viscosity measurements were recorded with a Physica MCR 51 rheometer from Anton Paar Germany GmbH (DE) in accordance with DIN EN ISO 3219:1994-10 at a shear rate of 250 s-1.

[0091] The film forming time (FFT, dry-hard time) and film drying times (FDT, set-to-touch time) were determined in a linear drying recorder according to ASTM D 5895:2013-06.

[0092] The tensile shear strength of a gapless beechwood/beechwood adhesive bond subjected to tensile forces parallel to the bonded surface was measured according to DIN EN 205:2016-12.

[0093] Syntheses

Example 1

[0094] A mixture of 175.0 g of polyoxymethylene-polypropylene oxide block copolymer having an OH number of 112 mg KOH/g prepared under double metal cyanide catalysis (polyol 1) and 214.5 g of polypropylene oxide polyether based on 1,2-diaminoethane having OH number of 60 mg KOH/g and an amine content of 0.7% by weight (polyol 7) is placed in a 1 liter flat flange vessel and stirred at 120° C. under a vacuum of 20 mbar for 1 hour. This was followed by cooling to 55° C. The obtained polyol mixture is metered over about 30 minutes into 571.0 g of an aromatic polyisocyanate based on diphenylmethane diisocyanate (MDI) having an NCO content of 31.5%, a content of 2,2′-MDI of 2.3%, a content of 2,4′-MDI of 12.6% and a content of 4,4′-MDI of 42.4% as well as a viscosity of 90 mPas at 25° C. (isocyanate 1). The mixture is then heated to 60° C., utilizing any exothermic reaction that may occur. The mixture is stirred at 60° C. until the isocyanate content is constant. This affords a brownish-colored polyisocyanate mixture having an NCO content of 15.2% by weight, a viscosity of 35 600 mPas (23° C.) and an average isocyanate functionality of 2.7.

Examples 2 to 3

[0095] The process described in example 1 was used to prepare further polyisocyanates using the polyols summarized in table 1. The resulting characteristics are likewise summarized in table 1.

Comparative Example 4 to 6

[0096] Further polyisocyanates were prepared by the process described in example 1 using the polyols summarized in table 1. The resulting characteristics are likewise summarized in table 1.

[0097] Performance Tests

[0098] Testing Reactivity as Reactive Adhesive

[0099] To compare reactivity the film forming time (FFT, dry-hard time) and film drying times (FDT, set-to-touch time) were measured in a linear drying recorder according to ASTM D 5895:2013 and viscosity was measured at 25° C. (on the basis of DIN EN ISO 3219:1994-10). The wet film thickness of the reactive adhesive was 250 m. The storage stability at 70° C. was also measured in the form of the viscosity increase over time. The polyisocyanate mixture is considered storage-stable if the viscosity has less than doubled over 14 days of storage at 70° C.

[0100] The inventive polyisocyanate mixture according to example 1 has a higher viscosity and comparable storage stability relative to example 4 (comparative). However, the reactivity of the inventive polyisocyanate mixture of example 1, which is reflected in shorter film formation and film drying times, is markedly higher than the reactivity of the comparative example.

[0101] This effect is even more marked in example 2. In contrast to comparative example 5 the reactivity of the inventive polyisocyanate is significantly higher than the reactivity of the comparative example.

[0102] The inventive polyisocyanate example 3 shows not only elevated reaction of the three recited examples but also the lowest viscosity.

[0103] Testing of Tensile Shear Strength as a Reactive Adhesive

[0104] To compare adhesive effect the tensile shear strength of a gapless beechwood/beechwood adhesive bond subjected to tensile forces parallel to the bonded surface was measured according to DIN EN 205:2016. Tensile shear strength was tested according to the time intervals summarized in the table below.

[0105] After 60 min the inventive polyisocyanate mixture according to example 1 experiences a higher force compared to example 4 (comparison) until the specimen breaks. This is also exhibited by examples 2 and 3, which experience a higher force than comparative examples 5 and 6 until the specimen breaks.

[0106] As reflected in the higher tensile strengths the adhesive strength of the inventive polyisocyanate mixture of example 1 is markedly higher than the adhesive strength of the comparative example.

TABLE-US-00001 TABLE 1 Summary of compositions and characteristics of the examples. Inventive Comparative Example Mixture 1 2 3 4 5 6 Polyisocyanate [g] 571.0 571.0 571.0 571.0 571.0 571.0 Polyol 1 [g] 175.0 — — — — — Polyol 2 [g] — 214.0 — — — — Polyol 3 [g] — — 250.0 — — — Polyol 4 [g] — — — 175.0 — — Polyol 5 [g] — — — — 214.0 — Polyol 6 [g] — — — — — 250.0 Polyol 7 [g] 214.5 214.5 214.5 214.5 214.5 214.5 NCO content: [% by wt.] 15.3 15.0 15.4 15.2 15.0 15.4 Viscosity [mPas (23° C.)] 41800 22800 21000 35600 19400 14700 Isocyanate functionality 2.7 2.8 2.8 2.8 2.8 2.8 FFT [min] 30 25 30 35 40 30 FDT [min] 90 80 80 95 95 85 Storage stability yes yes yes yes yes yes (over 14 d at 70° C.) Tensile shear strength 0.0 0.0 0.0 0.0 0.0 0.0 after 0.5 h [N/mm.sup.2] Tensile shear strength 6.8 1.9 2.0 3.9 0.6 1.3 after 1 h [N/mm.sup.2]