METHOD FOR PREPARING A MIXED SILANE-TERMINATED POLYMER

Abstract

The present invention relates to a process for preparing a mixed silane-terminated polymer by reacting a polyol component A) with a diisocyanate component B) comprising 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), at least one isocyanatosilane C) and an aminosilane E), in which the urethanization reaction is carried out in the presence of at least one catalyst D) which is free of organically bonded tin. The invention further relates to the use of the polymers thus obtained.

Claims

1. A process for preparing a mixed silane-terminated polymer by reacting a polyol component A) with a diisocyanate component B) comprising isophorone diisocyanate, with at least one isocyanatosilane C) and with an aminosilane E), in which the urethanization reaction is carried out in the presence of at least one catalyst D) which is free of organically bonded tin, wherein the process is conducted so that first, some of the hydroxyl groups of the polyol component A) are reacted with the diisocyanate component B) and, after reaching a desired NCO content, preferably when at least 40% of the NCO groups have reacted, in a second step the aminosilane is added in such an amount that, and reacted with the free NCO groups of the OH- and NCO-functional prepolymer obtained in the first step until, no free NCO groups are detectable in the reaction mixture any longer, and the still-free hydroxyl groups of the reaction product are then finally reacted with the isocyanatosilane C), wherein the catalyst D) comprises: an organometallic compound of magnesium, zinc, gallium, scandium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium or lutetium, an organometallic compound being understood to be a compound which has at least one ligand bonded to the abovementioned metals via an oxygen atom, and the ligands being selected from the group consisting of alkoxy group, sulfonate group, carboxylate group, dialkylphosphate group, dialkylpyrophosphate group and β-diketonate group, where all ligands may be identical or different from each other, or mixtures of the abovementioned compounds.

2. The process as claimed in claim 1, wherein the catalyst D) comprises: a beta-diketonate compound of magnesium, zinc, gallium, scandium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium or lutetium, a zinc carboxylate, or mixtures of the abovementioned compounds.

3. A process for preparing a mixed silane-terminated polymer by reacting a polyol component A) with a diisocyanate component B) comprising isophorone diisocyanate, with at least one isocyanatosilane C) and with an aminosilane E), in which the urethanization reaction is carried out in the presence of at least one catalyst D) which is free of organically bonded tin, wherein the process is conducted so that i) the hydroxyl groups of the polyol component A) are reacted simultaneously with the diisocyanate component B) and at least one isocyanatosilane C) in the presence of a catalyst D) and in a second reaction step, preferably after complete urethanization, the free NCO groups of the reaction product are then reacted with an aminosilane E), or ii) the isocyanatosilane C) is reacted with some of the hydroxyl groups of the polyol component A) and in a second step the still-free hydroxyl groups of the polymer are then reacted with the diisocyanate component B) and then, preferably after complete urethanization, an aminosilane E) is added in such an amount that, and reacted with the free NCO groups of the prepolymer obtained until, no free NCO groups are detectable in the reaction mixture any longer, wherein the catalyst D) comprises: an organometallic compound of magnesium, zinc, gallium, scandium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium or lutetium, an organometallic compound being understood to be a compound which has at least one ligand bonded to the abovementioned metals via an oxygen atom, and the ligands being selected from the group consisting of alkoxy group, sulfonate group, carboxylate group, dialkylphosphate group, dialkylpyrophosphate group and β-diketonate group, where all ligands may be identical or different from each other, or mixtures of the abovementioned compounds, wherein the sole use of ytterbium(III) acetylacetonate as catalyst D) is excluded.

4. The process as claimed in claim 3, wherein the catalyst D) comprises: a beta-diketonate compound of magnesium, zinc, gallium, scandium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, yttrium or lutetium, a zinc carboxylate, or mixtures of the abovementioned compounds, wherein the sole use of ytterbium(III) acetylacetonate as catalyst D) is excluded.

5. The process as claimed in claim 3, wherein the polyol component A) is a polyether polyol having a number-average molecular weight in a range from 3000 to 24 000 g/mol.

6. The process as claimed in claim 3, wherein the polyol component A) is a polyether polyol based on polypropylene oxide.

7. The process as claimed in claim 3, wherein the isocyanate component B) contains exclusively isophorone diisocyanate.

8. The process as claimed in claim 3, wherein the isocyanatosilane C) is a compound of the formula (II) ##STR00016## in which R.sup.1, R.sup.2 and R.sup.3 independently of one another are identical or different saturated or unsaturated, linear or branched, aliphatic or cycloaliphatic or optionally substituted aromatic or araliphatic radicals which have up to 18 carbon atoms and may optionally contain up to 3 heteroatoms from the group of oxygen, sulfur, nitrogen, preferably in each case alkyl radicals which have up to 6 carbon atoms and/or alkoxy radicals which have up to 6 carbon atoms and may contain up to 3 oxygen atoms, particularly preferably in each case methyl, methoxy and/or ethoxy, with the proviso that at least one of the radicals R.sup.1, R.sup.2 and R.sup.3 is joined to the silicon atom via an oxygen atom, and X is a linear or branched organic radical having up to 6, preferably 1 to 4, carbon atoms, particularly preferably a propylene radical (—CH.sub.2—CH.sub.2—CH.sub.2—).

9. The process as claimed in claim 3, wherein the isocyanatosilane C) used is 3-isocyanatopropyltrimethoxysilane.

10. The process as claimed in claim 3, wherein the aminosilane E) is a compound of the formula (VIII) ##STR00017## in which R.sup.1, R.sup.2, R.sup.3 and X have the definition given in claim 8 and R.sup.10 is hydrogen, a saturated or unsaturated, linear or branched, aliphatic or cycloaliphatic or an optionally substituted aromatic or araliphatic radical having up to 18 carbon atoms or a radical of the formula ##STR00018## in which R.sup.1, R.sup.2, R.sup.3 and X have the definition given above.

11. The process as claimed in claim 3, wherein the aminosilane E) is a compound of the formula (IX) ##STR00019## in which R.sup.1, R.sup.2 and R.sup.3 have the definition given in claim 8 X is a linear or branched organic radical having at least 2 carbon atoms and R.sup.11 and R.sup.12 independently of one another are saturated or unsaturated, linear or branched, aliphatic or cycloaliphatic or aromatic organic radicals which have 1 to 18 carbon atoms, are substituted or unsubstituted and/or have heteroatoms in the chain.

12. The process as claimed in claim 3, wherein the amount of aminosilane E) is chosen such that there are 0.9 to 1.2, preferably 0.95 to 1.2, particularly preferably 0.95 to 1.05 amino groups for each isocyanate group of the isocyanate- and silane-functional polymer formed in process step a).

13. The process as claimed in claim 3, wherein the molar amount of the isocyanatosilane C) used is in the range from 1 to 50 mol %, preferably in the range from 5 to 28 mol %, particularly preferably in the range from 10 to 28 mol %, very particularly preferably in the range from 10 to 25 mol %, and the molar amount of the diisocyanate B) used is accordingly in the range from 50 to 99 mol %, preferably in the range from 72 to 95 mol %, particularly preferably in the range from 72 to 90 mol %, very particularly preferably in the range from 75 to 90 mol %, based on the number of hydroxyl groups of polyol A).

14. The use of the silane-terminated polymers prepared according to the process as claimed in claim 1 as binders in coating compositions, sealants and adhesives, in particular in the construction sector and in the automobile industry.

Description

EXAMPLES

[0129] Unless stated otherwise, all percentages and all ppm figures relate to the total weight of the reaction mixture.

[0130] The NCO contents were determined by titrimetry according to DIN EN ISO 11909.

[0131] OH numbers were determined by titrimetry according to DIN 53240 T.2.

[0132] All viscosity measurements were made with a Physica MCR 51 rheometer from Anton Paar Germany GmbH (Germany) to DIN EN ISO 3219.

[0133] The Hazen color number was measured by spectrophotometry according to DIN EN ISO 6271-2:2004 with a LICO 400 spectrophotometer from Lange, Germany.

[0134] The reported molecular weights are in each case number-average molecular weights (Mn) which can be determined by gel permeation chromatography.

[0135] For the practical performance of the following examples, it should be noted that the contents in the substances used of the groups that are relevant to the respective reaction (e.g. amine content of the aminosilane) have been determined by specific determination methods (e.g. titration) and the amounts actually used have been calculated on the basis of contents of in each case 100%.

[0136] Synthesis of Mixed Silane-Terminated Polymers

[0137] Process a (Also Comparative Example)

[0138] In a 2 l sulfonation flask with lid, stirrer, thermometer and nitrogen flow, 1369.3 g (0.16 mol) of a propylene glycol with an OH number of 13.2 (Acclaim© Polyol 8200 N from Covestro Deutschland AG; Leverkusen, Germany) were prepolymerized with 35.8 g (0.16 mol) of isophorone diisocyanate and 34.2 g (0.16 mol) of 3-isocyanatopropyltrimethoxysilane (Geniosil® GF 40 from Wacker Chemie AG; Munich, Germany) at 60° C. with addition of 40 ppm (60 mg) of dibutyltin dilaurate until the theoretical NCO content of 0.47% had been reached. Subsequently, 56.2 g (0.16 mol) of diethyl N-(3-trimethoxysilylpropyl)aspartate (prepared according to EP-A 596 360, example 5) were rapidly added dropwise and the mixture was stirred until it was no longer possible to observe any isocyanate band in the IR spectrum. The polyurethane prepolymer having alkoxysilyl end groups that was obtained had a viscosity of 12 900 mPas and a color number of 16 APHA.

[0139] Process B (Also Comparative Example)

[0140] In a 2 l sulfonation flask with lid, stirrer, thermometer and nitrogen flow, 1369.3 g (0.16 mol) of a propylene glycol with an OH number of 13.2 (Acclaim® Polyol 8200 N from Covestro Deutschland AG; Leverkusen, Germany) were stirred with 34.2 g (0.16 mol) of 3-isocyanatopropyltrimethoxysilane (Geniosil® GF 40 from Wacker Chemie AG; Munich, Germany) at 60° C. with addition of 40 ppm (60 mg) of dibutyltin dilaurate until it was no longer possible to observe any isocyanate band in the IR spectrum. Subsequently, 35.8 g (0.16 mol) of isophorone diisocyanate were rapidly added dropwise and prepolymerization was effected until the theoretical NCO content of 0.47% had been reached. After addition of 56.2 g (0.16 mol) of diethyl N-(3-trimethoxysilylpropyl)aspartate (prepared according to EP-A 596 360, example 5), the mixture was stirred until it was no longer possible to observe any isocyanate band in the IR spectrum. The polyurethane prepolymer having alkoxysilyl end groups that was obtained had a viscosity of 13 600 mPas and a color number of 18 APHA.

[0141] Process C (Also Comparative Example)

[0142] In a 2 l sulfonation flask with lid, stirrer, thermometer and nitrogen flow, 1369.3 g (0.16 mol) of a propylene glycol with an OH number of 13.2 (Acclaim© Polyol 8200 N from Covestro Deutschland AG; Leverkusen, Germany) were prepolymerized with 35.8 g (0.16 mol) of isophorone diisocyanate at 60° C. with addition of 40 ppm (60 mg) of dibutyltin dilaurate until the theoretical NCO content of 0.47% had been reached. After addition of 56.2 g (0.16 mol) of diethyl N-(3-trimethoxysilylpropyl)aspartate (prepared according to EP-A 596 360, example 5), the mixture was stirred until it was no longer possible to observe any isocyanate band in the IR spectrum. Thereafter, 34.2 g (0.16 mol) of 3-isocyanatopropyltrimethoxysilane (Geniosil® GF 40 from Wacker Chemie AG; Munich, Germany) were rapidly added dropwise and the mixture was stirred again until it was no longer possible to observe any isocyanate band in the IR spectrum. The polyurethane prepolymer having alkoxysilyl end groups that was obtained had a viscosity of 13 000 mPas and a color number of 20 APHA.

[0143] These examples show that by using the tin-containing catalyst known from the prior art, irrespective of the process chosen, mixed silane-terminated polymers having a low viscosity can be obtained. The viscosity of the mixed silane-terminated polymers obtained in the process is also influenced, inter alia, by the choice of the catalyst.

[0144] The synthesis of the mixed silane-terminated polymers using an organotin-free catalyst D) is effected in this case according to the procedures described hereinabove, the DBTL catalyst not in accordance with the invention accordingly being replaced. The following viscosities of the obtained polymers resulted:

TABLE-US-00001 No. Catalyst (amount of catalyst) Process Viscosity CE 1 Valikat .sup.® Bi 2810 (bismuth(III) Process A 30 900 mPas neodecanoate) (160 ppm) CE 2 Valikat .sup.® Bi 2810 (bismuth(III) Process B 26 800 mPas neodecanoate) (160 ppm) CE 3 Valikat .sup.® Bi 2810 (bismuth(III) Process C 24 600 mPas neodecanoate) (160 ppm) CE 4 K-Kat 348 .sup.® (bismuth(III) Process A 29 700 mPas 2-ethylhexanoate) (160 ppm) CE 5 K-Kat 348 .sup.® (bismuth(III) Process B 29 800 mPas 2-ethylhexanoate) (160 ppm) CE 6 K-Kat 348 .sup.® (bismuth(III) Process C  30.00 mPas 2-ethylhexanoate) (160 ppm) IE 1 Zinc(II) 2-ethylhexanoate (160 ppm) Process A 17 800 mPas IE 2 Zinc(II) 2-ethylhexanoate (160 ppm) Process B 20 300 mPas IE 3 Zinc(II) 2-ethylhexanoate (160 ppm) Process C 20 400 mPas IE 4 Ytterbium(III) acetylacetonate (120 ppm) Process C 12 600 mPas IE 5 Gallium(III) acetylacetonate (160 ppm) Process A 17 100 mPas IE 6 Gallium(III) acetylacetonate (160 ppm) Process B 16 100 mPas IE 7 Gallium(III) acetylacetonate (160 ppm) Process C 21 200 mPas CE = comparative example IE = according to the invention