Aldiminosilanes

Abstract

An aldiminosilane of the formula (I), to the use thereof as adhesion promoters and/or crosslinking agents, and to curable compositions including same. The aldiminosilane of the formula (I) is odorless, pH-neutral, liquid at room temperature, and has a low sensitivity to heat. The hydrolysis of the aldiminosilane proceeds relatively slowly, and the aldiminosilane is highly effective as an adhesion promoter. Furthermore, the aldiminosilane exhibits excellent compatibility with curable compositions based on isocyanates, epoxides, or silanes, whereby such compositions do not exhibit a propensity for migration effects such as bleeding or substrate soiling after being cured. In particular, isocyanate group-containing compositions containing the aldiminosilane of the formula (I) are highly storage-stable regardless of the storage temperature and the isocyanate used.

Claims

1. An aldiminosilane of the formula (I) ##STR00011## where x is 0 or 1 or 2, R.sup.1 is a monovalent aliphatic or cycloaliphatic or arylaliphatic hydrocarbyl radical optionally containing ether groups and having 1 to 12 carbon atoms, R.sup.2 is a monovalent hydrocarbyl radical having 1 to 12 carbon atoms, A is an alkylene radical optionally having ether oxygen or amine nitrogen and having 1 to 12 carbon atoms, and Z is a radical of the formula (II) ##STR00012## where R is selected from the group consisting of branched 4-decyl, branched 4-undecyl, branched 4-dodecyl, branched 4-tridecyl and branched 4-tetradecyl radicals.

2. An aldiminosilane as claimed in claim 1, wherein R.sup.1 is methyl or ethyl.

3. An aldiminosilane as claimed in claim 1, wherein A is selected from the group consisting of methylene, 1,3-propylene, 4-aza-1,6-hexylene, 4,7-diaza-1,9-nonylene, 2-methyl-1,3-propylene, 1,4-butylene, 3-methyl-1,4-butylene and 3,3-dimethyl-1,4-butylene, where the numbering starts from the silicon atom.

4. A process for preparing aldiminosilanes as claimed in claim 1, in which at least one aminosilane of the formula (III) is combined with at least one aldehyde of the formula (IV) to form a reaction mixture, using the aldehyde stoichiometrically or in stoichiometric excess in relation to the primary amino group of the aminosilane, ##STR00013## and the water of condensation is removed from the reaction mixture by a suitable method, optionally with heating thereof.

5. A process for preparing aldiminosilanes as claimed in claim 1, in which at least one aldehyde of the formula (IV) is first combined with a volatile primary monoamine to form a reaction mixture, using the aldehyde stoichiometrically or in stoichiometric excess in relation to the primary amino group, ##STR00014## the water of condensation and any excess amine are removed from the reaction mixture by a suitable method, optionally with heating thereof, then the resulting aldimine intermediate is combined with at least one aminosilane of the formula (III) to form a reaction mixture, using the aminosilane stoichiometrically or in stoichiometric excess in relation to the aldimino group of the aldimine intermediate, ##STR00015## and finally the reaction mixture is heated and the volatile primary monoamine released and any excess aminosilane is removed from the reaction mixture.

6. A method comprising applying at least one aldiminosilane as claimed in claim 1 as an adhesion promoter and/or crosslinker.

7. An aldiminosilane composition comprising an aldiminosilane of the formula (I) ##STR00016## where x is 0 or 1 or 2, R.sup.1 is a monovalent aliphatic or cycloaliphatic or arylaliphatic hydrocarbyl radical optionally containing ether groups and having 1 to 12 carbon atoms, R.sup.2 is a monovalent hydrocarbyl radical having 1 to 12 carbon atoms, A is an alkylene radical optionally having ether oxygen or amine nitrogen and having 1 to 12 carbon atoms, and Z is an aryl radical substituted by an alkyl or alkoxy group and having a total of 12 to 26 carbon atoms, and at least one monomer and/or polymer having crosslinkable reactive groups.

8. The aldiminosilane composition as claimed in claim 7, wherein the aldiminosilane composition contains isocyanate groups that comprise at least one polyisocyanate and/or at least one polymer containing isocyanate groups.

9. The aldiminosilane composition as claimed in claim 7, wherein the composition is an adhesive or a sealant or a coating.

10. The aldiminosilane composition as claimed in claim 7, wherein the composition is a primer.

Description

EXAMPLES

(1) Working examples are adduced hereinafter, which are intended to further elucidate the invention described. Of course, the invention is not limited to these described working examples.

(2) Standard climatic conditions (SCC) refer to a temperature of 231 C. and a relative air humidity of 505%.

(3) Unless stated otherwise, the chemicals used were from Sigma-Aldrich.

(4) Aldehydes Used:

(5) Aldehyde-1: Fractionated aldehyde mixture obtained from formylation, catalyzed by means of HFBF.sub.3, of C.sub.10-14-alkylbenzene, containing mainly branched 4-(C.sub.10-14-alkyl)benzaldehydes. (Average aldehyde equivalent weight 290 g/eq)
2,2-Dimethyl-3-lauroyloxypropanal
Aldehyde-1 is a mixture of aldehydes of the formula (IV).
Preparation of Aldiminosilanes:

(6) Infrared spectra (FT-IR) were measured as undiluted films on a Nicolet iS5 FT-IR instrument from Thermo Scientific equipped with a horizontal ATR measurement unit with a diamond crystal. The absorption bands are reported in wavenumbers (cm.sup.1).

(7) Gas chromatograms (GC) were measured within the temperature range of 60 to 320 C. with a heating rate of 15 C./min and a run time of 10 min at 320 C. The injector temperature was 250 C. A Zebron ZB-5 column was used (L=30 m, ID=0.25 mm, dj=0.5 m) with a gas flow rate of 1.5 ml/min. Detection was by means of flame ionization (FID).

(8) Viscosity was measured with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 50 mm, cone angle 1, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.1 for viscosities <150 Pa.Math.s, shear rate 1 s.sup.1 for viscosities >150 Pa.Math.s)).

(9) Aldiminosilane A-1:

(10) 27.60 g of aldehyde-1 and 5.00 g of anhydrous magnesium sulfate formed an initial charge in a round-bottom flask under a nitrogen atmosphere. To this was slowly added dropwise 16.18 g of 3-aminopropyltrimethoxysilane while stirring and cooling. Then the reaction mixture was stirred at 70 C. for 30 min, the magnesium sulfate was filtered off, and then the reaction mixture was freed of volatile compounds on a rotary evaporator. A yellowish liquid having a viscosity at 20 C. of 146 mPa.Math.s was obtained, which had a GC-determined purity of 94.3% (retention time 16.6-19.3 min) and a content of unconverted aldehyde-1 of 3.0% (retention time 12.3-14.8 min).

(11) FT-IR: 2955, 2923, 2870, 2853, 2734, 1705, 1646, 1608, 1571, 1508, 1457, 1418, 1377, 1342, 1302, 1248, 1189, 1102, 1087, 1027, 1018, 940, 881, 865, 825, 777, 722, 699.

(12) Aldiminosilane A-2:

(13) The procedure was as described for aldiminosilane A-1, except that 20.00 g of 3-aminopropyltriethoxysilane was used instead of 3-aminopropyltrimethoxysilane. A yellowish liquid having a GC-determined purity of 90.5% (retention time 16.6-19.3 min) and a content of unconverted aldehyde-1 of 1.5% (retention time 12.3-14.8 min).

(14) FT-IR: 2957, 2923, 2872, 2854, 2733, 1706, 1647, 1609, 1571, 1509, 1456, 1419, 1389, 1378, 1342, 1300, 1248, 1223, 1211, 1166, 1102, 1080, 1018, 991, 954, 878, 863, 827, 790, 775, 722.

(15) Aldiminosilane R-1:

(16) The procedure was as described for aldiminosilane A-1, except that 27.00 g of 2,2-dimethyl-3-lauroyloxypropanal was used rather than aldehyde-1. A yellowish liquid was obtained.

(17) The aldiminosilanes A-1 and A-2 are inventive aldiminosilanes of the formula (I). The aldiminosilane R-1 is a comparative example according to WO 2005/058921.

(18) Preparation of Polymers Containing Isocyanate Groups

(19) Polymer P1:

(20) 400 g of polyoxypropylene diol (Acclaim 4200, from Covestro; OH number 28.5 mg KOH/g) and 52 g of diphenylmethane 4,4-diisocyanate (Desmodur 44 MC L, from Covestro) were reacted by a known process at 80 C. to give an NCO-terminated polyurethane polymer which is liquid at room temperature and has a content of free isocyanate groups of 1.85% by weight and a viscosity at 20 C. of 35.9 Pa.Math.s.

(21) Use as Adhesion Promoter

(22) Activator-1

(23) 2.5 g of aldiminosilane A-1 were dissolved in 250 g of dry ethyl acetate and stored with exclusion of moisture.

(24) Activator-2

(25) 2.5 g of aldiminosilane A-2 were dissolved in 250 g of dry ethyl acetate and stored with exclusion of moisture.

(26) Composition Z-1

(27) 1.5 g of aldiminosilane A-1 were mixed under a nitrogen atmosphere with 150 g of polymer P1 and stored with exclusion of moisture. The mixed composition had a viscosity at 20 C. of 36.4 Pa.Math.s after one day under standard climatic conditions. After storage in a closed container in an air circulation oven at 60 C. for 7 days, the viscosity was 44.3 Pa.Math.s at 20 C.

(28) Composition Z-2

(29) 1.5 g of aldiminosilane A-2 were mixed under a nitrogen atmosphere with 150 g of polymer P1 and stored with exclusion of moisture.

(30) As a measure of action as adhesion promoter, spacer tape was applied longitudinally to two glass plates (float glass; from Rocholl, Schnbrunn, Germany) having dimensions of 1015 cm on the air side so as to give three glass strips each of 28 cm. The first and second strips were each wiped once with an ethyl acetate-soaked hygiene wipe. The third strip was wiped once with a hygiene wipe wetted with activator-1 and with activator-2. Subsequently, the glass plates treated in this way were stored under standard climatic conditions for flashoff for 2 h. Then 6 g of polymer P1 were applied in a layer thickness of about 3 mm to each of the first and third strips. 6 g of composition Z-1 or of composition Z-2 were applied to the second strip in a layer thickness of about 3 mm.

(31) The glass plates thus coated were stored under standard climatic conditions for 7 days and then attempts were made to detach the cured polymer films from the glass plate. The bonding was described as very good when the cured polymer could not be removed from the glass substrate. (Even after several cuts transverse to the strip direction down to the glass substrate, by which the polymer was cut away from the glass, and pulling the polymer strip away vertically, it was not possible to detach the polymer from the glass substrate.) The bonding was described as none when the cured polymer could be fully detached from the glass substrate.

(32) The results are shown in tables 1 and 2.

(33) TABLE-US-00001 TABLE 1 Pretreatment Polymer strip Bonding Ethyl acetate Polymer P1 none Ethyl acetate Composition Z-1 very good Activator-1 Polymer P1 very good

(34) TABLE-US-00002 TABLE 2 Pretreatment Polymer strip Bonding Ethyl acetate Polymer P1 none Ethyl acetate Composition Z-2 very good Activator-2 Polymer P1 very good
Primer Compositions Z-3 and Z-4:

(35) 125.0 g of Sika Primer-209 N (pigmented primer containing isocyanate groups, from Sika Schweiz AG) was mixed with 11.09 g of aldiminosilane A-1 (=primer composition Z-3) or 10.94 g of aldiminosilane R-1 (=primer composition Z-4) and stored with exclusion of moisture.

Examples 1 to 3

(36) Primer compositions Z 3 and Z-4 were used as adhesion promoters on glass: a long flashoff time of 30 hours or 7 days was followed by application of Sikaflex-250 DM-5 (one-component moisture-curing polyurethane adhesive, from Sika Switzerland AG) and curing thereof, and the bonding thereof was tested. The reference used was Sika Primer-209 N.

(37) For each test, a glass plate was cleaned with isopropanol, wiped with a hygiene wipe soaked with Sika Aktivator-100 (adhesion-promoting cleaner, from Sika Schweiz AG) and, after a flashoff time of 10 min, the respective primer composition was applied in a thin layer with a sponge. After a flashoff time of 32 hours or 7 days under standard climatic conditions, Sikaflex-250 DM-5 that had been preheated to 60 C. was applied in the form of a triangular bead of width 10 mm and length 100 mm to the primer layer and the glass plate was stored under standard climatic conditions for 7 days, in the course of which the adhesive applied cured. Subsequently, the bonding of the adhesive bead on the glass plate was tested by making an incision into the bead at the end just above the bonding surface, holding the cut end of the bead with rounded tweezers and trying to pull the bead away from the substrate. Then the bead was incised again down to the substrate, the part of the bead that had been cut away was rolled up with the rounded tweezers and an attempt was again made to pull the bead away from the substrate. In this way, the bead was cut away from the substrate by pulling over a length of 80 mm. Subsequently, bonding was assessed with reference to the failure profile using the following scale:

(38) 1 (=very good) represents more than 95% cohesive failure

(39) 2 (=good) represents 75% to 95% cohesive failure

(40) 3 (=moderate) represents 25% to 75% cohesive failure

(41) 4 (=poor) represents less than 25% cohesive failure

(42) 5 (=no adhesion) represents 0% cohesive failure or 100% adhesive failure

(43) The results are reported in table 3.

(44) Examples 2 and 3 marked (Ref.) are comparative examples.

(45) TABLE-US-00003 TABLE 3 Example: 1 2 (Ref.) 3 (Ref.) Primer composition Flashoff time: Z-3 Z-4 Sika Primer-209 N Bonding of 32 h 1 1 2 Sikaflex 7 d 1 5 1 250 DM-5