Titanium complexes as vulcanization catalysts

Abstract

The invention relates to a curable composition comprising: a) at least one polymer having at least one silicon-containing group of formula Si(R.sup.1).sub.k(Y).sub.3-k as defined herein; b) at least one titanium complex of formula TiL(OR.sup.3).sub.2 wherein each R.sup.3 is independently selected from a C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms, preferably selected from silicon, sulfur, nitrogen or oxygen atoms, wherein preferably R.sup.3 is selected from n-butyl or isopropyl, and L is a deprotonated, tridentate ligand, and c) optionally at least one compound which has a hydrolyzable silicon-containing group and a weight average molecular weight in the range of 100 to 1000 g/mol, preparations containing these compositions and use thereof.

Claims

1. A curable composition comprising a) a polymer having at least one silicon-containing group of formula (1)
Si(R.sup.1).sub.k(Y).sub.3-k (1), wherein R.sup.1 is selected from a hydrocarbon radical containing 1 to 20 C atoms or a triorganosiloxane group of formula OSi(R.sup.2).sub.3, where each R.sup.2 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms; each Y is independently selected from a hydroxy group or a hydrolyzable group; and k is 0, 1, or 2; b) at least one titanium complex of formula (2)
TiL(OR.sup.3).sub.2(2), wherein each R.sup.3 is independently selected from a C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms; and L is a deprotonated, tridentate ligand; and c) optionally a compound which has a hydrolyzable silicon-containing group and a weight average molecular weight in the range of 100 to 1,000 g/mol measured by GPC according to DIN 55672-1:2007-08.

2. The curable composition according to claim 1, wherein each Y is independently selected from an oxime group, an alkoxy group, an acetoxy group or a lactate group.

3. The curable composition according to claim 1, wherein R.sup.3 is selected from n-butyl or isopropyl.

4. The curable composition according to claim 1, wherein c) the compound which has a hydrolyzable silicon-containing group is an aminosilane.

5. The curable composition according to claim 1, wherein polymer a) has a polymer backbone that is selected from the group consisting of alkyd resin, (meth)acrylate, (meth)acrylate salt, (meth)acrylamide, (meth)acrylamide salt, phenolic resin, polyalkylene, polyamide, polycarbonate, polyether, polyester, polyurethane, vinyl polymer, siloxane, and combinations of at least two of the above-mentioned polymers.

6. The curable composition according to claim 1, wherein L is selected from the group consisting of diamidoamine of formula (3), diamidochalcogenide of formula (4), and diamidopyridine of formula (5), all in a deprotonated form, ##STR00003## wherein R.sup.4 is independently selected from a silyl group of formula Si(R.sup.7).sub.3, where each R.sup.7 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms, or a C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms, R.sup.5 and R.sup.6 are independently selected from a C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms, X is a sulfur or an oxygen atom, and R.sup.6 is located at ortho, meta or para position relative to nitrogen.

7. The curable composition according to claim 6, wherein each R.sup.4 is independently selected from methyl, phenyl, Si(CH.sub.3).sub.3 or p-toluenesulfonyl.

8. The curable composition according to claim 6, wherein R.sup.5 and R.sup.6 are independently selected from methyl or phenyl.

9. The curable composition according to claim 1, wherein c) the compound which has a hydrolyzable silicon-containing group is selected from the group consisting of bis(trimethylsilyl)amine, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, bis[(3-triethoxysilyl)propyl]amine, bis[(3-trimethoxysilyl)propyl]amine, aminopropylmethyldiethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane, phenylaminomethyltrimethoxysilane, aminoethylaminopropylmethyldimethoxysilane, 3-(N-phenylamino)propyltrimethoxysilane, 3-piperazinylpropylmethyldimethoxysilane, 3-(N,N-dimethylaminopropyl)aminopropylmethyldimethoxysilane, and combinations of two or more of the above-mentioned compounds.

10. The curable composition according to claim 1, being free of metal catalysts other than the b) at least one titanium complex of formula (2).

11. A preparation containing the curable composition according to claim 1.

12. A preparation containing the curable composition according to claim 1 and further containing at least one compound selected from the group consisting of plasticizer, stabilizer, antioxidant, filler, reactive diluent, drying agent, adhesion promoter, UV stabilizer, rheological agent, solvent and mixtures thereof.

13. A method of curing a silicon-containing polymer by forming siloxane bonds, comprising: providing the silicon-containing polymer providing a titanium complex catalyst of formula (2)
TiL(OR.sup.3).sub.2(2), wherein each R.sup.3 is independently selected from a C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms or silicon, or R.sup.3 is selected from n-butyl or isopropyl; L is a tridentate ligand selected from the group consisting of diamidoamine of formula (3), diamidochalcogenide of formula (4), and diamidopyridine of formula (5), all in a deprotonated form, ##STR00004## wherein R.sup.4 is independently selected from a silyl group of formula Si(R.sup.7).sub.3, where each R.sup.7 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms, or C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms, R.sup.5 and R.sup.6 are independently selected from a C.sub.1-20 alkyl or aryl which may optionally contain one or more heteroatoms or silicon atoms; mixing the silicon-containing polymer and the titanium complex catalyst of formula (2) to form a curable, catalysed mixture; and exposing the curable, catalysed mixture to conditions under which siloxane bonds are formed.

14. The method of claim 13 wherein R.sup.4 is independently selected from methyl, phenyl, Si(CH.sub.3).sub.3 or p-toluenesulfonyl, R.sup.5 and R.sup.6 are independently selected from methyl or phenyl, X is a sulfur or an oxygen atom, and R.sup.6 is located at ortho, meta or para position relative to nitrogen.

15. The method of claim 13 wherein the curable, catalysed mixture is exposed to moisture to form siloxane bonds.

Description

EXAMPLES

Example 1: Preparation of Titanium Complex 1

(1) To a stirred suspension of the ligand (formula (3), R.sup.4=p-toluenesulfonyl; 2.01 g, 3.54 mmol) in toluene (30 mL), which was cooled to 0 C., a solution of Ti(NEt.sub.2).sub.2(n-BuO).sub.2 in toluene (1.12 mL, 3.54 mmol) was slowly added through a dropping funnel. The reaction mixture was stirred for two hours at 0 C. before it was warmed to room temperature. After stirring another five hours at room temperature the reaction mixture turned orange and cleared up. The solvent was evaporated under reduced pressure. Recrystallization from toluene/n-hexane gave titanium complex 1 as an orange solid.

(2) Yield: 1.6 g (2.11 mmol, 65%).

(3) Calculated for C.sub.33H.sub.47N.sub.3O.sub.8S.sub.3Ti (757.80 g.Math.mol.sup.1): C 52.30, H 6.25, N 5.54, S 12.69.

(4) Found: C 52.18, H 6.32, N 5.98, S 12.36. .sup.1H NMR (500 MHz, d8-toluene, 298 K): 0.43-0.95; (m, 6H, CH.sub.3), 0.96-1.53; (m, 8H, CH.sub.2), 1.58-1.64; (m, 9H, Ts-CH3), 2.96-3.64; (m, 8H, NCH.sub.2), 3.85-3.98; (m, 2H, OCH.sub.2), 6.30-6.79; (m, m-Ar-H), 7.05-7.17; (m, o-ArH), 7.26-7.45; (m, o-ArH), 7.00-8.00; (m, o-ArH). .sup.13C NMR (126 MHz, d8-toluene, 298 K): 14.5; (CH.sub.3), 14.5; (CH.sub.3), 14.7; (CH.sub.3), 19.9; (CH.sub.2), 20.0; (CH.sub.2), 21.3; (CH.sub.3), 21.5; (CH.sub.3), 21.6; (CH.sub.3), 32.4; (CH.sub.2), 35.8; (CH.sub.2), 48.2; (NCH.sub.2), 51.7; (NCH.sub.2), 53.5; (NCH.sub.2), 54.2; (NCH.sub.2), 75.6; (OCH.sub.2), 76.6; (OCH.sub.2), 79.9; (OCH.sub.2), 125.8; (m-CH), 127.9; (m-CH), 130.0; (o-CH), 130.1; (o-CH), 135.7; (p-C), 135.9; (p-C), 143.2; (i-C), 143.4; (i-C), 143.7; (i-C). CI-MS m/z: 758 [M].sup.+, 684 [M.sup.nBuO].sup.+. IR (neat, cm.sup.1, 297 K): v=2956 (m), 2930 (m), 2868 (m).

Example 2: Preparation of Titanium Complex 2

(5) To a stirred suspension of the ligand (formula (3), R.sup.4=p-toluenesulfonyl; 3.44 g, 6.08 mmol) in THF (10 mL), which was cooled to 60 C., 12.12 mmol of n-BuLi (4.85 mL of a 2.5 M solution in n-hexane) and additional 10 mL of toluene were added slowly. After stirring for 12 hours at room temperature the solvent was removed in vacuum and an orange solid was isolated. It was suspended in toluene (10 mL) and cooled to 60 C. A solution of TiCl.sub.2(i-PrO)2 (1.45 g, 6.01 mmol) in toluene (10 mL) was added drop wise. The reaction mixture was warmed up to room temperature and stirred for 4 hours. Removing the formed LiCI by filtration and evaporating the solvent gave titanium complex 2 as a slightly purple solid.

(6) Yield: 3.89 g (5.33 mmol, 89%).

(7) Calculated for C.sub.31H.sub.43N.sub.6O.sub.8S.sub.3Ti (729.75 g.Math.mol.sup.1): C 51.02, H 5.94, N 5.76, S 13.18.

(8) Found: C 51.85, H 6.23, N 5.51, S 12.02. .sup.1H NMR (250 MHz, d6-benzene, 298 K): 1.47; (d, .sup.3J.sub.HH 6.0 Hz, 12H, CH.sub.3), 1.93; (s, 9H, CH.sub.3), 2.89; (br s, 4H, NH.sub.2), 3.72; (br s, 4H, NCH.sub.2), 5.30; (br s, 2H, OCH), 6.78; (d, .sup.3J.sub.HH 8.0 Hz, 2H, m-ArH), 6.97; (d, .sup.3J.sub.HH 8.1 Hz, 4H, m-ArH), 7.48; (d, .sup.3J.sub.HH 8.2 Hz, 2H, o-ArH), 8.35; (d, .sup.3J.sub.HH 8.3 Hz, 4H, o-ArH). .sup.13C NMR (63 MHz, d6-benzene, 298 K): 21.2 (CH.sub.3), 21.4; (CH.sub.3), 25.7; (CH.sub.3), 47.5; (CH.sub.2), 51.1; (CH.sub.2), 82.7; (CH), 125.7; (m-CH), 129.3; (m-CH), 129.6; (o-CH), 129.6; (o-CH), 135.5; (p-C), 138.9; (p-C), 142.7; (i-C), 143.3; (i-C). MS m/z (CI): 730 [M].sup.+, 670 [M.sup.iPrO+1].sup.+, 628 [M2.sup.iPrO+1].sup.+, 574 [MTs].sup.+. IR (neat, cm.sup.1, 297 K): v=2928 (m), 2925 (m), 2892 (m).

Example 3: Preparation of Titanium Complex 3

(9) The ligand (formula (3), R.sup.4=trimethylsilyl; 1.32 g, 4.11 mmol) was dissolved in toluene (10 mL) and cooled to 55 C. with stirring. 8.22 mmol of n-BuLi (3.3 mL of a 2.5 M solution in n-hexane) and additional 7 mL of toluene were added slowly to the chilled solution giving a white precipitate. The suspension was stirred for 24 hours and then cooled to 40 C. A colourless solution of TiCl.sub.2(i-PrO).sub.2 (0.97 g, 4.11 mmol) in toluene (3 mL) was added drop wise. After stirring at room temperature for 72 hours the toluene was removed in vacuum. The residue was dissolved in n-heptane. Removing the precipitating LiCl by filtration and evaporating the solvent gave titanium complex 3 as a deeply red liquid.

(10) Yield: 1.20 g (2.48 mmol, 60%).

(11) Calculated for C.sub.19H.sub.49N.sub.3O.sub.2Si.sub.3Ti (483.73 g.Math.mol.sup.1): C 47.18, H 10.21, N 8.69. Found: C 40.88, H 9.34, N 9.29. .sup.1H NMR (300 MHz, d6-benzene, 298 K): 0.10-0.44; (m, 27H, 3.Math.TMS), 1.20-1.39; (m, 12H, CH.sub.3), 2.43-3.98; (m, 8H, NCH.sub.2) 2.48; (t, 2H, NCH.sub.2), 3.39; (t, 2H, NCH.sub.2), 4.50-4.69; (m, 1H, OCH), 4.72-4.90; (m, 1H, OCH). .sup.13C NMR (75 MHz, d6-benzene, 298 K): 0.8; (TMS), 1.6; (2.Math.TMS), 27.2; (CH.sub.3), 52.7; (CH.sub.2), 56.1; (CH.sub.2), 76.7; (CH).). .sup.29Si NMR (59.6 MHz, d6-benzene, 298 K): 0.33, 1.93, 5.20, 15.51. MS m/z (CI): 484 [M].sup.+, 468 [MCH.sub.3].sup.+, 424 [M.sup.iPrO].sup.+, 382 [MO.sup.iPr+CH.sub.3].sup.+, 320 [2b].sup.+. IR (neat, cm.sup.1, 297 K): v=2955 (m), 2896 (m), 2863 (m).

Example 4: Curing Performance Test

(12) The synthesized titanium complexes were tested in the crosslinking reaction of a silicone mixture consisting of ,-di-dialkoxyvinylsilyl-polydimethylsiloxane with a viscosity of about 80,000 cST (synthesized according to U.S. Pat. No. 5,663,269 A, 71%), polydimethylsiloxane with a viscosity of about 100 cST (17%), and fumed silica (Aerosil R 104, Evonik, 11%). 35 g of the uncured silicone mass and 1.385 mmol of the catalyst. The components were mixed in a dual asymmetric centrifugal mixer (SpeedMixer DAC 150.1 FVZ-K) at 3000 RPM for 150 seconds. Test strips of the silicone mixture were made and allowed to cure under the standard atmosphere.

(13) The skin-over time (SOT) and the depth of cure (DOC) after 24 h were measured following international quality standards. Skin-over time (SOT) is defined as the time required for the material to form a non-tacky surface film. The determination of the skin over time is carried out according to DIN 50014 under standard climate conditions (23+/2 C., relative humidity 50+/5%). The temperature of the sealant must be 23+/2 C., with the sealant stored for at least 24 h beforehand in the laboratory. The sealant is applied to a sheet of paper and spread out with a putty knife to form a skin (thickness about 2 mm, width about 7 cm). The stopwatch is started immediately. At intervals, the surface is touched lightly with the fingertip and the finger is pulled away, with sufficient pressure on the surface that an impression remains on the surface when the skin formation time is reached. The skin-over time is reached when sealing compound no longer adheres to the fingertip. The skin-over time is expressed in minutes.

(14) Depth of cure (DOC) is measured as the thickness of the cured material in a 1 cm-high probe according to ISO 4049.

(15) TABLE-US-00001 TABLE 1 Curing performance of different complexes in silicone rubbers. Complex SOT [min] DOC [mm] Titanium complex 1 according to Example 1 5-7 3.0 Titanium complex 2 according to Example 2 6 4.0 Titanium complex 3 according to Example 3 4-5 4.1 Ti(n-BuO).sub.4 (Comparative example 1) 8 2.7 DOTL* (Comparative example 2) 10 3.6 *DOTL: dioctyltin laureate