Paramagnetic titanium mixtures 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 (1)
—Si(R.sup.1).sub.k(Y).sub.3-k  (1),
wherein each R.sup.1 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms or a triorganosiloxane group of formula —O—Si(R.sup.2).sub.3, wherein 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 hydrolysable group; and k is 0, 1, or 2; b) at least one mixture of paramagnetic titanium complexes, characterized by a Landé g-factor of less than 2 detected by Electron Paramagnetic Resonance Spectroscopy; c) optionally, at least one compound which has a hydrolysable silicon-containing group and a molecular weight in the range of 100 to 1000 g/mol, an aminosilane preparations containing these compositions thereof.

Claims

1. A curable composition comprising: a) at least one polymer having at least one silicon-containing group of formula (1)
—Si(R.sup.1).sub.k(Y).sub.3-k  (1), wherein each R.sup.1 is independently selected from a hydrocarbon radical containing 1 to 20 C atoms or a triorganosiloxane group of formula —O—Si(R.sup.2).sub.3, wherein 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 hydrolysable group; and k is 0, 1, or 2; b) at least one mixture of paramagnetic titanium complexes having a Landé g-factor of less than 2 detected by Electron Paramagnetic Resonance Spectroscopy; and c) optionally, at least one compound which has a hydrolysable silicon-containing group and a molecular weight in the range of 100 to 1000 g/mol or an aminosilane.

2. The curable composition according to claim 1, wherein the Landé g-factor of the paramagnetic titanium complexes detected by Electron Paramagnetic Resonance Spectroscopy is in the range of from 1.90 to 1.99.

3. The curable composition according to claim 1, wherein the Landé g-factor of the paramagnetic titanium complexes detected by Electron Paramagnetic Resonance Spectroscopy is in the range of from 1.94 to 1.96.

4. The curable composition according to claim 1, wherein the mixture of paramagnetic titanium complexes is derived from at least one titanium complex of formula (2)
Ti(R.sup.3)(L).sub.3  (2), wherein each L is independently selected from a hydrolysable oxygen- or nitrogen-containing organic group, an alkoxy group; and R.sup.3 is selected from a hydrocarbon radical containing 1 to 20 C atoms, which may optionally contain one or more heteroatoms or silicon atoms.

5. The curable composition according to claim 4, wherein each L is independently selected from an alkoxy radical of formula OR.sup.4, wherein R.sup.4 is selected from an alkyl radical containing 1 to 8 C atoms, ethyl, isopropyl, or n-butyl.

6. The curable composition according to claim 4, wherein R.sup.3 is selected from an alkyl radical containing 1 to 10 C atoms, cyclopentadienyl or aryl.

7. The curable composition according to claim 4, wherein the mixture of paramagnetic titanium complexes is obtained by treatment under UV and/or Visible light irradiation.

8. The curable composition according to claim 1, wherein the mixture of paramagnetic titanium complexes is obtained by a heat treatment of at least one titanium complex of formula (2) at a temperature above its melting point under exclusion of air and moisture and under argon or nitrogen atmosphere,
Ti(R.sup.3)(L).sub.3  (2), wherein each L is independently selected from a hydrolysable oxygen- or nitrogen-containing organic group, an alkoxy group; and R.sup.3 is selected from a hydrocarbon radical containing 1 to 20 C atoms, which may optionally contain one or more heteroatoms or silicon atoms.

9. The curable composition according to claim 8, wherein the heat treatment is done simultaneously, or prior to, or after treatment under UV-Visible light irradiation.

10. The curable composition according to claim 9, wherein the UV-Visible light has a wavelength of from 150 to 700 nm.

11. The curable composition according to claim 1, wherein the polymer a) has a polymer backbone that is selected from alkyd resin, (meth)acrylate and (meth)acrylamide and the salts thereof, phenolic resin, polyalkylene, polyamide, polycarbonate, polyol, polyether, polyester, polyurethane, vinyl polymer, siloxane, and copolymers composed of at least two of the above-mentioned polymer classes.

12. The curable composition according to claim 1, wherein compound c) is present and comprises an aminosilane selected from the group comprising 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, or combinations of two or more of the above-mentioned compounds.

13. The curable composition according to claim 1, wherein the curable composition further comprises at least one compound selected from the group comprising plasticizer, stabilizer, filler, reactive diluent, drying agent, adhesion promoters, UV stabilizer, rheological aid, solvent, and mixtures thereof.

14. An adhesive, sealant, or coating material comprising the curable composition according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an Electron Paramagnetic Resonance Spectroscopy (EPR) spectrum of a mixture of paramagnetic titanium complexes in a silicone matrix at 300 K showing the presence of the paramagnetic titanium-III complexes.

(2) The following examples are used to explain the invention; however, the invention is not limited thereto.

EXAMPLES

Example 1: Preparation of Paramagnetic Titanium Complexes Mixture From trisisopropoxy(methyl)titanium

(3) This synthesis of trisisopropoxy(methyl)titanium is adapted from previously reported procedures by K. Clauß, (Justus Liebigs Annalen der Chemie 1968, 711, 19-21); and C. Ferreri (in Comprehensive Organic Synthesis Eds.: M. T. Editor-in-Chief: Barry, F. Ian, Pergamon, Oxford, 1991, pp. 139-172). In an oven-dried Schlenk flask, 18.3 mL (20 g, 77 mMol) of pure Chlorotitanium-(IV)-trisisopropoxide were dissolved in 200 mL of dry diethylether at room temperature under argon. The solution was cooled down to −78° C. in a dry ice/acetone bath and 47.5 mL (76 mMol) of methyllithium (1.6 M in diethylether) were added drop-wise (1-2 drops per second). After some minutes the clear solution became turbid. It was allowed to slowly warm to room temperature overnight while the stirring was continued. The resulting suspension was transferred with a cannula into a sintered-glass filter with a plug of celite and filtered. The obtained dark yellow solution was concentrated in vacuo to give an oily liquid. It was purified by bulb-to-bulb distillation (48-50° C., 0.01 Torr) to give 19.9 g (66.2 mMol) of the product as a clear yellow liquid (87% yield). .sup.1H NMR (300 MHz, Benzene-d.sub.6) δ 4.70 (hept, J=6.0 Hz, 3H), 1.30 (d, J=6.2 Hz, 18H), 0.99 (s, 3H). .sup.13C NMR (75 MHz, Benzene-d.sub.6) δ 128.38, 128.06, 127.74, 76.86, 40.17, 26.57.

(4) The product was stored in a translucent Schlenk-type vessel with rigorous exclusion of air and moisture under argon atmosphere. The closed vessel was exposed to direct sunlight at room temperature for several days until the color of the product changed from light yellow to green, indicating the formation of paramagnetic titanium-III derivatives. The presence of the paramagnetic titanium-III complexes was proved by EPR spectrometry at 300K with at least two signals where distinguished with g-factors of 1.956 and 1.943, characteristic of Ti-III species (see FIG. 1).

Example 2: Preparation of Formulations

(5) The obtained paramagnetic mixture was used as a catalyst in the following formulations.

(6) TABLE-US-00001 TABLE 1 Formulation 1 (alkoxy silicone without adhesion promoter) Raw material wt. % α,ω-dimethoxyvinyl-terminated 69.64 polydimethylsiloxane having a viscosity of 135,000 cST (See U.S. Pat. No. 5,663,269 for exact production specification) Polydimethylsiloxane having a viscosity of 100000 cST 4.09 Polydimethylsiloxane having a viscosity of 100 cST 15.30 Highly dispersed silicic acid (Aerosil R104) 9.67 Mixture of titanium complexes according to Example 1 1.30

(7) TABLE-US-00002 TABLE 2 Formulation 2 (oxime silicone with adhesion promoter) Raw material wt. % α,ω-dihydroxy-terminated 59.75 polydimethylsiloxane having a viscosity of 80,000 cST Mineral oil (G3H) 24.75 Methyltris(methylisobutylketoxime)silane 1.7 Methyltris(methylethylketoximo)silane 2.1 Vinyltris(methylethylketoxime)silane 0.5 Highly dispersed silicic acid (Aerosil 150) 10 Aminopropyltriethoxysilane 1.15 Mixture of titanium complexes according to Example 1 0.05

Example 3: Adhesion and Mechanical Property Test

Measurement of Skin Formation Time

(8) The determination of the skin formation time is carried out 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 approximately 2 mm, width approximately 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 formation time is reached when sealing compound no longer adheres to the fingertip. The skin formation time is expressed in minutes.

Measurement of Shore A Hardness

(9) The procedure is carried out in accordance with ISO 868.

Measurement of the Hardness Depth

(10) A sealant strand having a height of 10 mm (+/−1 mm) and a width of 20 mm (+/−2 mm) is applied with an appropriate spatula to a plastic sheet. After storage for 24 hours under standard climate conditions (23+/−2° C., relative humidity 50+/−5%), a piece is cut from the strand, and the thickness of the cured layer is measured with a slide gauge. The hardness depth is expressed in mm/24 h.

Measurement of Mechanical Properties (Tensile Test)

(11) The breaking strength and tensile stress values (modulus of elasticity) are determined by the tensile test in accordance with DIN 53504.

(12) Deviation from the norm: Dumbbell test specimens having the following dimensions are used as test pieces: thickness: 2+/−0.2 mm; width of web: 10+/−0.5 mm; length of web: approximately 45 mm; total length: 9 cm. The test is carried out under standard climate conditions (23+/−2° C., 50+/−5% relative humidity). The test is conducted after curing for 7 days.

(13) Procedure: A film of the sealing compound 2 mm thick is spread out. The film is stored for 7 days under standard climate conditions, and the dumbbell test specimens are then punched out. Three dumbbell test specimens are produced for each determination. The test is carried out under standard climate conditions. The test pieces must be acclimatized (i.e., stored) beforehand for at least 20 minutes at the test temperature. Prior to the measurement, the thickness of the test pieces is measured at RT with a slide gauge at least 3 locations; i.e., for the starting measurement length, preferably the ends and center of the dumbbell test specimens are measured. For elastic materials, it is recommended to take an additional measurement crosswise over the web. The average value is entered into the measurement program. The test pieces are clamped into the tensile testing machine in such a way that the longitudinal axis coincides with the mechanical axis of the tensile testing machine, and the largest possible surface area of the heads of the dumbbell test specimens is included without the web becoming jammed. The dumbbell test specimen is stretched to a pretensioning of <0.1 MPa at a feed rate of 50 mm/min. The curve of the change in force versus length is recorded at a feed rate of 50 mm/min.

(14) Evaluation: The following values are taken from the measurement: breaking strength in [N/mm.sup.2] and modulus of elasticity at 100% elongation in [N/mm.sup.2].

(15) The results of the measurements are shown in Table 3.

(16) TABLE-US-00003 TABLE 3 Formulations 1 and 2 and Comparative Formulations V1 and V2 Parameter F1 V1 F2 V2 Skin formation time (min) 47 30 16 17 Shore A 7d 23 18 16 17 Hardness depth (mm/24 h) 2.62 2.1 3.49 3.11 Modulus of elasticity at 0.3 0.3 0.24 0.24 100% (N/mm.sup.2) Breaking strength (N/mm.sup.2) 1.69 1.52 0.99 0.79 F1-F2 = Formulation 1-2; V1 = Formulation 1 with 1.30% by weight tetra-n-butyl titanate instead of the titanium catalyst provided according to the invention; V2 = Formulation 2 with 0.05% by weight dibutyltin acetate instead of the titanium catalyst provided according to the invention.