Silanes and Curable Compositions Containing Said Silanes as Crosslinkers

Abstract

The invention relates to a silane of the formula (1),

Si(R.sup.1).sub.m(R.sup.2).sub.n(R.sup.3).sub.4-(m+n)  (1)

as defined herein, where the silane has at least one group of the general formula (3):

##STR00001##

as defined herein, to a method for preparing the silane, and to curable compositions, containing the silane and at least one polyorganosiloxane.

Claims

1. A silane of the formula (1),
Si(R.sup.1).sub.m(R.sup.2).sub.n(R.sup.3).sub.4-(m+n)  (1) where each m is independently 0 or 1, each n is independently 0, 1, 2, or 3, and the sum n+m is a maximum of 3; each R.sup.1 independently stands for: a substituted or unsubstituted alkyl, alkenyl or alkynyl group, a substituted or unsubstituted cycloaliphatic group or aryl group, or a substituted or unsubstituted heteroalicyclic group or heteroaryl group; each R.sup.2 independently stands for a group of the general formula (2): ##STR00007## where each R.sup.4 independently stands for: hydrogen, or a substituted or unsubstituted alkyl, alkenyl, or alkynyl group; R.sup.5 stands for: a substituted or unsubstituted alkyl, alkenyl, or alkynyl group, or a group of the general formula (2-2):
—OR.sup.5-2  (2-2) where R.sup.5-2 stands for: a substituted or unsubstituted alkyl, alkenyl, or alkynyl group; or a group of the general formula (2-3): ##STR00008## where R.sup.5-3 stands for: a substituted or unsubstituted alkyl, alkenyl, or alkynyl group; each R.sup.3 independently stands for a group of the general formula (3): ##STR00009## where each R.sup.6 independently stands for: hydrogen or a substituted or unsubstituted alkyl, alkenyl, or alkynyl group; R.sup.7 stands for: hydrogen, a substituted or unsubstituted alkyl, alkenyl, or alkynyl group, a substituted or unsubstituted cycloaliphatic group or aryl group, R.sup.8, or a group —(CH.sub.2).sub.q—COOR.sup.9, where p is an integer from 2 to 10, and R.sup.9 stands for a substituted or unsubstituted alkyl, alkenyl, or alkynyl group, or a substituted or unsubstituted cycloaliphatic group or aryl group; R.sup.8 stands for a group of the general formula (4):
—R.sup.10—SiR.sup.11.sub.o(OR.sup.12).sub.3-o  (4) where o independently stands for 0, 1, or 2, R.sup.10 stands for an alkylene group, optionally interrupted by a heteroatom, each R.sup.11 independently stands for a substituted or unsubstituted alkyl, alkenyl, or alkynyl group, each R.sup.12 independently stands for: a substituted or unsubstituted alkyl, alkenyl, or alkynyl group, an acyl group; or a group of the formula (5): ##STR00010## where each R.sup.13 independently stands for: hydrogen; or a substituted or unsubstituted alkyl, alkenyl, or alkynyl group; R.sup.14 stands for: a substituted or unsubstituted alkyl, alkenyl, or alkynyl group.

2. The silane according to claim 1, wherein each R.sup.1 independently of one another stands for an alkyl group having 1 to 10 carbon atoms, or for an alkenyl group having 2 to 10 carbon atoms.

3. The silane according to claim 1, wherein each R.sup.2 independently of one another stands for a group of the formula (2), one of the R.sup.4 groups stands for hydrogen and the second R.sup.4 group stands for hydrogen or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and/or R.sup.5 stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

4. The silane according to claim 1, wherein each R.sup.2 independently of one another stands for a group of the formula (2-2), where R.sup.5-2 stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

5. The silane according to claim 1, wherein each R.sup.3 independently of one another stands for a group of the formula (3), one of the R.sup.6 groups stands for hydrogen and the second R.sup.6 group stands for hydrogen or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

6. The silane according to claim 1, wherein each R.sup.3 independently of one another stands for a group of the formula (3), and R.sup.7 stands for hydrogen, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or R.sup.8.

7. The silane according to claim 1, wherein each R.sup.3 independently of one another stands for a group of the formula (3), R.sup.8 stands for a group of the formula (4), R.sup.10 stands for an alkylene group of the formula —(CH.sub.2).sub.p—, and p is an integer from 1 to 6.

8. The silane according to claim 1, wherein each R.sup.3 independently of one another stands for a group of the formula (3), where R.sup.8 stands for a group of the formula (4), each R.sup.11 independently of one another stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and/or each R.sup.12 independently of one another stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

9. The silane according to claim 1, wherein each R.sup.3 independently of one another stands for a group of the formula (3), R.sup.8 stands for a group of the formula (4), and o stands for 0 or 1.

10. The silane according to claim 1, wherein m is 0 or 1, and/or n is 0, 1 or 2.

11. A method for preparing a silane according to claim 1, comprising: reacting a silane of the formula (5),
Si(R.sup.1).sub.m(R.sup.2).sub.4-m  (5) where m, and each R.sup.1 and each R.sup.2, in each case independently of one another, have the meanings given in claim 1, and at least one aminosilane compound of the general formula (6):
(HR.sup.7N)—R.sup.10—SiR.sup.11.sub.o(OR.sup.12).sub.3-o  (6) where o, R.sup.7, R.sup.10, and each R.sup.11 and each R.sup.12, in each case independently of one another, have the meanings given in claim 1.

12. The method according to claim 11, wherein the molar ratio of the silane of the formula (5) to the aminosilane compound of the general formula (6) is 2:1 to 30:1.

13. The method according to claim 11, comprising stirring the silane of the formula (5) and the aminosilane compound of the general formula (6) at 1 bar pressure and a temperature of 40 to 80° C., for at least 10 minutes.

14. A curable composition comprising at least one silane according to claim 1 and at least one polyorganosiloxane, whereby the polyorganosiloxane has at least one hydroxy group bound to a silicon atom.

15. The curable composition according to claim 14, further comprising at least one tin curing catalyst.

Description

EXAMPLES

Example 1: Preparation of a Silane of the Formula (1)

[0198] 5.5 g of vinyl tris(ethyl lactato)silane was mixed with 0.4 g of 3-aminopropyltriethoxysilane and heated to 70° C. The reaction mixture was stirred for an hour at 70° C. The NMR spectroscopy analysis of the reaction product showed that cleavage of ethanol and amidation of ethyl lactate groups have occurred. A silane of the formula (1) results.

Comparative Example 1 (VB1)

[0199] The comparison composition VB1 was prepared from the raw materials listed in Table 1. For this purpose, the polymer (α,ω-dihydroxy-terminated polydimethylsiloxane) and plasticizer were charged with the curing agent vinyl tris(ethyl lactato)silane and 3-aminopropyltriethoxysilane and stirred for 5 minutes and then vacuum is applied for 5 minutes. Next, the highly dispersed silicic acid was added with stirring and the mixture was evacuated. Lastly, the remaining aminosilanes and the catalyst were added and incorporated for 10 minutes under vacuum.

Example 2 (B2)

[0200] The composition of the invention B2 was prepared from the raw materials listed in Table 1. For this purpose, first a silane of the formula (1) was prepared according to Example 1 from vinyl tris(ethyl lactato)silane and 3-aminopropyltriethoxysilane and without an intermediate purification, it was combined with the polymer (α,ω-dihydroxy-terminated polydimethylsiloxane) and plasticizer and the mixture was stirred for 5 minutes and then vacuum was applied for 5 minutes. Next, the highly dispersed silicic acid was added with stirring and the mixture was evacuated. Lastly, the remaining aminosilanes and the catalyst were added and incorporated for 10 minutes under vacuum.

[0201] The prepared formulations VB1 and B2 were analyzed with respect to skin-over time, hardness, extensibility, and elongation and with respect to adhesion properties on different substrates. All tests were carried out with the freshly formulated composition and after 4 and 12 weeks of aging at 40° C./80% relative humidity. The results for the comparison formulation VB1 are presented in Table 2, and the results for the formulation of the invention B2 in Table 3.

[0202] A comparison of the results for the comparison formulation VB1 and formulation of the invention B2 shows that when the silane of the invention was used an improved curing behavior (shorter skin-over times with comparable to slightly improved curing depths) can be achieved, and the mechanical properties of the cured products are comparable. In addition, when the silane of the invention was used, an excellent adhesion (Cf1) was consistently achieved in all tested substrates, whereas the comparison formulations exhibited weaknesses during bonding of aluminum and wood.

TABLE-US-00001 TABLE 1 VB1 B2 % by % by Raw materials weight weight α,ω-Dihydroxy-terminated polydimethylsiloxane 49.2 49.2 with a viscosity of 80,000 cST Polydimethylsiloxane with a viscosity of 36.4 36.4 1000 cST (plasticizer) Vinyl tris(ethyl lactato)silane 5.5 3-Aminopropyltriethoxysilane 0.4 Silane of the formula (1) (vinyl tris(ethyl 5.9 lactato)silane and 3-aminopropyltriethoxysilane were mixed in a weight ratio of 55:4 and reacted for 1 hour at 70° C.) Highly dispersed silicic acid 7.4 7.4 Aminosilane (mixture of I) bis[3- 0.85 0.85 (trimethoxysilyl)propyl]amine and II) reaction product of 3-(N,N- dimethylamino)propyltrimethoxysilane and OH-terminated polydimethylsiloxane, whereby I) and II) are present in a weight ratio of 15:7) Curing catalyst (di-n-butyltin dilaurate (DBTL)) 0.25 0.25

TABLE-US-00002 TABLE 2 Properties of the comparison formulation VB1 4 weeks of 12 weeks of storage at storage at 40% relative 40% relative humidity and humidity and Formulation VB1 fresh 80° C. 80° C. Skin-over time (min) 7 20 30 Shore A 1d 15 13 8 Shore A 7d 25 22 22 Curing depth (mm/24 h) 4.1 4.2 4.2 E modulus at 100% 0.31 n.d. 0.24 (N/mm.sup.2) Breaking force (N/mm.sup.2) 1.2 n.d. 1.2 Elongation at break (%) 548 n.d. 574 Adhesion PVC Cf1 Cf1 Cf1 Brass Cf1 Cf1 Cf1 Glass Cf1 Cf1 Cf1 Aluminum (E6EV1) Af1 Af2 Af2 Tiles Cf1 Cf1 Cf1 GRP Cf1 Cf1 Cf1 Wood Cf1 Af1 Af2 n.d.: not determined GRP: glass fiber-reinforced plastic

TABLE-US-00003 TABLE 3 Properties of the formulation of the invention B2 4 weeks of 12 weeks of storage at storage at 40% relative 40% relative humidity humidity Formulation B2 Fresh and 80° C. and 80° C. Skin-over time (min) 6 8 18 Shore A 1d 14 13 7 Shore A 7d 25 22 20 Curing depth (mm/24 h) 4.0 4.5 4.3 E modulus at 100% 0.29 n.d. 0.24 (N/mm.sup.2) Breaking force (N/mm.sup.2) 1.1 n.d. 0.9 Elongation at break (%) 523 n.d. 443 Adhesion PVC Cf1 Cf1 Cf1 Brass Cf1 Cf1 Cf1 Glass Cf1 Cf1 Cf1 Aluminum (E6EV1) Cf1 Cf1 Cf1 Tiles Cf1 Cf1 Cf1 GRP Cf1 Cf1 Cf1 Wood Cf1 Cf1 Cf1 n.d.: not determined GRP: glass fiber-reinforced plastic

Measuring the Skin-Over Time:

[0203] The skin-over time is determined under standard climatic conditions (23+/−2° C., relative humidity 50+/−5%). The temperature of the sealant must be 23+/−2° C.; the sealant is to be stored beforehand for at least 24 hours in the laboratory. The sealant is applied to a sheet of paper and drawn out to a skin with a putty knife (thickness of about 2 mm, width of about 7 cm). A stopwatch is started immediately. The surface is touched lightly with the fingertip and the finger is removed again; the surface is pressed so greatly that an impression remains on the surface until the skin-over time is reached. The skin-over time is reached when sealant no longer adheres to the fingertip. The skin-over time is given in minutes.

Measuring the Shore a Hardness:

[0204] The procedure follows ISO 868.

Measuring Curing Depth:

[0205] A sealant strand with a height of 10 mm (+/−1 mm) and a width of 20 mm (+/−2 mm) is applied with an appropriate spatula to a plastic card. After storage for 24 hours under standard climatic conditions (23+/−2° C., relative humidity 50+/−5%), a piece is cut out of the strand and the thickness of the cured layer is measured using a vernier caliper. The curing depth is given in [mm/24 h].

Measuring the Mechanical Properties (Tensile Test):

[0206] The breaking force, elongation at break, and tensile stress values (E modulus) are determined in accordance with DIN 53504 using the tensile test.

[0207] Deviation from the Norm:

[0208] Dumbbell specimens with the following dimensions are used as the test pieces: thickness: 2+/−0.2 mm; gauge width: 10+/−0.5 mm; gauge length: about. 45 mm; total length: 9 cm. The test is carried out under standard climatic conditions (23+/−2° C., 50+/−5% rel. humidity). The test takes place after 7 days of curing.

[0209] Procedure:

[0210] A 2 mm-thick film is drawn out of the material. The film is stored for 7 days under standard climatic conditions and the dumbbells are then punched out. Three dumbbells are to be made for each test. The test is to be carried out under standard climatic conditions. The specimens must be acclimatized to the test temperature (i.e., stored) for at least 20 minutes before the measurement. Before the measurement, the thickness of the test specimens is to be measured at least 3 places at room temperature using a vernier caliper; i.e., in the case of the dumbbells, preferably the ends and the middle within the initial gauge length are to be measured. In the case of elastic materials, it is advisable in addition to measure the transverse gauge. The average value is to be entered in the measuring program. The test specimens are to be clamped in the tensile testing machine so that the longitudinal axis coincides with the mechanical axis of the tensile testing machine and the largest possible surface of the grips is grasped, without the narrow section being clamped. At a test speed of 50 mm/min, the dumbbell is tensioned to a preload of <0.1 MPa. The force-elongation curve is then recorded at a test speed of 50 mm/min.

[0211] Assessment: The following values are to be obtained from the measurement: breaking force in [N/mm.sup.2], elongation at break in [%], and E modulus at 100% elongation in [N/mm.sup.]

Measurement of Adhesion Properties:

[0212] The procedure was as follows for evaluating the adhesion properties of the compositions to a substrate:

[0213] Before the composition is applied, nonabsorbent substrates are cleaned with a solvent mixture consisting of acetone and isopropanol (mixing ratio of 1:3). Next, 3 beads each (about 1.5 cm wide and about 3 mm thick) of the material to be analyzed are applied to the substrate to be tested. The adhesion of the material is evaluated in each case after 2 weeks of prestorage under standard climatic conditions (23±2° C.) and (50±5% rel. humidity). For this purpose, one bead each is loosened about 1 cm from the substrate using a knife. The attempt is made to completely remove the bead by pulling on this piece at an angle of about 90°. The fracture between sealant and substrate is evaluated. The following are differentiated:

Af=adhesive failure
Cf=cohesive failure

[0214] Additional differentiation by scores of 1 to 3: 1=“considerable adhesion” to 3=“no adhesion”