Curable silicone compositions

Abstract

The invention relates to a curable composition, containing (A) at least one polyorganosiloxane, which has at least one hydroxy group bound to a silicon atom, (B) at least one 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, (C) at least one aminosilane, and (D) at least one tin compound,
wherein the composition is free of epoxysilane and the molar ratio of the aminosilane to the tin compound is 1:1 to 50:1, as well as to the preparation and use thereof.

Claims

1. A curable composition containing (A) at least one polyorganosiloxane, which has at least one hydroxy group bound to a silicon atom, (B) at least one 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 m independently stands for 0 or 1 and n independently for 0, 1, 2, 3, or 4, whereby the sum n+m is a maximum of 4; 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; a substituted or unsubstituted heteroalicyclic group or heteroaryl group; each R.sup.2 independently stands for a group of the general formula (2):
—OCR.sup.4.sub.2COOR.sup.5  (2) 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; each R.sup.3 independently stands for a group of the general formula (3):
—OCR.sup.6.sub.2CONR.sup.7R.sup.8  (3) 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 q 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 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):
—CR.sup.13.sub.2COOR.sup.14  (5) 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; and o independently stands for 0, 1, or 2, and (C) at least one aminosilane, and (D) at least one tin compound; wherein the composition is free of epoxysilane and the molar ratio of the aminosilane to the tin compound is 1:1 to 50:1.

2. The curable composition according to claim 1, wherein the molar ratio of the aminosilane to the tin compound is 10:1 to 40:1.

3. The curable composition according to claim 1, wherein the polyorganosiloxane which has at least one hydroxy group bound to a silicon atom is a polydiorganosiloxane which has at least one terminal hydroxy groups.

4. The curable composition according to claim 1, wherein the polyorganosiloxane, which has at least one hydroxy group bound to a silicon atom is an α, ω-dihydroxy-terminated polydimethylsiloxane.

5. The curable composition according to claim 1, wherein the silane is a silane of the formula (1), where each R.sup.1 independently of one another stands for an alkyl group having 1 to 10 carbon atoms, for an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and/or each R.sup.2 independently of one another stands for a group of the formula (2), where 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 R.sup.5 stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms.

6. The curable composition according to claim 1, wherein the silane is a silane of the formula (1), where the sum n+m is 4.

7. The curable composition according to claim 1, wherein the silane of the formula (1) is selected from methyl tris(ethyl lactato)silane, ethyl tris(ethyl lactato)silane, phenyl tris(ethyl lactato)silane, vinyl tris(ethyl lactato)silane, tetra(ethyl lactato)silane, and mixtures thereof.

8. The curable composition according to claim 1, wherein the silane is a silane of the formula (1), where the sum n+m is a maximum of 3 and each R.sup.3 independently of one another stands for a group of the formula (3), where one of the R.sup.6 groups stands for hydrogen and the second R.sup.6 group for hydrogen or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, R.sup.7 stands for hydrogen, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and R.sup.8 for a group of the formula (4), where R.sup.10 is an alkylene group of the formula —(CH.sub.2).sub.p—, where p is an integer from 1 to 6, each R.sup.11 independently of one another stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and each R.sup.12 independently of one another stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atom.

9. The curable composition according to claim 1, wherein the aminosilane is an aminosilane of the formula (6),
(R.sup.15R.sup.7N)—R.sup.10—SiR.sup.11.sub.o(OR.sup.12).sub.3-o  (6) where independently stands for 0, 1, or 2, 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, and R.sup.15 stands for hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group or a substituted or unsubstituted alkynyl group.

10. The curable composition according to claim 1, wherein the aminosilane is selected from 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, aminomethyltrimethoxysilane, aminomethyltriethoxysilane, 3-(N, N-dimethylamino)propyltrimethoxysilane, 3-(N, N-dimethylamino)propyltriethoxysilane, (N, N-dimethylamino)methyltrimethoxysilane, (N, N-dimethylamino)methyltriethoxysilane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilyl)propylamine, and mixtures thereof.

11. The curable composition according to claim 1, wherein the polyorganosiloxane and the silane of the formula (1) are present in the form of a prepolymer, whereby the prepolymer is the reaction product of the polyorganosiloxane and the silane of the formula (1).

12. The curable composition according to claim 1, wherein the tin compound is an organotin compound, selected from 1,3-dicarbonyl compounds of bivalent or tetravalent tin, dialkyltin(IV) dicarboxylates, dialkyltin(IV) dialkoxylates, dialkyltin(IV) oxides, tin(II) carboxylates, and mixtures thereof.

13. A method for preparing the curable composition according to claim 1, comprising mixing the polyorganosiloxane which has at least one hydroxy group bound to a silicon atom, the silane of the formula (1), the aminosilane, the tin compound, and optionally at least one further ingredient.

14. The method according to claim 13, comprising the steps of: mixing the polyorganosiloxane, which has at least one hydroxy group bound to a silicon atom and the silane of the formula (1) in the presence of the entire amount of the aminosilane or a portion thereof and optionally at least one plasticizer; adding the remaining portion of the aminosilane and optionally further ingredients; mixing all ingredients; and adding the tin compound to the mixture of other components.

15. An adhesive, sealing, or coating material comprising the curable composition according to claim 1.

16. Cured reaction products of the curable composition according to claim 1.

Description

EXAMPLES

Example 1

(1) The comparison compositions VB1 and VB3 and composition B2 of the invention were prepared by mixing the raw materials listed in Table 1. All three formulations are based on the same raw materials but differ in the quantitative ratio of the aminosilane to the tin compound. Only composition B2 contains these components in the ratio required according to the invention. All three formulations are free of epoxysilane.

(2) TABLE-US-00001 TABLE 1 VB1 B2 VB3 Parts by Parts by Parts by Raw materials weight weight weight α,ω-Dihydroxy-terminated 59.6 59.6 60.3 polydimethylsiloxane with a viscosity of 80,000 cST Polydimethylsiloxane with a 26.6 26.6 26.9 viscosity of 1000 cST Vinyl tris(ethyl lactato)silane 5.0 5.0 5.0 Highly dispersed silicic acid 7.4 7.4 7.4 Aminosilane (mixture of 3- 1, 2 1, 2 0.002 aminopropyltrimethoxy- silane and 3-(N,N- dimethylamino)propyltrimethoxy- silane in a weight ratio of 1.4:1) Tin compound (di-n- 0.02 0.2 0.2 butyltin dilaurate (DBTL)) Molar ratio of the tin 1:234 1:23 1:0.02 compound to aminosilane

(3) The prepared formulations were tested with respect to skin-over time, hardness, extensibility, and elongation. 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. The comparison formulation VB3 already crosslinks when the raw materials are mixed, so that no mechanical properties could be determined.

(4) A comparison of the results for the comparison formulation VB1 and formulation of the invention B2 shows that no workable curing behavior can be achieved for the comparison formulation after storage, and the mechanical properties of the cured product are insufficient. The formulation can no longer be cured at all even after 12 weeks of aging under the given conditions. The formulation therefore does not have an adequate storage stability.

(5) TABLE-US-00002 TABLE 2 Properties of the comparison formulation VB1 4 weeks of 12 weeks of storage at 40% storage at 40% relative relative humidity humidity Formulation VB1 Fresh and 80° C. and 80° C. Skin-overtime 12 38 Not measurable (min) Shore A 1 d Not measurable Not measurable Not measurable Shore A 7 d 11 Not measurable Not measurable Curing depth   3.1 Not measurable Not measurable (mm/24 h) E modulus at 100% Not measurable Not measurable Not measurable (N/mm.sup.2) Breaking force Not measurable Not measurable Not measurable (N/mm.sup.2) Elongation at Not measurable Not measurable Not measurable break (%)

(6) TABLE-US-00003 TABLE 3 Properties of the formulation of the invention B2 4 weeks of 12 weeks of storage at 40% storage at 40% relative humidity relative humidity Formulation B2 Fresh and 80° C. and 80° C. Skin-overtime (min) 18 27 45 Shore A 1 d 22 16 11 Shore A 7 d 30 29 25 Curing depth (mm/24 h) 3.6 3.8 3.7 E modulus at 100% 0.34 0.31 0.26 (N/mm.sup.2) Breaking force (N/mm.sup.2) 1.05 1.02 1.02 Elongation at break (%) 450 452 489
Measuring the Skin-Over Time:

(7) 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.

(8) Measuring the Shore a Hardness:

(9) The procedure follows ISO 868.

(10) Measuring Curing Depth:

(11) 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].

(12) Measuring the Mechanical Properties (Tensile Test):

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

(14) Deviation from the norm: 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.

(15) Procedure: 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.

(16) 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.2].