ENCAPPED CURABLE POLYORGANOSILOXANES

Abstract

The invention relates to curable polyorganosiloxanes with special silicon-containing terminal groups and curable compositions based on these polyorganosiloxanes, a special capped adhesion promoter, and a curing catalyst. These compositions have improved adhesion properties and excellent storage stability. The invention also relates to the use thereof.

Claims

1. A polyorganosiloxane containing at least one terminal group of the formula (I):
-A-Si(R.sup.1).sub.m(R.sup.2).sub.n(R.sup.3).sub.3-(m+n)  (I) wherein: A is a bond, —O— or a linear, branched or cyclic divalent group selected from hydrocarbon residues having 1 to 12 carbon atoms, alkylene, arylene, oxyalkylene, oxyarylene, siloxane-alkylene, siloxane-arylene, ester, amine, glycol, imide, amide, alcohol, carbonate, urethane, urea, sulfide, ether or a derivative or combination thereof; each R.sup.1 is independently selected from the group consisting of hydrogen, halogen, amino, oximino, a substituted or unsubstituted alkyl, alkenyl, alkenyloxy, alkynyl, alkylnyloxy, cycloaliphatic, cycloaliphatic-O—, aryl, aryloxy, heteroaryl, heteroaryloxy, heteroalicyclic, heteroalicyclicoxy, acyl, acyloxy group or a combination thereof; each R.sup.2 is independently a group of the general formula (2a) or (2b):
—O—Y—COOR.sup.4  (2a)
—O—(C.sub.2-4 Alkyl)  (2b) wherein Y is a substituted or unsubstituted (hetero)aromatic group having 4 to 14 ring atoms, a substituted or unsubstituted saturated or partially unsaturated 4- to 14-membered (hetero)cyclic group or —(C(R.sup.5).sub.2).sub.o—; R.sup.4 is a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; each R.sup.5 is independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic or aryl group; and o is an integer from 1 to 10; and C.sub.2-4 Alkyl is ethyl, propyl or butyl; each R.sup.3 independently is a group of the general formula (3):
—O—Y—CONR.sup.6R.sup.7  (3) wherein Y is as defined above; R.sup.6 is selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof or R.sup.1; R.sup.7 is a group of the general formula (4):
—R.sup.8—SiR.sup.9.sub.p(OR.sup.10).sub.3-p  (4) wherein R.sup.8 is an alkylene group, optionally interrupted by a heteroatom; each R.sup.9 is independently selected from the group consisting of hydrogen, halogen, amino, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; each R.sup.10 is independently selected from the group consisting of a substituted or unsubstituted alkyl, alkenyl, alkynyl, or acyl group; each p independently stands for 0, 1, or 2; m is independently 0, 1 or 2; and n is independently 1, 2, or 3, wherein the sum n+m is a maximum of 3; with the proviso that the polyorganosiloxane contains at least one terminal group of the formula (I) wherein at least one R.sup.2 is a group of formula (2a) and at least one terminal group of the formula (I) wherein at least one R.sup.2 is a group of formula (2b), wherein the at least one R.sup.2 that is a group of formula (2a) and the at least one R.sup.2 that is a group of formula (2b) can be the same or different; wherein said polyorganosiloxane is the reaction product of a polyorganosiloxane (Ia) having at least one reactive group A′ bound to a silicon atom with at least one compound of formula (Ib)
C.sup.a—Si(R.sup.1).sub.m(R.sup.2a).sub.n(R.sup.3).sub.3-(m+n)  (Ib) and at least one compound of formula (Ic)
C.sup.b—Si(R.sup.1).sub.m(R.sup.2b).sub.n  (Ic) wherein R.sup.2a is a group of the general formula (2a) and R.sup.2b is a group of the general formula (2b), wherein the mass ratio of the compound of formula (Ib) and the compound of formula (Ic) is 95:5 to 5:95; with C.sup.a and C.sup.b being a reactive group that reacts with the at least one reactive group A′ bound to a silicon atom to yield the linking group -A-; m is independently 0, 1 or 2; n is independently 1, 2, or 3, wherein the sum n+m is a maximum of 3 for the compounds of formula (Ib) and is 3 for the compounds of formula (Ic); optionally in the presence of a catalyst.

2. The polyorganosiloxane according to claim 1, wherein (i) C.sup.a is a leaving group of the general formula (2a); (ii) C.sup.b is a leaving group of the general formula (2b); and (iii) A′ is a nucleophilic group.

3. The polyorganosiloxane according to claim 1, wherein the catalyst is a compound of formula (Id)
D-R.sup.11—SiR.sup.12.sub.q(OR.sup.13).sub.3-q  (Id) wherein R.sup.11 is an alkylene group, optionally interrupted by a heteroatom; each R.sup.12 is independently selected from the group consisting of hydrogen, halogen, amino, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; each R.sup.13 is independently selected from the group consisting of a substituted or unsubstituted alkyl, alkenyl, alkynyl, or acyl group; q independently stands for 0, 1, or 2; and D is a nitrogen-containing group selected from the group of formula (Ie), (If) or (Ig) ##STR00005## wherein each R.sup.14 is independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; each R.sup.14a, R.sup.14b, R.sup.14c, R.sup.15 and R.sup.16 is independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; and r is 1, 2, 3 or 4.

4. The polyorganosiloxane according to claim 1, wherein (i) the polyorganosiloxane is a polydimethylsiloxane (PDMS); and/or (ii) A is a bond, —O— or a linear or branched divalent group of the formula —(CH.sub.2).sub.1-10—(Si(Alk).sub.2-O—Si(Alk).sub.2).sub.1-10—(CH.sub.2).sub.1-10, or a derivative thereof, with Alk being C.sub.1-10 alkyl.

5. The polyorganosiloxane according to claim 1, wherein (i) the sum of n+m is 3; and/or (ii) n is 2 or 3; and/or (iii) the polyorganosiloxane comprises (a) at least one terminal group of formula (I) with m being 0 and n being 3 or m being 1 and n being 2, wherein each R.sup.1 independently of one another stands for an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, or an aryloxy group having 6 to 14 carbon atoms, or an acyloxy group having 2 to 10 carbon atoms, or an alkenyloxy having 2 to 10 carbon atoms, or amino; and at least one R.sup.2 stands for a group of the formula (2a), wherein R.sup.4 stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and Y is a substituted or unsubstituted aromatic group having 6 carbon ring atoms, or —(C(R.sup.5).sub.2).sub.o—, wherein o is 1 and one of the R.sup.5 groups is hydrogen and the second R.sup.5 group is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or an (alkyl) ester thereof, wherein, if at least one R.sup.2 stands for a group of formula (2b), said R.sup.2 is ethoxy; and (b) at least one terminal group of formula (I) with m being 0 and n being 3 or m being 1 and n being 2, wherein each R.sup.1 independently of one another stands for an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, or an aryloxy group having 6 to 14 carbon atoms, or an acyloxy group having 2 to 10 carbon atoms, or an alkenyloxy having 2 to 10 carbon atoms, or amino; and at least one R.sup.2 stands for a group of the formula (2b), wherein, if at least one R.sup.2 stands for a group of formula (2a), R.sup.4 stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and Y is a substituted or unsubstituted aromatic group having 6 carbon ring atoms, or —(C(R.sup.5).sub.2).sub.o—, wherein o is 1 and one of the R.sup.5 groups is hydrogen and the second R.sup.5 group is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or an (alkyl) ester thereof.

6. The polyorganosiloxane according to claim 1, comprising at least two terminal groups of formula (I) and the groups Si(R.sup.1).sub.m(R.sup.2).sub.n(R.sup.3).sub.3-(m+n) in the terminal groups of formula (I) comprise groups selected from (i) methyl bis(ethyl lactato)silane, ethyl bis(ethyl lactato)silane, phenyl bis(ethyl lactato)silane, vinyl bis(ethyl lactato)silane, tri(ethyl lactato)silane, methyl bis(ethyl salicylato)silane, ethyl bis(ethyl salicylato)silane, phenyl bis(ethyl salicylato)silane, vinyl bis(ethyl salicylato)silane, tri(ethyl salicylato)silane, methyl bis(diethyl malato)silane, ethyl bis(diethyl malato)silane, phenyl bis(diethyl malato)silane, vinyl bis(diethyl malato)silane, tri(diethyl malato)silane and mixtures thereof; and (ii) methyl diethoxysilane, ethyl diethoxysilane, phenyl diethoxysilane, vinyl diethoxysilane, triethoxysilane, and mixtures thereof; and (iii) methyl ethyl lactate ethoxy silane, ethyl ethyl lactate ethoxy silane, phenyl ethyl lactate ethoxy silane, vinyl ethyl lactate ethoxy silane, bis(ethyl lactato) ethoxy silane, methyl ethyl salicylate ethoxy silane, ethyl ethyl salicylate ethoxy silane, phenyl ethyl salicylate ethoxy silane, vinyl ethyl salicylate ethoxy silane, bis(ethyl salicylato) ethoxy silane, methyl diethyl malato ethoxy silane, ethyl diethyl malato ethoxy silane, phenyl diethyl malato ethoxy silane, vinyl diethyl malato ethoxy silane, bis(diethyl malato) ethoxy silane and mixtures thereof.

7. Cured reaction products of the polyorganosiloxane according to claim 1.

8. A curable composition comprising (A) at least one polyorganosiloxane according to claim 1.

9. The curable composition according to claim 8, further comprising (B) at least one adhesion promoter.

10. The curable composition according to claim 8, further comprising (B) at least one adhesion promoter, wherein the (B) adhesion promoter is selected from the group consisting of aminosilanes or from capped adhesion promoters of formula (II):
B—R.sup.11—SiR.sup.12.sub.q(OR.sup.13).sub.3-q  (II) wherein R.sup.11 is an alkylene group, optionally interrupted by a heteroatom; each R.sup.12 is independently selected from the group consisting of hydrogen, halogen, amino, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; each R.sup.13 is independently selected from the group consisting of a substituted or unsubstituted alkyl, alkenyl, alkynyl, or acyl group; q independently stands for 0, 1, or 2; and B is a nitrogen-containing group selected from the group of formula (6), (7), (8), or (9) ##STR00006## wherein each R.sup.14, R.sup.14a, R.sup.14b, R.sup.14c, R.sup.15 and R.sup.16 is independently selected from the group consisting of hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; r is 1, 2, 3 or 4; R.sup.17 is selected from —Si(R.sup.19).sub.3; R.sup.18 is selected from —Si(R.sup.19).sub.3, hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, aryl, heteroaryl, and heteroalicyclic group or a combination thereof; and each R.sup.19 is independently selected from hydrogen, a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloaliphatic, or aryl group or a combination thereof; or wherein R.sup.17 and R.sup.18 combine to form together with the nitrogen atom to which they are attached a group of formula —Si(R.sup.19).sub.2—C.sub.2-3 alkylene-Si(R.sup.19).sub.2—.

11. The curable composition according to claim 10, further comprising (C) at least one curing catalyst; wherein (i) the amount of (A) polyorganosiloxane is from about 32 to about 97% by weight, relative to the total weight of the composition; and/or (ii) the amount of capped adhesion promoter (B) is from about 0.1 to about 5% by weight, relative to the total weight of the composition; and/or (iii) the amount of the curing catalyst is from about 0.05 to 2% by weight, relative to the total weight of the composition; and/or (iv) the curable composition essentially consists of (A), (B) and (C).

12. The curable composition according to claim 10, wherein the capped adhesion promoter is: (a) a ketimine of formula (II) with q being 0, R.sup.11 being methylene or propylene, each R.sup.13 being ethyl or methyl, and B being a group of formula (6), wherein (i) one R.sup.14 is methyl and the second R.sup.14 is isobutyl or methyl; or (ii) one R.sup.14 is hydrogen and the second R.sup.14 is phenyl; or (b) a silane of formula (II) with q being 0, R.sup.11 being methylene or propylene, each R.sup.13 being ethyl or methyl, and B being a group of formula (9), wherein R.sup.17 is —Si(R.sup.19).sub.3 and R.sup.18 is hydrogen, alkyl substituted with —Si(R.sup.19).sub.3, or —Si(R.sup.19).sub.3, and each R.sup.19 is independently alkyl.

13. The curable composition according to claim 8, further comprising (C) at least one curing catalyst.

14. The curable composition according to claim 8, further comprising (C) at least one curing catalyst selected from 1,3-dicarbonyl compounds of bivalent or tetravalent tin, dialyltin(IV) dicarboxylates, dialkyltin(IV) dialkoxylates, dialkyltin(IV) oxides, tin(II) carboxylates, and mixtures thereof.

15. The curable composition according to claim 8, wherein the curable composition further comprises one or more additional ingredients selected from the group consisting of plasticizers, fillers, bases, and adhesion promoters different from the capped adhesion promoter (B).

16. The curable composition according to claim 8, wherein the amount of methanol relative to the total amount of volatile alcohols that are released by complete hydrolysis of the silane groups is less than 15 mol %.

17. Cured reaction products of the curable composition according to claim 8.

Description

EXAMPLES

Example 1

[0181] The comparison compositions C1a and C1b and the compositions E1a and E1b according to the invention were prepared by mixing the raw materials 1-5 listed in Table 1. Compositions C1a and Ela were then directly mixed with the remaining materials 6-9, while compositions C1b and E1 b were incubated for 72 h before mixing with materials 6-9. The formulations additionally differ in the type of the crosslinking (capping) catalyst, crosslinking agent, curing catalyst and adhesion promoter used.

TABLE-US-00001 TABLE 1 E1a E1b C1a C1b Parts Parts Parts Parts by by by by Raw materials weight weight weight weight 1 a,ω-Dihydroxy-terminated 52.70 52.70 52.72 52.72 polydimethylsiloxane with a viscosity of 80,000 cST 2 Vinyl tris(ethyl lactato)silane 2.48 2.48 2.48 2.48 3a Triethoxyvinylsilane 2.48 2.48 3b Trimethoxyvinylsilane 2.48 2.48 4 Plasticizer (a,ω-Dimethyl- 33.15 33.15 33.39 33.39 terminated Polydimethylsiloxane with a viscosity of 1,000 cST) 5a Ketimine 1 (capping catalyst) 0.67 0.67 5b 3-aminopropyltrimethoxysilane 0.40 0.40 (capping catalyst) 6 Highly dispersed silicic acid 7.35 7.35 7.35 7.35 7 3-(N,N-dimethylamino) 0.50 0.50 0.50 0.50 propyltrimethoxysilane 8a 3-aminopropyltriethoxysilane 0.50 0.50 8b 3-aminopropyltrimethoxysilane 0.50 0.50 9a Dioctyltin dineodecanoate 0.18 0.18 9b Dioctyltin dilaurate (DOTL) 0.18 0.18

[0182] Ketimine 1 is a compound of formula (II), wherein q is 0, R.sup.11 is propylene, each R.sup.13 is ethyl and B is a group of formula (6) wherein one R.sup.14 is methyl and the second R.sup.14 is isobutyl.

[0183] Polymer (A) was formed from the α,ω-Dihydroxy-terminated polydimethylsiloxane and the vinyl tris(ethyl lactato)silane/triethxyvinylsilane/trimethoxyvinylsilane in a previous step in the presence of either the 3-aminopropyltrimethoxysilane as a catalyst (C1a/C1b) or ketimine 1 as the catalyst (E1a/E1b) according to the following procedure:

[0184] Procedure for Preparation:

[0185] A mixer equipped with a mechanical stirrer, vacuum pump, nitrogen pipe and a thermometer was charged with a, w-hydroxyl-terminated polydimethylsiloxane (viscosity: 80000 mPas) and plasticizer. After degassing (vacuum for several minutes) the endcapping catalyst (see above) was added. After 3 minutes of stirring, vinyl tris(ethyl lactato)silane, triethoxyvinylsilane and trimethoxyvinylsilane, respectively, was added. The mixture was stirred for 5 minutes at room temperature under nitrogen and for 5 additional minutes under vacuum. Finally, fillers, adhesion promoters, possible additives and curing catalyst are either directly added or added after 72 h incubation following the usual procedure for silicone composition preparation.

[0186] The prepared formulations were subjected to curing performance tests as follows:

[0187] Determination of Skin-over time (SOT): 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 (SOT) is expressed in minutes.

[0188] Measurement of Shore A hardness: Shore A hardness was measured according to ISO 868.

[0189] Determination of the depth of cure (DOC): A strip of the material with a height of 10 mm (+/−1 mm) and width of 20 mm (+/−2 mm) was applied over a plastic foil (PP) using a Teflon spatula. After storing the sample for 24 hours at normal conditions (23+/−2° C., relative humidity 50+/−5%), a section of the strip was cut off and the thickness of the cured layer was measured with a caliper. The depth of cure after 24 hours is expressed in millimeters.

[0190] Assessment of the mechanical properties (tensile test): The Tensile test determines the breaking force, elongation at break and yield stress value (e-module), according to DIN 53504. Deviation from the norm: dumbbell specimens with the following dimensions were used: thickness 2+/−0.2 mm; bar width 10+/−0.5 mm; bar length approx. 45 mm; total length 9 cm. The tests took place at normal conditions (23+/−2° C., relative humidity 50+/−5%). The measurement was carried out after 7 days of curing. Procedure: the prepolymer mixture (formulation) was spread on an even surface forming a film with a thickness of 2 mm. The film was allowed to cure under normal conditions (see above) for seven days, and then the dumbbell specimen was punched out. Three specimens were used for each determination. The test was carried out under normal conditions. The test specimens have to be at the same temperature at which the measurement will take place. Before the measurement, the thickness of the test specimens is determined at least at three different positions, at the middle and at the extremes, with a caliper. The mean value is introduced in the measuring software. The test specimens are clamped into the tensile tester so that the longitudinal axis coincides with the mechanical axis of the tensile tester and comprises the largest possible surface of the rod heads, without clamping the middle bar. Then the dumbbell is stretched to <0.1 MPa with a rate of 50 mm/min. Then, the force-elongation curve is recorded with a line speed of 50 mm/min. Evaluation: The following values are determined: breaking force in [N/mm.sup.2] elongation at break in [%] and modulus at 100% elongation in [N/mm.sup.2].

[0191] Peel Test:

[0192] If possible and needed, substrate (test panel) is cleaned prior to application using a suitable solvent. A strip of the material with a height of 10 mm (+/−1 mm) and width of 20 mm (+/−2 mm) was applied over the substrate using a Teflon spatula. The sample was stored for 7 days at normal conditions (23+/−2° C., relative humidity 50+/−5%). The cured material was cut back for at least 15 mm with a shape blade and the bead pulled by hand. Failure mode was recorded as following:

[0193] ✓Cohesion failure (CF) or alternatively cohesive/adhesive failure

[0194] ˜Adhesion failure (AF) with “strong resistance”

[0195] x Adhesion failure.

[0196] n.d.=not determined

TABLE-US-00002 TABLE 3 Properties of compositions prior to storage (directly after mixng) E1a E1b C1a C1b SOT (min) 11 13 8 17 Shore A 1 d 10 12 8 7 Shore A 7 d 20 18 20 20 cure through 2.86 2.78 2.56 2.46 (mm in 24 h) tack free after 24 h OK OK OK OK ADHESION PMMA ✓ ✓ x x Aluminum/Elox ✓ ✓ ✓ ✓ Brass ✓ ✓ ✓ ✓ Glass ✓ ✓ ✓ ✓ Concrete ✓ ✓ ✓ x Modulus at 100% 0.33 0.32 0.33 0.37 Elongation at break 530.8 541.8 517.9 476.7

TABLE-US-00003 TABLE 4 Properties of compositions after storage (8 weeks; 40° C., 80% humidity) E1a E1b C1a C1b SOT (min) 29 35 30 40 Shore A 1 d 2 2 n.d. 5 Shore A 7 d 15 15 16 18 cure through 3.30 3.39 n.d. 3.03 (mm in 24 h) tack free 24 h OK OK OK OK ADHESION PMMA ✓ ✓ x x Aluminum/Elox ✓ ✓ ✓ x Brass ✓ ✓ ✓ x Glass ✓ ✓ ✓ ✓ Concrete ✓ x x x Modulus at 100% 0.26 0.26 n.d. 0.32 Elongation at break 532.2 587.3 n.d. 531.3

[0197] The results show that the compositions of the invention have a better adhesion compared to the comparative compositions and show high storage stability.