Endcapped curable polyorganosiloxanes

Abstract

The invention relates to curable polyorganosiloxanes with special silicon-containing terminal groups and curable compositions based on these polyorganosiloxanes, a 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, alkoxy, alkenyl, alkenyloxy, alkynyl, alkylnyloxy, cycloaliphatic, cycloaliphatic-O—, aryl, aryloxy, heteroaryl, heteroaryloxy, heteroalicyclic, heteroalicyclicoxy, acyl, acyloxy group and a combination thereof; each R.sup.2 is independently a group of the general formula (2):
—O—Y—COOR.sup.4  (2) 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 and aryl group; and o is an integer from 1 to 10; 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 and a combination thereof or R.sup.7; 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 and a combination thereof; each R.sup.10 is independently selected from the group consisting of a substituted or unsubstituted alkyl, alkenyl, alkynyl, and 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; wherein said polyorganosiloxane is obtained by reacting a polyorganosiloxane (Ia) having at least one reactive group A′ bound to a silicon atom with a compound of formula (Ib)
C—Si(R.sup.1).sub.m(R.sup.2).sub.n(R.sup.3).sub.3−(m+n)  (Ib) with C 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- in the presence of a compound of formula (Ic) as a catalyst
D-R.sup.11—SiR.sup.12.sub.q(OR.sup.13).sub.3−q  (Ic) 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 and a combination thereof; each R.sup.13 is independently selected from the group consisting of a substituted or unsubstituted alkyl, alkenyl, alkynyl, and acyl group; q independently stands for 0, 1, or 2; and D is a nitrogen-containing group selected from the group of formula (Id), (Ie) or (If) ##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 and 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 and a combination thereof; and r is 1, 2, 3 or 4.

2. The polyorganosiloxane according to claim 1, wherein (i) C is a group of the general formula (2):
—O—Y—COOR.sup.4  (2); and (ii) A′ is a nucleophilic group or hydroxy.

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

4. The curable composition according to claim 3, wherein (i) the amount of polymer (A) is from about 32 to about 97% by weight, relative to the total weight of the composition; and/or (ii) the curable composition further comprises an amount of capped adhesion promoter (B) of from about 0.1 to about 5% by weight, relative to the total weight of the composition; and/or (iii) the curable composition further comprises an amount of (C) curing catalyst of from about 0.05 to 2% by weight, relative to the total weight of the composition; and/or (iv) the curable composition consists essentially of (A), (B) and (C).

5. The curable composition according to claim 3, 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).

6. The curable composition according to claim 3, comprising a (B) capped adhesion promoter and further comprising at least one adhesion promoter different from the (B) capped adhesion promoter selected from 3-(N,N-dimethylamino)propyl-trimethoxysilane, 3-(N,N-dimethylamino)propyltriethoxysilane, (N,N-dimethylamino)methyltrimethoxysilane, (N,N-dimethylamino)methyltriethoxysilane, 3-(N,N-diethylamino)propyltrimethoxysilane, 3-(N,N-diethylamino)propyltriethoxysilane, (N,N-diethylamino)methyltrimethoxysilane, (N,N-diethylamino)methyltriethoxysilane, bis(3-trimethoxysilyl)propylamine, and bis(3-triethoxysilyl)propylamine.

7. An adhesive, sealing, or coating material comprising the curable composition according to claim 3.

8. Cured reaction products of the curable composition according to claim 3.

9. The curable composition according to claim 3, further comprising: (B) at least one capped adhesion promoter 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 and a combination thereof; each R.sup.13 is independently selected from the group consisting of a substituted or unsubstituted alkyl, alkenyl, alkynyl, and 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 and 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, 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—.

10. The curable composition according to claim 9, 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.

11. The curable composition of claim 3, further comprising (C) at least one curing catalyst.

12. The curable composition according to claim 11, wherein the curing catalyst is a tin 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. The polyorganosiloxane or curable composition according to claim 1, wherein the polyorganosiloxane is a polydimethylsiloxane (PDMS).

14. The polyorganosiloxane or curable composition according to claim 1, wherein 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.

15. The polyorganosiloxane 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 isopropyl, 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, oximino, alkenyloxy having 2 to 10 carbon atoms, amino, or an alkoxy group having 1 to 4 carbon atoms; and/or each R.sup.2 independently of one another stands for a group of the formula (2), 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, carboxymethyl or an (alkyl) ester thereof.

16. The polyorganosiloxane according to claim 1, wherein (i) the sum n+m is 3; and/or (ii) n is 2 or 3.

17. The polyorganosiloxane according to claim 1, wherein the group Si(R.sup.1).sub.m(R.sup.2).sub.n(R.sup.3).sub.3−(m+n) in formula (I) is selected from 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.

Description

EXAMPLES

Example 1

(1) The comparative compositions C1a, C1b and C1c and the compositions E1 and E2 according to the invention were prepared by mixing the raw materials listed in Table 1. The formulations differ in the type of the capping catalyst and adhesion promoter used.

(2) TABLE-US-00001 TABLE 1 E1 C1a C1b C1c E2 C2 Parts Parts Parts Parts Parts Parts Raw materials by weight by weight by weight by weight by weight by weight α,ω-Dihydroxy-terminated 52.40 52.54 52.54 52.31 52.18 52.18 polydimethylsiloxane with a viscosity of 80,000 cST Vinyl tris(ethyl lactato)silane 4.94 4.95 4.94 4.93 4.92 4.92 Plasticizer (Polydimethylsiloxane 33.18 33.27 33.20 33.13 33.04 33.04 with a viscosity of 1,000 cST) Highly dispersed silicic acid 7.31 7.33 7.31 7.30 7.28 7.28 3-(N,N- 0.49 0.50 0.49 0.49 dimethylamino)propyltrimethoxysilane Ketimine 1 (adhesion promoter) 0.83 0.84 0.84 0.84 Ketimine 1 (capping catalyst) 0.67 0.39 Silane 1 (adhesion promoter) 2.01 2.01 n-Butyllithium (2.5M in hexanes) 0.84 (capping catalyst) Lithiummethanolate (capping 0.83 catalyst) 3-Aminopropyltrimethoxysilane 0.4 0.39 (capping catalyst) Tin compound (dioctyltin dilaurate 0.18 0.18 0.18 0.18 0.18 0.18 (DOTL))
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.
Silane 1 is a compound of formula (II), namely N,N-bis(trimethylsilyl)aminopropyl trimethoxysilane.

(3) Polymer (A) was formed from the α,ω-Dihydroxy-terminated polydimethylsiloxane and the vinyl tris(ethyl lactato)silane in a previous step in the presence of either the 3-aminopropyltrimethoxysilane as a catalyst (C1/C2) or ketimine 1 as the catalyst (E1/E2) according to the following procedure:

(4) Procedure for Preparation:

(5) A mixer equipped with a mechanical stirrer, vacuum pump, nitrogen pipe and a thermometer was charged with α,ω-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 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 (ketimine (E1/C1) or silane (E2/C2)), possible additives and curing catalyst are added following the usual procedure for silicone composition preparation.

(6) The prepared formulations were subjected to curing performance tests as follows:

(7) 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.

(8) Measurement of Shore A hardness: Shore A hardness was measured according to ISO 868.

(9) 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.

(10) 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].

(11) Peel Test:

(12) 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:

(13) ✓ Cohesion failure (CF) or alternatively cohesive/adhesive failure

(14) ˜ Adhesion failure (AF) with “strong resistance”

(15) Adhesion failure.

(16) TABLE-US-00002 TABLE 2 Properties of compositions prior to storage (directly after mixing) E1 C1a C1b C1c E2 C2 SOT (min) 12 11 30 28 7 10 Shore A 1 d 8 10 0 0 12 8 Shore A 7 d 16 18 4 4 16 16 cure through 3.13 2.83 3.38 2.57 3.86 3.8 (mm in 24 h) tack free after OK OK tacky tacky OK OK 24 h ADHESION PMMA ✓ ~ ✓ Aluminum/Elox ✓ ✓ ✓ ✓ Brass ✓ ✓ ✓ ✓ Glass ✓ ✓ ✓ ✓ Concrete ✓ ✓ ✓ Modulus at 100% 0.30 0.31  *  *  **  ** Elongation at 662 659  *  * N/A** N/A** break *No determination possible due to the softness of the “not fully cured” polymer films (still tacky and soft). N/A** No determination possible because cured polymer film stuck to the mold.

(17) TABLE-US-00003 TABLE 3 Properties of compositions after storage (8 weeks; 40° C., 80% humidity) E1 C1a SOT (min) 20 24 Shore A 1 d 5 6 Shore A 7 d 14 14 cure through 3.3 3.27 (mm in 24 h) tack free 24 h OK OK ADHESION PMMA ✓ ✓ Aluminum/Elox ✓ ✓ Brass ✓ ✓ Glass ✓ ✓ Concrete ✓ Modulus at 100% 0.25 0.26 Elongation at break 602 527

(18) The results show that the compositions of the invention have a better adhesion after storage and thus a higher storage stability compared to the comparative composition.