CURABLE SILICONE COMPOSITIONS CONTAINING ADDITIVES

Abstract

The invention relates to curable compositions based on polyorganosiloxanes with special silicon-containing terminal groups, an adhesion promoter, a curing catalyst, and an additive having a ketone functional moiety. These compositions have improved mechanical and adhesion properties and excellent storage stability. The invention also relates to the uses thereof.

Claims

1. A curable composition comprising (A) at least one 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 (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 or 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 or 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 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; (B) at least one adhesion promoter; (C) at least one curing catalyst; and (D) at least one additive having a ketone functional moiety of formula (III)
R.sup.31—C(═O)—R.sup.32 wherein R.sup.31 is selected from a substituted or unsubstituted alkyl, alkoxy, alkenyl, alkenyloxy, alkynyl, alkylnyloxy, cycloaliphatic, cycloaliphatic-O—, aryl, aryloxy, heteroaryl, heteroaryloxy, heteroalicyclic, heteroalicyclicoxy, acyl, acyloxy group or a combination thereof; and R.sup.32 is selected from 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 or a combination thereof; or wherein R.sup.31 and R.sup.32 combine to form together with the carbon atom to which they are attached a 5 to 20-membered substituted or unsubstituted alicyclic or heteroalicyclic group; wherein the additive of formula (III) comprises up to 24 carbon atoms.

2. The curable composition according to claim 1, wherein the polyorganosiloxane is a polydimethylsiloxane (PDMS).

3. The 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.

4. The curable composition 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 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; 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.

5. The curable composition according to claim 1, wherein the sum n+m is 3.

6. The curable composition 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.

7. The curable composition according to claim 1, wherein the sum n+m is a maximum of 2 and each R.sup.3 independently of one another stands for a group of the formula (3), wherein 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, R.sup.6 represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and R.sup.7 represents a group of the formula (4), where R.sup.8 is a C1-10 alkylene group, each R.sup.9 independently of one another stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and each R.sup.10 independently of one another stands for a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms; and p is 0 or 1.

8. The curable composition according to claim 1, wherein the at least one adhesion promoter comprises a compound selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, aminomethyltrimethoxysilane, aminomethyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, (N-2-aminoethyl)-3-aminopropyltrimethoxysilane, (N-2-aminoethyl)-3-aminopropyltriethoxysilane, diethylenetriaminopropyltrimethoxysilane, phenylaminomethyltrimethoxysilane, (N-2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-(N-phenylamino)propyltrimethoxysilane, 3-piperazinylpropylmethyldimethoxysilane, 3-(N,N-dimethylaminopropyl)aminopropylmethyldimethoxysilane, tri[(3-triethoxysilyl)propyl]amine, tri[(3-trimethoxysilyl)propyl]amine, and the oligomers thereof, 3-(N,N-dimethylamino)propyltrimethoxysilane, 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, bis(3-triethoxysilyl)propylamin, 4-amino-3,3-dimethylbutyltrimethoxy silane and 4-amino-3,3-dimetylbuthyltriethoxy silane, and mixtures thereof.

9. The curable composition according to claim 1, wherein the at least one adhesion promoter comprises a 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 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) ##STR00003## 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—.

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 according to claim 1, 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 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.

12. The curable composition according to claim 1, characterized in that the curing catalyst is 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.

13. The curable composition according to claim 1, wherein the additive (D) is selected from ketones and aldehydes of formula (III), wherein (i) R.sup.31 is selected from a substituted or unsubstituted C.sub.1-10 alkyl, C.sub.6-14 aryl and C.sub.5-13 heteroaryl; and R.sup.32 is hydrogen; or (ii) R.sup.31 and R.sup.32 are each independently selected from a substituted or unsubstituted alkyl, aryl, heteroaryl, or a combination thereof.

14. The curable composition according to claim 1, further comprising one or more additional ingredients selected from the group consisting of plasticizers, extenders, stabilizers, antioxidants, fillers, reactive diluents, drying agents, UV stabilizers, rheological aids, and solvents.

15. Cured reaction product of the curable composition according to claim 1.

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

Description

EXAMPLES

Example 1

[0170] The comparison composition C1 and the composition E1 according to the invention were prepared by mixing the raw materials listed in Table 1. The formulations differ only in that the inventive composition additionally comprises an additive with a ketone functional moiety, namely benzaldehyde.

TABLE-US-00001 TABLE 1 E1 C1 Parts by Parts by Raw materials weight weight α,ω-Dihydroxy-terminated 52.63 52.72 polydimethylsiloxane with a viscosity of 80,000 cST Vinyl tris(ethyl lactato)silane 4.96 4.97 3-Aminopropyltrimethoxysilane 0.40 0.40 Plasticizer (Polydimethylsiloxane 33.33 33.39 with a viscosity of 1,000 cST) Highly dispersed silicic acid 7.34 7.35 3-(N,N-dimethylamino) 0.50 0.50 propyltrimethoxysilane 3-Aminopropyltrimethoxysilane 0.50 0.50 Benzaldehyde 0.17 — Tin compound 0.18 0.18 (dioctyltin dilaurate (DOTL))

[0171] Polymer (A) was formed from the α,ω-Dihydroxy-terminated polydimethylsiloxane and the vinyl tris(ethyl lactato)silane using the 3-Aminopropyltrimethoxysilane (0.4 ppw) as a catalyst in the presence of the plasticizer in a previous step and then combined with the silicic acid filler, the remaining aminosilanes (adhesion promoters), the benzaldehyde, if used, and the curing catalyst.

[0172] The prepared formulations were subjected to curing performance tests as follows:

[0173] 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.

[0174] Measurement of Shore A hardness: Shore A hardness was measured according to ISO 868.

[0175] 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.

[0176] 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].

Peel Test:

[0177] 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: [0178] √ Cohesion failure (CF) or alternatively cohesive/adhesive failure [0179] ˜ Adhesion failure (AF) with “strong resistance” [0180] × Adhesion failure.

TABLE-US-00002 TABLE 3 Properties of compositions prior to storage (directly after mixing) E1 C1 SOT (min) 12 23 Shore A 1 d 10 13 Shore A 7 d 19 19 cure through (mm in 24 h) 3.66 3.48 tack 24 h tack free tack free ADHESION PMMA ✓ ~ Aluminum/Elox ✓ ✓ Brass ✓ ✓ Glass ✓ ✓ Concrete x x Modulus at 100% 0.32 0.33 Elongation at break 587.5 560.3

TABLE-US-00003 TABLE 4 Properties of compositions after storage (8 weeks; 40° C., 80% humidity) E1 C1 SOT (min) 31 40 Shore A 1 d 8 7 Shore A 7 d 17 17 cure through (mm in 24 h) 3.69 4.04 tack 24 h tack free tack free ADHESION PMMA x x Aluminum/Elox ✓ ✓ Brass ✓ x Glass ✓ ✓ Concrete x x Modulus at 100% 0.29 0.30 Elongation at break 647.7 554.1

[0181] The results show that the composition of the invention has a better adhesion and higher storage stability compared to the comparative composition.