FAST CURING TWO-COMPONENT SILICONE COMPOSITION HAVING ADJUSTABLE POT LIFE

Abstract

A two-component silicone composition made of a component A including a hydroxyl-group terminated polydiorganosiloxane P; between 0.05-5.0 wt. % water, relative to component A; and component B including a non-condensable polydiorganosiloxane; a catalyst K cross-linking polydiorganosiloxanes; between 0-50 wt. % of a first organosilane V1 according to formula (I), between 2-60 wt. % of a second organosilane V2 according to formula (II), up to 25 wt. % of organosilanes V3 having hydrolyzable alkoxysilane groups Si—ORa not falling under the formulae (I) and (II), with Ra being a hydrogen atom or monovalent, linear or branched alkyl group with 1-6 carbon atoms, Rb being a divalent, linear or branched alkyl group or alkenyl group with 2-20 carbon atoms, and Rc being a divalent, linear or branched alkyl group with 2-20 carbon atoms containing a secondary amino group; the composition containing less than 10 mole-%, relative to the amount of organosilane V2, of organosilanes with epoxy groups.

Claims

1. A two-component silicone composition consisting of a component A comprising i) at least one hydroxyl group-terminated polydiorganosiloxane P; ii) between 0.05% and 5.0% by weight of water, based on component A; and a component B comprising i) at least one noncondensable polydiorganosiloxane as plasticizer; ii) at least one catalyst K for the crosslinking of polydiorganosiloxanes; iii) between 0% and 50% by weight, based on component B, of at least one first organosilane V1 of formula (I) ##STR00011## iv) between 2% and 60% by weight, based on component B, of at least one second organosilane V2 of formula (II) ##STR00012## v) up to 25% by weight, based on component B, of further organosilanes V3 having hydrolyzable alkoxysilane groups Si—OR.sup.a that are not covered by the formulae (I) and (II), where R.sup.a is a hydrogen atom or a monovalent linear or branched alkyl radical having 1 to 6 carbon atoms, R.sup.b is a divalent linear or branched alkyl radical or alkenyl radical having 2 to 20 carbon atoms, and R.sup.c is a divalent linear or branched alkyl radical which has 2 to 20 carbon atoms and contains at least one secondary amino group; with the proviso that the composition contains less than 10 mol %, based on the amount of organosilane V2, of organosilanes having epoxy groups.

2. The two-component silicone composition as claimed in claim 1, wherein the hydroxyl group-terminated polydiorganosiloxane P is a polydiorganosiloxane P′ of the formula (I) ##STR00013## where the R.sup.1 and R.sup.2 radicals are independently linear or branched, monovalent hydrocarbyl radicals which have 1 to 12 carbon atoms and optionally include one or more heteroatoms, and optionally one or more C—C multiple bonds and/or optionally cycloaliphatic and/or aromatic components; and n is chosen such that the weight-average molecular weight M.sub.W of the polydiorganosiloxane P′ relative to polystyrene is 500 to 250,000 g/mol.

3. The two-component silicone composition as claimed in claim 2, wherein the hydroxyl group-terminated polydiorganosiloxane P is a polydiorganosiloxane P1 of the formula (I) where n is chosen such that the weight-average molecular weight M.sub.W of the polydiorganosiloxane P1 relative to polystyrene is 30,000 to 80,000 g/mol; or in that the polydiorganosiloxane P used is a mixture of i″) at least one hydroxyl group-terminated polydiorganosiloxane P2 of the formula (I) where n is chosen such that the weight-average molecular weight M.sub.W of the polydiorganosiloxane P2 relative to polystyrene is >80,000 to 250,000 g/mol; and ii″) at least one hydroxyl group-terminated polydiorganosiloxane P3 of the formula (I) where n is chosen such that the weight-average molecular weight M.sub.W of the polydiorganosiloxane P3 relative to polystyrene is 500 to ≤80,000 g/mol.

4. The two-component silicone composition as claimed in claim 2, wherein the R.sup.1 and R.sup.2 radicals are alkyl radicals having 1 to 5 carbon atoms.

5. The two-component silicone composition as claimed in claim 1, wherein organosilane V3 is a silane of the formula (III) ##STR00014## where the R.sup.3 radical is independently a linear or branched, monovalent hydrocarbyl radical which has 1 to 12 carbon atoms and optionally includes one or more heteroatoms, and optionally one or more C—C multiple bonds and/or optionally cycloaliphatic and/or aromatic components; the R.sup.4 radical is an R.sup.a radical; and p has a value of 0 to 4, with the proviso that, if p has a value of 3 or 4, at least p-2 R.sup.3 radicals each have at least one group reactive, with the hydroxyl groups of the polydiorganosiloxane P.

6. The two-component silicone composition as claimed in claim 1, wherein the R.sup.a radicals in all organosilanes V1, V2 and V3 is an alkyl radical having 1 to 5 carbon atoms, where portions of these R.sup.a radicals after hydrolysis of Si—OR.sup.a groups may be replaced by hydrogen atoms.

7. The two-component silicone composition as claimed in claim 1, wherein the catalyst K is an organotin compound.

8. The two-component silicone composition as claimed in claim 1, wherein organosilane V2 is at least one organosilane of formula (IIa) ##STR00015## where R.sup.d is a divalent linear or branched alkyl radical which has 2 to 10 carbon atoms and optionally contains a hydroxyl group and an ether oxygen, and R.sup.e is a divalent linear or branched alkyl radical having 2 to 10 carbon atoms.

9. The two-component silicone composition as claimed in claim 8, wherein the organosilane V2 is either an organosilane V2a in which the R.sup.d and R.sup.e radicals in formula (IIa) are both a divalent linear or branched alkyl radical having 2 to 10 carbon atoms; or an organosilane V2b in which the R.sup.e radical in formula (IIa) is a divalent linear or branched alkyl radical having 2 to 10 carbon atoms, and R.sup.d radical is a divalent linear or branched alkyl radical having 2 to 10 carbon atoms, and additionally one of the two structural elements shown in formula (IIb); or ##STR00016## a mixture of an organosilane V2a and an organosilane V2b, where the organosilanes V2a and V2b mentioned are present in component B in a weight ratio of between 1:2 and 2:1.

10. The two-component silicone composition as claimed in claim 9, wherein organosilane V2 comprises an organosilane V2a, and in that the catalyst K is present in component B in an amount between 0.1% by weight and 2% by weight, based on component B.

11. The two-component silicone composition as claimed in claim 9, wherein organosilane V2 consists of an organosilane V2b, and in that the catalyst K is present in component B in an amount between 1% by weight and 4% by weight, based on component B.

12. The two-component silicone composition as claimed in claim 1, wherein the weight ratio of component A to component B is ≥1:1.

13. A method comprising applying a two-component silicone composition as claimed in claim 1 as adhesive, sealant, coating or as casting compound.

14. A cured silicone composition, wherein it is obtainable from a two-component silicone composition as claimed in claim 1 by mixing component A with component B.

15. A method of adjusting pot life with the same mechanical properties after curing of a two-component silicone composition as claimed in claim 1, wherein the mixing ratio of component A to component B based on weight is selected arbitrarily within the range of component A to component B from 1:1 to 25:1.

Description

EXAMPLES

[0185] Working examples are adduced hereinafter, which are intended to further elucidate the invention described. The invention is of course not limited to these described working examples.

[0186] Preparation of the Silicone Compositions

[0187] The following compositions were produced:

[0188] As components A and B, the constituents listed in tables 1 and 2 were mixed with one another in the percentages by weight specified in a dissolver at room temperature under inert atmosphere, and stirred in until a macroscopically homogeneous paste was obtained.

[0189] The components A and B produced were introduced into the separate chambers of twin cartridges, and the cartridges were closed. On application, components A and B were mixed by static mixer.

[0190] Description of Test Methods

[0191] Viscosity was determined by rheometer (Anton Paar Physica MCR 101 in a plate-plate measurement setup, diameter of the plate: 25 mm) to DIN 53018. Freedom from tack of the composition was measured by mixing, by means of a tumbling mixer, components A and B that had been conditioned at 23° C. in a closed cartridge for 24 hours beforehand in a weight ratio as specified in the table. Subsequently, the mixed mass was applied to the rheometer, compressed to 0.5 mm and subjected to shear at a constant frequency (0.08 1/s). The rise in viscosity was plotted against time and measured up to a maximum value of 90′000 Pa.Math.s. The attainment of the viscosity of 90′000 Pa.Math.s is in good correlation with the freedom from tack determined manually on the mixed material and is therefore considered to be a systematically detected value for freedom from tack.

[0192] For determination of pot life (also called open time) of the composition, a mixed material was prepared analogously to the determination of freedom from tack. A wooden spatula was introduced into the mass. Every minute, the spatula was used to determine whether the mixed mass still has pasty character. As soon as the mass shows partial elastic behavior, the pot life is considered to have been attained.

[0193] Lap shear strength and elongation at maximum shear force were measured to DIN EN 1465 on films having a layer thickness of 2 mm that were stored at 23° C., 50% relative air humidity, for 7 days, at a measurement speed of 20 mm/min on a Zwick/Roell Z005 tensile tester. The values reported are the averages of three measurements.

[0194] Shore A hardness was determined to DIN 53505 after storage of the cured composition at 23° C. and 50% relative air humidity for 7 days.

[0195] The method of determining tear propagation resistance (TPR) and the production of the test specimens required for the purpose are described in DIN ISO 34-1. Measurement was effected on type C test specimens.

[0196] The method of determining elongation at maximum tensile force, force at 100% elongation and tensile strength and the production of the test specimens required for the purpose are described in ISO 527. Measurement was effected at 23° C. and 50% relative air humidity on a type 5A test specimen (ISO 527-2) and with a tension rate of 200 mm/min.

[0197] Preparation of Crosslinker V2b

[0198] 88.6 g of 3-aminopropyltriethoxysilane (Dynasylan® AMEO, Evonik) were mixed with 111.4 g of 3-glycidoxypropyltriethoxysilane (Dynasylan® GLYEO, Evonik) in a glass vessel under nitrogen atmosphere. The vessel was closed and left at 50° C. for 7 days. The resulting mixture, which was free of detectable epoxy groups, was used without workup as organosilane V2b.

TABLE-US-00001 TABLE 1 Two-component silicone compositions 1 to 6. Composition 1 Ref 2 3 4 5 6 A OH-term. PDMS .sup.a (viscosity (23° C.) 38.3 38.3 38.3 38.3 44.3 33.0 20′000 mPa .Math. s) (polymer P2) OH-term. PDMS .sup.a (viscosity (23° C.) 6′000 4.0 4.0 4.0 4.0 4.0 5.0 mPa .Math. s) (polymer P3) OH-term. PDMS a (viscosity (25° C.) 100 2.0 2.0 2.0 2.0 — 2.0 mPa .Math. s) (polymer P3) Plasticizer (Wacker ® AK 10) 6.0 6.0 6.0 6.0 6.0 — Plasticizer (Wacker ® AK 100) — — — — — 7.0 Polypropylene glycol dispersion additive 1.0 1.0 1.0 1.0 1.0 1.0 Silicone oil in water emulsion (50% H.sub.2O) 0.3 0.3 0.3 0.3 0.3 1.0 Hakuenka ® CCR-S (hydrophobized 19.0 19.0 19.0 19.0 19.0 38.0 precipitated chalk) Imercarb ® 74S (ground chalk) 28.0 28.0 28.0 28.0 28.0 10.0 Aerosil ® R972 (hydrophobic fumed silica) 1.5 1.5 1.5 1.5 1.5 1.5 Pigment — — — — — 3.0 B Vinyl-terminated PDMS .sup.b (plasticizer) 38.6 40.75 46.0 44.0 40.75 46.0 Dynasylan ® 1122 (crosslinker V2a) — 20.0 42.0 — 20.0 9.0 Crosslinker V2b (see preparation method) — 20.0 — 42.0 20.0 10.0 Geniosil ® GF 96 (aminotrimethoxysilane) 19.95 — — — — — Geniosil ® GF 80 (epoxytrimethoxysilane) 10.0 — — — — — Wacker ® Silane M1 Trimethoxy 9.0 — — — — — (methyltrimethoxysilane) (crosslinker V3) Wacker ® Cross-linker ET15 (crosslinker — — — — — 19.0 V1) Vinyltriethoxysilane (crosslinker V3) — — — — — 7.0 Monarch ® 570 (carbon black) 15.8 15.8 — — 15.8 — Aerosil ® R972 (hydrophobic fumed silica) 5.6 3.0 11.0 11.0 3.0 8.0 Catalyst .sup.c 0.45 0.45 1.0 3.0 0.45 1.0 .sup.a OH-term. PDMS: OH group-terminated polydimethylsiloxane; .sup.b Vinyl-term. PDMS: vinyl group-terminated polydimethylsiloxane having a viscosity to DIN 53018 of 20′000 mPa .Math. s; .sup.c organotin compound (dioctyltin dilaurate).

[0199] Pot Life and Freedom from Tack (Curing Time)

[0200] Table 2 shows that the compositions of the invention have a very low ratio of pot life to freedom from tack, and hence cure extremely rapidly after the pot life has ended.

TABLE-US-00002 TABLE 2 Measurement data for pot life and freedom from tack of compositions 1 to 3. The mixing ratio of component A to component B was always 13:1 (w/w). Composition 1 Ref 2 3 4 5 Pot life 29 min 33 min 21 min 125 min  94 min Freedom from 84 min 42 min 25 min 153 min 131 min tack (time until largely cured) Ratio of freedom 2.9 1.3 1.2 1.2 1.4 from tack: pot life

[0201] Mechanical Properties and Mixing Ratio

[0202] Table 3 shows that the alteration of the mixing ratio (weight) allows the pot life to be adjusted. However, the mechanical properties after curing remain virtually unaffected.

TABLE-US-00003 TABLE 3 Measurement data of composition 6 at various mixing ratios of component A:component B. n/m means that the value was not measured. Composition 6 Mixing ratio A:B (w/w) 7:1 10:1 13:1 16:1 Pot life [min] 4 7 11 16 Freedom from tack [min] n/m n/m 22 n/m Shore A hardness (7d SCC) 48 43 49 45 Lap shear strength (7d SCC) [MPa] 1.4 1.3 1.3 1.3 Elongation at maximum shear force 230 220 200 250 [%]

TABLE-US-00004 TABLE 4 Two-component silicone compositions 7 to 9. Composition 7 Ref 8 9 A OH-term. PDMS .sup.a (viscosity (23° C.) 33.9 33.5 33.2 20′000 mPa .Math. s) (polymer P2) OH-term. PDMS .sup.a (viscosity (23° C.) 6′000 5.1 5.1 5.0 mPa .Math. s) (polymer P3) OH-term. PDMS .sup.a (viscosity (25° C.) 100 2.0 2.0 2.0 mPa .Math. s) (polymer P3) Plasticizer (Wacker ® AK 100) 7.2 7.1 7.0 Polypropylene glycol dispersion additive 1.0 1.0 1.0 Silicone oil in water emulsion (50% H.sub.2O) — 1.0 2.0 Hakuenka ® CCR-S (hydrophobized 39.0 38.6 38.2 precipitated chalk) Imercarb ® 74S (ground chalk) 10.3 10.2 10.1 Aerosil ® R972 (hydrophobic fumed silica) 1.5 1.5 1.5 B Vinyl-terminated PDMS .sup.b (plasticizer) 46.0 46.0 46.0 Dynasylan ® 1122 (crosslinker V2a) 9.0 9.0 9.0 Crosslinker V2b (see preparation method) 10.0 10.0 10.0 Geniosil ® GF 96 (aminotrimethoxysilane) — — — Geniosil ® GF 80 (epoxytrimethoxysilane) — — — Wacker ® Silane M1 Trimethoxy — — — (methyltrimethoxysilane) (crosslinker V3) Wacker ® Cross-linker ET15 (crosslinker 19.0 19.0 19.0 V1) Vinyltriethoxysilane (crosslinker V3) 7.0 7.0 7.0 Monarch ® 570 (carbon black) — — — Aerosil ® R972 (hydrophobic fumed silica) 8.0 8.0 8.0 Catalyst .sup.c 1.0 1.0 1.0 .sup.a OH-term. PDMS: OH group-terminated polydimethylsiloxane; .sup.b Vinyl-term. PDMS: vinyl group-terminated polydimethylsiloxane having a viscosity to DIN 53018 of 20′000 mPa .Math. s; .sup.c organotin compound (dioctyltin dilaurate).

[0203] Influence of the Amount of Water

[0204] In order to study the influence of the amount of water in component B, experiments 7 to 9 were conducted. The mixtures were formulated and applied analogously to the preceding experiments 1-9. The compositions of experiments 7 to 9 are shown in table 4.

[0205] The test results are shown in table 5.

TABLE-US-00005 TABLE 5 Measurement data for pot life and mechanical properties of compositions 7 to 9. The mixing ratio of component A to component B was always 13:1 (w/w). Composition 7 Ref 8 9 Pot life [min] 18 9 8.5 Lap shear strength (7d SCC) [MPa] 1.28 1.49 1.52 Elongation at maximum shear force [%] 198 228 231 Tensile strength (7d RT) [MPa] 2.05 2.42 2.22 Force at 100% elongation [MPa] 1.3 1.73 1.64 Elongation at maximum tensile strength 229 176 169 [%] Shore A hardness (7d RT) 43 48 52 Tear propagation resistance [N/mm] 2.84 3.47 3.65

[0206] The data from table 5 show that, without water present in accordance with the invention, curing does take place, but the pot life becomes much longer and, surprisingly, the chemical data in reference example 7 are much worse.