SEALANT COMPOSITION

Abstract

A one-part room temperature vulcanisable (RTV) silicone composition containing a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate salt which cures to a silicone elastomer which may be used as a clear sealant which avoids discolouration and loss of adhesion upon aging.

Claims

1. A one-part room temperature vulcanisable (RTV) silicone composition comprising: (a) an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule and of the general formula
X.sub.3-nR.sub.nSi—(Z).sub.d—(O).sub.q—(R.sup.1.sub.ySiO.sub.(4-y)/2).sub.z—(SiR.sup.1.sub.2—Z).sub.d—SiR.sub.nX.sub.3-n  (1) in which each X is independently a hydroxyl group or a hydrolysable group, each R is an alkyl, alkenyl or aryl group, each R.sup.1 is an X group, alkyl group, alkenyl group or aryl group and Z is a divalent organic group; d is 0 or 1, q is 0 or 1 and (d+q)=1; n is 0, 1, 2 or 3, y is 0, 1 or 2, or optionally y is 2, and z is an integer such that organopolysiloxane polymer a)_has a viscosity of from 10,000 to 75,000 mPa.Math.s at 25° C., or optionally 10,000 to 60,000 mPa.Math.s at 25° C.; (b) a reinforcing filler comprising or consisting of fumed or pyrogenic silica filler which is optionally hydrophobically treated, in an amount of from about 5 to about 25 parts by weight per 100 parts by weight of organopolysiloxane polymer (a); (c) a silane adhesion promoter, in an amount of from about 0.10 to about 2.0 parts by weight per 100 parts by weight of organopolysiloxane polymer (a); and (d) a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate salt; and optionally, further comprising: (e) is cross-linker; and/or (f) is hydroxy scavenging agent selected from a disilazane or polysilazane.

2. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein organopolysiloxane polymer (a) is of the general formula
X.sub.3-nR.sub.nSi—(Z)—(R.sup.1.sub.ySiO.sub.(4-y)2).sub.z—(SiR.sup.1.sub.2—Z)—SiR.sub.nX.sub.3-n wherein n is 0 or 1, each of R, Z, R.sup.1, y, and z is as defined above, and each X is an alkoxy group.

3. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein catalyst (d) is the titanate (i) and is selected from the group consisting of tetra-n-butyl titanate, tetra-isopropyl titanate, tetra-(2-ethylhexyl)titanate, and combinations thereof, and optionally wherein catalyst (d) is chelated.

4. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein catalyst (d) is the metal carboxylate salt (ii) and the metal of the metal carboxylate salt (ii) is selected from the group consisting zinc, aluminium, bismuth, zirconium, and combinations thereof.

5. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein catalyst (d) is the metal carboxylate salt (ii) and is selected from the group consisting of zinc (II) carboxylates, aluminium (III) carboxylates, bismuth (III) carboxylates, zirconium (IV) carboxylates, zinc (II) alkylcarboxylates, aluminium (III) alkylcarboxylates, bismuth (III) alkylcarboxylates, zirconium (IV) alkylcarboxylates, and combinations thereof.

6. The A-one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein catalyst (d) is the metal carboxylate salt (ii) and is selected from the group consisting of zinc ethylhexanoate, bismuth ethylhexanoate, zinc stearate, zinc undecylenate, zinc neodecanoate, and iron (III) 2-ethylhexanoate.

7. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein the titanate and/or zirconate (i) and the metal carboxylate salt (ii) of catalyst (d) is provided in a molar ratio of 1:4 to 4:1.

8. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein the composition comprises from 0.33 to 5.3 parts by weight of catalyst (d); 0 to 8 parts by weight of cross-linker (e); and 0 to 8 parts by weight of hydroxy scavenging agent (f); in each case relative to 100 parts by weight of organopolysiloxane polymer (a).

9. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein the composition additionally comprises one or more plasticisers.

10. A method of making the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, the method comprising mixing all of the ingredients together.

11. An elastomeric sealant material which is the cured product of the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1.

12. The elastomeric sealant material in accordance with claim 11, which is a clear sealant.

13. A sealant suitable for use in the facade, insulated glass, window construction, automotive, solar and construction fields, wherein the sealant comprises or is formed from the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1.

14. A method for filling a space between two substrates so as to create a seal therebetween, the method comprising: a) providing the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, either b) or c): b) applying the silicone composition to a first substrate, and bringing a second substrate in contact with the silicone composition that has been applied to the first substrate, or c) filling a space formed by the arrangement of a first substrate and a second substrate with the silicone composition and curing the silicone composition.

Description

EXAMPLES

[0072] Compositions supporting the disclosure herein as well as comparative compositions using standard titanate catalysts were prepared using the compositions identified in Tables 1a and 1b below.

TABLE-US-00001 TABLE 1a composition of Examples determined parts by weight per 100 parts of Trimethoxysilyl capped PDMS polymer Ingredients Ex. 1 Ex. 2 Trimethoxysilyl capped PDMS polymer, 100 100 viscosity 65,000 mPa .Math. s Trimethyl terminated polydimethylsiloxane 12.58 12.58 viscosity 1000 mPa .Math. s AEROSIL ® R812(S) treated fumed silica 11.39 11.39 methyltrimethoxysilane 5.83 5.83 Adhesion Promoter 2.65 2.65 Catalyst 1 3.97 Catalyst 2 4.37

[0073] In Table 1a:

AEROSIL® R812(S) is a hexamethyldisilazane treated fumed silica, having a BET surface area of 300 m.sup.2/g, from Evonik (manufacturers value); [0074] catalyst 1 was a tetra isopropyl titanate: Ethylhexanoic acid zinc salt (Zn(EHA).sub.2)mixture in a ratio by weight of 2:1 (6 mmol of Ti and 3 mmol of Zn); Catalyst 2 was a tetra tertiary butyl titanate: Ethylhexanoic acid zinc salt (Zn(EHA).sub.2) mixture in a ratio by weight of 2:1;
The adhesion promoter used was the reaction product of (i) trimethoxymethylsilane, (ii) 3-aminopropyl trimethoxysilane and (iii) glycidoxypropyl trimethoxysilane.

[0075] It will be appreciated that the provision of the amounts of ingredients in parts by weight relative to 100 parts Trimethoxysilane capped PDMS polymer does not require the total composition to add up to 100 as would have been necessary if using Wt. %.

TABLE-US-00002 TABLE 1b composition of Comparative Examples determined parts by weight per 100 parts of Trimethoxysilyl capped PDMS polymer Comp. Comp. Comp. Ingredients 1 2 3 Trimethoxysilyl capped PDMS polymer, 100 100 100 viscosity 65,000 mPa .Math. s Trimethyl terminated polydimethylsiloxane 12.58 12.58 12.58 viscosity 1000 mPa .Math. s AEROSIL ® R812(S) treated fumed silica 11.39 11.39 11.39 methyltrimethoxysilane 5.83 5.83 5.83 Adhesion Promoter 2.65 2.65 2.65 tetra isopropyl titanate 2.25 Tetra tertiary butyl titanate 2.65 Ethylhexanoic acid zinc salt (Zn(EHA).sub.2) 1.72

[0076] In the compositions of Table 1b the catalyst consisted of 6 mmol of Ti and 3 mmol of Zn. The compositions were cured for 7 days at room temperature unless otherwise indicated and then were analysed for their physical properties. All testing in accordance with ASTM D412-98a(2002)e 1 were undertaken using dumbbell shaped test pieces.

TABLE-US-00003 TABLE 2a Physical Properties of Examples Properties Test Method Ex. 1 Ex. 2 Tack Free Time (TFT) (min) ASTM C679-15 24 14 Cure in Depth (CID) (mm/3 d) 4.1 4.05 Tensile Strength (MPa) ASTM D412-98a(2002)e1 1.92 2.02 Elongation (%) ASTM D412-98a(2002)e1 342.96 345.99 Modulus at 100% extension ASTM D412-98a(2002)e1 0.72 0.75 Shore A hardness ASTM D2240-97 29.9 31.4 Adhesion Aluminum Cohesive Failure ASTM C794-18 100 100 (CF %) Adhesion Aluminum 180° Peel Strength ASTM C794-18 5667.2 5898.4 (N/m) Adhesion Glass (CF %) ASTM C794-18 100 100 Adhesion Glass 180° Peel Strength (N/m) ASTM C794-18 5257.4 4646.2 Tensile Strength after aging at ASTM D412-98a(2002)e1 1.002 0.889 180° C. for 7 days (MPa) Elongation after aging at ASTM D412-98a(2002)e1 300.817 263.957 180° C. for 7 days (%) Shore A hardness after aging ASTM D2240-97 20 21.5 at 180° C. for 7 days

[0077] The cure in depth tests were undertaken to determine how far below the surface the sealant had hardened in 24 hours by filling a suitable container (avoiding the introduction of air pockets) with sealant, curing the sealant contained in the container for the appropriate period of time at room temperature (about 23° C.) and about 5000 relative humidity. After the appropriate curing time the sample is removed from the container and the height of the cured sample is measured.

[0078] The adhesion assessment results, were determined using the Dow Corporate Test method CTM 0293 which is publicly available and is based on ASTM D 903. Cohesive failure is Cohesive failure (CF) is observed when the coating itself breaks without detaching from the substrate (for example, steel plate). In some cases, a mixed failure mode may be observed; that is some areas peel-off (i.e. AF) while some remain covered with coating (i.e. CF). In such cases, the portions of surface displaying CF (% CF)

TABLE-US-00004 TABLE 2b Physical Properties of Comparative Examples Properties Test Method Comp. 1 Comp. 2 Comp. 3 Tack Free Time (TFT) (min) ASTM C679-15 80 37 >480 Cure in Depth (CID) (mm/3 d) 4.08 3.85 N.A. Tensile Strength (MPa) ASTMD412- 1.95 2.09 0.09 98a(2002)e1 Elongation (%) ASTM D412- 352.82 357.15 13.79 98a(2002)e1 Modulus at 100% extension ASTM D412- 98a(2002)e1 Shore A hardness ASTM D2240-97 27.2 29.5 N.A. Adhesion Aluminum (A1) (CF %) ASTM C794-18 100 100 0 Adhesion A1 180° Peel Strength (N/m) ASTM C794-18 4287.2 5324.0 <876 Adhesion Glass (CF %) ASTM C794-18 100 60 0 Adhesion Glass 180° Peel Strength (N/m) ASTM C794-18 4646.2 2837.1 <876 Tensile Strength after aging at 180° C. ASTM D412- 0.902 1.072 1.236 for 7 days (MPa) 98a(2002)e1 Elongation after aging at 180° C. for 7 ASTM D412- 343.75 371.941 513.918 days(%) 98a(2002)e1 Shore A hardness after aging ASTM D412- 16.5 18 13.5 at 180° C. for 7 days 98a(2002)e1

[0079] It can be seen that the Examples provided faster cure speed (indicated by TFT) compared to the comparative examples. While the metal salt Zn(EHA).sub.2 didn't show obvious cure properties (Comp.3), it can have synergy effect when added to Titanate. (Ex. 1 and 2).

[0080] Samples were aged to assess their long-term adhesion properties and their propensity for yellowing.

[0081] The Colour L*a*b* analysis was carried out using a CM-700d spectrophotometer from Konica Minolta Sensing Co., Ltd. Japan. The b value relates to yellowing. Test pieces used were dumbbell shaped.

[0082] Long term adhesion was assessed using both UV and QUV aging techniques followed by using a 1800 peel test in accordance with ASTM C794-18 results. In the case of UV aging after 7 days curing at room temperature, samples were put into a UV aging test chamber, Model SF/ZN-T available from Hefei Saifor Test Equipment Co., Ltd. Which had glass sides. Samples were exposed to UVA-340 nm Lamp at a distance of 20 cm with the chamber temperature maintained at about 45° C.

[0083] QUV aging is a standard accelerated weathering testing test adapted to mimic the real weather conditions using both light and water spray. The aging process was undertaken in a QUV-SPRAY Model unit manufactured by Q-Lab. The aging process followed ASTM G151-10 and G155-13. (the machine was Model, QUV-SPRAY manufactured by Q-Lab, Model, QUV-SPRAY).

TABLE-US-00005 TABLE 3a Colour Testing and Adhesion testing after Aging of Examples Properties Test Method Ex. 1 Ex. 2 Colour L*a*b* (after aging at 180° C. for 7 days) L* 77.73 79.82 a* −2.37 −2.78 b* 21.29 17.22 Adhesion GL UV 500 h (CF) (%) ASTMC794-18 100 100 Adhesion GL UV 500 h 180° Peel Strength (N/m) ASTMC794-18 5043.7 5113.8 Adhesion GL UV 1500 h (CF %) ASTMC794-18 100 100 Adhesion GL UV 1500 h 180° Peel Strength (N/m) ASTMC794-18 4255.7 4150.6 Adhesion GL UV 2000 h (CF %) ASTMC794-18 100 100 Adhesion GL UV 2000 h 180° Peel Strength (N/m) ASTMC794-18 3747.8 4535.9 Adhesion GL QUV 500 h (CF %) ASTM C794-18 40 0 Adhesion GL QUV 500 h 180° Peel Strength (N/m) ASTM C794-18 3660.2 2767.1 Adhesion AL QUV 500 h (CF %) ASTM C794-18 100 100 Adhesion AL QUV 500 h 180° Peel Strength (N/m) ASTM C794-18 4080.5 4693.5 Adhesion AL QUV 1000 h (CF %) ASTM C794-18 80 100 Adhesion AL QUV 1000 h 180° Peel Strength (N/m) ASTM C794-18 4220.6 3852.9

TABLE-US-00006 TABLE 3b Colour Testing and Adhesion testing after Aging of Comparative Examples Properties Test Method Comp. 1 Comp. 2 Comp. 3 Colour L*a*b* (180° C. 7 d) L* 74.38 76.96 79.68 a* −0.99 −1.97 −2.8 b* 30.89 26.18 14.23 Adhesion GL UV 500 h (CF %) ASTMC794-18 100 100 0 Adhesion GL UV 500 h 180° Peel ASTMC794-18 3064.8 3782.8 665.5 Strength (N/m) Adhesion GL UV 1500 h (CF %) ASTMC794-18 100 80 0 Adhesion GL UV 1500 h 180° Peel ASTMC794-18 2119.1 1453.6 0.0 Strength (N/m) Adhesion GL UV 2000 h (CF %) ASTMC794-18 100 0 0 Adhesion GL UV 2000 h 180° Peel ASTMC794-18 2627.0 945.7 0.0 Strength (N/m) Adhesion GL QUV 500 h (CF %) ASTMC794-18 0 0 100 Adhesion GL QUV 500 h 180° Peel ASTMC794-18 262.7 262.7 3152.3 Strength (N/m) Adhesion AL QUV 500 h (CF %) ASTMC794-18 50 100 100 Adhesion AL QUV 500 h 180° Peel ASTMC794-18 3117.3 3432.5 3502.6 Strength (N/m) Adhesion AL QUV 1000 h (CF %) ASTMC794-18 0 95 0 Adhesion AL QUV 1000 h 180° Peel ASTMC794-18 1506.1 2942.2 980.7 Strength (N/m)

[0084] It can be seen that, in the coloration testing after aging, the examples in accordance with the disclosure clearly show a lower value for b* indicating less yellowing than the comparatives using previous catalysts. It will also be appreciated that the compositions as described herein provide elastomers which perform better in the peel testing after aging than the comparative examples.