SEALANT COMPOSITION

Abstract

A one-part low modulus 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 low modulus silicone elastomer which may be used as a non-staining (clean) sealant having high movement capability.

Claims

1. A one-part condensation curable low modulus 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 30,000 to 80,000 mPa.Math.s at 25° C., or optionally from 40,000 to 75,000 mPa.Math.s at 25° C., in an amount of from 35 to 60% by weight of the composition; (b) a hydrophobically treated reinforcing filler in an amount of from 30 to 55% by weight of the composition; (c) one or more difunctional silanes, in an amount of from 0.5 to 5% by weight of the composition; (d) a catalyst comprising (i) a titanate and/or zirconate and (ii) a metal carboxylate; (e) an adhesion promoter, in an amount of from 0.1 to 1% by weight of the composition; and (f) one or more reactive silanes having at least three functional groups in an amount of from 0 to 3% by weight of the composition.

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 metal carboxylate salt (ii) and the metal of the metal carboxylate salt (ii) is selected from the group consisting of zinc, aluminium, bismuth, zirconium, and combinations thereof.

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 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.

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 ethylhexanoate, bismuth ethylhexanoate, zinc stearate, zinc undecylenate, zinc neodecanoate, and iron (III) 2-ethylhexanoate.

6. 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.

7. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, which is gunnable and/or self-levelling.

8. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, capable of being applied as a paste to a joint between two adjacent substrate surfaces where it can be worked, prior to curing, to provide a smooth surfaced mass which will remain in its allotted position until it has cured into an elastomeric body adherent to the adjacent substrate surfaces.

9. A silicone elastomer which is the reaction product of the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1.

10. The silicone elastomer in accordance with claim 9, which upon cure provides a sealant with a low modulus of ≤0.4 MPa at 100% elongation.

11. The silicone elastomer in accordance with claim 9, which is non-staining.

12. 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.

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, and 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.

15. The method for filling a space between two substrates in accordance with claim 14, wherein the space is filled by introducing the silicone composition by way of extrusion or through a sealant gun.

Description

EXAMPLES

[0113] The viscosity test was performed Brookfield DVIII Ultra with cone 52 under 5 rpm for 2 mins. Compositions were mixed and measured at room temperature (about 25° C.). The tests in accordance with ASTM D412-98a (2002) e1) used dumbbell test pieces.

[0114] A silicone masterbatch was prepared using the ingredients in Table 1a. The masterbatch was then used in each example/comparative example in combination with the catalyst indicated in Table 1b below.

TABLE-US-00001 TABLE 1a Silicone Masterbatch Ingredients % weight Trimethoxysilyl-terminated 46.5 polydimethylsiloxane having a viscosity of about 60,000 mPa .Math. s Vinylmethyldimethoxysilane 3.0 methylltrimethoxysilane 0.8 Precipitated calcium carbonate 30.5 Ground calcium carbonate 19.2

[0115] The ground calcium carbonate used was type 203A (4.6 μm) obtained from Qunxin Powder Technology and the precipitated calcium carbonate used in the masterbatch was XTCC 201 (60-70 nm with surface area 20 m.sup.2/g) from Xintai Nano Material. It is understood that both fillers were fatty acid treated.

[0116] The masterbatch was prepared in a Turello mixer using the following process at room temperature and pressure, unless otherwise indicated: [0117] The trimethoxysilyl-terminated polydimethylsiloxane was first introduced into the mixer and was stirred at 400 revolutions per minute (rpm) the methylvinyldimethoxy silane and methyltrimethoxy silane were then added and the mixture was mixed at 400 rpm for a further 5 min. The precipitated and ground calcium carbonates were then introduced gradually whilst mixing continued at 500 rpm. Once all the calcium carbonate had been introduced and mixed into the composition, the mixing speed was increased to 800 rpm and the mixture was mixed for a further two periods of 15 minutes under vacuum. After this the resulting masterbatch composition was stored until required.

[0118] The one-part silicone sealant composition was then prepared by mixing the masterbatch with the remaining ingredients using a Semco mixer in the amounts indicated in Table 1b below.

TABLE-US-00002 TABLE 1b Additional Ingredients added to the Masterbatch Comp. 1 Ex. 1 Ex. 2 Ingredients (wt. %) (wt. %) (wt. %) Silicone master batch 98.8 98.6 98.6 Tetra n-butyl titanate (TnBT) 0.1 0.1 0.1 N-(2-aminoethyl)-3-aminoisobutyl- 0.2 0.2 02 methyldimethoxysilane Standard chelated titanate catalyst 0.9 Catalyst 1 1.1 Catalyst 2 1.1

[0119] The Standard chelated Titanate catalyst was Diisopropoxy-bisethylacetoacetatotitanate supplied in combination with methyltrimethoxysilane in a weight ratio of 4:1; [0120] Catalyst 1 was a mixture of tetra tertiary butyl titanate (TtBT)+Ethylhexanoic acid zinc salt, (Zn(EHA).sub.2) in a weight ratio of 61:29; and [0121] catalyst 2 was a mixture of diisopropoxy-bisethylacetoacetatotitanate & Ethylhexanoic acid zinc salt, (Zn(EHA).sub.2) in a weight ratio of 16:9.

[0122] The compositions were cured at room temperature and pressure for 7 days after which the physical properties of different examples and comparative examples were then assessed. [0123] The results are summarized in Table 2a below. The tests in accordance with ASTM D412-98a (2002) e1 used dumbbell test pieces.

TABLE-US-00003 TABLE 2a Sealant physical properties after curing Comp. Ex. Ex. General properties 1 1 2 Skin over Time (SOT), min (ASTM C679-15) 18.00 19.00 19.00 Tack free time (TFT), min (ASTM C679-15) 47.00 47.00 53.00 Flow, mm (GB/T 13477.6) 4.00 4.50 3.00 Cure in depth (CID) after 1 day (mm) 1.79 1.92 1.53 CID after 2 days (mm) 2.65 2.75 2.60 Tensile Strength, MPa (Dumbell) 1.43 1.04 1.08 ASTM D412-98a (2002)e1) Elongation at Break (%)(ASTM 609.00 792.00 862.67 D412-98a (2002)e1) Modulus at 100% extension (MPa)(ASTM 0.49 0.37 0.34 D412-98a(2002)e1) Shore A hardness (ASTM C661-15) 23.80 18.60 18.15

[0124] 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 50% relative humidity. After the appropriate curing time the sample is removed from the container and the height of the cured sample is measured.

[0125] It can be seen that example 1 and 2 showed much lower tensile modulus than the comparative which used the traditional titanate catalyst alone while similar curing speed were obtained. As shown in sample preparation, high loading level of N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane were applied as polymer chain extender. However, with normal diisopropoxy-bisethylacetoacetatotitanate as catalyst, the cured sealant failed to meet the low modulus requirement (<0.4 MPa at 100% extension).However, catalysts using (Zn(EHA).sub.2 as part of the catalyst composition, gave sealant modulus reduced from 0.49 MPa to 0.37 MPa, even lower to 0.34 MPa, with other physical properties meeting performance expectations.

[0126] Samples of each example and the comparative were aged for 2 weeks at a temperature of 50° C. and then cured at 23° C. and 50% relative humidity for 7 days prior to assessment of their aging physical properties. The results are provided in Table 2b below.

TABLE-US-00004 TABLE 2b Physical property results after aging Aging 50° C. 2 Weeks Comp. 1 Ex. 1 Ex. 2 Skin over Time (SOT), min 80.00 80.00 80.00 (ASTM C679-15) Tack free time (TFT), min 120.00 120.00 150-170 (ASTM C679-15) Flow, mm (GB/ T 13477.6) 2.30 2.05 2.25 Cure in depth (CID) after 1 day (mm) 2.84 2.63 2.56 CID after 2 days (mm) 2.00 2.50 2.00 Tensile Strength, (MPa) (ASTM 1.23 0.86 1.01 D412-98a(2002)e1) Elongation at Break (%)(ASTM 872.67 889.00 947.33 D412-98a(2002)e1) Modulus at 100% extension (MPa) 0.31 0.22 0.22 (ASTM D412-98a(2002)e1) Shore A hardness (ASTM C661-15) 14.90 8.60 8.40

[0127] As shown, using catalyst as hereinbefore described results in a reduction in modulus at 100% extension of the one-part alkoxy non-staining (clean) sealant described herein without any sacrifice in the values of other properties. Hence compositions as described herein provide a practical way to make one-part alkoxy non-staining (clean) sealant to meet the low modulus standards.