SEALANT COMPOSITION

Abstract

A one-part low modulus room temperature vulcamsable (RTV) silicone composition comprising a titanate and/or zirconate catalyst which cures to a low modulus silicone elastomer which has a good adhesion profile and may be used as a non-staining (clean) sealant having high movement capability which compositions contains an aminosilane adhesion promoter having two hydroxyl or hydrolysable groups per molecule in an amount of 0.1-3.75% by weight of the composition.

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—Si—R.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 calcium carbonate reinforcing filler having a surface area of from 2.5 to 12 m.sup.2/g and an average particle size of >0.1 μm, in an amount of from 30 to 60% by weight of the composition; (c) one or more difunctional silane chain extenders having two hydroxyl or hydrolysable groups per molecule, in an amount of from 0.2 to 5% by weight of the composition; (d) a titanate and/or zirconate catalyst, in an amount of from 0.2 to 1.0% by weight of the composition; and (e) an aminosilane adhesion promoter having two hydroxyl or hydrolysable groups per molecule, in an amount of from 0.1 to 3.75% by weight of the composition; and optionally, further comprising: (f) one or more silane cross-linkers having at least three hydroxyl and/or hydrolysable groups per molecule, 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 the reinforcing filler (b) comprises a hydrophobically treated precipitated calcium carbonate having a surface area of from 5.0 to 12 m.sup.2/g and an average particle size of >0.1 μm.

4. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein the reinforcing filler (b) comprises a hydrophobically treated precipitated calcium carbonate wherein at least 75% of the particles are within a particle size distribution of 0.075 to 0.4 μm.

5. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein the aminosilane adhesion promoter (e) is of the general formula
R.sup.4(R′O).sub.2Si—Z.sup.1—N(H)—(CH.sub.2).sub.mNH.sub.2 in which R.sup.4 is an alkyl group containing from 1 to 10 carbon atoms; each R′ is the same or different and is H or R.sup.4, Z.sup.1 is a linear or branched alkylene group having from 2 to 10 carbon atoms, and m is from 2 to 10.

6. The one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1, wherein the aminosilane adhesion promoter (e) is N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane.

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 ≤0.45 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 sealant comprising or formed from the one-part room temperature vulcanisable (RTV) silicone composition in accordance with claim 1.

15. 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.

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

Description

EXAMPLES

[0074] The polymer viscosities mentioned were performed in accordance with Corporate test method CTM 0050, which is publicly available, and which is based on ASTM D 1084-16 method B, using a Brookfield HBDV-III Ultra Rheometer equipped with a cone-and-plate geometry using spindle 52. at room temperature (about 25° C.). The tests in accordance with ASTM D412-16 used dumbbell test pieces. The compositions were all prepared in a dental mixer using the following process at room temperature and pressure, unless otherwise indicated.

[0075] The ethylene trimethoxysilyl-terminated polydimethylsiloxane was first introduced into the mixer and was stirred and then the remaining ingredients were added and the composition was thoroughly mixed at each stage to generate the final composition.

[0076] The one-part silicone sealant composition was prepared to the formulations below in Tables 1a and 1b using a suitable mixer e.g. a Semco mixer in the amounts indicated. Several examples were prepared utilizing N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane as adhesion promoter, these are depicted in Table 1a.

TABLE-US-00001 TABLE 1a Composition of Examples 1-5 (weight %) Ingredient Type Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ethylene trimethoxysilyl-terminated polydimethylsiloxane 46.89 44.50 46.72 46.72 46.72 having a viscosity of about 65,000 mPa.s Polymer Vinylmethyldimethoxysilane 3.41 3.41 3.41 3.41 3.92 methyltrimethoxysilane 0.35 0.35 0.35 0.35 N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane 0.34 0.34 0.43 0.34 0.29 Titanium tetra-tert-butoxide 0.60 0.60 0.60 0.45 0.51 Treated precipitated calcium carbonate 1 48.40 50.44 48.13 48.46 47.90 Methylacetoacetate 0.36 0.36 0.36 0.27 0.31 100 100 100 100 100

[0077] A series of comparatives using alternative adhesion promoters but otherwise the same general sealant compositions were also prepared using the compositions depicted in Table 1b. Treated precipitated calcium carbonate 1 has a surface area (BET method) of 9.8 m.sup.2/g and an average particle size determined by size exclusion microscopy (SEM) and image analysis of about 0.15 μm.

TABLE-US-00002 TABLE 1b Composition of Comparative Examples C1-C3 (weight %) Ingredient C1 C2 C3 Ethylene trimethoxysilyl-terminated polydimethylsiloxane 44.50 44.50 44.50 having a viscosity of about 65,000 mPa.s Vinylmethyldimethoxysilane 3.41 3.41 3.41 methyltrimethoxysilane 0.35 0.35 0.35 N-(2-aminoethyl)-3-aminopropyltrimethoxysilane 0.34 Adhesion Promoter 2 0.34 bis (3-trimethoxysilylpropyl)amine 0.34 Titanium tetra-tert-butoxide 0.60 0.60 0.60 Treated precipitated calcium carbonate 1 50.44 50.44 50.44 Methylacetoacetate 0.36 0.36 0.36 Total 100 100 100

[0078] Adhesion Promoter 2 was the reaction product of trimethoxymethylsilane; 3-aminopropyl trimethoxysilane and glycidoxypropyl trimethoxysilane. Regarding the comparative adhesion promoters, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is very similar to N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane in structure, but the former has a propyl group as opposed to an isobutyl group and is a trifunctional silane as opposed to a difunctional silane. The bis (3-trimethoxysilylpropyl)amine has two trifunctional silane groups. Adhesion Promoter 2 is a reaction product of a mixture of amino silanes and epoxide silanes.

[0079] All the compositions were mixed in the same manner and cured for twenty one days before testing unless otherwise indicated. Test pieces were then utilised to assess physical properties.

[0080] Tensile Strength, elongation and modulus at 100% extension were measured using ASTM D412-16, test method A. A 75 mL of slab material was drawn down on a polyethylene film and cured for 21 days at room temperature. Dumbbell test pieces (sometimes referred to as “Dogbones”) were cut using die DIN S2 and pulled on MTS Systems Corp Alliance RT/5 Testing Machine at 50.8 cm/min using 100 N load cell. Data was collected and analyzed using Test Works Elite V 4.3.1 Software systems. The results are an average of three dumbbells per slab. Shore A durometer tests were made in accordance with ASTM D2240-15. The results are depicted in Tables 2a, 2b and 2c.

TABLE-US-00003 TABLE 2a Durometer, tensile strength and elongation for the comparative and inventive examples. Ex. Ex. Ex. Ex. Ex. C1 C2 C3 1 2 3 4 5 Durometer 42 38 34 27 30 29 28 29 (Sh. A) Tensile 1.93 1.92 2.27 1.6 2.01 2.37 2.09 2.03 Strength (MPa) Elongation 743 911 1158 1387 1251 1408 1443 1264 (%)

TABLE-US-00004 TABLE 2b Modulus results at specific Extensions for Examples 1 to 5 (ASTM D 412-16) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Modulus (MPa) at an extension of 12.5% 0.18 0.17 0.19 0.17 0.20 Modulus (MPa) at an extension of 25% 0.24 0.25 0.27 0.24 0.27 Modulus (MPa) at an extension of 50% 0.30 0.32 0.34 0.32 0.34 Modulus (MPa) at an extension of 100% 0.36 0.39 0.41 0.39 0.42 Modulus (MPa) at an extension of 150% 0.39 0.44 0.45 0.44 0.46 Modulus (MPa) at an extension 200% 0.42 0.48 0.49 0.48 0.50

TABLE-US-00005 TABLE 2c Stress results at specific Strains for Comparatives 1 to 3 (ASTM D 412-16) C1 C2 C3 Modulus (MPa) at an extension of 12.5% 0.25 0.28. 0.23 Modulus (MPa) at an extension 25% 0.40 0.35 0.32 Modulus (MPa) at an extension 50% 0.53 0.45 0.41 Modulus (MPa) at an extension of 100% 0.69 0.55 0.5 Modulus (MPa) at an extension of 150% 0.81 0.63 0.56 Modulus (MPa) at an extension of 200% 0.90 0.69 0.61

[0081] It may be appreciated from Tables 2b and 2c that the lowest modulus can be obtained with the inventive example.

[0082] Peel strength or Adhesion-in-peel results were tested according to ASTM C794-18 with the following modifications. The stainless-steel screens were cleaned with xylene and primed using DOWSIL™ 1200 OS primer. The substrates were cleaned using isopropanol and allowed to dry. No tape was used to make the peel but any excess along the screen was cut using a knife and trimmed to 1.27 cm width before pulling. The samples were pulled on a tensiometer (Instron or MTS Alliance RT/5, Texture Analyzer), at a rate of 5.08 cm/min for a distance of 2.54 cm. The data reported are after 21 days cure at room temperature. It was deemed that a peel strength to any substrate was sufficiently strong if it was ≥3.0 kN/m and the modulus at 100% extension was deemed acceptable if in the range of 0.207-0.448 MPa. All the examples shown above passed all of these criteria but only the result of Ex. 2 is shown in the results Tables 3a merely as improvements.

TABLE-US-00006 TABLE 3a Peel strength or Adhesion-in-peel results for Ex. 2 and C1-C3 on glass, anodized aluminum, brick, and fluoropolymer coating. Examples Substrates C1 C2 C3 Ex. 2 Glass (kN/m) 5.19 8.34 8.96 5.17 std dev 0.18 0.46 0.70 0.47 Anodized (kN/m) 1.88 3.17 4.73 4.89 aluminum std dev 0.11 0.25 0.49 0.39 Brick (kN/m) 6.63 7.78 6.91 4.47 std dev 0.60 0.49 1.93 2.07 Fluoropolymer (kN/m) 0.00 1.00 0.82 3.70 coating std dev 0.00 0.09 0.07 0.19

[0083] Based on the criteria set only the Example 2 results in Table 3a were good enough to pass every criteria, the comparatives were only partially successful. As shown, the comparative compositions only passed some. The passing of the criteria based on the results in Table 3a above is indicated by the ticks shown in Table 3b below.

TABLE-US-00007 TABLE 3b Measurements Criteria C1 C2 C3 Ex. 2 Adhesion to glass 3.0 kN/m ✓ ✓ ✓ ✓ Adhesion to brick 3.0 kN/m ✓ ✓ ✓ ✓ Adhesion to anodized 3.0 kN/m ✓ ✓ aluminum Adhesion to fluoropolymer 3.0 kN/m ✓ coating 100% Modulus 0.207-0.448 ✓ MPa

[0084] Only Ex. 2 was found to have a consistent adhesion profile for the 4 tested substrates when compared with the 3 comparative examples. For one-part silicone sealant compositions utilizing titanate and/or zirconate catalysts, adhesion to both brick and fluoropolymer coating is challenging and was demonstrated successfully only when using a dimethoxy silane such as N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane as the adhesion promoter. The one-part condensation curable low modulus room temperature vulcanisable (RTV) silicone compositions as hereinbefore described gave much better results than the comparatives using alternative adhesion promoters.

[0085] A further set of the Examples Ex. 1 to Ex. 5 were prepared and cured and tested as described above with respect to Peel strength or Adhesion-in-peel on different substrates to show that the adhesion of these compositions is functioning on other substrates as well as those given previously. They were specifically tested on porous stones substrates as well as a fluoropolymer coated substrate all of which are known to be problematic to adhere to for these types of sealant compositions. Testing was undertaken as described above and the same criteria was relied on with respect to whether adhesion was successful or not. The results are depicted in Table. 4a below and the criteria passed is shown in Table 4b.

TABLE-US-00008 TABLE 4a Peel strength or Adhesion-in-peel results for Examples Ex. 1 to Ex. 5 on brick, marble, fluoropolymer coating, and limestone. Examples Ex. Ex. Ex. Ex. Ex. Substrates 1 2 3 4 5 Brick kN/m 6.24 4.21 5.52 4.31 5.75 Std Dev 0.33 0.39 0.28 0.26 0.44 Marble kN/m 2.23 3.23 5.05 5.73 2.86 Std Dev 0.05 0.14 0.68 0.32 0.07 Fluoropolymer kN/m 3.49 3.93 3.82 3.14 4.36 coating Std Dev 0.27 0.16 0.11 0.10 0.23 Limestone kN/m 3.77 3.45 3.07 4.00 3.44 Std Dev 0.23 0.09 0.18 0.24 0.12

TABLE-US-00009 TABLE 4b Ex. Ex. Ex. Ex. Ex. Measurements Criteria 1 2 3 4 5 Adhesion to brick 3.0 kN/m ✓ ✓ ✓ ✓ ✓ Adhesion to marble 3.0 kN/m ✓ ✓ ✓ ✓ ✓ Adhesion to 3.0 kN/m ✓ ✓ ✓ ✓ ✓ fluoropolymer coating Adhesion to limestone 3.0 kN/m ✓ ✓ ✓ ✓ ✓ 100% Modulus 0.207-0.448 MPa ✓ ✓ ✓ ✓ ✓

[0086] It will be seen that peel strength or adhesion-in-peel results with the exception of composition Ex. 2 on marble passed.

[0087] The compositions above all used treated precipitated calcium carbonate 1 as the filler. It was decided to compare results of such formulations, exemplified here in Table. 5 by Ex. 2 again, with some precipitated calcium carbonate fillers commonly used in silicone sealant formulations. Comparative 4 utilised Ultra-PFLEX® precipitated calcium carbonate and comparative 5 utilised Winnofil®SPM precipitated calcium carbonate as shown in Table 5 below.

TABLE-US-00010 TABLE 5 Composition of Comparative Examples 4 and 5 (weight %) Ingredient Type C4 (wt. %) C5 (wt. %) Ethylene trimethoxysilyl-terminated 44.5 44.5 polydimethylsiloxane having a viscosity of about 65,000 mPa.s Vinylmethyldimethoxysilane 3.41 3.41 methyltrimethoxysilane 0.35 0.35 N-(2-aminoethyl)-3- 0.34 0.34 aminoisobutylmethyldimethoxysilane Titanium tetra-tert-butoxide 0.60 0.60 Ultra-PFLEX® precipitated calcium carbonate 50.44 Winnofil® SPM precipitated calcium carbonate 50.44 treated precipitated calcium carbonate 1 Methylacetoacetate 0.36 0.36

[0088] Ultra-PFLEX® precipitated calcium carbonate is a commonly used hydrophobically treated precipitated calcium carbonate in silicone sealant compositions from Specialty Minerals having an average particle size of about 0.07 m (supplier information test method not supplied) and a surface area of about 21 m.sup.2/g (supplier information test method not supplied). Winnofil®SPM is a commonly used hydrophobically treated precipitated calcium carbonate is another commonly used precipitated calcium carbonate in silicone sealant compositions from Imerys having an average particle size of <0.1 μm (supplier information test method not supplied) and a surface area of from about 15 to 24 m.sup.2/g (BET Method), no further details provided.

[0089] The comparative examples therefore have higher surface areas and lower particle sizes than treated precipitated calcium carbonate 1 used in all the above examples and comparatives.

The compositions were prepared in an analogous fashion to those described above and were cured for 21 days before they were tested for their physical properties.

TABLE-US-00011 TABLE 6a Durometer, tensile, elongation and stress at different strain for the comparative and inventive examples using different fillers. C4 C5 Ex. 2 Durometer (Sh. A) 44 53 33 Tensile (MPa) 3.16 3.57 1.82 Elongation (%) 895 775 1194

TABLE-US-00012 TABLE 6b Stress results at specific Strains for comparatives 4 and 5 compared to Ex. 2 C4 C5 Ex. 2 Modulus (MPa) at an extension of 12.5% 0.26 0.36 0.20 Modulus (MPa) at an extension of 25% 0.38 0.55 0.28 Modulus (MPa) at an extension of 50% 0.53 0.77 0.36 Modulus (MPa) at an extension of 100% 0.78 1.10 0.43 Modulus (MPa) at an extension of 150% 1.00 1.38 0.46 Modulus (MPa) at an extension of 200% 1.20 1.65 0.50

[0090] It will be appreciated that Ex. 2 had a much lower modulus.

[0091] Peel strength or Adhesion-in-peel results were tested according to ASTM C794-18 with the same modifications as described above. The resulting Peel strength or Adhesion-in-peel values are provided in Table 7a below with an indication of successfully passing the criteria identified indicated in Table 7b.

TABLE-US-00013 TABLE 7a Peel strength or Adhesion-in-peel results for C4 and C5 compared to Ex. 2 on glass, anodized aluminum, brick, and fluoropolymer coating. Example Substrates C4 C5 Ex. 2 Glass (kN/m) 13.3 12.4 9.1 std dev 1.9 3.0 1.5 Anodized aluminum (kN/m) 15.6 16.4 9.9 std dev 2.0 1.6 1.1 Brick (kN/m) 6.0 2.4 5.2 std dev 1.6 0.1 0.6 Fluoropolymer coating (kN/m) 2.3 1.3 4.4 std dev 0.2 0.1 0.6

TABLE-US-00014 TABLE 7b Measurements Criteria C4 C5 Ex. 2 Adhesion to glass 3.5 kN/m ✓ ✓ ✓ Adhesion to Anodized Aluminum 3.5 kN/m ✓ ✓ ✓ Adhesion to brick 3.5 kN/m ✓ ✓ Adhesion to Fluoropolymer 3.5 kN/m ✓ coating 100% Modulus 0.207-0.448 ✓ MPa

[0092] It will be appreciated that the only composition out of C4, C5 and Ex. 2, used here as an example of the disclosure herein, which results in a low modulus sealant is Ex. 1. It will also be appreciated that comparing these comparatives with Ex. 2 it can be seen Ex. 1 had a comparatively good/consistent adhesion profile.