POLYDIORGANOSILOXANE PREPARATION

Abstract

A process for end-capping a dimethylsilanol terminated polydiorganosiloxane with one or more di, tri and/or tetra alkoxysilanes in the presence of a basic end-capping catalyst starting material is provided. An acidic stabilizing/neutralising agent is subsequently added. The acidic stabilizing/neutralising agent is selected from one or more fatty acids having from 8 to 26 carbons; an alkane sulphonic acid having from 1 to 10 carbons; acidic fumed silica and/or one or more acidic liquid polybutadienes or a mixture thereof. The resulting capped polymeric material may be utilized as a polymer in, e.g., an organopolysiloxane elastomer composition.

Claims

1. A process for preparing an alkoxy-terminated polydiorganosiloxane from a silanol-terminated polydiorganosiloxane starting material, the process comprising: step (i) reacting the silanol terminated polydiorganosiloxane starting material with one or more polyalkoxy silane starting material(s) of the structure
(R.sup.2—O).sub.(4-b)—Si—R.sup.1.sub.b where b is 0, 1 or 2, R.sup.2 is an alkyl group having from 1 to 15 carbons and R.sup.1 is a monovalent hydrocarbon radical, optionally R.sup.1 is R.sup.2 or is selected from cycloalkyl groups, alkenyl groups, aryl groups, aralkyl groups aminoalkyl groups, (meth)acrylate groups, glycidyl ether groups and groups obtained by replacing all or part of the hydrogen in the preceding organic groups with halogen; in the presence of a basic end-capping catalyst starting material; and step (ii) adding an acidic stabilizing/neutralising agent selected from one or more fatty acids having from 8 to 26 carbons; an alkane sulphonic acid having from 1 to 10 carbons; acidic fumed silica and/or one or more acidic liquid polybutadienes or a mixture thereof.

2. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim h wherein the basic end-capping catalyst consists of one or more linear, branched or cyclic molecules comprising at least one amidine group, guanidine group, or derivatives of the amidine group and/or guanidine group or a mixture thereof in an amount of from 0.0005 to 0.75 wt. % of the starting materials composition.

3. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 2, wherein the amidine or guanidine group(s) in the end-capping catalyst are selected from silicon containing molecules or organic molecules containing one of the groups (1) to (4) depicted below: ##STR00006## wherein each R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.8 is the same or different and is selected from hydrogen, an alkyl group, a cycloalkyl group, a phenyl group, an aralkyl group or alternatively R.sup.4 and R.sup.5 or R.sup.6 and R.sup.5 or R.sup.7 and R.sup.5 or R.sup.8 and R.sup.4 may form optionally heterogeneously substituted alkylene group to form a ring structure, wherein the heterogeneous substitution is by means of an oxygen or nitrogen atom.

4. The process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein the end-capping catalyst is selected from 1,1,3,3-tetramethylguanidine, 2-[3-(trimethoxy silyl)prop yl]-1,1,3,3-tetramethylguanidine, 2-[3-(methyldimethoxysilyl)prop yl]-1,1,3,3-tetramethylguanidine, Triazabicyclodecene (1,5,7-Triazabicyclo[4.4.0]dec-5-ene), 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1,5-Diazabicyclo[4.3.0]non-5-ene, and/or 1,8-diazabicyclo[5.4.0]undec-7-ene.

5. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein the stabilizing/neutralising agent is selected from one or more fatty acids having from 10 to 20 carbons; an alkane sulphonic acid having from 1 to 10 carbons; acidic fumed silica and/or one or more anhydride functionalised liquid polybutadienes or a mixture thereof.

6. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein the stabilizing/neutralising agent is selected from oleic acid, acidic fumed silica, a maleic anhydride adduct of a low molecular weight 1,4-cis polybutadiene which has succinic anhydride groups randomly distributed along the polymer chains, or a mixture thereof.

7. The process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein the acidic fumed silica of the stabilizing/neutralising agent either is or is not pre-treated to render it hydrophobic prior to addition.

8. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein after adding the acidic stabilizing/neutralising agent the alkoxy terminated polydiorganosiloxane final product is stored for a period of up to 12 months prior to use.

9. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein the one or more polyalkoxy silane(s) are provided in excess such that unreacted polyalkoxy silane is available to function as a cross-linker when utilised for making an organopolysiloxane elastomer composition.

10. The process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein the alkoxy terminated polydiorganosiloxane is subsequently used as an ingredient in an organopolysiloxane elastomer composition by mixing the following ingredients: (a) the alkoxy terminated polydiorganosiloxane end-product prepared in accordance with the preceding process; (b) filler; (d) a condensation cure catalyst; and optionally (c) cross-linker; and/or (e) adhesion promoter.

11. The A-process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim 1, wherein step (ii) takes place after step (i) with the stabilizing/neutralising agent being added to an alkoxy terminated polydiorganosiloxane polymer reaction end-product in an amount of from 0.05 to 2.5 wt. % of the starting materials.

12. The process for preparing an alkoxy terminated polydiorganosiloxane in accordance with claim Mc wherein step (ii) takes place during the preparation organopolysiloxane elastomer composition with the stabilizing/neutralising agent being added in an amount of from 0.05 to 2.5 wt. % of the starting materials.

13. An alkoxy end-capped, polydiorganosiloxane polymer obtainable or obtained from the process of claim 1.

14. An organopolysiloxane elastomer composition obtainable or obtained from the process of claim 10.

15. A silicone elastomer which is the reaction product obtained by curing the organopolysiloxane elastomer composition prepared in accordance with claim 10.

16. An alkoxy terminated polydiorganosiloxane prepared in accordance with the process of claim 1, present in a sealant in at least one of the facade, insulated glass, window construction, automotive, solar and construction fields.

Description

EXAMPLES

[0181] All viscosity measurements were undertaken using a Brookfield® rotational viscometer with spindle LV-4 (designed for viscosities in the range between 1,000-2,000,000 mPa.Math.s and adapting the speed according to the polymer viscosity, unless otherwise indicated and measurements were taken at 25° C.

TABLE-US-00001 TABLE 1 Starting materials used to prepare alkoxy end-capped polymer - proportions of each starting material and acidic stabilizing/neutralising agent provided in grams Material Comp. Ex. 1 Ex. 1 Ex. 2 Ex. 3 Polymer 1 50 50 50 50 Vinyl trimethoxy silane 1.4 1.4 1.4 1.4 Methyl trimethoxy silane (MTM) 1.4 1.4 1.4 1.4 1 wt. % TBD in MTM 0.2 0.2 0.2 0.2 Oleic acid 0.1 0.2 Polyvest ® MA 75 0.1

[0182] Polymer 1 indicated in Table 1 was a dimethylsilanol terminated polydimethyl siloxane having a viscosity of about 50,000 mPa.Math.s which was alkoxy end-capped during the reaction described below. TBD was 1,5,7-Triazabicyclo[4.4.0]dec-5-ene. Polyvest® MA 75 was obtained from Evonik Corporation and is defined in the manufacturer's datasheet as “a maleic anhydride functionalized adduct of a low molecular weight 1,4-cis liquid polybutadiene which has succinic anhydride groups randomly distributed along the polymer chains”.

[0183] The alkoxy end-capping reaction was carried out using the following process in a speed mixer: [0184] 1) A 1 wt. % solution of TBD end-capping catalyst in methyl trimethoxy silane was initially prepared by dissolving TBD end-capping catalyst in methyl trimethoxy silane to prepare an end-capping catalyst solution; [0185] 2) The polymer, vinyl trimethoxy silane, methyl trimethoxy silane and catalyst solution were then introduced into the speed mixer mixing cup and were mixed at a speed of about 2500 rpm for two periods of 20 seconds; [0186] 3) The mixture resulting from step 2 was then left to react at room temperature for a period of 30 minutes, which was found to result in the end-capping reaction having gone to completion; [0187] 4) When present the oleic acid or Polyvest® MA 75 was then added to the reaction product of step (3) and were mixed at a speed of about 2500 rpm for two periods of 20 seconds.

[0188] The variation of viscosity of the alkoxy end-capped polymer reaction product from the above processes was assessed over time and to determine how long the level of stability of each alkoxy end-capped polymer product prepared. The viscosity test was performed using a Brookfield DVIII Ultra with cone 52 under 5 rpm for 1 min. Compositions were mixed and measured at room temperature (about 25° C.). The results are depicted in Table 2 below.

TABLE-US-00002 TABLE 2 Variation in viscosity of the polymer reaction end-product from the reaction described above in Table 1. Comp. Ex. 1 Ex. 1 Ex. 2 Ex. 3 Time after mixing Viscosity (mPa .Math. s) 14 hours 39053 39688 37307 37783 4 days 31099 10 days 40164 36830 27783 17 days 20797 40006 37942 39370 33 days 13018 41752 38577 40482 52 days 8366 40799 37307 40006 90 days Not tested 39053 36989 40482 150 days Not tested 40323 36989 41434

[0189] As seen from Table 2 compositions containing 0.1 wt. % or higher of oleic acid or Polyvest® MA 75 remained stable even after 5 months of aging at room temperature. However, it was found that the comparative example which was not stabilized as described herein was only stable for a few days.

[0190] In the following there is provided a continuous process commencing with the preparation of an alkoxy end-capping of the silanol polymer and the use of the resulting polymer reaction end-product as a mixture of polymer and cross-linker for an organopolysiloxane elastomer composition. The ingredients in Tables 3a and 3b are provided such that the total compositions of all ingredients per organopolysiloxane elastomer composition add up to 100 wt. % of the composition.

TABLE-US-00003 TABLE 3a Relative amounts (wt. % of total composition) of the ingredients used in the end-capping reaction. Comp. Comp. Ex. 2 Ex. 4 Ex. 3 Ex. 5 Polymer 1 47.65 47.63 39.38 37.36 Plasticiser 9.64 10 Vinyl trimethoxy silane 1.40 1.40 1.25 1.25 Methyl trimethoxy silane (MTM) 1.40 1.20 1.35 1.35 1 wt. % TBD in MTM 0.20 0.20 0.15 0.15 Oleic acid 0.10

[0191] The plasticiser used in Table 3a was a trimethyl terminated polydimethylsiloxane having a viscosity of 100 mPa.Math.s at 25° C.

[0192] The alkoxy end-capping reaction using the ingredients of Table 3a was carried out using the following process in a speed mixer. [0193] 1) A 1 wt. % solution of TBD end-capping catalyst in methyl trimethoxy silane was initially prepared by dissolving TBD end-capping catalyst in methyl trimethoxy silane and then the vinyl trimethoxysilane was added to provide an end-capping catalyst solution; [0194] 2) The polymer, and plasticiser were mixed together in a 10 litre Turello mixer at about 400 rpm; [0195] 3) The end-capping catalyst mixture was then introduced into the mixture resulting from step 2 above and this combination was then stirred at 400 rpm for 15 minutes at room temperature; [0196] 4) After the 15 minutes of mixing the oleic acid or the like neutralising agent/stabilizing agent was added to the mixture and mixed in to provide a stabilized alkoxy end-capped polymer reaction end-product as hereinbefore described;

[0197] In these examples the above formed the first part of a continuous process to prepare an organopolysiloxane elastomer composition. The remaining ingredients in the composition are identified in Table 3b.

TABLE-US-00004 TABLE 3b Relative amounts (wt. % of total composition) of the ingredients used in the preparation of the organopolysiloxane elastomer compositions Comp. Comp. Ex. 2 Ex. 4 Ex. 3 Ex. 5 Dimethylbis(N-ethylacetamido)silane 0.25 0.25 Hexamethyldisilazane 1.50 1.50 Precipitated calcium carbonate having 32.12 32.12 37.14 an average particle size of 60-70 nm Fumed silica having an average BET 4.30 surface area of 130-170 m.sup.2/g Ground calcium carbonate having a D50 15.21 15.3 8.70 43.56 average particle size of 4.6 μm Dimethyl tin dineodecanoate 0.50 0.50 Tyzor ® PITA SM 1.10 1.10 Bis(lauroyloxy)dioctyltin 0.08 0.08 Dibutyl tin dilaurate 0.05 0.05 tetra n-butyl titanate 0.10 N-[3-(Trimethoxysilyl)propyl]ethyl- 0.070 0.12 0.25 0.25 enediamine Bis(trimethoxysilylpropyl)amine 0.08 Tris [3-(trimethoxysilyl)propyl] 0.15 0.15 isocyanurate

[0198] Tyzor® PITA SM is a blend of Diisopropoxy-bisethylacetoacetatotitanate in methyl trimethoxy silane (80/20 wt. ratio) and is commercially available from Dorf Ketal Chemicals, LLC. In example 5 above the stabilizing/neutralising agent relied upon is the fumed silica which is naturally mildly acidic however, in this instance for the continuous process it was preferred to introduce condensation cure catalyst and adhesion promoter (when present) before introducing the fillers. For the avoidance of doubt Dimethylbis(N-ethylacetamido)silane is a chain-extender.

[0199] To generate the one-part, organopolysiloxane elastomer composition utilising the product of the alkoxy end-capping reaction above, the following further steps were undertaken:— [0200] 5) the condensation cure catalyst and adhesion promoter(s) were premixed to form a mixture 2; [0201] 6) Once step 4 (above) was completed the mixture 2 was introduced into the mixer and everything was mixed for a further 5 minutes; [0202] 7) the fillers were then added. These were calcium carbonate(s) in Ex. 4 and Comparative examples 2 and 3 but in the case of Ex. 5 fumed silica was added in combination with the calcium carbonate and its acidic nature was relied upon to neutralise and stabilize the TBD end-capping catalyst from the alkoxy end capping process; The fillers were added gradually into the pot; [0203] 8) After the filler was thoroughly mixed then add hexamethyldisilazane was added; and [0204] 9) the composition was then further mixed under vacuum for 10 min after which the final one-part, organopolysiloxane elastomer compositions was packaged.

[0205] The final one-part, organopolysiloxane elastomer compositions prepared by the above processes were then assessed for their general physical properties, initially, after 2 weeks of aging at 50° C. and after 4 weeks of aging at 50° C. with the results depicted in Tables 4a, 4b and 4c respectively.

TABLE-US-00005 TABLE 4a General assessment of physical properties in the absence of aging Comp. Comp. General properties Ex. 2 Ex. 4 Ex. 3 Ex. 5 TFT, min (ASTM C679-15) 28 25 18 60 Flow, mm (ASTM D2202 - 2 3 5.5 7 00(2019)) Extrusion Rate, g/min (ASTM 146 130 219 237 C1183-04) Tensile, MPa (ASTM D412- 1.97 1.37 1.99 1.32 98a(2002)e1) Duro, shore A (ASTM C661-15) 28.7 37.45 23.7 28.65

TABLE-US-00006 TABLE 4b General assessment of physical properties after 2 weeks of aging at 50° C. Comp. Comp. Aging 50° C. Ex. 2 Ex. 4 Ex. 3 Ex. 5 TFT, min (ASTM C679-15) Not cure >60 Not cure 37 Extrusion Rate, g/min (ASTM 781 156 294 228 C1183-04) Tensile, MPa (ASTM D412- / 1.71 / 1.20 98a(2002)e1) Duro, shore A (ASTM / 27.15 / 27.85 C661-15)

TABLE-US-00007 TABLE 4c General assessment of physical properties after 4 weeks of aging at 50° C. Comp. Comp. Aging 50° C. Ex. 2 Ex. 4 Ex. 3 Ex. 5 TFT, min (ASTM C679-15) Not Cure >80 Not cure 43 Extrusion Rate, g/min (ASTM / 258 / 230 C1183-04) Tensile, MPa (ASTM D412- / 1.62 / 1.2 98a(2002)e1) Elongation (%)(ASTM D412- / 393 / 474 98a(2002)e1) Duro, shore A (ASTM C661-15) / 26.35 / 27

[0206] As seen from Tables 4a, 4b and 4c, with 0.1% or higher of oleic acid or in the case of Ex. 5 fumed silica as neutralising agent/stability agent in a one-part, organopolysiloxane elastomer composition per examples 4 and 5 the small amount of acidic neutralising agent/stabilizing agent added after completion of the alkoxy end-capping reactions, a stable one-part, organopolysiloxane elastomer composition was evident in the case of Examples 4 and 5 with a pretty good shelf life. While the comparative examples showed very poor shelf life. After 50° C. aging for 2 weeks, the extrusion rate increased significantly and the sample couldn't cure anymore.