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 an end-capping catalyst starting material is provided. The end-capping catalyst starting material comprises 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. The resulting capped polymeric material may be utilized as a polymer in, e.g., a polydiorganosiloxane elastomer composition.

Claims

1. A process for preparing an alkoxy end-capped polydiorganosiloxane from a silanol terminated polydiorganosiloxane starting material, the process comprising: 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 and groups obtained by replacing all or part of the hydrogen in the preceding organic groups with halogen; in the presence of an end-capping catalyst starting material consisting 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.

2. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the end-capping catalyst starting material comprises linear, branched or cyclic silicon containing molecules or linear, branched or cyclic organic molecules containing one or more 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.

3. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the end-capping catalyst starting material comprises one or more of 1,1,3,3-tetramethylguanidine, 2-[3-(trimethoxysilyl)propyl]-1,1,3,3-tetramethylguanidine, 2-[3-(methyldimethoxysilyl)propyl]-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 1,8-diazabicyclo[5.4.0]undec-7-ene.

4. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the process takes place in a static mixer.

5. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the alkoxy end-capped polydiorganosiloxane is not stabilized, neutralised or stabilized and neutralised upon completion of the process and/or does not have the end-capping catalyst starting material removed at the end of the process.

6. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the end-capping catalyst can be added directly as a solid or in solution in a compatible silicone or organic solvent or in one of the polyalkoxy silane starting materials being utilised to end-cap the silanol-terminated polydiorganosiloxane.

7. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the process takes place at a temperature of between 30 to 100° C.

8. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein after completion of the process, the alkoxy end-capped polydiorganosiloxane final product is stored for a period of from 3 to 7 days prior to use.

9. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein the polyalkoxy silane is provided in excess such that unreacted polyalkoxy silane is available to function as a cross-linker when utilised for making a sealant composition.

10. The process for preparing an alkoxy end-capped polydiorganosiloxane in accordance with claim 1, wherein alkoxy end-capped polydiorganosiloxane is subsequently used as an ingredient in a polydiorganosiloxane elastomer composition prepared by mixing the following ingredients: (a) the alkoxy end-capped, polydiorganosiloxane polymer reaction 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. An alkoxy end-capped, polydiorganosiloxane polymer obtainable or obtained from the process of claim 1.

12. A polydiorganosiloxane elastomer composition obtainable or obtained from the process of claim 10.

13. The polydiorganosiloxane elastomer composition in accordance with claim 12, wherein the polydiorganosiloxane elastomer composition additionally comprises an —OH scavenger.

14. The polydiorganosiloxane elastomer composition in accordance with claim 12, wherein the composition is a one-part composition and the condensation cure catalyst (d) is a tin-based catalyst.

15. A silicone elastomer obtained by curing the polydiorganosiloxane elastomer composition prepared in accordance with claim 12.

16. An alkoxy end-capped polydiorganosiloxane polymer 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

[0133] Unless otherwise indicated, All viscosity measurements were undertaken using either a Brookfield® rotational viscometer with spindle LV-4 (designed for viscosities in the range between 1,000-2,000,000 mPa.Math.s or a Brookfield® rotational viscometer with spindle LV-1 (designed for viscosities in the range between 15-20,000 mPa.Math.s) for viscosities less than 1000 mPa.Math.s and adapting the speed (shear rate) according to the polymer viscosity and measurements were taken at 25° C.

Example 1

[0134] A Max100 speedmixer cup was charged with: [0135] (i) 40 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 42 mPa.Math.s and an average of 3.7 wt. % Si—OH groups per molecule; and [0136] (ii) 47 g methyltrimethoxy silane.
0.6 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was then added and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. for 18 hours.

[0137] After the 18-hour period the resulting product was complete providing give a reaction end-product of methyldimethoxy-terminated polydimethylsiloxane with >99.6% conversion as measured by .sup.29Si NMR and also .sup.1H NMR. Conversion was measured by observing the disappearance of silanol signal (.sup.29Si NMR (80 MHz, CDCl.sub.3) δ −12 and .sup.1H NMR (400 MHz, CDCl.sub.3) δ 0.85) and corresponding appearance of methyldimethoxysilyl end-caps (.sup.29Si NMR (80 MHz, CDCl.sub.3) δ −48 and .sup.1H NMR (400 MHz, CDCl.sub.3) δ 3.48).

Comparative Example 1

[0138] A Max100 speedmixer cup was charged with [0139] (i) 40 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 42 mPa.Math.s and an average of 3.7 wt. % Si—OH groups per molecule and [0140] (ii) 47 g methyltrimethoxy silane.

[0141] The resulting mixture was mixed for three periods of 20 seconds at 2000 rpm and then left at 23° C. for one week. The mixture was analyzed using .sup.1H and .sup.29Si NMR after the 1-week period and no evidence of any reaction having taken place was observed. The reaction end-product only contained unreacted starting materials.

Example 2

[0142] A Max40 speedmixer cup was charged with: [0143] (i) 10 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 42 mPa.Math.s and an average of 3.7 wt. % Si—OH groups per molecule; and [0144] (ii) 5.9 g methyltrimethoxy silane.
0.05 g of DBU was then added and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting reaction mixture was then left at 23° C. The reaction mixture was analyzed at 2 and 24 hours by NMR using the polydimethylsiloxane backbone signal as an internal standard (.sup.1H NMR (400 MHz, CDCl.sub.3) δ 3.48, 0.06). By comparison of the relative amount of alkoxysilane end-capping groups compared to polydimethylsiloxane backbone, the reaction was determined to have proceeded with >99.6% conversion in 2 hours to give a methyldimethoxy-terminated polydimethylsiloxane product.

Comparative Example 2

[0145] A Max100 speedmixer cup was charged with: [0146] (i) 10 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 42 mPa.Math.s and an average of 3.7 wt. % Si—OH groups per molecule; and [0147] (ii) 5.9 g methyltrimethoxy silane.
0.05 g of 2-ethylhexanoic acid (2-EHA) and 0.05 g of DBU was then added (i.e., using 2-EHA as catalyst and DBU as co-catalyst) and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The reaction mixture was analyzed at 2 and 24 hours by NMR using the polydimethylsiloxane backbone signal as an internal standard (.sup.1H NMR (400 MHz, CDCl.sub.3) δ 3.48, 0.06). By comparison of the relative amount of alkoxysilane end-capping groups compared to polydimethylsiloxane backbone, the reaction was determined to have proceeded with 90% conversion in 2 hours to give methyldimethoxy-terminated polydimethylsiloxane product.

[0148] This is a lower conversion than measured in example 2.

Comparative Example 3

[0149] A Max100 speedmixer cup was charged with: [0150] (i) 10 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 42 mPa.Math.s and an average of 3.7 wt. % Si—OH groups per molecule; and [0151] (ii) 5.9 g methyltrimethoxy silane.
0.017 g of barium oxide was then added and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. and analyzed by NMR at 2 and 24 hours using .sup.1H NMR (400 MHz, CDCl.sub.3). The reaction showed approximately 21% conversion by NMR analysis to alkoxysilane-terminated product at 2 hours, however, by 24 hours, the reaction appeared cloudy and .sup.1H NMR revealed a complex mixture of unidentified products. Furthermore, while methyltrimethoxysilane was added in excess, no silane starting material was observed after 24 hours, suggesting further undesired reaction and decomposition.

Example 3

[0152] A Max300 speedmixer cup was charged with: [0153] (i) 250 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0154] (ii) 4.3 g methyltrimethoxy silane.
The mixture was stirred and then 0.001 g 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was added. The mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. for 18 hours. After the 18-hour period the reaction had completed providing give a reaction end-product of methyldimethoxy-terminated polydimethylsiloxane with >99.6% conversion as measured by .sup.1H NMR (400 MHz, CDCl.sub.3).

Comparative Example 4

[0155] A Max100 speedmixer cup was charged with: [0156] (j) 10 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 42 mPa.Math.s and an average of 3.7 wt. % Si—OH groups per molecule; and [0157] (ii) 5.9 g methyltrimethoxy silane.
0.36 g of a Pt solution (1.3 wt % platinum, 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complex in dimethylvinylsiloxy-terminated dimethyl siloxane) was then added, and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. and analyzed by NMR at 96 hours using .sup.29Si NMR (80 MHz, CDCl.sub.3). The reaction showed approximately 0% conversion by NMR analysis to alkoxysilane-terminated product.

Comparative Example 5

[0158] A Max100 speedmixer cup was charged with: [0159] (j) 40 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0160] (ii) 0.69 g methyltrimethoxy silane.
0.04 g of a 0.4 M lithium trimethylsilanolate solution in toluene was added. The mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. and analyzed by NMR at 24 hours using .sup.29Si NMR (80 MHz, CDCl.sub.3). The reaction showed approximately 0% conversion by NMR analysis to alkoxysilane-terminated product.

Example 4

[0161] A Max100 SpeedMixer cup was charged with: [0162] (k) 40 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0163] (ii) 1.65 g 1,6-bis(trimethoxysilyl)hexane.
The mixture was stirred and then 0.0002 g 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was added. The mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. for 18 hours. After the 18 hour period the resulting product was complete providing give a reaction end-product of methyldimethoxy-terminated polydimethylsiloxane with >99.6% conversion as measured by .sup.1H NMR (400 MHz, CDCl.sub.3) and .sup.29Si NMR (80 MHz, CDCl.sub.3).

Example 5

[0164] A Max100 SpeedMixer cup was charged with: [0165] (1) 40 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0166] (ii) 0.79 g vinyltrimethoxysilane.
The mixture was stirred and then 0.0002 g 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was added. The mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. for 2 hours. After the 2 hour period the resulting product was complete providing give a reaction end-product of methyldimethoxy-terminated polydimethylsiloxane with >99.6% conversion as measured by .sup.1H NMR (400 MHz, CDCl.sub.3) and .sup.29Si NMR (80 MHz, CDCl.sub.3).

Example 6

[0167] A Max300 SpeedMixer cup was charged with: [0168] (m) 250 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0169] (ii) 4.3 g methyltrimethoxysilane.
The mixture was mixed for three periods of 20 seconds at 2000 rpm. Initial viscosity was measured by ARES cone and plate rheometer. Then 0.0011 g 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was added and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. Viscosity was measured using an ARES cone and plate rheometer cone and plate rheometer at different time points. and the resulting viscosity of the material is given below in Table 1.

TABLE-US-00001 TABLE 1 Time (h) 0 72 168 (7 days) 336 (14 days) Viscosity (mPa .Math. s) 46,389 47,338 45,205 41,239

[0170] As shown, this reaction mixture can be stored at room temperature for 168 h without change, and 336 h with slight degradation.

Example 7

[0171] A Max300 SpeedMixer cup was charged with: [0172] (n) 250 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0173] (ii) 4.3 g methyltrimethoxysilane.
The mixture was mixed for three periods of 20 seconds at 2000 rpm. Initial viscosity was measured using an ARES cone and plate rheometer. Then 0.0110 g 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was added and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. Viscosity was measured using an ARES cone and plate rheometer at different time points. Viscosity of the material is given below in Table 2.

TABLE-US-00002 TABLE 2 Time (h) 0 72 168 336 Viscosity (mPa .Math. s) 46,316 41,052 24,130 7,771

[0174] As shown, the reaction mixture can be stored at room temperature for 72 h without degradation.

Example 8

[0175] A Max300 SpeedMixer cup was charged with: [0176] (i) 250 g of a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule; and [0177] (ii) 4.3 g methyltrimethoxysilane.
The mixture was mixed for three periods of 20 seconds at 2000 rpm. Initial viscosity was measured using an ARES cone and plate rheometer. Then 0.1100 g 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was added and the mixture was mixed for three periods of 20 seconds at 2000 rpm. The resulting mixture was then left at 23° C. Viscosity was measured by an ARES cone and plate rheometer at different time points. Viscosity of the material is given below in Table 3.

TABLE-US-00003 TABLE 3 Time (h) 0 72 168 336 Viscosity (mPa .Math. s) 48,737 5,245 1,041 550

[0178] As shown, the reaction mixture stored at room temperature for 72 h already shows significant degradation.

Examples 9-15

[0179] In the following embodiments the end-capped polymer made in accordance with the current disclosure was prepared as a first step in the preparation of a sealant composition using a variety of silanes. In examples 9 to 15 a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s and an average of 0.05 wt. % Si—OH groups per molecule was mixed with an assortment of potential capping silanes and a catalyst. The catalyst used was a 2% solution of Triazabicyclodecene (TBD) in toluene. The mixture was stirred for 20 seconds @ 2000 rpm in a SpeedMixer and was then heated to a temperature of 50° C. maintained at that temperature to react for 60 minutes at which point the resulting mixture was sampled and analyzed by .sup.1H NMR to determine the reaction had gone to completion.

[0180] The compositions used are identified in Table 4 below.

TABLE-US-00004 TABLE 4 ingredients for End-capping process described herein Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Polymer 86.80 86.80 86.80 86.80 86.80 86.80 86.80 Vinyltrimethoxy silane 1.70 1.70 2.70 1.70 1.70 methyltrimethoxysilane 1.0 1.0 Isobutyltrimethoxy silane 1.0 Phenyltrimethoxysilane 2.0 1,6- 3.4 bis(trimethoxysilyl)hexane Catalyst in toluene 0.008 0.002 0.002 0.002 0.002 0.002 0.002

[0181] The polymer used in Table 1 was a dimethylsilanol terminated polydimethylsiloxane having a viscosity of 56,000 mPa.Math.s at 25° C. and an average of 3.7 wt. % Si—OH groups per molecule. In this instance the catalyst was provided in a solution of toluene. It was later found to be optimum for the catalyst to be provided in a solution of another starting material, usually a polyalkoxy silane.

[0182] The alkoxy end-capped, polydiorganosiloxane polymer reaction end-product resulting from preparation as described herein and with respect to the Ex. 4-10 in Table 1 were each used to prepare a sealant formulation by taking the alkoxy end-capped, polydiorganosiloxane polymer reaction end-product and adding the ingredients indicated in Table 5 below:

TABLE-US-00005 TABLE 5 Ingredients for sealant formulation added to the end-capped polymers made above. Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 AP 1.10 1.10 1.10 1.10 1.10 1.10 1.10 DBTDL 0.16 0.16 0.16 0.16 0.16 0.16 0.16 Filler 8.0 8.0 8.0 8.0 8.0 8.0 8.0 HMDZ 2.5 2.5 2.5 2.5 2.5 2.5 2.5

[0183] In Table 5, DBTDL is the tin-based catalyst dibutyltin dilaurate; The adhesion promoter (AP) used was aminopropylaminoethyltrimethoxysilane. HMDZ is hexamethyldisilazane and is used as a scavenger; and the filler used was CAB-O-SIL LM-150 fumed silica from the Cabot Corporation

[0184] In the present series of examples, the sealant composition was prepared by initially adding adhesion promotor and tin catalyst into the alkoxy end-capped, polydiorganosiloxane polymer reaction end-product which contained polymer and an excess of polyalkoxysilane for use a cross-linker. These ingredients were then mixed together for 20 seconds at 2000 rpm in a SpeedMixer. The filler was then introduced into the mixture and the resulting composition was mixed for 40 seconds at 2000 rpm. Subsequently stabilizer (HMDZ) was added and the resulting mixture was again mixed for 20 seconds at 2000 rpm. The sealant composition was then stored for future use. The different compositions were tested for their physical properties and the results are depicted in Table 6 below.

TABLE-US-00006 TABLE 6 Physical Property results of sealant compositions made in accordance with Table 5 above. Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Rheo good good good good good good flowable SOT (min) 15 15 10  5 20 15 20 TFT (min) 40 40 35 35 30 30 25 24 hour shelf good good good good good good good stability 1-day cure good good good good good good good

[0185] In Table 6 RHEO was a visual assessment as to whether the final product provided a non-sag or a flowable composition. The term good used in with respect to Rheo in Table 6 indicates that the composition was a non-sagging composition.

[0186] Skin over time (SOT) and tack free time (TFT) were measured in accordance with ASTM C679-15.

[0187] 24 hour shelf stability was a visual test to determine whether or not the sealant composition gelled in the first 24 hours after the completion of the process. This can happen if the polymer end-capping process was not sufficiently complete before introduction of the tin-based catalyst. A stable material will be unchanged from the initial rheology, and specifically it will be un-gelled. A polymer used which is insufficiently capped prior to fully formulating in this tin chemistry will gel in the package in a short period. Good in this respect in Table 6 indicates the composition is un-gelled after 24 hours. The test sample was evaluated with a spatula for rheology.

[0188] 24 hour cure evaluation was used to assess whether or not the cured elastomer has cured into a well-formed elastomer. This test involves to drawing down a 100 mil slab of sealant and allow to cure for 24 hours. The “cure evaluation” was peeling up the slab and pulling, while observing its mechanical properties. If the elastomeric product “peels up” and is elastic, it has passed the evaluation and was identified as “Good” in Table 6. A material which did not pass is still in a paste state and is therefore recorded as “uncured”.