A METHOD FOR PREPARING POLYORGANOSILOXANES

Abstract

The present disclosure relates to a method for preparing polyorganosiloxanes, comprising the following steps: a) reacting together a hydroxyl-terminated polysiloxane and a dialkoxysilane or an oligomer thereof in the presence of Catalyst 1, and b) reacting the product of Step a) with an endcapper in the presence of Catalyst 2 to form the polyorganosiloxane. According to this method, poly-organosiloxanes with an appropriate degree of the polymerization and viscosity are prepared by the polycondensation and equilibration reactions sequentially, and can significantly reduce the viscosity, and improve the flowability and thermal conductivity of the resulting silicone compositions, compared with other polysiloxanes at the same high thermally conductive filler loading.

Claims

1-19. (canceled)

20. A method for preparing polyorganosiloxanes, comprising the followings steps: a) reacting together a hydroxyl-terminated polysiloxane of Formula I and a dialkoxysilane of Formula II or an oligomer thereof in the presence of Catalyst 1, ##STR00006## where p is an arbitrary integer between 10 and 60, R.sub.1 is a methyl or ethyl group, R.sub.2 is a C6-C18 alkyl group, R.sub.3 is a C1-C18 alkyl group, q is an arbitrary integer between 1 and 8; b) reacting the product of Step a) with an endcapper in the presence of Catalyst 2 to form the said polyorganosiloxane.

21. The method of claim 20, wherein the reaction of Step a) is a polycondensation reaction, and/or a equilibration reaction occurs in Step b).

22. The method of claim 20, wherein the polyorganosiloxane has the structural formula as shown in Formula III below: ##STR00007## where a is an arbitrary integer between 6 and 18, n is an arbitrary number between 0.7 and 20, m is an arbitrary number between 10 and 1500, m/n is an arbitrary number greater than 20, X represents one or more groups selected from among vinyl, alkoxy and hydroxyl.

23. The method of claim 22, wherein part of X are alkoxy groups.

24. The method of claim 23, wherein at least 20 mol % of X, based on the total number of moles of the X groups, are alkoxy groups.

25. The method of claim 22, wherein part of X are vinyl groups.

26. The method of claim 25, wherein at least 45 mol % of X, based on the total number of moles of the X groups, are vinyl groups.

27. The method of claim 22, wherein at least 65 mol % of X and at least 20 mol % of X, based on the total number of moles of the X groups, are respectively vinyl groups and alkoxy groups.

28. The method of claim 22, wherein m is an arbitrary number between 10 and 380 and m/n is an arbitrary number between 20 and 500.

29. The method of claim 28, wherein m is an arbitrary number between 60 and 160 and m/n is an arbitrary number between 50 and 150.

30. The method of claim 22, wherein the polyorganosiloxane of Formula III has a dynamic viscosity of from 10 to 200 mPa.Math.s at 25° C.

31. The method of claim 20, wherein the dialkoxysilane or oligomer thereof is used in an amount such that it can provide 0.2-0.5 moles of alkoxy groups per mole of silanol groups in the hydroxyl-terminated polysiloxane.

32. The method of claim 20, wherein the reaction of Step a) is carried out at 80-100° C.

33. The method of claim 20, wherein both R.sub.1 and R.sub.2 in Formula II are methyl groups, and q is 1.

34. The method of claim 20, wherein the endcapper has the structural formula as shown in Formula IV and/or V below: ##STR00008## where t is an arbitrary integer between 0 and 20, and R.sub.4 is a C1-C6 alkyl group.

35. The method of claim 34, wherein the endcapper is used in an amount such that it can provide 0.2-0.5 moles of vinyl groups per mole of silanol groups in the hydroxyl-terminated polysiloxane.

36. The method of claim 20, wherein the reaction of Step b) is carried out at 100-140° C.

37. The method of claim 20, wherein both Catalyst 1 and Catalyst 2 are quaternary ammonium hydroxides.

38. The method of claim 37, wherein the total amount of Catalysts 1 and 2, based on solid form, ranges from 0.01 to 0.05 wt %, relative to the weight of the hydroxyl-terminated polysiloxane.

Description

DESCRIPTION OF DRAWINGS

[0074] FIG. 1 shows a .sup.1H NMR spectrum (1a) and a .sup.29Si NMR spectrum (1b) of the polyorganosiloxane Polymer A-1 obtained in Example 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0075] The present invention is further illustrated by the following examples, but is not limited to the scope thereof. Any experimental methods with no conditions specified in the following examples are selected according to the conventional methods and conditions, or product specifications.

[0076] Characterization of structural formula and number-average molecular weight of polyorganosiloxanes

[0077] Determined by .sup.1H NMR spectroscopy and .sup.29Si NMR spectroscopy.

[0078] .sup.1H NMR spectroscopy

[0079] Test solvent: deuterated chloroform

[0080] Internal standard substance: TMS-free chloroform

[0081] Spectrometer: Bruker Avance III HD 400

[0082] Sampling head: 5 mm BBO probe

[0083] Measured Parameters:

[0084] Pulse sequence (Pulprog)=zg30

[0085] TD=65536

[0086] NS=64

[0087] DS=2

[0088] SWH=7211.54 Hz

[0089] FIDRES=0.11 Hz

[0090] AQ=4.54 s

[0091] RG=86.97

[0092] DW=69.33 μs

[0093] DE=6.50 μs

[0094] TE=298.2 K

[0095] D1=5 s

[0096] SFO1=400.15 MHz

[0097] Some measurement parameters may need to be adjusted appropriately depending on the type of spectrometer.

[0098] .sup.29Si NMR spectroscopy

[0099] Test solvent: deuterated benzene

[0100] Relaxation reagent: chromium acetylacetonate

[0101] No internal standard substance added

[0102] Spectrometer: Bruker Avance III HD 400

[0103] Sampling head: 5 mm BBO probe

[0104] Measured Parameters:

[0105] Pulse sequence=zgig60

[0106] TD=65536

[0107] NS=2048

[0108] DS=4

[0109] SWH=16025.64 Hz

[0110] FIDRES=0.24 Hz

[0111] AQ=2.04 s

[0112] RG=196.53

[0113] DW=31.20 μs

[0114] DE=13.00 μs

[0115] TE=298.1 K

[0116] D1=5 s

[0117] SFO1=79.49 MHz

[0118] Some measurement parameters may need to be adjusted appropriately depending on the type of spectrometer.

[0119] Each group unit of the polyorganosiloxane and the number of moles thereof are obtained primarily by .sup.1H NMR integration, and the type of groups is further determined by .sup.29Si NMR spectroscopy. When performing an integration, first the baseline of NMR spectrum is leveled, then the peak integration interval is selected, in which each peak is integrated for more than three times to calculate the average peak area with the relative deviation <1%. Finally, the molecular composition of the polysiloxane is analyzed by end-group method to obtain the structural formula of the polysiloxane, whereby its number-average molecular weight is calculated.

[0120] Determination of Viscosity of the Silicone Composition

[0121] It is carried out in accordance with DIN EN ISO 3219: Determination of viscosity of polymers and resins in the liquid state or as emulsions or dispersions using a rotational viscometer with defined shear rate (ISO 3219:1993).

[0122] The raw materials used in the following examples are all commercially available, with detailed information as follows:

[0123] WACKER® FINISH WS 62 M, a hydroxyl-terminated polydimethylsiloxane having a dynamic viscosity of 50-110 mPa.Math.s, measured at 25° C. according to DIN 51562, supplied by Wacker Chemicals;

[0124] Basic catalyst, an aqueous solution of tetramethylammonium hydroxide at a concentration of 25 wt %;

[0125] Endcapper, vinyltetramethyldisiloxane, supplied by TCI;

[0126] ELASTOSIL® VINYLPOLYMER 120, a polydimethylsiloxane containing vinyl groups, having a dynamic viscosity of 120 mPa.Math.s measured at 25° C., supplied by Wacker Chemicals;

[0127] Alumina A, spherical alumina powder having an average particle size of 40 μm;

[0128] Alumina B, spherical alumina powder having an average particle size of 5 μm;

[0129] Alumina C, spherical alumina powder having an average particle size of 20 μm;

[0130] Alumina D, spherical alumina powder having an average particle size of 2 μm;

[0131] Zinc oxide, non-spherical zinc oxide powder having an average particle size of 5 μm;

[0132] WACKER® AK 100, a polydimethylsiloxane having a kinematic viscosity of about 100 mm.sup.2/s measured at 25° C. according to DIN 53019, supplied by Wacker Chemicals.

[0133] Unless otherwise specified, “wt %” in the table below is based on the total weight of the thermally conductive silicone composition.

Example 1: Preparation of Polyorganosiloxanes Polymer A

[0134] (a) The hydroxyl-terminated polysiloxane, dialkoxysilane and basic catalyst were added to a flask under a nitrogen atmosphere, stirred and heated to 80-100° C. to carry out a polycondensation reaction for 2-4 h;

[0135] (b) The endcapper was added to the flask under a nitrogen atmosphere, and heated to 100-140° C. to carry out an equilibration reaction for 3-6 h;

[0136] (c) The resulting mixture was further heated to 160° C. to decompose the catalyst for 1 h under a nitrogen atmosphere;

[0137] (d) The above resulting mixture was transferred to a distillation flask, distilled at 175° C. and 30 mbar for 2 h to remove low boilers (mostly small molecular cyclosiloxanes), and finally cooled to room temperature to obtain the polyorganosiloxane.

[0138] Table 1 lists the amount of raw materials and process parameters for each Polymer A variant.

[0139] Table 2 lists the structural formula, number-average molecular weight, and dynamic viscosity at 25° C. of each Polymer A variant determined by .sup.1H NMR spectroscopy and

.SUP.29.Si NMR Spectroscopy.

[0140]

TABLE-US-00001 TABLE 1 Polymer Polymer Polymer Polymer A-1 A-2 A-3 A-4 WACKER ® FINISH WS 62 M 1264 680 565 680 (Kg) Octyldimethoxymethylsilane (Kg) 37.2 20 17 / Dodecyldiethoxymethylsilane (Kg) / / / 25 Basic catalyst (Kg) 1.05 0.6 0.62 0.6 Endcapper (Kg) 29.76 16 50 16 Polycondensation temperature 95 85 85 85 (° C.) Polycondensation time (h) 2 2 2 2 Equilibration temperature (° C.) 120 120 120 120 Equilibration time (h) 3.5 3 3 3

TABLE-US-00002 TABLE 2 Mn Viscosity Structural Formula (g/mol) (mPa .Math. s) Polymer ((H.sub.2C═CH)(CH.sub.3).sub.2SiO).sub.1.54((CH.sub.3).sub.2SiO).sub.89.50((CH.sub.3)(C.sub.8H.sub.17)SiO).sub.0.99(Si(OCH.sub.3)(CH.sub.3).sub.2).sub.0.46 6989.8 130 A-1 Polymer ((H.sub.2C═CH)(CH.sub.3).sub.2SiO).sub.1.46((CH.sub.3).sub.2SiO).sub.78.89((CH.sub.3)(C.sub.8H.sub.17)SiO).sub.0.81(Si(OCH.sub.3)(CH.sub.3).sub.2).sub.0.54 6171.7 124 A-2 Polymer ((H.sub.2C═CH)(CH.sub.3).sub.2SiO).sub.1.00((CH.sub.3).sub.2SiO).sub.150.10((CH.sub.3)(C.sub.8H.sub.17)SiO).sub.1.50(Si(OCH.sub.3)(CH.sub.3).sub.2).sub.1.00 11555.4 NA A-3 Polymer ((H.sub.2C═CH)(CH.sub.3).sub.2SiO).sub.1.20((CH.sub.3).sub.2SiO).sub.133.40((CH.sub.3)(C.sub.12H.sub.25)SiO).sub.1.40(Si(OCH.sub.3)(CH.sub.3).sub.2).sub.0.80 10243.2 240 A-4

[0141] Among all the Polymer A variants, Polymer A-1 has a polydispersity index (Mw/Mn) of 1.826, which was determined by PSS SECcurity gel permeation chromatography with reference to DIN 55672, using tetrahydrofuran as the eluent.

Example 2: Thermal Conductivity Test

[0142] According to the formulation in Table 3, the polyorganosiloxanes Polymer A-1, Polymer B (ELASTOSIL® VINYLPOLYMER 120) and thermally conductive fillers were mixed to obtain thermally conductive silicone Compositions N-1 to N-4′. The viscosities of the compositions were measured at shear rates of 0.5 s.sup.−1 and 25 s.sup.−1. The results show that Polymer A-1 is more effective in reducing the viscosity of the composition than Polymer B at the same thermally conductive filler loading.

TABLE-US-00003 TABLE 3 Components Composition Composition Composition Composition (wt %) N-1 N-2 N-3 N-4′ Polymer A-1 10 10 15 / Polymer B / / / 15 Alumina A 60 / / / Alumina B 30 / 85 85 Alumina C / 60 / / Alumina D / 30 / / Viscosity of Composition (mPa .Math. s) D = 0.5 s.sup.−1 17600 41600 132000 423000 D = 25 s.sup.−1 13800 12700 36500 81300

[0143] According to the formulation in Table 4, the polyorganosiloxanes Polymers A-1, A-2, A-4, Polymer B and thermally conductive fillers were mixed to obtain thermally conductive silicone compositions N-5 to N-8′. The viscosities of the compositions were measured at a shear rate of 10 s.sup.−1. The results show that Polymer A, the polyorganosiloxanes of the present disclosure, are more effective in reducing the viscosity of the composition than Polymer B at the same thermally conductive filler loading, while Polymer A-1 is slightly superior to Polymers A-2 and A-4 in reducing viscosity.

TABLE-US-00004 TABLE 4 Components Composition Composition Composition Composition (wt %) N-5 N-6 N-7 N-8′ Polymer A-1 10 / / / Polymer A-2 / 10 / / Polymer A-4 / / 10 / Polymer B / / / 10 Alumina A 25 25 25 25 Alumina B 36 36 36 36 Zinc oxide 29 29 29 29 Viscosity of Composition (mPa .Math. s) D = 10 s.sup.−1 72000 100000 128000 580000

[0144] In Table 5, the viscosity reducing effect of the polyorganosiloxane Polymer A-1 is compared with that of Polymer C (a silicone oil with the structural formula (CH.sub.3).sub.3SiO((CH.sub.3).sub.2SiO).sub.80((CH.sub.3)(C.sub.8H.sub.17)SiO).sub.2Si(CH.sub.3).sub.3, characterized by NMR spectroscopy, and a dynamic viscosity of 100 mPa.Math.s measured at 25° C., which is prepared with reference to “The method for preparing long chain alkyl silicone oil using hydrogen silicone oil as a starting material” in the last third paragraph, Page 413, Synthesis and Application of Organic Silicon Products [M], Beijing: Chemical Industry Press, 2009, Lai Guoqiao, Xing Songmin et al.) at the same thermally conductive filler loading. The results show that Polymer A-1 is more effective in reducing the viscosity than Polymer C.

TABLE-US-00005 TABLE 5 Components (wt %) Composition N-5 Composition N-9′ Polymer A-1 10 / Polymer C / 10 Alumina A 25 25 Alumina B 36 36 Zinc oxide 29 29 Viscosity of Composition (mPa .Math. s) D = 1 s.sup.−1 422000 687000

[0145] Table 6 investigates the viscosity changes of the polyorganosiloxanes Polymer A-1 and Polymer D (WACKER® AK 100) at a thermally conductive filler loading of 90% and 91%. The results show that Polymer A-1 can significantly reduce the viscosity, and thus improve the flowability and processability, of the resulting compositions, compared with Polymer D at the same thermally conductive filler loading. In addition, for the compositions with the same viscosity, Polymer A-1 accepts a higher level of thermally conductive fillers than Polymer D, thereby increasing the thermal conductivity of the composition. It should be noted that Polymer D is well known for its bleeding-out tendency during the molding, storage and use of a thermally conductive silicone composition thereof.

TABLE-US-00006 TABLE 6 Components Composi- Composi- Composi- Composi- (wt %) tion N-5 tion N-10 tion N-11′ tion N-12′ Polymer A-1 10 9 / / Polymer D / / 10 9 Alumina A 25 25.3 25 25.3 Alumina B 36 36.4 36 36.4 Zinc oxide 29 29.3 29 29.3 Viscosity of Composition (mPa .Math. s) D = 10 s.sup.−1 72000 122000 130000 184000