Method for Preparing Polyorganosiloxanes (Pos) by Ring (S) - Opening Polymerization and/or Pos Redistribution in the Presence of Carbene (S) and Pos Compounds Produced by Said Method

Abstract

A method for preparing polyorganosiloxanes (POS) by a ring-opening polymerization and/or linear, non-linear or cyclic POS redistribution in the presence of a nucleophilic carbene. The initial efficiency of the POS conversion is substantially increased at low temperature, resulting in less residual content of initial POS.

Description

EXAMPLES

Generalities

The precursor imidazolium salt 1 is prepared according to the conventional procedure described in the literature using HBF₄ as Brönsted acid. It has the following structure:

The other starting materials are commercially available.

Example 1

10 g of octamethylcyclotetrasiloxane (D4) and 100 mg of hexamethyldisiloxane (M2) are mixed in a 30 ml flask. 100 mg of imidazolium salt 1 (0.34 mmol) and 39 mg of t-BuOK (0.34 mmol) are placed in a weighing tube. 0.5 ml of anhydrous THF is added and the suspension obtained is rapidly added to the flask containing the M2 and the D4.

The reaction mixture is stirred at ambient temperature for 24 h. It gradually becomes viscous and a silicon NMR analysis shows that 95% of the D4 has polymerized and is in the form of a polysiloxane chain.

Example 2

10 g of octamethylcyclotetrasiloxane (D4) and 100 mg of hexamethyldisiloxane (M2) are mixed in a 30 ml flask. 100 mg of imidazolium salt 1 (0.34 mmol) and 39 mg of t-BuOK (0.34 mmol) are placed in a weighing tube. 0.5 ml of anhydrous THF is added and the suspension obtained is rapidly added to the flask containing the M2 and the D4.

The reaction mixture is stirred at 60° C. for 2 h. It gradually becomes viscous and a silicon NMR analysis shows that 95% of the D4 has polymerized and is in the form of a polysiloxane chain.

Counterexample 1

10 g of octamethylcyclotetrasiloxane (D4) and 100 mg of hexamethyldisiloxane (M2) are mixed in a 30 ml flask. 39 mg of t-BuOK (0.34 mmol) are placed in a weighing tube. 0.5 ml of anhydrous THF is added and the suspension obtained is rapidly added to the flask containing the M2 and the D4.

The reaction mixture is stirred at ambient temperature for 24 h. It remains very fluid and the silicon NMR analysis shows that less than 5% of the D4 has polymerized.

Counterexample 2

10 g of octamethylcyclotetrasiloxane (D4) and 100 mg of hexamethyldisiloxane (M2) are mixed in a 30 ml flask. 39 mg of t-BuOK (0.34 mmol) are placed in a weighing tube. 0.5 ml of anhydrous THF is added and the suspension obtained is rapidly added to the flask containing the M2 and the D4.

The reaction mixture is stirred at 60° C. for 2 h. It becomes slightly more viscous and silicon NMR analysis shows that only 30% of the D4 has polymerized so as to be in the form of a polysiloxane chain.

Discussions:

The above examples show that it is possible to polymerize octamethyltetracyclosiloxane (D4), in the presence of a chain limiter (with diaminocarbene-type catalysts at ambient temperature and in temperature. The rate of conversion of the D4 is greater than or equal to 95% relative to the initial amount. The structure of the polyorganosiloxane obtained is identical to that of an oil of H47 type.

Claims

1-27. (canceled)

28. A method for preparing polyorganosiloxanes (POSs) by ring-opening and/or redistribution polymerization of POSs, in the presence of a catalyst (C), wherein said catalyst (C) comprises at least one carbene.

29. The method of claim 28, wherein the carbene of catalyst (C) comprises two nonbonding electrons, which are in the singlet or triplet, preferably singlet, form.

30. The method of claim 28, wherein the carbene of catalyst (C) has a general structure represented by formula (Io):

31. The method of claim 30, wherein the carbene of catalyst (C) has a general structure represented by formula (I), (I′) or (I″):

32. The method of claim 30, wherein the carbene of catalyst (C) corresponds to formula (II) or (II′):

33. The method of claim 28, wherein the carbene is prepared separately, and/or is generated in situ from at least one precursor.

34. The method of claim 33, wherein the precursor is a salt corresponding to the carbene, which is reacted with at least one base, so as to generate the carbene in situ.

35. The method of claim 34, wherein the corresponding salt is at least one corresponding heterocyclic salt of general formula (III) or (III′):

36. The method of claim 28, wherein said method is carried out, by homogeneous catalysis, in a liquid reaction medium in which are at least partially solubilized said catalyst (C) and/or its precursor(s) and the initial POSs, and optionally at least one base.

37. The method of claim 28, wherein the solubility of said catalyst (C) and/or its precursor(s) is controlled by means of at least one solubilization helper and/or by using at least one carbene substituted with at least one appropriate group.

38. The method of claim 28, wherein said method is performed at a temperature T (° C.) such that T≦200, preferably 100≦T≦150, and even more preferably T≦100.

39. The method of claim 28, wherein the concentration of catalyst (C), in mol per 100 g of initial POSs, in a reaction medium is such that [C]≦1, preferably 10−5≦[C]≦10−1 and even more preferably 10−5≦[C]≦10−3.

40. The method of claim 28, wherein the initial POSs comprise cyclic POSs (POScy), preferably chosen from those corresponding to general formula (XI) below:

41. The method of claim 28, wherein the initial POSs are linear and are preferably selected from those of general formula (XII.1): Ra—[(Rb)2Si—O—]p—Si(Rb)2—Ra  (XII.1)

42. The method of claim 41, wherein a final POS/POScy ratio in the reaction medium is greater than 85/15, preferably greater than or equal to 90/10, and even more preferably greater than or equal to 95/5.

43. The method of claim 31, wherein the following are used: POSs substituted with catalytic functions able to generate carbenes, and preferably catalytic functions derived from products of formula (Io), (I) or (I′);and/or silanes of formula: (OR*)4-aSi(Rc)a

44. The method of claim 32, wherein the following are used: POSs substituted with catalytic functions able to generate carbenes, and preferably catalytic functions derived from products of formula (II) or (II′);and/or silanes of formula: (OR*)4-aSi(Rc)a

45. The method of claim 35, wherein the following are used: POSs substituted with catalytic functions able to generate carbenes, and preferably catalytic functions derived from products of formula (III) or (III′);and/or silanes of formula: (OR*)4-aSi(Rc)a

46. A composition that can be used in particular for the preparation of polyorganosiloxanes (POSs) by polymerization and/or redistribution of POSs, comprising linear or nonlinear POSs and/or cyclic POSs (POScy);a catalyst (C) comprising at least one carbene in which the two nonbonding electrons are preferably in the singlet form; with the exclusion of any catalyst formed by at least one metal/carbene complex, in particular Pt/carbene;optionally, at least one solvent;and, optionally, linear POSs, for example polydialkyl (e.g. methyl)siloxanes MDpM with p=0 to 20, preferably 0 to 10, and more preferably p=0: namely, disiloxanes, for example those belonging to the group comprising hexamethyldisiloxane (M2), vinylated M2 and hydrogenated M2.

47. The composition of claim 46, wherein the carbene of catalyst (C) comprises two nonbonding electrons, which are in the singlet or triplet, preferably singlet, form.

48. The composition of claim 46, wherein the initial POSs comprise cyclic POSs (POScy), preferably chosen from those corresponding to general formula (XI) below:

49. The composition of claim 46, wherein catalyst (C) is generated in situ from at least one precursor chosen from the group comprising at least one salt corresponding to the carbene, capable of reacting with at least one base, so as to generate the carbene in situ.

50. The composition of claim 46, further comprising at least one solubilization helper and/or the carbene is substituted with at least one solubilizing group.

51. The composition of claim 46, wherein the concentration of catalyst (C), in mol per 100 g of initial POSs, in a reaction medium is such that [C]≦1, preferably 10−5≦[C]≦10−1 and even more preferably 10−5≦[C]≦10−3.

52. A silicone composition, comprising: at least one POS obtained by polymerization and/or redistribution of POSs;at least one residue of catalyst (C) comprising at least one carbene.

53. A silicone composition comprising at least one POS obtained by ring opening and then polymerization and/or redistribution of POSs, and in particular of POScy, having a final POS/POScy ratio of greater than 85/15, preferably greater than or equal to 90/10, and even more preferably greater than or equal to 95/5.

54. POSs substituted with catalytic functions able to generate carbenes, preferably derived from products of formula (Io), (I) or (I′) as defined in claim 31.

55. POSs substituted with catalytic functions able to generate carbenes, preferably derived from products of formula (II) or (II′) as defined in claim 32.

56. POSs substituted with catalytic functions able to generate carbenes, preferably derived from products of formula (III) or (III′) as defined in claim 35.

57. Silanes of formula: (OR*)4-aSi(Rc)a

58. Silanes of formula: (OR*)4-aSi(Rc)a

59. Silanes of formula: (OR*)4-aSi(Rc)a

60. Use of a carbene comprising two non-bonding electrons, which are in the singlet or triplet, preferably triplet form, as a catalyst or cocatalyst in the preparation of POSs by polymerization and/or redistribution of POSs.