Siloxane mixtures

Patent metadata

Field	Value
Publication number	US-9862869-B2
Application number	US-201314409341-A
Country	US
Kind code	B2
Filing date	Jun 11, 2013
Priority date	Jun 29, 2012
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

The invention provides mixtures, liquid at 25° C., of methylpolysiloxanes comprising at least two methylpolysiloxanes selected from linear compounds of the general formula I Me 3 SiO-(Me 2 SiO)x-SiMe 3 (I), and cyclic compounds of the general formula II (Me 2 SiO)y (II), wherein the mixture comprises at least one linear methylpolysiloxane of the general formula I and at least one cyclic methylpolysiloxane of the general formula II, Me means methyl radical, x has values greater than or equal to zero and the arithmetic mean of x, weighted by the molar proportions, over all linear methylpolysiloxanes is between 3 and 20, y has values greater than or equal to 3 and the arithmetic mean of y, weighted by the molar proportions, over all cyclic methylpolysiloxanes is between 3 and 6, the numerical ratio of the Me 3 Si— chain ends groups in the compounds of the general formula I to the sum of the Me 2 SiO— units in the compounds of the general formulae I and II is at least 1:2 and at most 1:10, and further definitions are described in claim 1 , and the use of the mixtures as heat carrier fluids.

First claim

The invention claimed is:

1. A mixture of methylpolysiloxanes containing at least two methylpolysiloxanes selected from linear compounds of the general formula I
Me 3 SiO-(Me 2 SiO) x —SiMe 3   (I)

and cyclic compounds of the general formula II
(Me 2 SiO) y   (II)

where
the mixture contains at least one linear methylpolysiloxane of the general formula I and at least one cyclic methylpolysiloxane of the general formula II,
Me is a methyl radical,
x has values greater than or equal to zero and an arithmetic mean of x over all the linear methylpolysiloxanes, weighted by molar proportions, is between 3 and 20,
y has values greater than or equal to 3 and an arithmetic mean of y over all the cyclic methylpolysiloxanes, weighted by molar proportions, is between 3 and 6,
a numerical ratio of Me 3 Si— chain end groups in the compounds of the general formula I to a sum total of Me 2 SiO— units in the compounds of the general formulae I and II is at least 1:2 and at most 1:10,
proportions of the linear methylpolysiloxanes of the general formula I are each independently,
for x=zero, between zero and 14% by mass,
for x=1 to 3, in each case between zero and 14% by mass,
for x=4 and 5, in each case between zero and 14% by mass,
for x=6 to 9, in each case between zero and 16% by mass,
for x=10 and 11, in each case between zero and 12% by mass,
for x=12 to 14, in each case between zero and 10% by mass,
for x=15 to 28, in each case between zero and 10% by mass,
for x=29 and 30, in each case between zero and 8% by mass,
for x=31 to 34, in each case between zero and 4% by mass,
for x=35 to 40, in each case between zero and 2% by mass,
for x=41 to 70, in each case between zero and 1% by mass, and,
for x greater than 70, in each case between zero and 0.5% by mass, proportions of the cyclic methylpolysiloxanes of the general formula II are each independently,
for y=3, between zero and 10% by mass,
for y=4, between zero and 30% by mass,
for y=5, between zero and 15% by mass,
for y=6, between zero and 10% by mass,
for y=7, between zero and 8% by mass,
for y=8 to 11, in each case between zero and 5% by mass,
for y=12 to 15, in each case between zero and 2.5% by mass,
for y=16 to 19, in each case between zero and 2% by mass,
for y=20 to 40, in each case between zero and 1% by mass, and,
for y greater than 40, in each case between zero and 0.5% by mass,
a sum of the proportions of all the cyclic methylpolysiloxanes of the general formula II is at least 10% by mass and at most 40% by mass, and
wherein the mixture consists of 1-10% by mass of linear methylpolysiloxanes of the general formula I in which x assumes values between zero and 8 and the arithmetic mean of x, weighted by the molar proportions, is between zero and 1.5, and 15-30% by mass of cyclic methylpolysiloxanes of the general formula II in which y assumes values between 3 and 12 and the arithmetic mean of y, weighted by the molar proportions, is between 3.5 and 5, and 60-84% by mass of linear methylpolysiloxanes of the general formula I, in which x assumes values between 4 and 70 and the arithmetic mean of x, weighted by the molar proportions, is between 4 and 15, including the limits stated in each case, where the mixture has a viscosity at 25° C. of less than 10 mPa*s.

2. The mixture as claimed in claim 1 , in which the arithmetic mean of x over all the linear methylpolysiloxanes, weighted by the molar proportions, is between 4 and 15.

3. The mixture as claimed in claim 1 , in which the arithmetic mean of y over all the cyclic methylpolysiloxanes, weighted by the molar proportions, is between 3.5 and 5.5.

4. The mixture as claimed in claim 1 , in which the numerical ratio of the Me 3 Si— chain end groups in the compounds of the general formula I to the sum total of Me 2 SiO— units in the compounds of the general formulae I and II is at least 1:2.5 and at most 1:8.

5. The mixture as claimed in claim 1 , in which physical properties selected from density, vapor pressure, viscosity, heat capacity and thermal conductivity of the mixture, after attainment of a constant temperature between 300° C. and 600° C. under exclusion of air, change by not more than 15% before attainment of an equilibrium composition.

6. A method of transferring heat, said method comprising providing a mixture as claimed in claim 1 as a heat transfer fluid and heating the mixture to transfer heat.

7. The method as claimed in claim 6 for solar thermal devices.

8. The method as claimed in claim 6 , wherein the mixture is heated to temperatures of 200° C. to 550° C.

9. The mixture as claimed in claim 2 , in which the arithmetic mean of y over all the cyclic methylpolysiloxanes, weighted by the molar proportions, is between 3.5 and 5.5.

10. The mixture as claimed in claim 9 , in which the numerical ratio of the Me 3 Si— chain end groups in the compounds of the general formula I to the sum total of Me 2 SiO— units in the compounds of the general formulae I and II is at least 1:2.5 and at most 1:8.

11. The mixture as claimed in claim 10 , in which physical properties selected from density, vapor pressure, viscosity, heat capacity and thermal conductivity of the mixture, after attainment of a constant temperature between 300° C. and 600° C. under exclusion of air, change by not more than 15% before attainment of an equilibrium composition.

Assignees

• Wacker Chemie Ag

Inventors

• Hoffmann Florian
• Stohrer Juergen

Classifications

• C08G77/045

  containing less than 25 silicon atoms · CPC title

• F24J2/4649

  Mechanical Engineering · mapped topic

• C08L83/00

  Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers · CPC title

• C08L83/04

  Polysiloxanes · CPC title

• C09K5/10 Primary

  Liquid materials · CPC title