WO2016145274A1

WO2016145274A1 - Method of removing organopolysiloxanes from a mixture of organopolysiloxanes

Info

Publication number: WO2016145274A1
Application number: PCT/US2016/021918
Authority: WO
Inventors: Chad A. BUESING; Michael A. DEPIERRO; Michael A. HAUSINGER; Dennis G. VAN KOEVERING
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 2015-03-11
Filing date: 2016-03-11
Publication date: 2016-09-15
Anticipated expiration: 2017-09-11

Abstract

A method for removing cyclic organopolysiloxanes from an organopolysiloxane mixture, the method comprising: i) contacting an organopolysiloxane mixture comprising a cyclic organopolysiloxane and a non-cyclic organopolysiloxane with nitrogen to form a first stream comprising the nitrogen and the cyclic organopolysiloxane and a second stream comprising the non-cyclic organopolysiloxane.

Description

METHOD OF REMOVING CYCLIC ORGANOPOLYSILOXANES FROM A MIXTURE OF

ORGANOPOLYSILOXANES

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] None

FIELD OF THE INVENTION

[0002] The present invention relates, generally, to a method of removing cyclic organopolysiloxanes from a mixture of cyclic organopolysiloxanes and non-cyclic organopolysiloxanes comprising contacting the mixture with nitrogen to form a first stream comprising the non-cyclic organopolysiloxanes and a second stream comprising the nitrogen and the cyclic organopolysiloxane.

BACKGROUND OF THE INVENTION

[0003] Most manufacturers of siloxanes include a specification for maximum content of volatile material for siloxane products because volatile materials can cause performance issues in end uses or applications for the siloxane products. In addition, regulations may also require the reduction of some specific volatile materials in siloxane products. Therefore, processes to purify siloxanes are important to the production of siloxanes, and the removal of volatile materials from low molecular weight siloxanes has been a challenge in siloxane production. In particular, the removal of volatile cyclic siloxanes from low molecular weight, reactive, non-cyclic siloxanes has been a challenge for manufacturers.

[0004] Various methods of removing cyclic organopolysiloxanes or volatile

organopolysiloxanes from organopolysiloxanes using various gases have been reported. For example, the use of steam to remove volatile cyclic siloxanes from short chain, silanol- terminated siloxanes by stripping in a distillation column has been disclosed. In addition, removing low molecular weight siloxanes by bringing a multiplicity of jets of siloxane into contact with gaseous carbon dioxide has been disclosed. In this method, some carbon dioxide dissolves in the purified siloxane and creates layers of purified siloxane and unpurified siloxane that then must be separated, and the lower purity siloxane may then be recirculated in the process to increase its purity. The entrained carbon dioxide is removed from the purified siloxane to give the purified product. The carbon dioxide is either released into the atmosphere or recirculated in the process after precipitation of the entrained volatiles. Further, a process for removing cyclic siloxanes from a siloxane emulsion has been disclosed in which cyclic siloxanes are stripped out of the emulsion using a falling film evaporator. [0005] Even though processes have been disclosed to remove volatile materials, including cyclic siloxanes, from siloxanes, these process still can be improved. For example, the processes described operate at higher temperatures. Operating at these higher

temperatures make the processes more energy intensive, creates more byproducts, and may increase chain lengths of non-cyclic polysiloxanes. Further, the processes may add additional materials, such as water or moisture, to the organopolysiloxane product. Still further, the processes may not allow for the efficient recirculation of a gas used for the removal of the volatile organopolysiloxane. Finally, to reduce the cyclic polysiloxane amounts in the non-cyclic polysiloxane in these processes can require the recirculation of the non-cyclic polysiloxane in the process increasing the time and energy required of the process.

[0006] Thus, a need still exists for a process to remove cyclic organopolysiloxanes from non-cyclic reactive, and/or non-reactive, organopolysiloxanes, such as those which are silanol end-blocked, with improved efficiency and that are conducted at lower temperatures to avoid the associated chain lengthening, byproducts, and energy requirements; that do not add unwanted materials to the organopolysiloxane product; and that allow for the efficient recycle of a gas used to remove the volatile organopolysiloxane in the process.

BRIEF SUMMARY OF THE INVENTION

[0007] The present invention is directed to a method for removing cyclic

organopolysiloxanes from a mixture of organopolysiloxanes, the method comprising: i) contacting an organopolysiloxane mixture comprising a cyclic organopolysiloxane and a non- cyclic organopolysiloxane with nitrogen to form a first stream comprising the nitrogen and the cyclic organopolysiloxane and a second stream comprising the non-cyclic

organopolysiloxane.

[0008] The method of the invention for removing cyclic organopolysiloxane from a non- cyclic organopolysiloxane provides a purified organopolysiloxane with low levels of cyclic organopolysiloxane with good efficiency. The method allows for the quick separation of the cyclic from the non-cyclic organopolysiloxane so that recycling of the non-cyclic

organopolysiloxane in the process to reduce the amount of cyclic organopolysiloxanes to acceptable levels is reduced or eliminated, and the chain length of the non-cyclic

organopolysiloxanes is not substantially increased in the process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a schematic representation of one embodiment of the present process. DETAILED DESCRIPTION OF THE INVENTION

[0010] The Brief Summary and Abstract are incorporated here by reference. The invention embodiments, uses and advantages summarized above are further described below.

[0011] Aspects of the invention are described herein using various common conventions. For example, all states of matter are determined at 25 °C and 101 .3 kPa unless indicated otherwise. All % are by weight unless otherwise noted or indicated. All % values are, unless otherwise noted, based on total amount of all ingredients used to make the composition, which adds up to 100%. Any Markush group comprising a genus and subgenus therein includes the subgenus in the genus, e.g., in "R is hydrocarbyl or alkenyl," R may be alkenyl, alternatively R may be hydrocarbyl, which includes, among other subgenuses, alkenyl.

[0012] Aspects of the invention are described herein using various patent terms. For example, "alternatively" indicates a different and distinct embodiment. "Comparative" as used in comparative example, comparative process or comparative method means a non- invention experiment and should not be interpreted as prior art. "Comprises" and its variants (comprising, comprised of) are open ended. "Consists of" and its variants (consisting of) are closed ended. "Contacting" means bringing into physical contact. "May" confers a choice, not an imperative. Optionally" means is absent, alternatively is present.

[0013] For illustration, the invention is described with reference to an embodiment of the invention depicted in Figure 1 ; however, the invention is not limited to this one embodiment. One skilled in the art will recognize that the invention can be practiced using a number of slight variations of the method not described herein, and these variations are within the scope of the invention.

[0014] As used herein "azeotroping solvent" is intended to mean a substance added to an organopolysiloxane mixture in order to form an azeotropic mixture for azeotropic distillation.

[0015] A method for removing cyclic organopolysiloxanes from a mixture of

organopolysiloxanes, the method comprising:

i) contacting an organopolysiloxane mixture comprising a cyclic organopolysiloxane and a non-cyclic organopolysiloxane with nitrogen to form a first stream comprising the nitrogen and the cyclic organopolysiloxane and a second stream comprising the non-cyclic organopolysiloxane.

[0016] With reference to Figure 1 , nitrogen 120 and an organopolysiloxane mixture 100 comprising a cyclic organopolysiloxane and a non-cyclic organopolysiloxanes are contacted in i) to form a first stream 190 comprising the nitrogen and the cyclic organopolysiloxane and a second stream 240 comprising the non-cyclic organopolysiloxane. [0017] The nitrogen is available commercially. One skilled in the art would know how to obtain and use nitrogen.

[0018] The organopolysiloxane mixture comprises a cyclic organopolysiloxane and a non- cyclic organopolysiloxane, alternatively a cyclic organopolysiloxane, a non-cyclic

organopolysiloxane, and an azeotroping solvent. The cyclic organopolysiloxane comprises 3 to 10, alternatively 3 to 8, alternatively 4 to 5 silicon atoms in the polymer ring and has monomer units of the formula -R2S1O2/2-, wherein each R is independently C-| _-| Q hydrocarbyl, alternatively 0-1 .4 hydrocarbyl, alternatively R is 0-1 .4 alkyl, alternatively methyl.

Examples of hydrocarbyl groups represented by R include, but are not limited to, methyl, ethyl, propyl, 1 -methylethyl, butyl, 1 -methylpropyl, 2-methylpropyl, 1 ,1 -dimethylethyl, pentyl, I methylbutyl, 1 -ethylpropyl, 2-methylbutyl, 3-methylbutyl, 1 ,2-dimethylpropyl, 2,2- dimethylpropyl, hexyl, heptyl, octyl, nonyl, and decyl; cycloalkyl, such as cyclopentyl, cyclohexyl, and methylcyclohexyl; aryl, such as phenyl and naphthyl; alkaryl such as tolyl and xylyl; aralkyl, such as benzyl and phenethyl; alkenyl, such as vinyl, allyl, and propenyl, butenyl, hexenyl, and octenyl; arylalkenyl, such as styryl and cinnamyl; and alkynyl, such as ethynyl and propynyl. Examples of cyclic organopolysiloxanes include, but are not limited to, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane,

hexadecamethylcyclooctasiloxane, octadecamethylcyclononasiloxane, and

eicosamethylcyclodecasiloxane.

[0019] The cyclic organopolysiloxane can be a mixture of cyclic organopolysiloxanes. Examples of mixtures of cyclic organopolysiloxanes include, but are not limited to, a mixture comprising at least two of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane, alternatively a mixture comprising

octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane.

[0020] Cyclic organopolysiloxanes according to the invention are available commercially. One skilled in the art would know how to make cyclic organopolysiloxanes.

[0021] The non-cyclic organopolysiloxane in the organopolysiloxane mixture may be a linear, branched, or a mixture of linear and branched organopolysiloxanes, alternatively a linear, branched, or mixture of linear or branched silanol end-capped organopolysiloxanes. As used herein, "silanol end-capped" means that the organopolysiloxane has an SiOH group on at least one terminus, alternatively two or more termini, of an organopolysiloxane chain.

[0022] The non-cyclic organopolysiloxane in the organopolysiloxane mixture has a viscosity below 1000 cSt, alternatively below 100 cSt, alternatively below 50 cSt. Viscosity is measured at 25 °C using a Ubbelohde glass capillary, gravity-flow viscometer according to ASTM D-445, IP 71 , where a clean, dry calibrated viscometer that will yield a flow time of greater than 80 s with the sample is used. The viscometer is loaded in the correct manner as required by the viscometer. The tube is placed in a constant temperature bath and allowed to reach equilibrium (at least 15 min. at 25 C). Suction or Pressure is used to adjust the head level of the sample to a point about 5 mm above the first timing mark. The sample is allowed to flow freely, and the timer is started as the meniscus passes the first timing mark. The timer is stopped as the meniscus passes the second timing mark, and the time is recorded to the nearest 0.1 s. The test is repeated without refilling the tube, and the average is used in calculating the viscosity. The viscometer is calibrated using either primary or secondary standards.

[0023] The non-cyclic organopolysiloxane in the organopolysiloxane mixture comprises one or more of the polymer units according to the formula -R2S1O2/2. -R3S1O-1 /2,

-R2(OH)SiO-| /2, -RS1O3/2, and S1O4/2, alternatively -R2S1O2/2, -R3S1O1 /2, -RS1O3/2, and R2(OH)SiO-| /2, alternatively -R2S1O2/2. and -R2(OH)SiO-| /2, where R is as defined above, hydrogen, or an amino, amido, cyano, sulfido, epoxy, or aziridino group.

[0024] In one embodiment, the non-cyclic organopolysiloxane has a boiling point at or below 220 °C, alternatively below 215 °C, alternatively below 200 °C, alternatively below 150 °C, alternatively from 120 to 220 °C, alternatively from 120 to 215 °C

[0025] Examples of non-cylic organopolysiloxanes include, but are not limited to linear and branched silanol end-capped polydimethylsiloxane or polydimethylhydrogensiloxanes of varying viscosity and molecular weight, tetrakis-(trimethylsilyl)siloxane, tetrakis- (dimethylsiloxy)siloxane, tris-(trimethylsilyl)(hydroxy)siloxane, tris- (dimethylhydroxysilyl)(hydroxyl)siloxane, tris-(dimethylsilyl)siloxane, tris- (trimethyl(hydroxy)silyl)siloxane, tris-(trimethysilyl)siloxane.

[0026] As used herein, "polyorganosilane" and "organopolysiloxane" may be used interchangeably and are intended to mean polymers containing siloxane linkages (i.e., - Si(R)2-0-Si(R)2") in the polymer backbone and with organic groups attached to some of the silicon atoms as well.

[0027] The non-cyclic organopolysiloxanes may be a mixture of non-cyclic

organopolysiloxanes of varying viscosity, molecular weight and structure that give an overall viscosity as described above. [0028] Non-cyclic organopolysiloxanes, cyclic organopolysiloxane and mixtures of non- cyclic and cyclic organopolysiloxanes according to the invention are available commercially. One skilled in the art would know how to make non-cyclic organopolysiloxanes according to the invention.

[0029] The organopolysiloxane mixture may comprise other cyclic organopolysiloxanes of greater molecular weight and viscosity than those described above that remain with the non- cyclic organopolysiloxane in the method of the invention and are not separated from the non- cyclic organopolysiloxane.

[0030] The organopolysiloxane mixture may comprise an azeotroping solvent. Azeotropic and azeotropic-like mixtures are known in the art. For example, the following patents, the descriptions of which are all incorporated herein by reference, describe azeotropic mixtures: U.S. Pat. Nos. 5,492, 647A; 5,478,493A; 5,454,970A; 5,454,972. Azeotropic mixtures are mixtures of the components that vaporize with no change in the composition of the vapor from the liquid. Specifically, azeotropic mixtures boil without changing composition and evaporate at a temperature below their boiling point without changing composition.

Accordingly, an azeotropic mixture may include mixtures of two components over a range of proportions where each specific proportion of the two components is an azeotropic mixture at a certain temperature but not necessarily at other temperatures. The vapor pressure of low boiling azeotropic mixtures is higher, and the boiling point is lower, than the individual components. In fact, the azeotropic mixture has the lowest boiling point of any composition of its components. Thus, an azeotropic mixture can be obtained by distillation of a mixture whose composition initially departs from that of the azeotropic mixture.

[0031] An azeotropic-like mixture is a mixture of two components that acts like an azeotropic mixture. Thus azeotropic-like mixtures have constant boiling characteristics, or have a tendency not to fractionate upon boiling or evaporation. In an azeotropic-like mixture, the composition of the vapor formed during boiling or evaporation is identical or substantially identical to the composition of the original liquid. During boiling or evaporation, the liquid changes only minimally, or to a negligible extent, if it changes at all. In other words, it has about the same composition in vapor phase as in liquid phase when employed at reflux. In contrast, the liquid composition of non-azeotropic-like mixtures change to a substantial degree during boiling or evaporation. By definition, azeotropic-like mixtures include all ratios of the azeotropic mixtures boiling within one °C of the minimum boiling point at 760 Torr.

[0032] An azeotroping solvent according to our invention is a material that forms an azeotropic mixture or azeotropic-like mixture with all or a portion of the cyclic organopolysiloxanes or the non-cyclic organopolysiloxanes in the organopolysiloxane mixture, alternatively the cyclic organopolysiloxane, alternatively the

octamethylcyclotetrasiloxane in the organopolysiloxane mixture.

[0033] The azeotroping solvent is at least one solvent selected from the group consisting of a) n-butyl lactate, b) ethyl lactate, c) isopropyl lactate, d) 1 -butoxy-2-ethanol, e) 1 - methoxy-2-propanol, f) n-propoxypropanol, g) 1 -butoxy-2-propanol, h) 2- pentanol, 2-methyl- 1 -pentanol, i) 3-methyl-3-pentanol, j) 1 -hexanol, k) cyclohexanol, I) 2-methylcyclohexanol, m) 4-methylcyclohexanol, n) 1 -heptanol, and o) a mixture of any two or more of a) through n). The azeotroping solvents of the invention are available commercially.

[0034] The amount of cyclic organopolysiloxane in the organopolysiloxane mixture can vary. Typically, the organopolysiloxane mixture comprises up to 50% (w/w), alternatively up to 25% (w/w), alternatively up to 15% (w/w), alternatively from 0.01 % to 50% (w/w), alternatively from 0.01 % to 25% (w/w), alternatively from 0.1 % to 25%, alternatively from 1 .0% to 15% (w/w), based on the weight of the cyclic organopolysiloxane and non-cyclic organopolysiloxane, of cyclic organopolysiloxane. Once skilled in the art would know how to determine the amount of cyclic organopolysiloxane in the organopolysiloxane mixture.

[0035] The amount of non-cyclic organopolysiloxane in the organopolysiloxane mixture can vary. The organopolysiloxane mixture comprises at least 50%, alternatively at least 75%, alternatively at least 85%, alternatively from 50 to 99.9999% (w/w) alternatively from 75 to 99.9999% (w/w), alternatively from 85 to 99.999% (w/w), alternatively 85 to 99.99% (w/w), based on the weight of the cyclic organopolysiloxane and the non-cyclic

organopolysiloxane, of non-cyclic organopolysiloxane.

[0036] Methods of making organopolysiloxane mixtures according to the invention are known in the art. For example, the organopolysiloxane mixture may be made by the hydrolysis and condensation of organohalosilanes followed by partial separation by distillation. The organopolysiloxane mixture may also be made by the rearrangement reaction of low molecular weight linear organopolysiloxanes. The azeotroping solvent may be added to and mixed with the organopolysiloxane mixture either in a separate kettle or inline as the organopolysiloxane is transported to the equipment used for contacting with the nitrogen. One skilled in the art would know how to make cyclic organopolysiloxanes, non- cyclic organosiloxanes, and the organopolysiloxane mixture according to the invention.

[0037] The first stream comprises the nitrogen and cyclic organopolysiloxane.

Alternatively, the first stream comprises the nitrogen, the cyclic organopolysiloxane, and the non-cyclic organopolysiloxane. The nitrogen, the cyclic organopolysiloxane, and the non- cyclic organopolysiloxane in the first stream in i) are as described above.

[0038] The first stream 190 in i) comprises up to 80% (w/w), alternatively up to 75% (w/w), alternatively from 50 to 75% (w/w), based on the weight of the nitrogen and cyclic and non- cyclic organopolysiloxane, of cyclic organopolysiloxane.

[0039] The first stream 190 in i) comprises up to 10 %, alternatively from 0.5 to 7% (w/w), alternatively from 1 to 5% (w/w), based on the weight of the nitrogen and cyclic and non- cyclic organopolysiloxane, of non-cyclic organopolysiloxane.

[0040] The second stream 240 comprises the non-cyclic organopolysiloxane from the organopolysiloxane mixture minus the cyclic organopolysiloxane removed in i). The chemical structure and viscosity of the non-cyclic organopolysiloxane 240 is as described above for the non-cyclic organopolysiloxane in the organopolysiloxane mixture.

[0041] The second stream 240 may still comprise cyclic organopolysiloxane. The concentration of the cyclic organopolysiloxane in the second stream is less than the cyclic organopolysiloxane concentration in the organopolysiloxane mixture. The second stream 240 may comprise less than 1 %, alternatively less than 10,000 ppm, alternatively, less than 1 ,000 ppm, alternatively less than 100 ppm, based on the weight of the cyclic and non-cyclic organopolysiloxane, of cyclic organopolysiloxane. The chemical structure and viscosity of the cyclic organopolysiloxane are as described above for the organopolysiloxane mixture.

[0042] The mole ratio of the nitrogen 120 to the organopolysiloxane mixture 100 contacted in i) is from 0.05 to 0.5, alternatively from 0.05 to 0.25. One skilled in the art would know how to adjust the nitrogen and organosiloxane mixture flow rates in column 290 to achieve the ratios of nitrogen to the organopolysiloxane mixture.

[0043] The nitrogen and organopolysiloxane mixture are contacted in column 290. The column 290 may comprise a stripping section 291 and may comprise a reflux section 292. When both are present, the stripping section 291 is below the reflux section 292. In one embodiment, the column comprises both a stripping section 291 and a reflux section 292 alternatively a stripping section and no flux section. One skilled in the art would know what a column with a stripping and reflux sections is.

[0044] The nitrogen stream 120 enters the column 290 below the stripping section 291 and flows up through the stripping section 291 contacting the organopolysiloxane mixture 100 and then, with the cyclic organopolysiloxane removed from the organopolysiloxane mixture 100, through the reflux section 292, if present, before exiting the column in the first stream 190. The first stream 190 exits the column near the top of the column. The nitrogen 120 and organopolysiloxane mixture 100 flow countercurrent through column 290,

alternatively through stripping section 291 .

[0045] The temperature of the nitrogen 120 contacted in i) is not critical. The temperature of the nitrogen may be from 20 °C to 150 °C, alternatively from 40 °C to 145 °C, alternatively from 120 °C to 140 °C. The temperature of the nitrogen may be achieved by preheating the nitrogen prior to contacting in i). One skilled in the art would know how to adjust the temperature of nitrogen by, for example, sending the gas through a heater.

[0046] The organopolysiloxane mixture 100 may enter the column above the stripping 291 and above or below the reflux 292 section, when present, alternatively below the reflux section 292 of the column 290 and flows countercurrent to the direction of nitrogen 120 flow in the stripping section. The second stream 240 exits the column near the bottom of the stripping section 291 of the column 290.

[0047] One skilled in the art would know how to achieve the flow of nitrogen 120 and the organopolysiloxane mixture 100 through the column 290. The process may be continuous process, where the nitrogen 120 and the organopolysiloxane mixure 100 are continually flowed countercurrently through the column 290.

[0048] The temperature of the organopolysiloxane mixture 100 in i) may vary. The organopolysiloxane mixture 100 contacted in i) may have a temperature from 120 to 200 °C, alternatively from 130 to 180 °C, alternatively from 140 to 160 °C.

[0049] The temperature of the organopolysiloxane in i) may be achieved by preheating the organopolysiloxane mixture prior to contacting with the nitrogen using a heater 110. One skilled in the art would know how to preheat the organopolysiloxane mixture and how to adjust the temperature of the organopolysiloxane mixture using a heater 110. Any heater suitable for preheating the organopolysiloxane mixture of the invention may be used as the heater 110.

[0050] The temperature of the stripping section 291 of the column may vary. Typically the temperature is from 1 15 to 175 °C, alternatively from 120 to 160 °C, alternatively from 125 to 150 °C. One skilled in the art would know how to vary the temperature in the stripping section of a column depending upon the composition of the organopolysiloxane mixture.

[0051 ] The temperature of the reflux section 292 of the column may vary. In one embodiment, the temperature is from 80 to 1 90 °C, alternatively from 85 to 180 °C, alternatively from 90 to 150 °C. One skilled in the art would know how to vary the temperature in the reflux section of a column depending upon the composition of the organopolysiloxane mixture. [0052] The pressure in the column 290 may be from atmospheric to below atmospheric pressure, alternatively from 0 to 27 kPa, alternatively from 10 to 17 kPa. One skilled in the art would know how to vary the pressure in the column 290. As used herein, "pressure" is intended to refer to gauge pressure and not absolute pressure, which does not include atmospheric pressure.

[0053] The water content of the second stream is less than or equal to 1000 μg/g, alternatively less than or equal to 850 μg/g, alternatively less than or equal to 800 μg/g, alternatively less than or equal to 500 μg/g, based on the weight of the entire second stream. The amount of water in the second stream can be measured by Karl Fisher titration as described in the examples.

[0054] A portion of the cyclic organopolysiloxane may be removed from the first stream 190 in ii) to form a partially purified first stream 180 and a third stream 150 comprising the portion of the cyclic organopolysiloxane removed from the first stream. The cyclic organopolysiloxane may be removed from the first stream by condensing the cyclic organopolysiloxane from the first stream 190 in a condenser 160, alternatively the cyclic organopolysiloxane may be removed using an absorber 210 as described below for iii). The cyclic organopolysiloxane in the third stream 150 and removed in ii) is as described above for i). One skilled in the art would know how to use a condenser 160 to remove the cyclic organopolysiloxane from the first stream 190.

[0055] In iii), the first stream 190 from i), or, when ii) is present, the first stream 190 from i) or the partially purified first stream 180 from ii) may be contacted with a cool

organopolysiloxane comprising an organopolysiloxane, wherein the cool organopolysiloxane is at a temperature up to 60 °C, alternatively up to 40 °C, alternatively from 0 to 40 °C, alternatively from 20 to 40 °C, and the first steam from 190 of the partially purified first stream from 180 are at a temperature from 30 °C to 170 °C, alternatively from 40 Ό to 160 °C, alternatively from 50 °C to 100 °C, in an absorber 210 to form a purified nitrogen stream 200 and a cyclic-containing cool organopolysiloxane stream 270. One skilled in the art would know the meaning of an absorber. For example, the absorber may consist of a tank 210 containing the cool organopolysiloxane where the first stream 190 is either bubbled^' through the cool organopolysiloxane or flowed over the top of the cool organopolysiloxane or flowed over, for example, a falling film or droplets of the cool organopolysiloxane. Absorbers are available commercially.

[0056] The cool organopolysiloxane comprises an organopolysiloxane, and the

organopolysiloxane in the cool organopolysiloxane is not limited except that it must able to absorb the cyclic organopolysiloxane from the first stream from i) or the partially purified stream from ii). In one embodiment, the organopolysiloxane comprised by the cool organopolysiloxane is as described for the non-cyclic organopolysiloxane in the

organopolysiloxane mixture above. In one embodiment, the cool organopolysiloxane comprises organopolysiloxane from the first stream 240.

[0057] In one embodiment, the cool organopolysiloxane comprises from no detectable amounts to a small amount of cyclic organopolysiloxane. A small amount of cyclic organopolysiloxane means an amount that will not negatively impact the absorption of the cyclic organopolysiloxane from the first stream from i) or the partially purified stream from ii), alternatively less than 1 %, alternatively less than 10,000 ppmw, alternatively, less than 1 ,000 ppmw, alternatively less than 100 ppmw, alternatively from 1 to 1000 ppmw, alternatively from 1 to 100 ppmw, based on the weight of the cyclic and non-cyclic organopolysiloxane in the cool organopolysiloxane, of cyclic organopolysiloxane.

[0058] The cyclic-containing cool organopolysiloxane stream 270 in iii) may comprise the cyclic organopolysiloxane from the first stream 190 or the partially purified first stream 180 and the organopolysiloxane from the cool organopolysiloxane 220. The nitrogen and cyclic organopolysiloxane are as described for i) above.

[0059] The cyclic-containing cool organopolysiloxane stream 270 from iii) comprises up to 1 % w/w, alternatively up to 10,000 ppmw, alternatively up to 1 ,000 ppmw, alternatively up to 100 ppmw, alternatively from 1 to 100 ppmw, of cyclic organopolysiloxane. The cyclic organopolysiloxane in the cyclic-containing organopolysiloxane stream 270 from iii) is as described for i) above.

[0060] In iv), the purified nitrogen stream 200 from iii) is optionally contacted with the organopolysiloxane mixture 100 in i). The purified nitrogen steam 200 may be from 0% to 100%, alternatively from greater than 0 to 100% of the nitrogen contacted in i).

[0061] The amount of cyclic organopolysiloxane in the purified nitrogen stream 200 affects the efficiency of the removal of cyclic organopolysiloxane from the organopolysiloxane mixture in i), with increasing amounts of cyclic organopolysiloxane in the purified nitrogen stream 200 reducing the efficiency of the removal of cyclic organopolysiloxane from the organopolysiloxane mixture. When contacted in i), the purified nitrogen stream 200 may have up to 10,000 ppmw alternatively up to 7000 ppmw, alternatively from 1 to 7000 ppmw, alternatively up to 4000 ppmw, alternatively from 1 to 4000 ppmw, alternatively up to 1000 ppmw, alternatively from 1 to 1000 ppmw, alternatively up to 100 ppmw, alternatively from 1 to 100 ppmw based on the weight of the cyclic organopolysiloxane and the nitrogen, of cyclic organopolysiloxane

[0062] In one embodiment, a portion of the second stream 240 from i) is cooled in v) using a chiller 230 to form the cool organopolysiloxane in iii). The cool organopolysiloxane may comprise from 0 to 100%, alternatively from greater than 0 to 100% of the second stream from i). Therefore, the cool organopolysiloxane in iii) comprises cyclic, alternatively non- cyclic, alternatively a mixture of cyclic and non-cyclic organopolysiloxanes. One skilled in the art would know how to use a chiller 230 to cool the second stream 240 to form the cool organosiloxane in iii). Any chiller suitable for chilling organopolysiloxanes may be used.

[0063] In vi), the cyclic-containing cool organopolysiloxane stream 270 may be contacted with the nitrogen 120 in i). The cyclic-containing cool organopolysiloxane 270 is contacted with the nitrogen by introducing the cyclic-containing cool organopolysiloxane 270 to the column 290 near the top of the of column 290 or the top of the reflux section 292, if present. The cyclic-containing cool organopolysiloxane is contacted with nitrogen in i) to separate the cyclic organopolysiloxane from the non-cyclic organopolysiloxane.

[0064] In vii), when ii) is present, a portion of the third stream 150 from ii) may be contacted with the nitrogen in i) by introducing the third stream 150 into column 290 near the top of the column 290, or, if present, near the top of the reflux section 292 of column 290. The cyclic organopolysiloxane in third stream 150 and the reaction conditions for the contacting with the nitrogen in i) are as described in i).

[0065] The method of the invention removes a cyclic organopolysiloxane from a non-cyclic organopolysiloxane providing a purified non-cyclic organopolysiloxane with low levels of cyclic organopolysiloxane with good efficiency. The method allows for the quick separation so that recycling of the non-cyclic organopolysiloxane in the process to further reduce the cyclic organopolysiloxane in the non-cyclic organopolysiloxane to acceptable levels is reduced, thereby decreasing the possibility of increasing chain length, viscosity, branching, silanol content, or other characteristics of the non-cyclic organopolysiloxane.

[0066] The cyclic and non-cyclic organopolysiloxanes separated in the present method can be sold commercially or used to make polysiloxanes of different molecular weights and structures. For example, the cyclic organopolysiloxanes may be polymerized to make linear polysiloxanes of particular chain lengths or equilibrated to make cyclic organopolysiloxanes of different ring sizes. The non-cyclic organopolysiloxanes may also be further reacted and redistributed to make different products. These products are sold into many different end-use applications. EXAMPLES

[0067] The invention is further illustrated by, and an invention embodiment may include any combinations of features and limitations of, the non-limiting examples thereof that follow.

[0068] The following examples are included to demonstrate particular embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention. Unless otherwise indicated, all percentages are in weight % (wt. %). When the unit 'parts per million' (ppm) are used in the example, it is based on weight. The following table describes the abbreviations used in the examples: Table 2. List of abbreviations used in the examples.

Test Methods

[0069] Water content was measured by Karl Fischer using a Metrohm 774 oven accessory and Metrohm 851 coulometric titrator. Samples were heated to 130 °C during analysis.

[0070] The quantities and identities of polysiloxanes were determined by analyses using a gas chromatograph equipped with capillary column, flame ionization detector and a headspace autosampler. The system was calibrated by analyzing known standards of polysiloxanes relative to an internal standard (mesitylene). Sample preparation included the use of hexamethyldisilazane to serve as an endcapping agent for the hydroxy terminated linear species.

[0071] The base experiments of Examples 1 -4 were based on Aspen models of the system.

Example 1

OH-endblocked dimethyl silicone fluid (Dow Corning 4-2737 Fluid) is fed into a 12-tray glass column at 151 °C and 5.6 g/min. The starting material had %OH of 4.12, 1 .1 % D4, and 1 .3% D5. Nitrogen is fed in countercurrent at 310 standard cubic centimeters per minute into the system, and the system is operated at a pressure of 13.2 kPa. The final product had 4.17% OH, a non-detectable level of D4, and 0.12% D5.

Example 2

OH-endblocked dimethyl silicone fluid (Dow Corning 4-2737 Fluid) was fed into a 12-tray glass column at 145 °C and 4.5 g/min. The starting material had %OH of 4.2, 1 .15% D4, and 1 .26% D5. Nitrogen was fed in countercurrent at 680 standard cubic centimeters per minute into the system, and the system was operated at a pressure of 13.2 kPa. The final product had 4.24% OH, 0.06% D4 (octamethylcyclotetrasiloxane), and a non-detectable level of D5 (decamethylcyclopentasiloxane). This experiment was conducted with a nitrogen recycle. The nitrogen was passed through a water-cooled condenser, returned to atmospheric pressure using a vacuum pump, and recycled to the system.

Example 3

OH-endblocked dimethyl silicone fluid (JS-209) was fed into a 12-tray glass column at 154 °C and 2.3 g/min. The starting material had %OH of 7.4, 7.0% D4, and 4.7% D5. Nitrogen was fed in countercurrent at 496 standard cubic centimeters per minute into the system, and the system was operated at a pressure of 13.2 kPa. The final product had 7.54% OH, 0.03% D4, and 0.04% D5.

This experiment is conducted with a nitrogen recycle. The nitrogen is passed through a water-cooled condenser, returned to atmospheric pressure using a vacuum pump, and recycled to the system.

Example 4

[0072] OH-endblocked dimethyl silicone fluid is fed into a process substantially matching Figure 1 . The starting material contained 4.7% (w/w) D4 and 4.1 % (w/w) D5. Conditions are controlled. The organopolysiloxane is 160 degrees C; the mass ratio of nitrogen to the organopolysiloxane feed is 0.1 ; the recycled nitrogen is about 120 degrees C; the column pressures are at 100 mm Hg. The cool organopolysiloxane in iii) and condenser are at 40 degrees C. Modeling of the process shows the product organopolysiloxane from the bottom of the column contains less than 200 ppm of both D4 and D5 and is used as the source of the cooled organopolysiloxane in the absorber in iii). The recirculated nitrogen gas stream contains less than 50 ppmw D5 and less than 3500 ppmw D4.

Example 5

[0073] An organopolysiloxane mixture (of 1 .55% octamethylcyclotetrasiloxane, 1 .49% decamethylcyclopentasiloxane, 0.82% dodecamethylcyclohexasiloxane, and the remainder consisting of a mixture of higher molecular weight linear and cyclic organopolysiloxanes) comprising a volatile organopolysiloxane and a non-volatile organopolysiloxane (4.9% volatile and 95.1 % non-volatile components) at a temperature of 155 °C was contacted with nitrogen gas in a column at an overhead pressure of 95 mmHg and overhead temperature of 87.8 °C and an organopolysiloxane mixture to nitrogen feed ration of 9.7:1 to form a first stream comprising a gaseous mixture of nitrogen and the volatile organopolysiloxane (56.1 % volatile components and 43.9% nitrogen) and a second stream comprising the non-volatile organopolysiloxane (0.045% octamethylcyclotetrasiloxane, 0.006%

decamethylcyclopentasiloxane, 0.097% dodecamethylcyclohexasiloxane and a mixture of higher molecular weight linear and cyclic organopolysiloxanes) with less than a 15% change in viscosity and less than 3% change in silanol content between the original mixture and second stream .

[0074] A portion of the volatile organopolysiloxane from the first stream was removed using a condenser to form a partially purified first stream comprising the nitrogen and the residual volatile organopolysiloxane and a third stream comprising the portion of the volatile organopolysiloxane removed from the first stream at a pressure of 95 mmHg and temperature of 43.3 °C, with the third stream comprised of <5% water, <5%

hexamethylcyclotrisiloxane, 30.5% octamethylcyclotetrasiloxane, 29.5%

decamethylcyclopentasiloxane, 14.3% dodecamethylcyclohexasiloxane, and the remainder comprised of other higher molecular weight linear and cyclic organopolysiloxanes.

[0075] The partially purified first stream comprising the nitrogen and residual volatile organopolysiloxane was then contacted, at 91 .5 mmHg, with a cool organopolysiloxane liquid (comprising less than 0.2% (w/w) octamethylcyclotetrasiloxane,

decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane, and the remainder a mixture of higher molecular weight linear and cyclic organopolysiloxanes and at 31 °C) to form a purified gas stream and a volatile-containing cool organopolysiloxane stream comprising the cool organopolysiloxane and the volatile organopolysiloxane. The volatile- containing cool organopolysiloxane stream comprised about 17%

octamethylcyclotetrasiloxane, decamethylcyclotetrasiloxane, and

dodecamethylcyclohexasiloxane, and the remainder comprised of other linear

organopolysiloxanes.

[0076] The purified nitrogen stream was then recycled and contacted with the

organopolysiloxane mixture, where the purified nitrogen steam formed 100% of the gas contacted, at the conditions described above.

[0077] Approximately 8% of the second stream above was cooled to 31 °C to form the cool organopolysilixane liquid contacted with the partially purified first stream comprising nitrogen. The volatile-containing cool organopolysiloxane stream was recycled and contacted with the nitrogen in the column, and the third stream was recycled and contacted with the nitrogen in the column at a mass ratio of 0.8:1 of the third stream to the inert gas.

Claims

That which is claimed is:

1 . A method for removing cyclic organopolysiloxanes from a mixture of

organopolysiloxanes, the method comprising:

2. The method of claim 1 , further comprising

ii) optionally removing a portion of the cyclic organopolysiloxane from the first stream to form a partially purified first stream and a third stream comprising the portion of the cyclic organopolysiloxane removed from the first stream; and

iii) contacting the first stream from i) or, when ii) is present, the first stream from i) or the partially purified first stream from ii) with a cool organopolysiloxane comprising an organopolysiloxane at a temperature from 20 °C to 60 °C to form a purified nitrogen stream and a cyclic-containing cool organopolysiloxane stream;

iv) optionally contacting the purified nitrogen stream from iii) with the

organopolysiloxane mixture in i), where the purified nitrogen stream forms from greater than 0% to 100% of the nitrogen contacted in i);

v) optionally cooling a portion of the second stream from i) to form the cool organopolysiloxane in iii) where the cooled portion of the second stream from i) forms from > 0% to 100% of the cool organopolysiloxane in iii);

vi) optionally contacting the cyclic-containing cool organopolysiloxane stream from iii) with the nitrogen in i);

vii) optionally when ii) is present, contacting the third stream from ii) with the nitrogen in i).

3. The method of claim 2, wherein one or more of ii), iv), v), and vi) are present as in one of the following limitations a) through o):

a) v and vi; b) ii and iv; c) ii and v; d) ii and vi; e) ii, iv and v; f) ii, iv and vi; g) ii, v, and vi; h) ii, iv, v and vi; i) iv and v; j) iv and vi; k) iv, v, and vi; I) ii; m) iv, n) v, or o) vi.

4. The method of claim 2 or 3, wherein i) is conducted at a pressure from 0 to 27 kPa.

5. The method of one of claims 2-4, wherein the method includes a column positioned substantially vertically and optionally having a reflux section above a stripping section, wherein the nitrogen and the organopolysiloxane mixture in i) are contacted in the stripping section of the column by introducing the nitrogen in i) into the column below the stripping section, and introducing the organopolysiloxane mixture in i) into the column above the stripping section wherein the nitrogen and organopolysiloxane mixture flow

countercurrently through the stripping section of the column, and wherein the first stream in i) exits the column above stripping section and above the reflux section, if present, and the second stream in i) exits the column below the stripping section.

6. The method as in claim 5, wherein when iv) is present, the purified nitrogen stream from iii) is introduced into the column below the stripping section, wherein when vi) is present, the cyclic-containing cool organopolysiloxanes stream from iii) is introduced into the column at the top of the column and reflux section, if present, and wherein when vii) is present, the cyclic organopolysiloxane removed in ii) is introduced into the column at the top of the column and reflux section, if present, in i).

7. The method as in claim 5, wherein the cool organopolysiloxane comprises less than 1000 ppmw of cyclic organopolysiloxane.

8. The method as in any one of the preceding claims, wherein the

organopolysiloxane mixture further comprises an azeotroping solvent.

9. The method as in any one of the preceding claims, wherein the mole ratio of the nitrogen to the organopolysiloxane mixture in i) is from .05 to 0.25.

10. The method as in any one of the preceding claims, wherein the cyclic organopolysiloxane in the organopolysiloxane mixture comprises at least one of

hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or dodecamethylcyclohexasiloxane.

1 1 . The method as in any one of the preceding claims, wherein the organopolysiloxane mixture in i) comprises up to about 15% (w/w) of the cyclic

organopolysiloxane, based on the weight of the cyclic organopolysiloxane and the non-cyclic organopolysiloxane.

12. The method as in any one of the preceding claims, wherein the temperature of the cool organopolysiloxanes is from 20 to 40 °C and the organopolysiloxane mixture in i) is at a temperature from 140 °C to 160 °C and has a viscosity up to and including 50 cSt.

13. The method as in any one of the preceding claims, wherein the cool

organopolysiloxane in iii) has a viscosity up to and including 50 cSt.

14. The method as in any one of the preceding claims, wherein the process is a continuous process and the moisture content of the second stream is less than or equal to 1000 μg/g, based on the weight of the entire second stream.

15. The method of any one of the preceding claims, wherein the non-cyclic organopolysiloxane in the organopolysiloxane mixture is silanol end-capped and wherein the organopolysiloxane mixture is preheated before contacting with the nitrogen in i).