Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/0834—Compounds having one or more O-Si linkage
  • C07F7/0838—Compounds with one or more Si-O-Si sequences
  • C07F7/0872—Preparation and treatment thereof
  • C07F7/0874—Reactions involving a bond of the Si-O-Si linkage
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/12—Organo silicon halides
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/21—Cyclic compounds having at least one ring containing silicon, but no carbon in the ring
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency

Definitions

• This invention relates to a method of minimizing the processing steps normally involved in the recovery of hydrogen chloride in a process of hydrolyzing chlorosilanes to produce a hydrolyzate containing polysiloxanes.
• the ratio of cyclic to linear oligomers, as well as the chain length of the linear siloxanes, is controlled by the conditions of the hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents.
• the hydrolysis of dimethyldichlorosilane is performed by either a batch or a continuous process. In the typical industrial operation, dimethyldichlorosilane is mixed with water in a continuous reactor. The mixture of hydrolyzate and aqueous HCl is separated, preferably by using a simple decanter, which is essentially maintenance-free.
• other means may also be utilized, including variations which combine coalescence technology with gravity separation.
• the cyclic oligomers and the linear oligomers are subsequently separated by distillation. Water can be added to the hydrolyzate, the cyclic oligomers, or the linear oligomers for additional chloride removal.
• the complete conversion of dimethyldichlorosilane to only linear oligomers is also possible in the continuous hydrolysis operation. In this operation, the cyclic oligomers are separated from the linear oligomers by a stripping process, and the cyclic oligomers are mixed with the dimethyldichlorosilane. This mixture undergoes equilibration to chloro- terminated oligomers, and is subsequently hydrolyzed.
• silanol-stopped linear oligomers are then used in the manufacture of other silicone polymers.
• these silanol-stopped linear oligomers are reacted with a suitable endblocking agent such as hexamethyldisiloxane in the presence of a catalyst to obtain low and medium viscosity trimethysiloxy terminated polydimethylsiloxanes .
• the invention is directed to a method of hydrolyzing chlorosilanes.
• one or more chlorosilanes are fed to a first super-azeotropic hydrochloric acid distillation column, chloride free water is fed to a second sub-azeotropic hydrochloric acid distillation column, HCl gas is removed from the upper portion of the first column, saturated aqueous HCl is removed from the lower portion of the first column and recirculated to the upper portion of the first column, a mixture of cyclosiloxanes and chlorosiloxanes are removed from the first column and fed to the second column, substantially chloride free cyclosiloxanes and non-volatile substantially chloride free siloxanes are removed from the second column, and aqueous HCl is removed from the second column and recirculated to the first column.
• the process equipment includes a first super-azeotropic hydrochloric acid distillation column A, a second sub-azeotropic hydrochloric acid distillation column B, a heat exchanger C for adding heat to the first column A, and a heat exchanger D that vaporizes a portion of the stream containing sub-azeotropic aqueous HCl being recirculated to the first column A as more concentrated liquid sub-azeotropic acid, and to the second column B as a less concentrated vapor stream.
• the heat exchanger D is equipped to allow flow or portions of flow from the bottom of the second column B to the first column A, back to the second column B, or externally.
• the first column A contains no inlet for feeding water to the first column A.
• the water needed for the hydrolysis reaction being carried out in the first column A comes from the sub-azeotropic aqueous HCl stream that is re-circulated from the second column B to the first column A, or it can be provided from an external stream of 1-36 percent aqueous HCl.
• a chlorosilane such as R ⁇ SiCl, and RHSiCl2, where R is as defined below
• R is as defined below
• the chlorosilane injected into the front of the hydrolysis process is continuously contacted in stages with aqueous phases of decreasing HCl concentration. Reaction water is added to the process at the final stage of reaction/extraction, and is pumped counter-currently through each stage until it is eventually reacted with the feed chlorosilane.
• Various numbers of stages may be utilized for reaction/extraction to maximize chloride ion recovery and production of siloxanes, with a minimal residual chloride concentration in the final product.
• Ion exchange technology may be used to reduce the final product chloride concentration to less than 0.2 parts per million (ppm).
• ppm parts per million
• “Substantially chloride free” as used herein means less than 5 ppm chloride, alternatively less than 1 ppm chloride, alternatively less than 0.5 ppm chloride and alternatively less than 0.2 ppm chloride
• surfactants may be used in the process to affect the percentage of the cyclic and the linear siloxane species present in the final product.
• Alkaline salt forms of alkyl sulfonates may be used for this purpose, but must first be treated to remove the alkali metal.
• An ion exchange process may be used for cation removal, and for conversion from the salt form to the alkyl sulfonic acid form of the surfactant.
• This invention is directed to a continuous process to hydrolyze chlorosilanes to produce substantially chloride-free volatile cyclosiloxanes and substantially chloride-free nonvolatile linear siloxanes, while recovering chloride as hydrogen chloride gas.
• the process comprises two countercurrent steps that hydrolyze the chlorosilane to a target molecular weight, separate the volatile and nonvolatile siloxane components at temperatures below their boiling points, while at the same time, separating hydrochloric acid into a stream containing weak or sub-azeotropic aqueous HCl, and hydrogen chloride gas.
• the first step of the process hydrolyzes the chlorosilanes in super-azeotropic hydrochloric acid, to produce liquid cyclosiloxanes, chlorosiloxanes, and HCl gas.
• the cyclic fraction and the molecular weight of the siloxanes in the first column A can be controlled by the contact time between the siloxane and aqueous phases, and by the temperature and pressure in the first column.
• the second step of the process further hydrolyzes and polymerizes the chlorosiloxanes, while separating the volatile and the nonvolatile siloxane streams in the presence of sub-azeotropic hydrochloric acid.
• the cyclic fraction and the molecular weight in the second column B can be controlled by the contact time between the siloxane and aqueous phases, and by the temperature and pressure in the second.
• the cyclosiloxanes removed from the upper portion of the second column contain more than 95 percent of cyclosiloxanes having less than six silicon atoms.
• Fresh water is fed to the second step of the process.
• the sub-azeotropic hydrochloric acid produced in the second step of the process is recycled to the first step of the process.
• the content of the first column and the second column can be agitated mechanically or as a result of turbulence produced by the vapor/liquid contact within the first column and the second column.
• the process is also capable of recovering chloride from external sources of, for example, 1-36 percent aqueous HCl as HCl gas.
• the chlorosilane feed for the process can contain chlorosilanes of the formula R.2SiCl2- R can be hydrogen or a hydrocarbon radical such as an alkyl group containing 1-20 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group.
• the hydrocarbon radical can be a group such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec- butyl, pentyl, hexyl, phenyl, tolyl, benzyl, and beta-phenylethyl.
• chlorosilanes include compounds such as dimethyldichlorosilane (CH3)2SiCl2, diethyldichlorosilane (C2H5)2SiCl2, di-n-propyldichlorosilane (n-C3H7)2SiCl2, di-i-propyldichlorosilane (i-C3H7)2SiCl2, di-n-butyldichlorosilane (n-G ⁇ H ⁇ SiC ⁇ , di-i-butyldichlorosilane (i-C ⁇ Hc ⁇ SiC ⁇ , di-t-butyldichlorosilane (t-C4H ⁇ .)2SiCl2, n-butylmethyldichlorosilane CH3(n-C4Hc))SiCl2, octadecylmethyldichlorosilane
• chlorosilanes such as R.3SiCl can also be used, where R is the same as defined above.
• a preferred chlorosilane for example, is trimethylchlorosilane (013)3 SiCl. Mixtures of the above chlorosilanes can also be used.
• the chlorosilane(s) can be fed to the first column as a liquid or a vapor.
• the process of the instant invention uses an essentially stoichiometric amount of water in the hydrolysis, in relation to chloride present on the chlorosilane fed to the process.
• a stoichiometric equivalence is considered as meaning one mole of water per two moles of chloride added to the process as chlorosilanes.
• the stoichiometric amount of water is introduced into the process by feeding it to the second sub- azeotropic hydrochloric acid distillation column B.
• Azeotropic is considered as meaning that the composition is a liquid mixture which retains the same composition in the liquid phase as in the vapor phase as the mixture is distilled at any given pressure.
• the processes in columns A and B herein are capable of operation in three modes, namely, a first essentially stoichiometric mode, a second excess of the stoichiometric amount mode, and a third sub or less than the stoichiometric amount mode. In the first stoichiometric mode, all of the water required for both columns A and B is fed to the second column B.
• water exiting the lower portion of the first column A and recycled is essentially saturated with hydrogen chloride.
• essentially saturated is meant that under the process conditions, the water leaving the first column A contains a concentration of hydrogen chloride, such that additional chloride released as a result of the hydrolysis reaction, is evolved from the process as gaseous hydrogen chloride.
• the process can be conducted at temperatures ranging from -6 0 C to about 150 0 C. Preferred temperatures are within a range of about -3 °C to 22 °C for the first column A, and within a range of about 100 °C to 110 0 C for the second column B.
• the pressure within the first column A can range from 2-50 psig, while the pressure within the second column B can range from 0-30 psig.
• the method of hydrolyzing chlorosilanes involves feeding one or more chlorosilanes to the first super-azeotropic hydrochloric acid distillation column A, feeding chloride free water to the second sub-azeotropic hydrochloric acid distillation column B, removing HCl gas from the upper portion of the first column A, removing saturated aqueous HCl from the lower portion of the first column A and recirculating it to the upper portion of the first column A, feeding cyclosiloxanes and chlorosiloxanes from the first column A to the second column B, removing chloride free cyclosiloxanes from the upper portion of the second column B and non- volatile substantially chloride free siloxanes from a lower portion of the second column B, and removing aqueous HCl from the lower portion of the second column B and recirculating it to the first column A.
• a portion of the saturated aqueous HCl recirculated to the upper portion of the first column A can be heated in the heat exchanger C to provide the energy to vaporize the HCl produced in the chlorosilane hydrolysis reaction.
• the aqueous HCl removed from the lower portion of the second column can also be heated and a first portion can be recirculated back into the second column B, while a second heated portion can be recirculated to the first column A.
• the concentration of the aqueous HCl removed from the lower portion of the second column B can be varied, depending upon the mode of operation of the system as a whole, i.e., stoichiometric mode, excess of stoichiometric mode, and sub or less than stoichiometric mode.
• the aqueous HCl removed from the lower portion of the second column can be a stream containing less than the azeotropic concentration of aqueous HCl, preferably a stream containing 0-50 percent of the azeotropic concentration of aqueous HCl, and more preferably a stream containing 0-25 percent, alternatively 0.1 to 25 percent, of the azeotropic concentration of aqueous HCl.
• the water added to column B can be the only source of water added to the system and it can be chloride free.
• the substantially chloride free water added to column B can be the only water added to column B.
• Dimethyldichlorosilane and sub-azeotropic hydrochloric acid was fed to a first super-azeotropic hydrochloric acid distillation column A at mass flow rates of F and 0.17 F respectively.
• the dimethyldichlorosilane reacted with the water present in the first column A to form cyclosiloxanes, chlorosiloxanes, saturated aqueous hydrochloric acid, and hydrogen chloride gas.
• the first column A was operated at 10-12 psig and approximately —3 °C to 22 °C.
• the cyclosiloxane/chlorosiloxane product of the first column A was fed at a flow rate of 0.57 F to a second sub-azeotropic hydrochloric acid distillation column B, operated at 0-3 psig and approximately 100-110 °C.
• Fresh chloride free water was fed to the second column B at a rate of 0.14 F.
• the chlorosiloxane fed to the second column B was washed to substantially chloride free siloxanes by the chloride free water, and the resulting hydrochloric acid was removed from the second column B as a stream containing 5 percent aqueous HCl.
• the stream containing 5 percent aqueous HCl was heated in a heat exchanger D, and a portion was fed to the first column A at a rate of 0.17 F as 10-20 percent aqueous HCl to hydrolyze the dimethyldichlorosilane.
• the remaining portion of the 5 percent aqueous HCl was vaporized in heat exchanger D and recirculated to a lower portion of the second column B as ⁇ 5 percent aqueous HCl vapor.
• the first column A included a heat exchanger C for adding heat to vaporize the HCl gas exiting the upper portion of the first column A.
• the washed siloxanes present in the second column B were simultaneously separated into a > substantially chloride free cyclosiloxane stream containing > 95 percent of D3-D5, i.e., hexamethycyclotrisiloxane D3, octamethylcyclotetrasiloxane D4, and decamethylcyclopentasiloxane D5, and a substantially chloride-free siloxane stream.
• the non-volatile stream can be recovered as the end product, or as noted above, it can be further reacted with a suitable endblocking agent such as hexamethyldisiloxane, in the presence of a catalyst, to obtain low and medium viscosity trimethysiloxy terminated polydimethylsiloxanes.
• a suitable endblocking agent such as hexamethyldisiloxane

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Silicon Polymers (AREA)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (1)

Family

ID=36617096

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (13)

Citations (1)

Family Cites Families (8)

• 2006
  • 2006-03-15 KR KR1020077022338A patent/KR101208324B1/ko active Active
  • 2006-03-15 JP JP2008504112A patent/JP4388588B2/ja active Active
  • 2006-03-15 WO PCT/US2006/009508 patent/WO2006104702A1/en not_active Ceased
  • 2006-03-15 US US11/883,987 patent/US7479567B2/en active Active
  • 2006-03-15 EP EP06738553A patent/EP1863823B1/en active Active
  • 2006-03-15 CN CN2006800071072A patent/CN101133068B/zh active Active

Patent Citations (1)

Also Published As

Similar Documents

Legal Events