Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2/00—Addition polymers of aldehydes or cyclic oligomers thereof or of ketones; Addition copolymers thereof with less than 50 molar percent of other substances
  • C08G2/10—Polymerisation of cyclic oligomers of formaldehyde
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D323/00—Heterocyclic compounds containing more than two oxygen atoms as the only ring hetero atoms
  • C07D323/04—Six-membered rings
  • C07D323/06—Trioxane
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2/00—Addition polymers of aldehydes or cyclic oligomers thereof or of ketones; Addition copolymers thereof with less than 50 molar percent of other substances
  • C08G2/28—Post-polymerisation treatments
• • 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
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/582—Recycling of unreacted starting or intermediate materials

Definitions

• the invention relates to a process for the preparation of polyoxymethylene homopolymers or copolymers, according to which trioxane is first prepared in a monomer plant, purified and then optionally polymerized with the addition of suitable comonomers in a polymerization plant.
• Polyoxymethylene polymers (POM, also called polyacetals) are obtained by homo- or copolymerization of 1,3,5-trioxane (trioxane in short), formaldehyde or another formaldehyde source. The conversion is usually not complete, but the POM crude polymer still contains up to 40% unreacted monomers.
• Such residual monomers are, for example, trioxane and formaldehyde, and optionally co-used comonomers such as 1,3-dioxolane, 1,3-butanediol formal or ethylene oxide.
• POM is here summarized for homopolymers or copolymers.
• the residual monomers must be removed by processing, for example by degassing from the crude polymers.
• the residual monomers to be separated must be recycled, usually by recycling, preferably in the Polymer process or in the process for the preparation of the monomers.
• the residual monomers can be recycled directly into the polymerization reactor or in its feed, or in the monomer plant.
• polymerization inhibitors for example water, alcohols, ammonia or amines are frequently used by known processes in order to suppress the spontaneous polymerization of trioxane.
• the solution consists in a process for the preparation of polyoxymethylene homo- or copolymers by homo- or copolymerization of trioxane or additionally of suitable comonomers, after which first
• Trioxane in a monomer plant by acid-catalyzed reaction of a highly concentrated aqueous formaldehyde solution in a reactor to give a trioxane / formaldehyde / water mixture
• suitable comonomers are fed to a polymerization plant, in which the crude polyoxymethylene homo- or copolymer is prepared in a polymerization reactor which still contains residual monomers and which is degassed in one or more stages to give one or more vapor streams which optionally have one Capacitor are fed to give a condensate, which is recycled to the polymerization and one or more gaseous, formaldehyde-containing streams, and a doxtgasten Polyoxymethylenhomo- or copolymers, the an extruder or kneader is fed and mixed therein with conventional additives and processing agents, to obtain a polymer melt and
• Polyoxymethylene homopolymers or copolymers are known as such and are commercially available.
• the homopolymers are prepared by polymerization of formaldehyde or, preferably, trioxane; Comonomers are also used in the preparation of the copolymers.
• POM polymers have at least 50 mole percent of repeating units - CH 2 O - in the polymer backbone.
• Polyoxymethylene copolymers are preferred, in particular those which, in addition to the repeating units -CH 2 O-, have up to 50, preferably 0.01 to 20, in particular 0.1 to 10 mol% and very particularly preferably 0.5 to 6 mol%. at recurring units.
• R 1 to R 4 are independently a hydrogen atom, a Ci-bis group or a halogen-substituted alkyl group having 1 to 4 carbon atoms and R 5 is a - CH 2 -, -CH 2 O -, a Ci to C4 alkyl or Ci to C 4 -haloalkyl-substituted methylene group or a corresponding oxymethylene group, and n has a value in the range of 0 to 3.
• these ring opening groups of cyclic ethers can be introduced into the copolymers.
• Preferred cyclic ethers are those of the formula
• R 1 to R 5 and n have the abovementioned meaning.
• Oxymethylenterpolymerisate for example, by reacting trioxane, one of the cyclic ethers described above with a third monomer, preferably bifunctional compounds of the formula
• Preferred monomers of this type are ethylene diglycide, diglycidyl ether and diether from glycidylene and formaldehyde, dioxane or trioxane in the molar ratio 2: 1 and diether from 2 mol glycidyl compound and 1 mol of an aliphatic diol having 2 to 8 carbon atoms such as the diglycidyl ethers of ethylene glycol, 1 , 4-butanediol, 1,3-butanediol, cyclobutane-l, 3-diol, 1,2-propanediol and cyclohexane-l, 4-diol, to name just a few examples.
• End-group-stabilized polyoxymethylene polymers which have predominantly C-C or -O-CH 3 bonds at the chain ends are particularly preferred.
• the preferred polyoxymethylene copolymers have melting points of at least 150 ° C. and weight average molecular weights M.sub.w in the range from 5,000 to 300,000, preferably from 7,000 to 250,000, g / mol. Particular preference is given to POM copolymers having a nonuniformity (M w / M n ) of from 2 to 15, preferably from 2.5 to 12, particularly preferably 3 to 9.
• the measurements are generally carried out by gel permeation chromatography (GPC) -EC (size exclusion chromatography), the M n - Value (number average molecular weight) is generally determined by GPC-SEC.
• the molecular weights of the polymer can be adjusted to the desired values by the regulators customary in the trioxane polymerization and by the reaction temperature and residence time.
• Suitable regulators are acetals or formals of monohydric alcohols, the alcohols themselves and the small amounts of water which act as chain transfer agents and whose presence can generally never be completely avoided.
• the regulators are used in amounts of from 10 to 10,000 ppm, preferably from 20 to 5,000 ppm.
• Initiators are the cationic initiators customary in the trioxane polymerization.
• Proton acids such as fluorinated or chlorinated alkyl and aryl sulfonic acids, e.g. Perchloric acid, trifluoromethanesulphonic acid or Lewis acids, e.g. Tin tetrachloride, arsenic pentafluoride, phosphoric pentafluoride and boron trifluoride and their complex compounds and salt-like compounds, e.g. Boron trifluoride etherates and triphenylmethylene hexafluorophosphate.
• fluorinated or chlorinated alkyl and aryl sulfonic acids e.g. Perchloric acid, trifluoromethanesulphonic acid or Lewis acids, e.g. Tin tetrachloride, arsenic pentafluoride, phosphoric pentafluoride and boron trifluoride and their complex
• the initiators are used in amounts of about 0.01 to 1000 ppm, preferably 0.01 to 500 ppm and in particular from 0.01 to 200 ppm. In general, it is advisable to add the initiator in dilute form, preferably in concentrations of 0.005 to 5 wt .-%.
• solvents there may be used inert compounds such as aliphatic, cycloaliphatic hydrocarbons e.g. Cyclohexane, halogenated aliphatic hydrocarbons, glycol ethers, etc. may be used. Particular preference is given to triglyme (triethylene glycol dimethyl ether) as solvent and 1,4-dioxane.
• cocatalysts can be included.
• these are alcohols of any kind, for example aliphatic alcohols having 2 to 20 C atoms, such as t-amyl alcohol, methanol, ethanol, propanol, butanol, pentanol, hexanol; aromatic alcohols having 2 to 30 C atoms, such as hydroquinone; halogenated alcohols having 2 to 20 C atoms, such as hexafluoroisopropanol; Very particular preference is given to glycols of any type, in particular diethylene glycol and triethylene glycol; and aliphatic dihydroxy compounds, in particular diols having 2 to 6 carbon atoms, such as 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclohexanediol, 1,4-
• the stabilizing components may contain sterically hindered phenols as described in EP-A 129369 or EP-A 128739.
• the polymerization mixture is preferably deactivated directly after the polymerization, preferably without a phase change taking place.
• the deactivation of the initiator residues is generally carried out by adding deactivators (terminating agents) to the polymerization melt.
• deactivators are e.g. Ammonia and primary, secondary or tertiary, aliphatic and aromatic amines, e.g. Trialkylamines such as triethylamine, or triacetonediamine.
• basic-reacting salts such as soda and borax, furthermore the carbonates and hydroxides of the alkali metals and alkaline earth metals, and also alkoxides, such as sodium ethanolate.
• the deactivators are usually added to the polymers in amounts of preferably 0.01 ppmw (parts per million by weight) up to 2 wt .-%.
• alkali or Erdalkalialkyle are preferred as deactivators, which have 2 to 30 carbon atoms in the alkyl radical.
• Particularly preferred metals are Li, Mg and Na, with n-butyllithium being particularly preferred.
• Trioxane POMs are typically obtained by bulk polymerization using any reactors with high mixing efficiency.
• the reaction can be carried out homogeneously, e.g. in a melt, or heterogeneous, e.g. as polymerization to a solid or solid granules.
• Suitable examples are tray reactors, plowshare mixers, tubular reactors, list reactors, kneaders (e.g., Buss kneaders), extruders with, for example, one or two screws, and stirred reactors, which reactors may comprise static or dynamic mixers.
• the melted polymer produces a so-called melt seal, whereby volatile constituents remain in the extruder.
• the above monomers are metered into the polymer melt present in the extruder, taken together or separately from the initiators (catalysts), at a preferred temperature of the reaction mixture of 62 to 114 ° C. Loading vorzugt the monomers (trioxane) are metered into a molten state, for example at 60 to 120 0 C. Due to the exothermic nature of the process must typically only the polymer are melted in the extruder at the start of the process; subse- landedd the amount of heat released sufficient to melt the formed POM polymer or to keep molten.
• the melt polymerization is generally carried out at 1.5 to 500 bar and 130 to 300 0 C, and the residence time of the polymerization mixture in the reactor is usually 0.1 to 20, preferably 0.4 to 5 min.
• the polymerization is preferably carried out to a conversion of more than 30%, for example 60 to 90%.
• a crude POM which, as mentioned, contains considerable proportions, for example up to 40%, of unreacted residual monomers, in particular trioxane and formaldehyde.
• Formaldehyde can also be present in the crude POM if only trioxane was used as the monomer since it can be formed as a degradation product of the trioxane.
• other oligomers of formaldehyde may also be present, e.g. the tetrameric tetroxane.
• the process according to the invention uses trioxane as monomer for the preparation of the POM, for which reason the withdrawn residual monomers also contain trioxane, moreover usually 0.5 to 10% by weight of tetroxane and 0.1 to 75% by weight of formaldehyde.
• trioxane is first prepared in a monomer unit in a purity which meets the specification requirements required for use as a monomer in the polymer system: it may be pure trioxane, ie. H. a stream having a minimum content of 97.5% by weight, preferably 99% by weight or 99.5% by weight of trioxane or also of ultrapure trioxane, d. H. a stream with a minimum content of 99.9 wt .-% trioxane.
• trioxane / formaldehyde / water mixture distillation or crystallization of the trioxane / formaldehyde / water mixture to give crude trioxane as and workup of the crude trioxane in one or more further process steps to obtain polymerizable trioxane and pure water.
• this may be a method as described, for example, in DE 102004051118.7.
• the distillation of the trioxane / formaldehyde / water mixture from the reactor into a column which may be connected in a preferred variant of the method with the reactor to form a unit, such that the rising from the reactor vapors directly into the column and the liquid leaving the column enters the reactor directly.
• the crude trioxane stream from this first column is fed to a second column for overhead removal of low boilers.
• the bottom stream from the low boiler separation column is worked up in a pure trioxane column, from which a trioxane stream is obtained in a purity corresponding to the above-defined pure trioxane or also ultrapure trioxane, which is fed to the polymer plant as side draw or bottom stream.
• the top stream from the pure trioxane column is fed to a further column in which water is withdrawn via bottom and a top stream, which is recycled to the first distillation column.
• the polymerizable trioxane, d. H. the pure or ultrapure trioxane-containing stream corresponding to the above definition is fed to a polymerization plant which is operated in a known manner, for example in accordance with the process described in DE 102005002413.0.
• the POM is preferably first prepared in a polymerization reactor by bulk polymerization, which still contains residual monomers.
• degassing is degassed in one or more stages in known degassing devices, for example in degassing pots (flash pots), degassing extruders with one or more screws, thin film evaporators, spray dryers or other conventional degassing devices. Particularly preferred are degassing (flash) pots.
• the degassing of the crude polyoxymethylene is operated in such a way that is degassed in a first flash to below 6 bar absolute, to obtain a gaseous gen stream and a liquid stream, which is supplied to a second flash, which is operated at below 2 bar absolute, to obtain a vapor stream, which is recycled to the monomer plant.
• the pressure in the first stage preferably 2 to 18, especially 2 to 15 and particularly preferably 2 to 10 bar, and in the second stage preferably 1.05 to 4, in particular 1.05 to 3.05 and especially preferably 1.05 to 3 bar.
• the residual monomers liberated during degassing are optionally withdrawn as one or more vapor streams and fed to a condenser.
• the condenser is preferably operated in such a way that the condensate stream obtained in this case has a higher trioxane content in comparison to the uncondensed vapor stream.
• additives are, for example, lubricants or mold release agents, colorants such.
• pigments or dyes flame retardants, antioxidants, stabilizers against exposure to light, formaldehyde scavengers, polyamides, nucleating agents, fibrous and powdery fillers or reinforcing agents or antistatics and other additives or mixtures thereof.
• the desired product POM is obtained as a melt.
• the inventors have found that it is possible to recycle all of the formaldehyde-containing secondary streams obtained in the polymer plant directly, ie as they are produced in the polymer system, into the monomer system without chemical modification and without the addition of auxiliaries. Both the material composition and the energy content of these streams are used in the monomer plant and thus in the overall process for the production of POM.
• gaseous, formaldehyde-containing secondary streams which accumulate in the one-stage or multistage expansion of the polymer melt from the polymerization reactor and remain in the gaseous state of aggregation after condensation are recycled into the polymer plant according to the invention.
• the gaseous formaldehyde-containing stream from the polymer plant is recycled to the first column of the monomer plant.
• the operating conditions in the condenser are preferably adjusted in such a way that the proportion of trioxane in the gaseous formaldehyde-containing stream from the polymer plant, which is recycled to the monomer plant, less than 80 wt .-%, preferably less than 60 wt .-%, especially preferably less than 40 wt .-% is.
• This stream usually has a formaldehyde content of preferably at least 25% by weight, more preferably at least 50% by weight.
• the extruder or Kneader dome At the extruder or kneader dome accumulate one or more other formaldehyde-containing side streams, the extruder or Kneader exhaust, the invention also directly, d. H. recycled without chemical or physical change in the monomer plant.
• a negative pressure is usually generated, often in a first stage in the range of less than 800 mbar and in a second stage at lower pressure, often in the range of less than 500 mbar.
• the extruder or Kneterabgas is taken up according to the invention in the liquid ring pump, which is already present in the monomer process to a water-rich liquid stream, in particular the top stream from the reactor for the production of trioxane upstream evaporation of the formaldehyde feed stream from a starting concentration of about 10 to 60 wt .-%, in particular from about 15 to 45 wt .-% to the pressure of the fourth column, for the separation of water, to compress.
• the extruder exhaust gas taken up in the liquid ring pump is compressed to a pressure of 2 to 7 bar absolute, preferably to about 5 bar absolute.
• the single figure shows the schematic representation of a preferred system for carrying out the method according to the invention.
• An aqueous formaldehyde solution FA is concentrated in an evaporator V to form a highly concentrated aqueous formaldehyde solution having a formaldehyde content of at least 60% by weight, stream 1.
• Stream 1 is reacted in a reactor R to trioxane, which is obtained as trioxane / formaldehyde / water mixture 2, a first distillation column KII is fed and therein a top stream 3, containing crude trioxane, separated.
• the sump stream 4 from the first distillation column KII is recycled in front of the reactor R and a partial stream thereof, stream 5, is discharged.
• the crude trioxane overhead stream 3 from the first column KII is fed to a second column KIII, in which overheads, stream 6, containing in particular methyl-IaI, methanol and methyl formate, are separated off.
• the bottoms stream 7 from the second distillation column KIII is fed to a third column, the trioxane pure column KIV, from which a trioxane stream 8 is withdrawn as a side draw or via the bottom, which contains polymerizable trioxane and can thus be fed to the polymer plant.
• the top stream 9 from the third distillation column KIV is fed to a further fourth column KV, in which water is withdrawn as bottom stream 10, and a top stream 11, which is recycled to the first distillation column KII.
• the polymerisable trioxane-containing stream 8 from the third distillation column KIV is fed in the polymer plant to the polymerization reactor P, wherein crude POM, stream 12, is obtained under elevated pressure by bulk polymerization.
• Stream 12 still contains residual monomers which, in the preferred embodiment shown in the figure
• Variant be degassed in two stages.
• a first degassing stage Fl falls to a vapor stream 13, which is recycled to the condenser K, there partially condensed, to obtain a condensate stream 15, which in the polymerization reactor
• Monomer plant, in the first column K II, is recycled.
• a second degassing stage F2 in the preferred embodiment shown in the figure, at lower pressure compared to the first degassing stage, another vapor stream 14 is withdrawn, which is also directly recycled to the first column K II of the monomer unit.
• the partially degassed POM, stream 17 is fed to an extruder E and mixed therein with conventional additives and processing agents to obtain a polymer melt 19 and an extruder exhaust gas 18 which is fed to a liquid ring pump F which is operated with the overhead stream from the formaldehyde FA evaporator V. becomes.
• the extruder exhaust gas 18 is taken up in the liquid of the liquid ring pump F, compressed to the pressure of the fourth distillation column KV and supplied as a stream 19 of the same.
• the crude POM stream 12 from the polymerization reactor P is degassed in two stages, to obtain the vapor streams 13 and 14th
• the vapor stream 13 is partially condensed in the condenser K, to obtain the condensate stream 15 and the vapor stream 16th
• the vapor streams 14 and 16 are recycled to the monomer plant for the production of trioxane, as well as the extruder exhaust gas 18.
• the gaseous formaldehyde-containing streams 14 and 16 and the extruder exhaust gas 18 are each precipitated with 5 times the amount of water and then recycled into the trioxane plant. profiled.
• the extruder exhaust gas 18 is in this case deposited using a liquid ring pump in water.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)

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• 2006
  • 2006-08-25 BR BRPI0615387A patent/BRPI0615387A2/pt not_active IP Right Cessation
  • 2006-08-25 KR KR1020087007152A patent/KR20080050429A/ko not_active Application Discontinuation
  • 2006-08-25 JP JP2008527475A patent/JP2009506155A/ja not_active Withdrawn
  • 2006-08-25 EP EP06793021A patent/EP1922346A1/de not_active Withdrawn
  • 2006-08-25 AU AU2006283847A patent/AU2006283847A1/en not_active Abandoned
  • 2006-08-25 WO PCT/EP2006/065693 patent/WO2007023187A1/de active Application Filing
  • 2006-08-25 CN CNA200680035584XA patent/CN101273073A/zh active Pending
  • 2006-08-25 CA CA002620161A patent/CA2620161A1/en not_active Abandoned
  • 2006-08-25 US US12/064,893 patent/US20080234459A1/en not_active Abandoned
• 2008
  • 2008-02-26 NO NO20080971A patent/NO20080971L/no not_active Application Discontinuation

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