WO2013113879A1 - Copolymères de polyoxyméthyléne - Google Patents

Copolymères de polyoxyméthyléne Download PDF

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WO2013113879A1
WO2013113879A1 PCT/EP2013/052041 EP2013052041W WO2013113879A1 WO 2013113879 A1 WO2013113879 A1 WO 2013113879A1 EP 2013052041 W EP2013052041 W EP 2013052041W WO 2013113879 A1 WO2013113879 A1 WO 2013113879A1
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polymer
weight
molecular weight
mol
pom
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PCT/EP2013/052041
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Bernd-Steffen Von Bernstorff
Laurence POTTIÉ
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Basf Se
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    • 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
    • C08G2/18—Copolymerisation of aldehydes or ketones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L59/00—Compositions of polyacetals; Compositions of derivatives of polyacetals

Definitions

  • the invention relates to low molecular weight polyoxymethylene copolymers, processes for their preparation and their use.
  • Polyoxymethylene homopolymers or copolymers also referred to as polyacetal or polyformaldehyde or POM, are generally high molecular weight thermoplastics which exhibit high stiffness, low coefficients of friction and excellent dimensional stability and thermal stability. Therefore, they are used in particular for the production of precision parts.
  • the high strength, hardness and rigidity in a wider temperature range make them advantageous for molding applications.
  • the further processing takes place, for example, by injection molding at temperatures in the range of 180 to 230 ° C, as well as by extrusion.
  • the preparation of polyoxymethylene is carried out, for example, by direct polymerization of formaldehyde or by cationic or transition metal-centered cationic polymerization of trioxane.
  • the end groups are frequently protected by etherification or esterification.
  • copolymers for example by copolymerization of trioxane with 1, 4-dioxane.
  • the unstable end groups are degraded by hydrolysis to formaldehyde for stabilization.
  • Typical copolymers ® for example, under the brand names Hostaform ® from Ticona / Celanese and Ultra form available from BASF SE.
  • the homopolymer typically has a melting point of about 178 ° C, the copolymer of about 166 ° C.
  • US 6,388,049 relates to low molecular weight polyoxymethylene polymers and compositions containing them.
  • Preparation Examples 14 to 16 give trioxane-based and butanediol-formal copolymers in which methylal was used as regulator.
  • the added amount of comonomer is in each case 1, 46 mol%, corresponding to about 4.4 wt .-% butanediol formal.
  • Number average molecular weights of 1100, 5500 and 35000 g / mol are obtained.
  • Polyoxymethylene is also used as a binder for powder injection molding.
  • POM molding compounds are processed by injection molding into moldings and subsequently debinded and sintered. Since the high loading of the POM with the inorganic powders impairs the flowability, it is necessary to use well-flowing POM materials in order to keep the pressures required during the injection molding to a reasonable level.
  • a flow improver should have a very good miscibility with POM and show a rapid degradation under an acid-gas atmosphere in order to avoid defects in the desired moldings.
  • the object is achieved by a polyoxymethylene copolymer having a weight average molecular weight (M w ) in the range of 5000 to 15,000, preferably 5000 to 10,000 g / mol or 6000 to 13,000, preferably 6000 to 9000 g / mol or 6500 to 1 1000, especially preferably 6500 to 8000 g / mol, in particular 7000 to 7500 g / mol, characterized in that it is based on the polymer, at least 90 wt .-% of trioxane and butanediol as monomers tolei tet, with a proportion of butanediol , based on the polymer, in the range of 0.5 to 4 wt .-%, preferably 1 to 4 wt .-%, preferably 2 to 3.5 wt .-%, in particular 2.5 to 3 wt .-%.
  • M w weight average molecular weight
  • the number average molecular weight (M n ) is preferably 3000 to 6000 g / mol, particularly preferably 3200 to 5000 g / mol, in particular 3500 to 4100 g / mol. In this molecular weight range, a particularly advantageous flow improvement is achieved for polyoxymethylene homopolymers or copolymers having a higher molecular weight.
  • a polyoxymethylene copolymer according to the present invention which has a proportion of butanediol formal, based on the polymer, in the range of 1 to 4 % By weight, shows a higher crystallinity and a higher hardness in spite of the low molecular weight due to the compared to US 6,388,049 reduced comonomer. In spite of good viscosity-reducing properties for polyoxymethylene homopolymers or copolymers having a higher molecular weight, this results in an advantageous hardness of these polymer blends and thus advantageous mechanical properties for use.
  • the molecular weight determination can be carried out as described in the examples.
  • the determination of the molecular weights is usually carried out by gel permeation chromatography (GPC) or SEC (Size Exclusion Chromatography).
  • GPC gel permeation chromatography
  • SEC Size Exclusion Chromatography
  • the number average molecular weight is generally determined by GPC-SEC.
  • the object is also achieved according to the invention by a process for preparing polyoxymethylene copolymers obtained by polymerization of trioxane, optionally comonomers, in the presence of at least one cationic initiator, and at least one di (Ci -6 alkyl) than as a controller and the obtainable by this process polymers ,
  • the object is also achieved by using the above polyoxymethylene encopolymers as a viscosity-modifying additive for polyoxymethylene homopolymers or copolymers having a weight-average molecular weight of at least 50,000 g / mol.
  • the ratio between weight average molecular weight (M w ) and number average molecular weight (M n ), also referred to as polydispersity or M w / M n is in the range of 1.5 to 3.0, preferably 1.5 to 2, 45th
  • Polyoxymethylene copolymers (POM) generally have at least 50 mol% of repeating units - CH 2 O - in the main polymer chain.
  • Polyoxymethylene copolymers are preferred which in addition to the recurring units -CH 2 0- still up to 50, preferably 0.01 to 20, in particular 0, 1 to 10 mol% and very particularly preferably 0.5 to 6 mol% of recurring units
  • said R 1 to R 4 independently represent a hydrogen atom, a Crbis C 4 alkyl group or a halogen-substituted alkyl group having 1 to 4 carbon atoms and R 5 is a -CH 2 -, -CH 2 0 -, a C to C 4 Alkyl or C 1 to C 4 haloalkyl-substituted methylene group or a corresponding oxymethylene group and n is a Value in the range of 0 to 3 has.
  • these groups can be introduced into the copolymers by ring opening of cyclic ethers.
  • 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, 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-1, 3-diol, 1, 2-propanediol and cyclohexane-1, 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 polymers according to the invention are derived, based on the polymer, from at least 90% by weight of trioxane and butanediol formal as monomers.
  • the polyoxymethylene copolymers are derived, preferably exclusively, from trioxane and butanediol formal as monomers, with a content of butanediol formal, based on the polymer or on the monomers, in the range of 0.5 to 4 wt .-%, preferably 1 to 4 wt .-%, preferably 2 to 3.5 wt .-%, in particular 2.5 to 3 wt .-%.
  • 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 inventive polymer at the chain ends based on the polymer, 3 to 6 wt .-% of radicals of the general formula -OR, wherein R is Ci-6-alkyl, preferably Ci -4 alkyl.
  • the polyoxymethylene copolymer of the invention based on the polymer or the sum of monomers and regulators, 3.75 to 4.25 wt .-%, preferably 3.8 to 4.2 wt .-%, in particular 3 , 9 to 4.1 wt .-% methylal or an equimolar amount of another di (Ci -6- alkyl) acetal concomitantly used as a regulator.
  • butylaI n-butyl
  • z. B. industrially, also used as a controller.
  • butylal n-butylal
  • z. B. industrially, also used as a controller.
  • butylal n-butylal
  • the use of butylal as a regulator is a further advantage over the polyoxymethylene copolymers known from US Pat. No. 6,388,049. Preference is given to using butylalI as regulator in the preparation of the polymer.
  • Butylal based on the polymer, in an amount of 0.5 to 4 wt .-%, particularly preferably 1 to 3.5 wt .-%, in particular 1, 5 to 2.5 wt .-%, is preferably used.
  • polyoxymethylene copolymers with particularly suitable mecha- These properties make them useful as a viscosity-modifying additive for higher molecular weight polyoxymethylene homo- or copolymers without significantly affecting mechanical properties, particularly hardness.
  • the number average of the polyoxymethylene copolymer is more preferably 3000 to 6000 g / mol, more preferably 3200 to 5000 g / mol, especially 3500 to 4100 g / mol.
  • This special combination of molecular weight, comonomer content, comonomer selection, regulator fraction and regulator selection leads to particularly suitable mechanical properties which allow the advantageous use as a viscosity-modifying additive for relatively high molecular weight polyoxymethylene homopolymers or copolymers.
  • Initiators also referred to as catalysts
  • catalysts are the cationic initiators customary in the trioxane polymerization.
  • Proton acids are suitable, such as fluorinated or chlorinated alkyl- and arylsulfonic acids, for example perchloric acid, trifluoromethanesulfonic acid or Lewis acids, for example tin tetrachloride, arsenic pentafluoride, phosphoric pentafluoride and boron trifluoride, and their complex compounds and salt-like compounds, for example boron trifluoride etherates and triphenylmethylene hexafluorophosphate.
  • the initiators (catalysts) 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.
  • Suitable solvents for this purpose are inert compounds such as aliphatic, cycloaliphatic hydrocarbons such as cyclohexane, halogenated aliphatic hydrocarbons, glycol ethers, etc. can be used. Particular preference is given to triglyme (triethylene glycol dimethyl ether) as solvent and 1,4-dioxane.
  • cationic initiators Bronsted acids in an amount in the range of 0.01 to 1 ppm (preferably 0.02 to 0.2 ppm, in particular 0.04 to 0.1 ppm), based on the sum of monomers and regulators, used.
  • HCI0 4 is used as a cationic initiator or initiator.
  • cocatalysts can be included.
  • 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-cyclohexanedimethanol and neopentyl glycol.
  • Monomers, initiators, cocatalyst and, if appropriate, regulators may be premixed in any way or may also be added to the polymerization reactor separately from one another.
  • the stabilizing components may contain sterically hindered phenols as described in EP-A 129369 or EP-A 128739.
  • the preparation of polyoxymethylene copolymers according to the invention is carried out by polymerization of trioxane, butanediol and optionally ren further comonomers, in the presence of at least one cationic initiator and at least one di (CI_ 6 alkyl) acetal as regulator.
  • the polymerization mixture is preferably deactivated directly after the polymerization, preferably without a phase change taking place.
  • the deactivation of the initiator residues (catalyst residues) is generally carried out by adding deactivators (terminating agents) to the polymerization melt.
  • deactivators are, for example, ammonia and primary, secondary or tertiary, aliphatic and aromatic amines, for example 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 metal or alkaline earth metal alkyls are preferred as deactivators which have 2 to 30 C atoms in the alkyl radical.
  • Particularly preferred metals are Li, Mg and Na, with n-butyllithium being particularly preferred.
  • from 3 to 30 ppm, preferably from 5 to 20 ppm, in particular from 8 to 15 ppm, based on the sum of monomers and regulator, of a chain terminating agent can be used.
  • sodium methylate is used as a chain terminator.
  • POMs from trioxane and butanediol formal are generally obtained by bulk polymerization, using any reactors with high mixing efficiency can.
  • the reaction can be carried out homogeneously, for example in a melt, or heterogeneously, for example as polymerization to a solid or solid granules.
  • Suitable examples are shell reactors, ploughshare mixers, tube reactors, Listreaktoren, kneaders (eg Busskneter), extruders with, for example, one or two screws, and stirred reactors, the reactors may have static or dynamic mixer.
  • the trioxane polymerization can be thought of as three reaction steps, the initiation, the propagation and transfer reactions.
  • chain transfer to the polymer, to a protic species such as water, or to a transfer agent such as butylal can occur.
  • the transfer reactions to other polymer chains allow the random distribution of the comonomer units along the polymer chains. These reactions occur between the carbonium of one active chain and the oxygen of another polymer chain as long as active carbonium ions are present in the reaction mixture.
  • Chain transfer agents or regulators such as methylal or butylal are preferably used, which are added in the desired amount to the monomer mixture.
  • the butylal content is usually about 0.35 wt% and the weight average molecular weight of the POM is about 97,000 g / mol, with a ratio M w / M n of about 4 ; 2.
  • the POM polymerization has no termination step.
  • the living polymer is in equilibrium with formaldehyde monomer until a comonomer end group is achieved which is a stable end group.
  • a process for stabilizing the polymer ends is therefore the depolymerization of the unstable chain ends until only stable comonomer end groups remain.
  • This process is used in the shell-and-roll process in which the polymers obtained have a majority of methylal or butylal derived end groups (eg, -O- (CH 2 ) 4 -OH).
  • the chain ends can also be deactivated by adding an alkaline compound. This procedure is used in particular in continuous processes in which living end groups are typically inactivated with sodium methoxide.
  • the resulting polymer has a plurality of -CH 2 -O-CH 3 end groups.
  • 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, together or separately from the initiators (catalysts), at a preferred temperature of the reaction mixture of 62 to 1400C.
  • the monomers (trioxane) are preferably also metered in a molten state, for example at 60 to 120.degree.
  • the polymer Due to the exothermic nature of the process, the polymer usually only has to be melted in the extruder at the start of the process; Subsequently, the amount of heat released is sufficient to melt the molten POM polymer or to keep it molten.
  • the melt polymerization is generally carried out at 1, 5 to 500 bar and 130 to 300 ° C, and the residence time of the polymerization mixture in the reactor is usually 0.1 to 20, preferably 0.4 to 5 min. Preferably, the polymerization is carried out to a conversion above 30%, e.g. 60 to 90%.
  • a crude POM is frequently obtained which, as mentioned, contains considerable proportions, for example up to 40%, of unreacted residual monomers, in particular trioxane and formaldeyde.
  • 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.
  • This crude POM is preferably degassed in one or more stages in known degassing devices, for example in degassing pots (flash pots), vented extruders with one or more screws, thin film evaporators, spray dryers or other conventional degassing devices. Particularly preferred are degassing pots (flash pots).
  • the degassing of the raw POM is operated in such a way that is degassed in a first flash to below 6 bar absolute, to obtain a gaseous stream and a liquid stream, which is fed to a second flash, which is operated at below 2 bar absolute , obtaining a vapor stream, which is recycled into the monomer plant.
  • the pressure in the first stage is preferably 2 to 18, in particular 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 amount.
  • the judicialtgaste Polyoxymethylenhomo- or copolymers can then be fed to an extruder or kneader and therein with conventional additives and processing aids (additives), provided in the usual amounts for these substances.
  • Such additives are, for example, lubricants or mold release agents, colorants such as pigments or dyes, flame retardants, antioxidants, light stabilizers, formaldehyde scavengers, polyamides, nucleating agents, fibrous and pulverulent fillers or reinforcing agents or antistatics and other additives or mixtures thereof.
  • lubricants or mold release agents colorants such as pigments or dyes, flame retardants, antioxidants, light stabilizers, formaldehyde scavengers, polyamides, nucleating agents, fibrous and pulverulent fillers or reinforcing agents or antistatics and other additives or mixtures thereof.
  • the preferred shell-batch process batch process involves the following steps:
  • a non-closed reaction vessel (“shell") is filled with the liquid monomer / comonomer mixture Initiator is pumped by, for example, an HPLC pump. at a temperature in the range of preferably 60 to 100 ° C., more preferably 70 to 90 ° C., in particular 75 to 85 ° C.
  • a solvent may be used, the boiling point of which is more than 100 ° C., and is miscible with the monomers.
  • the initiator preferably aqueous HCI0 4 in a solvent
  • the polymerization and crystallization take place simultaneously in the third step, at the end of which, after the homogeneous reaction, there is a solid polymer block.
  • the induction time is often less than 120 seconds, for example 20 to 60 seconds.
  • the solid crude POM is removed from the shell, mechanically reduced, and further processed in an extruder, for example, by depolymerization to reach stable end groups (degassing).
  • stabilizers and other ingredients can be added.
  • a mixture of antioxidant, acid scavenger and nucleating agent can be considered.
  • the preparation of the POM copolymers according to US Pat. No. 6,388,049 in completely molten state takes place in tubular reactors.
  • the blend production takes place in two series-connected reactors.
  • the resulting polymer may be ground into a coarse powder, sprayed with a buffer solution, and then fed to the extruder.
  • the buffer serves to neutralize acids remaining in the melt.
  • the synthesis should be fast; d. H. have a short induction period.
  • the resulting oligomers should be rapidly and completely solidified in the polymerization and form a polymer block which does not adhere too strongly to the container wall.
  • the preparation of the low molecular weight POM is particularly advantageously possible by using a small amount of initiator, a high amount of regulator and capping the chain ends.
  • the low molecular weight POM thus obtained is both thermally stable and chemical resistant and has a viscosity which may be lower by a factor of 1000 compared to a conventional high molecular weight POM as heretofore used in catamold compositions ,
  • the low molecular weight POM as a viscosity modifying additive for POM having a weight average molecular weight of at least 50,000 g / mol, preferably at least 80,000 g / mol
  • the addition to a thermally and chemically stable POM system will increase its viscosity by a factor of at least 10 can be reduced without appreciably affecting the mechanical strength of the high molecular weight POM.
  • the obtained polymer block was then ground to a powder and refluxed for one hour in an extraction solution of methanol, water and sodium carbonate. After cooling, the polymer was filtered off and washed with a washing solution of aqueous sodium carbonate. The powder was then dried and the weight loss was determined. This procedure gives an indication of the polymerization yield since remaining monomers or lowest molecular weight oligomers are extracted in this step.
  • the living centers of the crude polymer chains as well as residual acid sites are partially extracted or neutralized. All cations should be neutralized to obtain a polymer that is stable enough for further study or further processing. Acid residues would otherwise shift the balance towards formaldehyde and affect thermal stability.
  • GV N 2 The weight loss (GV) in percent of a sample of 1, 2 g of granules with heating to 222 ° C for 2 hours under nitrogen.
  • the sample was weighed out to an accuracy of 0.1 mg in a jacketed vessel consisting of two test tubes (normal test tube, 100 ⁇ 10 mm, custom-made, thick-walled test tube 100 ⁇ 12.5 mm).
  • the molecular weight determination of the polymers was carried out by size exclusion chromatography in a SEC apparatus.
  • This SEC apparatus consisted of the following separation column combination: a guard column of length 5 cm and diameter 7.5 mm, a second linear column of length 30 cm and diameter 7.5 mm. Release material in both columns was PL-HFIP gel from Polymer Laboratories.
  • the detector used was a differential refractometer from Agilent G1362 A.
  • a mixture of hexafluoroisopropanol with 0.05% trifluoroacetic acid potassium salt served as eluent.
  • the flow rate was 0.5 ml / min at a column temperature of 40 ° C.
  • Yield stress, yield strain, breaking stress and elongation at break were determined to ISO 527 (23 ° C, 50 mm / min).
  • the Charpy notched impact strength was determined to ISO 179 1 eA (F) (23 ° C, 2.9 m / s).
  • the POM used for the initially described Catamold method corresponds to the Ultraform ® Z2320, which is prepared with a butyral content of 0.35 wt .-%.
  • butylal To reduce the molecular weight was subsequently increased the proportion of Butylal.
  • the proportion of butanediol-comonomer was in each case unchanged 2.7% by weight, based on the polymer.
  • the initiator concentration was 0.2 ppm based on the monomers.
  • the oligomers of the invention have a very low melt viscosity.
  • the low molecular weight POM according to the invention can be used particularly advantageously as a viscosity-modifying additive for polyoxymethylene homopolymers or copolymers having a weight-average molecular weight of at least 50,000 g / mol.
  • the low molecular weight POM according to the invention are chemically and mechanically stable and reduce neither the overall strength nor the overall mechanics when mixed with high molecular weight POM.
  • the viscosity of the high molecular weight POM can be greatly reduced, the effect being retained in several melt passes. No formaldehyde evaporates, the POM blend remains a solid, and therefore the classic Catamold manufacturing process can also be performed with the POM blends.
  • FIG. 1 shows the dependence of the size exclusion chromatography (SEC) detector signal in arbitrary units, plotted against the molecular weight in g / mol.
  • the solid line shows the molecular weight distribution for mixing for one minute
  • the triangles show the molecular weight distribution after mixing for 2 minutes
  • the circles show the molecular weight distribution for a mixing time of 5 minutes. It was found that the molecular weight distribution remains the same at the three mixing times, which indicates a stability of the polymer blend.
  • the bimodal molecular weight distribution resulting from the blend polymers is retained. It does not come to a molecular weight balance by transacetalization.
  • the molding compositions are not brittle, but still have a high strength.
  • the POM blends are suitable in an advantageous manner for the metal or ceramic powder-injection molding after the Catamold ® process.
  • the POM molding materials are subjected to a threefold melting and shearing: when mixing the two polymer components, when the metal or ceramic powder is introduced, and finally during injection molding.
  • a recycling and reuse of parts of the injection-molded body, such as the sprues there is a further thermal stress.
  • the inorganic material powder particularly metal powders or ceramic powders contain. These powders are typically first coated with a thin layer of polyethylene and then compounded in a polyoxymethylene binder. This Catamold granulate is then processed by injection molding into a green body, transferred by debinding in a brown body and then sintered to a sintered shaped body. The process is known as Metal Injection Molding (MIM) and allows the production of metal or ceramic moldings with complex shapes.
  • MIM Metal Injection Molding
  • the Catamold granules have a content of inorganic fillers of about 90 wt .-%.
  • the green bodies produced using polyoxymethylene homo- or copolymers have very good mechanical properties, in particular dimensional stability.
  • the debinding is often carried out by the action of an acidic atmosphere, for example HN0 3 atmosphere at 1 10 to 140 ° C with degradation of the POM binder.
  • an acidic atmosphere for example HN0 3 atmosphere at 1 10 to 140 ° C with degradation of the POM binder.
  • the inorganic particles are connected to one another via their thin polyethylene coating. Due to the acidic depolymerization of the POM, the binder can be removed without residue.
  • the sintering of the brown body preferably follows in a sintering furnace at temperatures in the range of about 1100 to 1500 ° C to obtain the desired metal or ceramic shaped body.
  • the metal or ceramic particles must be transported homogeneously with the molding compound.
  • a suitable property spectrum of flowability and creep compliance is often achieved by POM with a weight average molecular weight above about 85,000 g / mol.

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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Abstract

L'invention concerne des copolymères de polyoxyméthylène spéciaux ayant une masse moléculaire moyenne en poids (MW) comprise entre 5000 et 15.000 g/mole, et un procédé de production par polymérisation du trioxane et éventuellement de comonomères en présence d'au moins une amorce cationique et d'au moins un di(alkyle en C1-6-) acétal en tant qu'agent de transfert de chaîne.
PCT/EP2013/052041 2012-02-02 2013-02-01 Copolymères de polyoxyméthyléne WO2013113879A1 (fr)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
US10961384B2 (en) 2014-05-21 2021-03-30 Basf Se Process for improving the flexural toughness of moldings

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EP0128739A1 (fr) 1983-06-08 1984-12-19 Polyplastics Co. Ltd. Procédé de préparation de homo- ou copolymères de trioxane
EP0129369A1 (fr) 1983-06-17 1984-12-27 Polyplastics Co. Ltd. Procédé de préparation de copolymères de trioxane
US6388049B1 (en) 1999-07-01 2002-05-14 Asahi Kasei Kabushiki Kaisha Low-molecular weight oxymethylene polymer and composition thereof
WO2006074997A1 (fr) 2005-01-13 2006-07-20 Basf Aktiengesellschaft Matiere de moulage contenant un polyoxymethylene et une zeolithe
DE102005034490A1 (de) * 2005-07-20 2007-01-25 Basf Ag Zusatzstoff-freies Verfahren zur Herstellung von Polyoxymethylenen
WO2007023187A1 (fr) 2005-08-26 2007-03-01 Basf Aktiengesellschaft Procede pour produire des homopolymeres ou des copolymeres de polyoxymethylene
WO2009077415A1 (fr) 2007-12-19 2009-06-25 Basf Se Procédé de production d'homopolymères et de copolymères de polyoxyméthylène par homopolymérisation ou copolymérisation de trioxane, à partir de méthanol

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Publication number Priority date Publication date Assignee Title
EP0128739A1 (fr) 1983-06-08 1984-12-19 Polyplastics Co. Ltd. Procédé de préparation de homo- ou copolymères de trioxane
EP0129369A1 (fr) 1983-06-17 1984-12-27 Polyplastics Co. Ltd. Procédé de préparation de copolymères de trioxane
US6388049B1 (en) 1999-07-01 2002-05-14 Asahi Kasei Kabushiki Kaisha Low-molecular weight oxymethylene polymer and composition thereof
WO2006074997A1 (fr) 2005-01-13 2006-07-20 Basf Aktiengesellschaft Matiere de moulage contenant un polyoxymethylene et une zeolithe
DE102005034490A1 (de) * 2005-07-20 2007-01-25 Basf Ag Zusatzstoff-freies Verfahren zur Herstellung von Polyoxymethylenen
WO2007023187A1 (fr) 2005-08-26 2007-03-01 Basf Aktiengesellschaft Procede pour produire des homopolymeres ou des copolymeres de polyoxymethylene
WO2009077415A1 (fr) 2007-12-19 2009-06-25 Basf Se Procédé de production d'homopolymères et de copolymères de polyoxyméthylène par homopolymérisation ou copolymérisation de trioxane, à partir de méthanol

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US10961384B2 (en) 2014-05-21 2021-03-30 Basf Se Process for improving the flexural toughness of moldings

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