Classifications

• • 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
  • C08L59/04—Copolyoxymethylenes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/09—Carboxylic acids; Metal salts thereof; Anhydrides thereof
  • C08K5/098—Metal salts of carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/10—Esters; Ether-esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/13—Phenols; Phenolates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/34—Heterocyclic compounds having nitrogen in the ring
• • 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
• • 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
  • C08L59/02—Polyacetals containing polyoxymethylene sequences only

Definitions

• the present invention relates to impact-modified polyoxymethylene molding compositions which are suitable for the production of moldings or extrudates.
• the products manufactured with it are particularly stable in processing and are characterized by low formaldehyde emissions and low odor.
• polyoxymethylenes Since their market launch about 40 years ago, polyoxymethylenes have established themselves as extremely useful technical materials in many applications. Polyoxymethylene is widely used, in particular, as a construction material in automobile construction, in the electrical industry and in medical technology. Polyoxymethylene molding compounds require a certain level of mechanical properties such as stiffness, hardness and toughness, which makes the use of these materials possible for technical components such as gears, levers and many others.
• the published values for the yield stress are between 60 and 70 N / mm 2 . Values between 2400 and 3100 N / mm 2 are found for the tensile modulus of elasticity of unmodified copolymers. The elongation at break is between 10 and 30%.
• polyoxymethylenes have too low impact strength.
• Impact modifiers are organic additives such as crosslinked or uncrosslinked elastomers or graft copolymers composed of a rubber-elastic, single-phase core and one hard graft cover used.
• Impact-modified polyoxymethylene molding compositions are known from the patent literature, for example polyoxymethylene (DE 1 193 240) modified with polyurethanes, polyoxymethylene (DE 1 931 392) modified with a two-phase mixture of polybutadiene and styrene / acrylonitrile (ABS), with a Butadiene-produced graft copolymer modified polyoxymethylene (DE 1 964 156), a polyoxymethylene (DE 2 659 357) equipped with modified polysiloxanes or silicone rubbers and finally with a graft copolymer which consists of a rubber-elastic, single-phase core based on polydiene and a hard, single or multi-phase graft shell, for example composed of poly (alkyl) acrylates, poly (alkyl) acrylonitriles or polystyrene, modified polyoxymethylene (EP 0156285 B1).
• Impact-modified polyoxymethylene molding compositions therefore often have high formaldehyde emissions. Impurities such as residual monomers or solvents contained in the impact modifiers are released during the processing of impact-modified polyoxymethylene molding compositions and during use of the moldings produced therefrom. The emission of formaldehyde and impurities in the impact modifiers lead to an unpleasant smell, which impairs the use of these materials in many fields of application.
• Stabilizers are added for this purpose.
• stabilizers for the polyacetal phase are polyamides, amides of polybasic carboxylic acids, amidines, hydrazines, ureas, poly (N-vinyllactams) and alkaline earth metal salts of aliphatic, preferably hydroxyl-containing, one- to three-base carboxylic acids with 2-20 carbon atoms.
• oxidation stabilizers and Called light stabilizers have not yet been able to remedy the lack of high emissions.
• known stabilizers and stabilizer systems which reduce the formaldehyde emission lead to an impairment of the mechanical property profile.
• the object of the present invention is to provide polyoxymethylene molding compositions in which the formaldehyde emission previously observed is reduced while maintaining the mechanical property profile.
• the molded parts that are produced from these molding compositions should have a low odor.
• polyoxymethylene molding composition containing:
• (G) ad 100% by weight of a polyoxymethylene polymer. It has surprisingly been found that the polyoxymethylene molding compositions according to the invention have a significantly reduced formaldehyde emission compared to the prior art. The reduction in emissions is caused by the interaction between the cyclic stabilizer with at least one ring nitrogen atom and the carboxylic acid salt. In contrast to other stabilizer systems, which can be used to reduce the emission of polyoxymethylene molding compounds, the level of mechanical properties, especially the impact strength and strength, is retained.
• the molding composition according to the invention contains 0.01-1.0% by weight, preferably 0.03-0.3% by weight, of a cyclic stabilizer, component (A), which contains at least one
• Examples are pyrrolidine, piperidine, pyrrole, pyridine, purine, indole, carbazole, tryptophan, oxazole, imidazole, thiazole, picoline, lutidine, collidine, quinoline, pyridazine, pyrimidine, pyrazine and their derivatives.
• Heterocyclic compounds having at least one nitrogen atom as hetero atom, which is adjacent to either an amino-substituted carbon atom or a carbonyl group, such as, for example, pyridazine, pyrimidine, pyrazine, pyrrolidone, aminopyridine and compounds derived therefrom, are advantageous.
• aminopyridine and compounds derived therefrom are aminopyridine and compounds derived therefrom.
• all aminopyridines are suitable, such as melamine, 2,6-diaminopyridine, substituted and dimeric aminopyridines and pyrrolidone and compounds derived therefrom and mixtures prepared from these compounds.
• suitable pyrrolidones are, for example, imidazolidinone and compounds derived therefrom, such as, for example, hydantoin, the derivatives of which are particularly advantageous, and allantoin and its derivatives are particularly advantageous of these compounds.
• Triamino-1,3,5-triazine (melamine) and its derivatives such as, for example, melamine-formaldehyde condensates and methylolmelamine, are also particularly advantageous.
• Melamine, methylolmelamine, melamine-formaldehyde condensates and allantoin are very particularly preferred.
• the cyclic stabilizers which contain at least one nitrogen atom in the ring, can be used individually or in combination. 0.001-0.5% by weight of a metal salt of a carboxylic acid are used as component (B).
• Salts of fatty acids in particular salts of higher fatty acids with 10-32 carbon atoms, preferably 14-32 carbon atoms, are advantageous, and salts of montanic acids and stearic acid are particularly preferred.
• Preferred metals are those which occur as mono- or divalent ions, for example alkali and alkaline earth metals, in particular alkaline earth metals.
• Magnesium and calcium for example calcium stearate, are particularly preferred. Magnesium stearate is very particularly preferred as component (B).
• component (C) 5-50% by weight, preferably 5 to 40% by weight, particularly preferably 7 to 30% by weight, of an impact modifier are used as component (C).
• Impact modifiers can be used individually or as a mixture of polyurethanes, two-phase mixtures of polybutadiene and styrene / acrylonitrile (ABS), modified polysiloxanes or silicone rubbers, or graft copolymers made of a rubber-elastic, single-phase core based on polydiene and a hard graft shell (core-shell or Core-shell structure). In the latter case
• Component (C) consists' of particles predominantly, preferably a core-shell structure having more than 70%.
• the core is formed by a rubber-elastic polymer phase onto which the hard shell, which can also consist of several layers, is grafted.
• the core is preferably single-phase, that is to say that the core consists predominantly, preferably completely, of the rubber-elastic soft phase and contains only small amounts, preferably none, of inclusions of hard polymer components of the shell.
• the graft copolymer usually consists of 40 to 95% by weight, advantageously 60 to 90% by weight, particularly advantageously 70 to 80% by weight of the rubber-elastic core.
• the proportion of the shell (shells) is 5 to 60% by weight, advantageously 10 to 40% by weight, particularly advantageously 20 to 30% by weight.
• the core generally consists of polydienes, such as. As polybutadiene or polyisoprene and can contain up to 10% by weight, advantageously up to 5% by weight, of comonomer units. Styrene or acrylonitrile can advantageously be used as comonomer.
• the core polymer can also be cross-linked and have a gel fraction, measured in toluene, of generally greater than 70% and preferably greater than 80%.
• As a crosslinker can Example use divinylbenzene.
• the shell of the particles consists of hard polymers which are grafted onto the core as a graft substrate. In this case, the shell can be of single or multi-layer design, advantageously of two-shell construction. If there is more than one shell, the different layers advantageously consist of different polymers or copolymers.
• the first layer is advantageously cross-linked. If necessary, the other layers can also be cross-linked.
• Unsaturated nitriles, acrylates, methacrylates, vinyl esters, styrene derivatives, for example, are suitable as monomers which lead to suitable polymers of the particle shell.
• Acrylonitrile, methacrylonitrile, acrylates and methacrylates with an alcohol component which has 1 to 6, preferably 1 to 4, carbon atoms are advantageous such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, tert-butyl methacrylate.
• Vinyl acetate, vinyl ether, N-vinyl-N-methylacetamide, vinyl pyrrolidone are also advantageously usable as vinyl esters, styrene, ⁇ -methyl styrene and vinyl toluene, for example, can advantageously be used as styrene derivatives.
• copolymers of at least two of the aforementioned monomer groups and monomers can also be used, in particular copolymers of the styrene derivatives mentioned with the other monomers.
• Copolymers which are produced from a mixture comprising 20 to 80% by weight of acrylonitrile or methacrylonitrile with 80 to 20% by weight of the other monomers mentioned, in particular acrylates, methacrylates and vinyl esters, are particularly advantageous.
• graft polymers which have a double-shell shell structure, the first shell made of polystyrene, the second, outer shell made of a poly (meth) acrylate, which is particularly preferably partially crosslinked.
• crosslinking monomers such as multifunctional olefins, for example divinylbenzene, ethylene glycol dimethacrylate, butylene glycol dimethacrylate or triallyl cyanurate.
• the glass transition temperatures of component (C) described above are between -40 ° C. and -120 ° C., preferably below -60 ° C. especially between -80 ° C and -120 ° C.
• the preparation of the graft copolymers which can be used as component (C) with a core-shell structure is known and can be carried out by single-stage polymerization in the case of a single-shell shell or by multi-stage polymerization in the case of a multi-shell shell, as described, for example, in US Pat. No. 3,985,704, to which reference is made becomes.
• the graft copolymerization is carried out by means of water-soluble initiators or by means of activated initiator systems, one component of which is at least water-soluble, as described, for example, in CB Bucknall, "Toughened Plastics", page 98, Applied Science Publisher LTD, 1977 (London)). or multistage graft copolymerization is based on a polydiene which is preferably in the form of an aqueous latex with a defined average particle size, particularly preferably in the range from 0.1 to 5 ⁇ m, and which is very particularly preferably partially crosslinked.
• the monomer or the monomer mixture is polymerized in the presence of the polydiene, the majority of the monomers being grafted onto the polydiene particles.
• the amount of polydiene is generally 40 to 95% by weight and the amount of the monomer or monomer mixture is 5 to 60% by weight, based in each case on the total amount.
• the graft yield achieved is between 60 and 95%, preferably between 80 and 90%.
• the graft polymerization is carried out in solution or emulsion, preferably in aqueous
• the finely divided polydiene latex is added with the addition of the usual polymerization aids such as emulsifying or suspending aids, radical initiators, regulators, etc., the monomers or the monomer mixture are added and polymerized at temperatures between 30 and 95 ° C., preferably 50 to 80 ° C.
• the initiator is water-soluble; water-soluble peroxides, percarbonates or perborates, for example, can be used as initiators.
• redox system multi-component initiator system (redox system)
• at least one component must be water-soluble.
• emulsifiers also called dispersants, aliphatic and aromatic sulfates, sulfonates, salts of carboxylic acids, such as dresinates.
• dispersants aliphatic and aromatic sulfates, sulfonates, salts of carboxylic acids, such as dresinates.
• carboxylic acids such as dresinates
• graft polymerization and the workup generally take place as described in US Pat. No. 3,985,704.
• a monomer or a monomer mixture for example styrene
• core polymer for example butadiene-styrene copolymer
• Monomer mixture used optionally in the presence of a crosslinker.
• the average particle size of the particles is advantageously 0.1 to 5 ⁇ m.
• Graft copolymers that can be used as component (C) are also materials in which the core consists predominantly or completely of preferably partially crosslinked polyacrylic acid esters or polymethacrylic acid esters, the alcohol component of which contains 1 to 15 carbon atoms, preferably 1 to 8 carbon atoms.
• Suitable comonomers are olefinic monomers, advantageously butadiene, cyclooctadiene, vinyl ether and haloalkyl acrylates.
• the gel fraction, measured in toluene, is preferably at least 50%, particularly preferably at least 70%.
• those described above can be used
• Monomers and monomer mixtures are used.
• the particle sizes are also in the same range.
• Graft polymers based on polyacrylic acid esters and polymethacrylic acid esters are described, for example, in DE 1964156, DE 2116653, EP 50265, EP 60601 and EP 64207, to which reference is made.
• the core of the graft polymer can also be wholly or partly made of one
• Silicone rubber and / or uninjured organopolysiloxanes exist.
• the monomers and / or monomer mixtures described above can be grafted onto this core, which preferably contains graft-active functional groups. These materials are described, for example, in DE 2659357, to which reference is made.
• Component (C) preferably contains a diluent, especially if the core of the graft polymer consists of partially crosslinked polyacrylic acid esters or polymethacrylic acid esters.
• the diluent is a low-melting, advantageously polymeric substance which is readily miscible in the melt with the graft polymers used as an impact modifier.
• this diluent is particularly advantageous if the graft polymers are crosslinked to such an extent that they no longer form Dissolve the diluent, a two-phase system forms and the interfacial tension allows a fine distribution of the graft polymers in the diluent.
• the graft polymer is preferably located predominantly in the edge region of the two-phase system. With an increasing amount of graft polymer, this is also increasingly found in the core and with a further increasing amount of the graft polymer also outside the two-phase system in the matrix polymer, component (G).
• a uniform distribution of the two-phase system and of the graft polymer in component (G) is very particularly advantageous, in particular if the graft polymer is predominantly located at the edge of the two-phase system.
• the melting point of the diluent should be less than 250 ° C, preferably 180 to 210 ° C.
• the amount of the diluent is 10 to 95%, advantageously 30 to 70%, particularly advantageously 40 to 60%, based on the sum of the graft polymer and the diluent.
• Polyurethanes, segmented copolyesters and ethylene-vinyl acetate copolymers can be used particularly advantageously as diluents.
• Suitable diluents are known to the person skilled in the art and are described, for example, in DE 2818240 and DE 2523991, to which reference is made.
• the diluent can advantageously be mixed with the graft polymer before addition to component (G).
• Polyurethane preferably thermoplastic polyurethane
• the polyurethanes which can be used according to the invention are known products which are described, for example, in DE 1193240, DE 2051028 and in the plastic paperback (Saechtling, 27th edition, Hanser Verlag 1998) on pages 523 to 542, to which reference is made , They are prepared in a known manner by polyaddition from polyisocyanates, in particular diisocyanates, polyesters, polyethers, polyesteramides, polyacetals or other suitable hydroxy or amino compounds, such as, for example, hydroxylated polybutadiene, or mixtures of the aforementioned compounds.
• chain extenders such as low molecular weight polyols, in particular diols, polyamines, in particular diamines or water, are also used.
• Suitable diisocyanates are, for example, diisocyanates of the general formula I.
• R is a divalent, straight-chain or branched aliphatic radical with 1 to 20, preferably 2 to 12 carbon atoms or a divalent cycloaliphatic radical with 4 to 20, preferably 6 to 15 carbon atoms or a divalent, substituted or unsubstituted aromatic radical with 6 to 25, preferably Is 6 to 15 carbon atoms.
• Diisocyanates of this type which are particularly preferred are the hexamethylene diisocyanate, and also 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanate.
• R in the above formula I denotes a cycloaliphatic radical, this is preferably the unsubstituted or substituted cyclohexane radical.
• diisocyanates of this type are 1, 2- or 1, 4-di- (isocyanatomethyl) cyclohexane or isophorone diisocyanate.
• R can also represent a combination of divalent open-chain aliphatic and cycloaliphatic radicals and, for example, the meaning
• Ri is a saturated, straight-chain or branched aliphatic radical having 1 to 8, preferably 1 to 3 carbon atoms.
• the two rings here preferably represent the unsubstituted cyclohexane, while R-j preferably denotes the methylene, ethylene, methylmethylene or dimethylmethylene group.
• alkylidene radical - (CH2) n - with n 2 to 12. Examples include the ethylidene, propylidene, pentamethylene and hexamethylene radical and the 2-methylpentamethylene , the 2,2,4-trimethyl-hexamethylene or the 2,4,4-
• Diisocyanates of this type which are particularly preferred, are hexamethylene diisocyanate and 2,2,4- and 2,4,4-trimethylhexamethylene di-isocyanate.
• R in the above formula I represents a divalent aromatic radical, this is preferably the toluene, diphenylmethane, phenylene or naphthalene radical.
• suitable diisocyanates are: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, diphenyl-methane-4,4'-diisocyanate, 3,3 '-Dimethyldiphenylmethan- 4,4'-diisocyanate, 4-3,3'Dimethyl , 4, ' -diphenylene diisocyanate (3,3'-bitoluene-4,4 ' - diisocyanate), m-phenylene diisocyanate, p-phenylene diisocyanate, o-phenylene diisocyanate, chlorophenylene-2,4-toluene diisocyanate, 3,3 ' -DichlorodiphenyI-4,4 '
• R in the above formula I denotes a cycloaliphatic radical, this is preferably the unsubstituted or substituted cyclohexane radical.
• diisocyanates of this type are 1, 2- or 1, 4-di- (isocyanatomethyl) cyclohexane or isophorone diisocyanate.
• the diisocyanates of the formula I can also be used in oligomeric form, for example in dimeric or trimeric form.
• blocked polyisocyanates can also be used in a known manner, which are obtained from the isocyanates mentioned, for example reaction with phenol or caprolactam.
• aliphatic polyhydroxyl compounds are polyethers such as
• polyester amides, polyacetals and preferably aliphatic polyesters can be used for this purpose, all of these compounds having free OH end groups.
• the preferred aliphatic polyesters are essentially uncrosslinked polyesters with molecular weights from 500 to 10,000, preferably from 500 to 5000.
• the acid component they are derived from unbranched and / or branched aliphatic dicarboxylic acids, such as e.g. Dicarboxylic acids of the general formula
• n 0 to 20, preferably 4 to 10, in particular adipic acid and sebacic acid.
• Cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acids and mixtures with the above aliphatic dicarboxylic acids can also be used for this purpose.
• the alcohol components for these polyesters are, above all, unbranched or branched aliphatic primary diols, such as Diols of the general formula
• m 2 to 12, preferably 2 to 6 means.
• 1, 4-Bitanediol, 1, 6-hexanediol and 2,2, -DimethylpropandioI-1, 3 and diethylene glycol may be mentioned here in particular.
• Cycloaliphatic diols, such as bis-hydroxymethylcyclohexane, or mixtures with the aliphatic diols are also suitable for this.
• the polyesters can be prepared from one dicarboxylic acid and one diol, but also, as mentioned, from mixtures of several dicarboxylic acids and / or several diols.
• chain extenders in the production of the polyurethanes especially low molecular weight polyols, especially diols, and polyamines, especially diamines or water, are to be considered.
• the polyurethanes used according to the invention are preferably thermoplastic and thus preferably essentially uncrosslinked, that is to say they can be repeatedly melted without any significant signs of decomposition.
• Their reduced specific viscosities, measured at 30 ° C in dimethylformamide, are usually 0.5 to 3 dl / g, preferably 1-2 dl / g.
• the values for the elongations at break are expediently 800 to 1500%, preferably 1000 to 1500%, while the Shore hardness A is at most 90, advantageously not more than 81, preferably between 50 and 85, particularly preferably between 60 and 80, in particular between 65 and 80 and the glass transition temperatures are usually not higher than 0 ° C, advantageously not higher than -10 ° C, particularly advantageously not higher than -20 ° C.
• component (D) As the sterically hindered phenol compound, component (D), 0.0 to 2.0% by weight, preferably 0.1 to 1.0% by weight, particularly preferably 0.2 to 1.0% by weight, can be used.
• examples of such compounds are pentaerythrityl tetrakis - [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 1010, from Ciba Geigy), triethylene glycol bis- [3- (3-tert.
• At least one stabilizer from the group of benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives can be used as component (E) in an amount of 0.0-1.0% by weight, preferably 0.0-0.8% by weight. be included.
• Preferred is 2- [2'-hydroxy-3 ', 5'-bis (1, 1-dimethylbenzyl) phenyl] benzot ⁇ azole, which as Tinuvin 234 (Ciba Geigy) is commercially available.
• Component (F) may contain 0.0-0.8% by weight, preferably 0.0-0.5% by weight, very particularly preferably 0.4% by weight, of a sterically hindered amine for light stabilization (HALS) in the molding composition according to the invention.
• HALS sterically hindered amine for light stabilization
• 2,2,6,6-tetramethyl-4-piperidyl compounds e.g. Bis- (2, 2,6,6-tetramethyl-4-piperidyl) sebazate (Tinuvin 770, company Ciba Geigy) or the polymer of dimethyl succinate and 1- (2-hydroxyethyl) -4-hydroxy-2, 2.6 , 6-tetramethyl-4-piperidine (Tinuvin 622, from Ciba Geigy).
• the polyoxymethylene polymers (G) used as the base material for the molding compositions according to the invention can be polyoxymethylene homo- or copolymers. Such polymers are known to the person skilled in the art and are described in the literature.
• the homopolymers are generally polymerized by
• Formaldehyde or trioxane prepared the polymerization can be initiated cationically or anionically.
• Alkylene groups can contain 2-8 carbon units, linear or branched.
• polyoxymethylenes as described for example in DE-A 29 47 490, are generally unbranched linear
• Polymers which generally contain at least 80%, preferably at least 90%, oxymethylene units (-CH 2 O-).
• polyoxymethylene includes both homopolymers of formaldehyde or its cyclic oligomers such as trioxane or tetroxane and corresponding copolymers.
• Homopolymers of formaldehyde or trioxane are those polymers whose hydroxyl end groups are chemically stabilized against degradation in a known manner, for example by esterification or etherification.
• Copolymers are polymers of formaldehyde or its cyclic oligomers, especially trioxane, and cyclic ethers, cyclic acetals and / or linear polyacetals.
• Such polyoxymethylene homo- or copolymers are known per se to the person skilled in the art and are described in the literature. In general, these polymers have at least 50 mol% of -CH 2 0- recurring units in the Polymer backbone.
• the homopolymers are generally prepared by polymerizing formaldehyde or trioxane, preferably in the presence of suitable catalysts.
• suitable catalysts are, for example, boron trifuoride and trifluoromethanesulfonic acid.
• polyoxymethylene copolymers are preferred as component (G), in particular those which, in addition to the repeating units -CH 2 0-, also contain up to 50, preferably from 0.1 to 20 and in particular 0.5 to 10 mol% of repeating units
• R 1 to R 4 independently of one another are a hydrogen atom, a C 1 -C 4 -alkyl group or a halogen-substituted alkyl group having 1 to 4 C atoms and R 5 is a -CH 2 -, -CH 2 O-, a C to C 4 alkyl or C to C 4 haloalkyl substituted methylene group or a corresponding oxymethylene group and n has a value in the range from 0 to 3.
• These groups can advantageously be introduced into the copolymers by ring opening of cyclic ethers.
• Preferred cyclic ethers are those of the formula
• R4 where R 1 to R 5 and n have the meaning given above.
• Copolymers of 99.5-95 mol% of trioxane and 0.5 to 5 mol% of one of the aforementioned comonomers are particularly advantageous.
• component (G) are oxymethylene terpolymers, for example by reacting trioxane, one of the cyclic ethers described above and with a third monomer, preferably a bifunctional compound of the formula
• Preferred monomers of this type are ethylene diglycide, diglycidyl ether and diether from glycidylene and formaldehyde, dioxane or trioxane in a molar ratio of 2: 1 and diether from 2 mol of glycidyl compound and 1 mol of an aliphatic diol having 2 to 8 carbon atoms, such as, for example, the diglycidyl ether 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.
• the preferred polyoxymethylene copolymers have melting points of at least 150 ° C. and molecular weights (weight average) M w in the range from 2000 to 1,000,000, preferably from 7,000 to 150,000. End group-stabilized polyoxymethylene polymers which have CC bonds at the chain ends are particularly preferred.
• the polyoxymethylene polymers used generally have a melt index (MVR value 190 / 2.16) from 0.3 to 100 cm 3/10 min (ISO 1133).
• Particularly preferred are polyoxymethylene polymers that essentially Have oxymethylene and oxyethylene units in the polymer chain.
• the proportion of oxyethylene units in the structural units of the polymer chain is 0.1 to 15 mol%, preferably 0.2 to 10 mol%.
• the melt index MFI measured according to ISO 1133 at 190 ° C and 2.16 kg coating weight, is 0.5 -75 g / 10 min, preferably 2-60 g / 10 min and particularly preferably 5-35 g / 10 min.
• Number average molecular weight is at least 5000 g / mol and at most 100000 g / mol, determined by GPC in dimethylacetamide at 150 to 160 ° C.
• the polyoxymethylene copolymers can be produced using generally known production processes. A possible process is, for example, the copolymerization of trioxane with dioxolane in the presence of generally customary amounts of BF 3 and methylal. Polyoxymethylene polymers, in the production of which trifluoromethanesulfonic acid was used, are preferred.
• the molding composition according to the invention can contain further conventional additives individually or as a mixture up to 40% by weight, e.g. Carbon blacks, for example conductivity blacks, acid scavengers, antioxidants, UV stabilizers, adhesion promoters, mold release agents, substances for improving electrical conductivity, antistatic agents, nucleating agents such as polyoxymethylene terpolymers or talc,
• Carbon blacks for example conductivity blacks, acid scavengers, antioxidants, UV stabilizers, adhesion promoters, mold release agents, substances for improving electrical conductivity, antistatic agents, nucleating agents such as polyoxymethylene terpolymers or talc,
• Colorants such as inorganic pigments, for example titanium dioxide, ultramarine blue, cobalt blue or organic pigments and colors such as phthalocyanines, anthraquinones, fillers such as glass spheres, wollastonite, chalk, clay, molybdenum disulfide or graphite, inorganic or organic fibers such as glass fibers, carbon fibers or aramid fibers, lubricants such as soaps and esters, stearyl stearate, montanic acid esters, partially saponified montanic acid esters, stearic acids, polar and / or non-polar polyethylene waxes, poly- ⁇ -olefin oligomers, silicone oils, polyalkylene glycols and perfluoroalkyl ethers, polytetrafluoroethylene, ultra-high molecular weight polyethylene, paraffins, solid and liquid, stearin and liquid, stearin, thermoplastic Elastomers and other polymers such as EPDM (ethylene-propy
• the polyoxymethylene molding compositions according to the invention can be produced using the customary and known mixing processes, such as granulation, extrusion, kneading, etc.
• the molding compositions according to the invention are preferably produced by mixing polyoxymethylene polymer with additives and stabilizers and then granulating the mixture.
• the colored polyoxymethylene molding compositions according to the invention have a significantly reduced emission.
• the reduction in the release of formaldehyde can already occur during the production of the molding composition, e.g. observed during granulation and also during processing.
• the polyoxymethylene molding composition according to the invention thus makes a contribution to occupational hygiene and safety.
• the formaldehyde emission from molded parts that were produced by injection molding or extrusion is significantly reduced.
• the formaldehyde emission measured on plates with a wall thickness of 1 mm after a storage period of 24 h, is advantageously less than 40 mg / kg, particularly advantageously less than 30 mg / kg, very particularly advantageously less than 20 mg / kg, according to VDA 275.
• the mechanical properties of the molding compositions according to the invention correspond to the usual requirements for commercial polyoxymethylene products, so that the fields of application and common for polyoxymethylene
• the molding compositions according to the invention are interior fittings and cladding for means of transport such as automobiles, airplanes, etc., household goods, toy articles, baby articles and electronic and electrotechnical components and devices.
• the molding compositions according to the invention are particularly suitable for the production of apparatus and instruments, or parts thereof, for medical applications.
• the molding compositions produced according to the invention have the lowest formaldehyde emission in comparison to the currently commercially available products, have defect-free surfaces and high color stability when the moldings are exposed to light or heat for a long time. Reference is hereby expressly made to all references mentioned in this patent application. These references are therefore part of the disclosure of this patent application.
• Formaldehyde emission panels with a wall thickness of 1 mm are made from the colored polyoxymethylene molding compounds. After a storage period of 24 h, the formaldehyde emission from the plates was determined in accordance with VDA 275 (VDA recommendation No. 275, Documentation Automotive Engineering July 1994).
• Test specimen production The polyacetal granules are injection molded into platelets with the dimensions 80 * 50 * 1 mm.
• An Kraus Maffei KM 120 / 340B injection molding machine is used with the following injection molding parameters: melt temperature 195 ° C, flow front speed 200 mm / s, mold wall temperature 85 ° C, holding pressure 900 bar, holding pressure time 30 s, cooling time 10 s, back pressure 0 to 10 bar.
• the test specimens are stored for 24 hours in a standard climatic cabinet at 23 ° C and 50% relative humidity.
• Test Two test specimens are hung in a 1 l glass bottle over 50 ml of electric water on a stainless steel hook and stored for 3 hours in a forced-air drying cabinet at 60 ° C.
• test specimens are removed from the test bottle. 5 ml of sample solution are pipetted into a test tube, the test tube is annealed at 95 ° C for 10 minutes. Now 3 ml of acetylacetone and 3 ml of a 20% ammonium acetate solution are added to the test tube. The formaldehyde forms with the reagents the diacetyldihydrolutidine complex, the absorption of which is determined photometrically at 412 nm. The formaldehyde concentration in the sample solution is calculated from the absorption.
• Brabender test The polyoxymethylene molding compound is sheared at 210 ° C in a Brabender mixer with a twin screw.
• the escaping formaldehyde is discharged with an inert gas stream and absorbed in a sodium sulfite solution.
• the sodium sulfite solution is titrated so that the formaldehyde released is determined quantitatively.
• the result is the release of formaldehyde as a function of time.
• the rate of degradation is determined from the slope of the curve by linear extrapolation.
• Hostaform C 9021 was used as the polyoxymethylene.
• the polymer contained 3.4% dioxolane as a comonomer, and trifluoromethanesulfonic acid was used as the initiator.
• the polymer contained 3.4% dioxolane as a comonomer, and boron trifluoride was used as an initiator.
• the polymer contained 5.6% dioxolane as a comonomer, and trifluoromethanesulfonic acid was used as the initiator.
• Irganox 1010 from Ciba Specialty Chemicals was used as the antioxidant.
• Licowax E or Licowax C from Clariant were used as flow aids.
• Eurelon from Vantico and dicyandiamide (DCD) were used to reduce the emission, optionally in combination with magnesium stearate.
• Paraloid EXL 2600 from Röhm & Haas was used as the impact-resistant component.
• the test specimens for the determination of the tensile modulus of elasticity, the yield stress and the elongation at break as well as the plates for determining the formaldehyde emission were formed from the granules of the examples and comparative examples by injection molding.
• the examples according to the invention always show a lower formaldehyde emission of the molded parts (VDA 275 test) and a lower formaldehyde emission during processing (Brabender test).
• Table 3 shows the mechanical properties of some examples and comparative examples. It can be seen that the mechanical properties remain comparatively good. When using polyoxymethylene polymers in which trifluoromethanesulfonic acid was used as an initiator, particularly low emission values can be achieved. It can be seen from Example 25 and Comparative Example 25 that a reduction in formaldehyde emission can be achieved with comparable mechanical properties even with colored molding compositions.
• the base polymer polyoxymethylene copolymer
• 94.4% by weight of trioxane, 5.6% by weight of dioxolane and 350 ppm of methylal were placed in a batch reactor at a temperature of 80 ° C. and a pressure of approx. 1 bar. 30 ppm BF 3 were added. The quantities are based on the total monomer mixture.
• the crude polymer formed was suspended in a water / triethylamine mixture and then hydrolyzed at 170 ° C. in a water / methanol (10/90) mixture. When cooling to room temperature, the polymer precipitated out as a fine powder and was filtered off with suction, washed with water and dried.
• the product has a melt index (MFI) of 9 g / 10 min).
• MFI melt index
• the following components are combined and mixed intensively in a Henschel mixer: 190 g acetylene black, 330 g Kronos 2220, 240 g Sicotangelb K 2112, 20 g Renolbraun EKX 851, 300 g Irganox 245, 200 g Licowax E, 70 g melamine, 50 g Magnesium stearate, 400 g Tinuvin 234, 400 g Tinuvin 770, 13 kg Paraloid EXL 2600 (manufacturer Rohm & Haas), ad 100 kg polyoxymethylene base polymer.
• the mixture is granulated on a twin-screw extruder.
• Mechanical properties tensile modulus of elasticity 2100 N / mm 2 , yield stress 44.6 N / mm 2 , elongation at break 61%; Formaldehyde emission according to VDA 275: 16 mg / kg,
• a Henschel mixer 190 g acetylene black, 330 g Kronos 2220, 240 g Sicotangelb K 2112, 20 g Renolbraun EKX 851, 600 g Irganox 245, 200 g Licowax C, 50 g Eurelon, 30 g Dicyandiamide, 400 g Tinuvin 234, 400 g Tinuvin 770, 13 kg Paraloid EXL 2600 (manufacturer Rohm & Haas), ad 100 kg polyoxymethylene
• Basispoylmeren The mixture is granulated on a twin-screw extruder.
• the base polymer is identical to the base polymer used in Example 25.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Vehicle Interior And Exterior Ornaments, Soundproofing, And Insulation (AREA)

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