EP0802947A1

EP0802947A1 - Weather-resistant polyoxymethylene moulding compounds

Info

Publication number: EP0802947A1
Application number: EP95937074A
Authority: EP
Inventors: Sabine Kielhorn-Bayer; Ulrich Eichenauer
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1994-11-26
Filing date: 1995-11-15
Publication date: 1997-10-29
Also published as: JPH10509995A; DE4442167A1; WO1996017009A1

Abstract

The invention concerns thermoplastic moulding compounds containing: A) 10 to 99 wt % of a polyoxymethylene homo or copolymer; B) 0.05 to 2 wt.% of an isocyanurate of formula (I), in which R?1, R2, R3¿ mean identical or different groups (10) and R4, R5, independently of each other, designate hydrogen or a C¿1?-C4 alkyl group and n is an integer from 1 to 3, or of a triazine derivative of formula (II) or their mixtures, in which R?a¿ designates hydrogen, an aliphatic group with 1 to 12 carbon atoms, a phenyl group, (a), (b), wherein R6 stands for a C¿1?-C4 alkyl group, (c), wherein R?7, R8¿ mean identical or different hydrogen or C¿1?-C4 alkyl groups, (d), wherein R?9¿ stands for hydrogen or a methyl group and m is an integer between 0 and 20, (e), (f), R?b and Rc¿, independently of each other, designating hydrogen, halogen, a cyano group or a C¿1?-C4 alkyl group; C) 0.05 to 2 wt.% of at least one sterically hindered phenol compound; D) 0.05 to 2 wt.% of at least one sterically hindered amine compound; E) 0 to 2 wt.% of at least one stabilizer selected from the group comprising benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives; and F) 0 to 80 wt.% of conventional processing aids and additives. The weight percentages of components A) to F) total 100 %.

Description

Weather-stable polyoxymethylene molding compounds

description

The invention relates to thermoplastic molding compositions containing

A) 10 to 99% by weight of a polyoxymethylene homo- or copolymer,

B) 0.05 to 2% by weight of an isocyanurate of the formula I.

in which

R ¹ , R ² , R ^{3 are the} same or different radicals

)

and R ⁴ , R ^{5 are} independently hydrogen or one

Represent C ₁ -C ₄ alkyl group and

n is an integer from 1 to 3, or a triazine derivative of the formula II or its

Mixtures

where R ^{a is} hydrogen, an aliphatic radical having 1 to 12 carbon atoms, a phenyl radical,

where R ^{6 represents} a C ₁ -C ₄ alkyl group,

where R ⁷ , R ^{8 are the} same or different radicals hydrogen or

, C ₁ -C ₄ alkyl,

where R ^{9 is} hydrogen or a

Is methyl group and m is an integer from 0 to 20,

.

R ^b , R ^c independently of one another represent hydrogen, halogen, a cyano group or a C ₁ - to C ₄ -alkyl group

C) 0.05 to 2 wt .-% of at least one sterically hindered

Phenolic compound

D) 0.05 to 2 wt .-%, at least one sterically hindered

Amine compound E) 0 to 2% by weight of at least one stabilizer selected from the group of benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives F) 0 to 80% by weight of conventional processing aids and

Additives, the weight percentages of components A) to F) giving 100%.

In addition, the invention relates to the use of such molding compositions for the production of moldings of any kind and the moldings thus obtained. POM polymers are characterized by a large number of excellent properties, so that they are suitable for a wide variety of technical applications.

Since this polymer is widely used for so-called outdoor applications, many additives are known from the prior art which suggest stabilization for the respective applications.

According to the teaching of EP-A 368 635, POM molding compositions which contain a sterically hindered phenol with triazine functionality are distinguished by improved UV stability.

Stabilizer combinations of high molecular weight polyalkylpiperidines for thermoplastics are described in EP-A 252 877.

Sterically hindered amines based on oxopiperazyltriazine are used according to EP-A 448 037 for UV stabilization of POM.

Combinations of sterically hindered amines and benzotriazole compounds for POM are known from EP-A 171 941 and JP-A 60/195 155 and 63/193 950.

For black coloring in the younger application

DE-A 44 04 081 proposes the addition of certain types of carbon black to benzotriazole compounds and sterically hindered amines.

EP-A 586 988 discloses the addition of small amounts of polyamide in combination with benzotriazoles and sterically hindered amines for UV stabilization. From EP-A 293 253, EP-A 328 714 and EP-A 289 142

Stabilizer combination known, which in particular the

Counteract yellowing and / or discoloration. From the

DE-A 33 15 115 also discloses the addition of polypiperidine compounds which are said to bring about increased stability against oxidation.

Despite these measures, known polyoxymethylene molding compounds have insufficient weather stability, i.e. for outdoor applications such as Door handles on the car, colored bumpers and interior applications such as painted speaker grilles will crack after some time. In Japan there is also the requirement for some applications that up to 600 h weathering according to the so-called Sunshine test (83 ° C, without dew and irrigation, only bright phase), no crack formation on the surface may occur with a 60x magnification of the microscope. Similar criteria apply to such indoor and outdoor applications in the USA, which are checked according to SAE J 1885. The stabilized POM molding compositions known to date do not meet these requirements.

The object of the present invention was therefore to improve the weather stability of polyoxymethylene molding compositions.

This object was achieved by the POM molding compositions defined at the outset according to claim 1.

Preferred embodiments can be found in the subclaims.

The stabilizer combination according to the invention synergistically increases the weathering stability of the polyoxymethylene, so that cracking has been considerably minimized even for long-term use under extreme conditions.

As component A), the molding compositions according to the invention contain 10 to 99, preferably 40 to 99% by weight and in particular 50 to 99% by weight of a polyoxymethylene homopolymer or copolymer.

Such polymers 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 recurring units -CH ₂ O- in the main polymer chain. The homopolymers are generally prepared by polymerizing formaldehyde or trioxane, preferably in the presence of suitable catalysts. In the context of the invention, polyoxymethylene copolymers are preferred as component A, in particular those which, in addition to the repeating units -CH ₂ O-, also contain up to 50, preferably 0.1 to 20 and in particular 0.3 to 10 mol% of repeating units

where R ¹ to R ¹ independently of one another are a hydrogen atom, a C ₁ to 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 ₁ - to

C ₄ alkyl or C ₁ 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

where R ⁴ to R ⁵ and n have the meaning given above. Examples include ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane and 1,3-dioxepane as cyclic ethers and linear oligo- or polyformals such as polydioxolane or polydioxepane as comonomers.

Also suitable as component A) are oxymethylene terpolymers which, for example, by reacting trioxane, one of the cyclic ethers described above, with a third monomer, preferably a bifunctional compound of the formula

where Z is a chemical bond, -O-, ORO- (R = C ₁ - to C ₈ -alkylene or C ₂ - to C ₈ -cycloalkylene).

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 with 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.

Processes for the preparation of the homopolymers and copolymers described above are known to the person skilled in the art and are described in the literature, so that further details are unnecessary here.

The preferred polyoxymethylene copolymers have melting points of at least 150 ° C. and molecular weights (weight average) M _w in the range from 5000 to 200,000, preferably from 7000 to 150,000. End group-stabilized polyoxymethylene polymers which have CC bonds at the chain ends are particularly preferred.

The molding compositions according to the invention contain, as component B), 0.05 to 2, preferably 0.1 to 1 and in particular 0.2 to 0.6% by weight of an isocyanurate of the formula I.

in which

R ¹ , R ² , R ^{3 are the} same or different radicals

- mean

and R ⁴ , R ^{5 are} independently hydrogen or one

Represent C ₁ -C ₄ alkyl group and

n is an integer from 1 to 3, or a triazine derivative of the formula II or mixtures thereof

in which

R ^{a is} hydrogen, an aliphatic radical having 1 to 12 carbon atoms, a phenyl radical,

_,

, where R ^{6 represents} a C ₁ -C ₄ alkyl group,

where R ⁷ , R ^{8 are the} same or different radicals hydrogen or

, C ₁ -C ₄ alkyl,

where R ^{9 is} hydrogen or a

Is methyl group and m is an integer from 0 to 20,

. .

represents and

R ^b , R ^c independently of one another represent hydrogen, halogen, a cyano group or a C ₁ - to C ₄ -alkyl group.

Preferred radicals R ⁴ and R ⁵ are hydrogen or methyl and n is preferred 1. Preferred radicals R ^b and R ^c are chlorine, fluorine, tertiary butyl, methyl and hydrogen.

A particularly preferred compound I is triglycidyl isocyanurate:

*

Triglycidyl isocyanurate is available under the trademark Araldite ^® PT 810 (Ciba Geigy) in the trade. Processes for the preparation of the isocyanurates of the formula I are known to the person skilled in the art, for which reason further details are unnecessary.

Triazine derivatives of formula II are under the trademark

Tinuvin ^® (Ciba Geigy) commercially available.

Preferred triazine derivative as component B) is .

2- (4,6-Diphenyl-1,3,5-triazin-2yl) -5 - [(hexyl) oxy] phenol

(Tinuvin ^® 1577).

Suitable sterically hindered phenols C) are in principle all compounds with a phenolic structure which have at least one sterically demanding group, preferably at least 2 sterically hindered OH groups per molecule on the phenolic ring.

Preferably, e.g. Compounds of the formula

in which mean:

R ¹ and R ^{7 are} an alkyl group, a substituted alkyl group or a substituted triazole group, where the radicals R ¹ and R ^{2 may be the} same or different and

R ^{3 is} an alkyl group, a substituted alkyl group, an alkoxy group or a substituted amino group. Antioxidants of the type mentioned are described for example in the

DE-A-27 02 661 (US-A-4 360 617).

Another group of preferred sterically hindered phenols is derived from substituted benzene carboxylic acids, in particular substituted benzene propionic acid. Particularly preferred compounds from this class are

Compounds of the formula

where R ⁴ , R ⁵ , R ⁷ and R ⁸ independently of one another are C ₁ -C ₈ -alkyl groups, which in turn can be substituted (at least one of them is a sterically demanding group) and R ^{6 is} a divalent aliphatic radical with 1 to 10 C- Atoms that can also have CO bonds in the main chain.

Preferred compounds corresponding to this formula are

Irganox ^® 245 from Ciba-Geigy)

(Irganox ^® 259 from Ciba-Geigy)

(Irganox ^® 1010 from Ciba-Geigy)

Examples include sterically hindered phenols:

2,2'-methylene-bis (4-methyl-6-tert-butylphenol), 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] , Pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], distearyl-3,5-di-tert-butyl-4-hydroxybenzyl-phosphonate, 2.6 , 7-Trioxa-1-phosphabicyclo- [2.2.2] oct-4-yl-methyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate, 3,5-di-tert-butyl-4- hydroxyphenyl-3,5-distearyl-thiotriazylamine,

2- (2'-hydroxy3'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2,6-di-tert-butyl-4-hydroxymethylphenol, 1,3,5- Trimethyl-3,4,6-tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -benzene, 4,4'-methylene-bis- (2,6-di-tert-butylphenol) , 3,5-di-tert-butyl-4-hydroxy-benzyl-dimethylamine and N, N'-hexamethylene-bis-3,5-di-tert-butyl-4-hydroxyhydrocinnamide. Have proven to be particularly effective and are therefore preferably used 2, 2 '-methylene-bis- (4-methyl-6-tert-butylphenyl), 1,6-hexanediol-bis- [3,5-di-tert. -butyl-4-hydroxyphenyl) propionate (Irganox ^® 259), pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and the above-described Irganox ^® 245 of the company Ciba Geigy, which is particularly suitable.

The antioxidants (C), which can be used individually or as mixtures, are used in an amount of 0.05 to 2% by weight, preferably 0.1 to 1.0% by weight and in particular 0.2 to

0.6 wt .-% used.

The molding compositions according to the invention contain as component D) 0.05-2, preferably 0.1-1 and in particular 0.2-0.6% by weight of at least one sterically hindered amine compound, for example compounds of the formula preferably come

into consideration, where R is the same or different alkyl radicals

R 'is hydrogen or an alkyl radical and

A 'is an optionally substituted 2- or 3-membered

Alkylene chain means.

Preferred component D) are derivatives of 2,2,6,6-tetramethylpiperidine such as: 4-acetoxy-2,2,6,6-tetramethylpiperidine,

4-stearoyloxy-2,2,6,6-tetramethylpiperidine,

4-aryloyloxy-2,2,6,6-tetramethylpiperidine,

4-methoxy-2,2,6,6-tetramethylpiperidine,

4-benzoyloxy-2,2,6,6-tetramethylpiperidine,

4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine,

4-phenoxy-2,2,6,6-6-tetramethylpiperidine,

4-benzoxy-2,2,6,6-tetramethylpiperidine,

4- (phenylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine. Furthermore are

Bis (2,2,6,6-tetramethyl-4-piperidyl) oxalate,

Bis (2,2,6,6-tetramethyl-4-piperidyl) malonate,

Bis (2,2,6,6-tetramethyl-4-piperidyl) adipate,

Bis (1,2,2,6,6-pentamethyl-piperidyl) sebacate,

Bis (2,2,6,6-tetramethyl-4-piperidyl) terephthalate,

1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) ethane,

Bis (2,2,6,6-tetramethyl-4-piperidyl) hexamethylene-1,6-dicarbamate, bis (1-methyl-2,2,6,6-tetramethyl-4-diperidyl) adipate and

Tris (2,2,6,6-tetramethyl-4-piperidyl) benzene-1,3,5-tricarboxylate is suitable.

In addition, higher molecular weight piperidine derivatives such as the dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol or

Poly-6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl (2,2,6,6-tetramethyl-4-piperidinyl) imino-1,6 -hexanediyl (2,2,6,6-tetramethyl-14-piperidinyl) imino suitable, which, like bis (2,2,6,6-tetramethyl-4-piperidyl) sebazate, are particularly suitable.

Such compounds are commercially available under the names Tinuvin ^® or Chimasorb ^® (registered trademark of Ciba-Geigy AG).

Uvinul ^® 4049 H from BASF AG may be mentioned as a further particularly preferred amine compound D):

The molding compositions according to the invention can contain 0-2, preferably 0-1 and in particular 0-0.6% by weight of at least one stabilizer from the group of benzotriazole derivatives or benzophenone derivatives or aromatic benzoate derivatives as component E).

Suitable benzotriazole derivatives are:

2- (2-hydroxy-5-methylphenyl) benzotriazole,

2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole,

2- (3,5-di-t-amyl-hydroxyphenyl) benzotriazole,

2- (2'-hydroxy-3 ', 5'-diisoamylphenyl) benzotriazole,

2- (2'-hydroxy-4-octoxyphenyl) benzotriazole,

2- (2H) -benzotriazol-2-yl) -4,6-bis- (1,1-dimethylpropyl) phenol and 2- (2H-benzotriazol-2-yl) -4- (1,1-dimethylpropyl) -6- (1-methylpropyl) phenol.

Such compounds are commercially available under the name Tinuvin® (registered trademark of Ciba Geigy AG).

Preferred benzotriazole derivatives are:

2,4-dihydroxybenzophenone,

2-hydroxy-4-methoxybenzophenone,

2-hydroxy-4-octoxybenzophenone,

2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone,

2,2'-dihydroxy-4,4'-dimethoxybenzophenone,

2-hydroxy-4-methoxy-5-sulphobenzophenone and

2-hydroxy-4-oxybenzylbenzophenone.

Examples of aromatic benzoate derivatives are p-t-butylphenyl salicylate and p-octylphenyl salicylate.

The molding compositions according to the invention can be used as component F)

0 to 80, preferably 0 to 50% by weight and in particular 0 to

Contain 40% by weight of conventional additives and processing aids.

Potassium titanate whiskers, carbon and preferably glass fibers may be mentioned as reinforcing fillers in amounts of up to 50% by weight, preferably up to 40% by weight, the glass fibers e.g. in the form of glass fabrics, mats, nonwovens and / or glass silk rovings or cut glass silk made of low-alkali E-glass with a diameter of 5 to 200 μm, preferably 8 to 50 μm, the fibrous fillers can be used according to their Incorporation preferably have an average length of 0.05 to 1 μm, in particular 0.1 to 0.5 μm. Other suitable fillers are, for example, wollastonite, calcium carbonate, glass balls, quartz powder, silicon and boron nitride or mixtures of these fillers.

Preferred combinations of fillers are: wollastonite with glass fibers, with mixing ratios of 5: 1 to 1: 5 being preferred.

Other additives are, in amounts of up to 50, preferably 0 to 40,% by weight, impact-modifying polymers (also referred to below as rubber-elastic polymers or elastomers).

Preferred types of such elastomers are the so-called ethylene-propylene (EPM) or ethylene-propylene-diene (EPDM) rubbers.

EPM rubbers generally have practically no more double bonds, whereas EPDM rubbers can have 1 to 20 double bonds / 100 carbon atoms. Examples of diene monomers for EPDM rubbers are conjugated dienes such as isoprene and butadiene, non-conjugated dienes having 5 to 25 carbon atoms such as penta-1, 4-diene, hexa-1, 4-diene, Hexa-1,5-diene, 2,5-dimethylhexa-1,5-diene and octa-1,4-diene, cyclic dienes such as cyclopentadiene, cyclohexadienes, cyclooctadienes and dicyclopentadiene, and alkenylnorbornenes such as 5-ethylidene-2-norbornene, 5 -Butylidene-2-norbornene, 2-methallyl-5-norbornene, 2-isopropenyl-5-norbornene and tricyclodienes such as 3-methyltricyclo (5.2.1.0.2.6) -3,8-decadiene or mixtures thereof. Hexa-1,5-diene-5-ethylidene-norbornene and dicyclopentadiene are preferred. The diene content of the EPDM rubbers is preferably 0.5 to 50, in particular 1 to 8,% by weight, based on the total weight of the rubber.

The EPDM rubbers can also be grafted with other monomers, e.g. with glycidyl (meth) acrylates, (meth) acrylic acid esters and (meth) acrylamides.

Another group of preferred rubbers are copolymers of ethylene with esters of (meth) acrylic acid. In addition, the rubbers can also contain monomers containing epoxy groups. These epoxy group-containing monomers are preferably obtained by adding epoxy group-containing monomers of the general

Formulas I or II to the monomer mixture built into the rubber

wherein R ⁶ - R ^{10 represent} hydrogen or alkyl groups with 1 to 6 carbon atoms and m is an integer from 0 to 20, g is an integer from 0 to 10 and p is an integer from 0 to 5. The radicals R ⁶ to R ^{8 are} preferably hydrogen, where m is 0 or 1 and g is 1. The corresponding compounds are allyl glycidyl ether and vinyl glycidyl ether.

Preferred compounds of the formula II are epoxy group-containing esters of acrylic acid and / or methacrylic acid, such as glycidyl acrylate and glycidyl methacrylate.

The copolymers advantageously consist of 50 to 98% by weight

Ethylene, monomers containing 0 to 20% by weight of epoxy groups and the remaining amount of (meth) acrylic acid esters. Copolymers of are particularly preferred

50 to 98, in particular 55 to 95% by weight of ethylene,

in particular 0.3 to 20 wt .-% glycidyl acrylate and / or

0 to 40, in particular 0.1 to 20% by weight of glycidyl methacrylate, and 1 to 50, in particular 10 to 40% by weight of n-butyl acrylate

and / or 2-ethylhexyl acrylate.

Further preferred esters of acrylic and / or methacrylic acid are the methyl, ethyl, propyl and i- or t-butyl esters.

In addition, vinyl esters and vinyl ethers can also be used as comonomers.

The ethylene copolymers described above can be prepared by processes known per se, preferably by random copolymerization under high pressure and elevated temperature. Appropriate methods are generally known.

Preferred elastomers are also emulsion polymers, the production of which e.g. in Blackley in the monograph "Emulsion Polymerization" is described. The emulsifiers and catalysts that can be used are known per se.

In principle, homogeneous elastomers or those with a shell structure can be used. The shell-like structure is determined by the order of addition of the individual monomers; The morphology of the polymers is also influenced by this order of addition. Representative here are as monomers for the production of the rubber part of the elastomers acrylates such as n-Butyl acrylate and 2-ethylhexyl acrylate, corresponding methacrylates, butadiene and isoprene and mixtures thereof. These monomers can be combined with other monomers such as e.g. Styrene, acrylonitrile, vinyl ethers and other acrylates or methacrylates such as methyl methacrylate, methyl acrylate, ethyl acrylate and propyl acrylate can be copolymerized.

The soft or rubber phase (with a glass transition temperature below 0 ° C) of the elastomers can be the core, the outer shell or a middle shell (for elastomers with more than two shell structure); in the case of multi-layer elastomers, several shells can also consist of a rubber phase.

If, in addition to the rubber phase, one or more hard components (with glass transition temperatures of more than 20 ° C.) are involved in the construction of the elastomer, these are generally obtained by polymerizing styrene, acrylonitrile, methacrylonitrile,

α-Methylstyrene, p-methylstyrene, acrylic acid esters and methacrylic acid esters such as methyl acrylate, ethyl acrylate and methyl methacrylate as main monomers. Besides that, here too

lower proportions of other comonomers are used.

In some cases it has proven to be advantageous to use emulsion polymers which have reactive groups on the surface. Such groups are e.g. Epoxy, amino or amide groups, as well as functional groups, by using monomers of the general formula

can be introduced, where the substituents can have the following meaning:

R ^{15 is} hydrogen or a C ₁ to C ₄ alkyl group,

R ^{16 is} hydrogen, a C ₁ to C ₈ alkyl group or an aryl group, in particular phenyl,

R ^{17 is} hydrogen, a C ₁ to C ₁₀ alkyl, a C ₆ to C ₁₂ aryl group or OR ₁₈

R ^{18 is} a C ₁ to C ₈ alkyl or C ₆ to C ₁₂ aryl group, which may optionally be substituted by O- or N-containing groups,

X is a chemical bond, a C ₁ to C ₁₀ alkylene or

C ₆ -C ₁₂ arylene group or

The graft monomers described in EP-A 208 187 are also suitable for introducing reactive groups on the surface.

Further examples include acrylamide, methacrylamide and substituted esters of acrylic acid or methacrylic acid such as

(N-t-Butylamino) ethyl methacrylate, (N, N-dimethylamino) ethyl acrylate, (N, N-dimethylamino) methyl acrylate and (N, N-diethylamino) ethyl acrylate. The particles of the rubber phase can also be crosslinked. Monomers which act as crosslinkers are, for example

Buta-1,3-diene, divinylbenzene, diallyl phthalate and dihydrodicyclopentadienyl acrylate and the compounds described in EP-A 50 265.

So-called graft-linking monomers can also be used, i.e. Monomers with two or more polymerizable double bonds, which react at different rates during the polymerization. Compounds are preferably used in which at least one reactive group polymerizes at about the same rate as the other monomers, while the other reactive group (or reactive groups) e.g. polymerizes much slower (polymerize). The different polymerization speeds result in a certain proportion of unsaturated double bonds in the rubber. If a further phase is subsequently grafted onto such a rubber, the double bonds present in the rubber react at least partially with the graft monomers to form chemical bonds, i.e. the grafted phase is at least partially linked to the graft base via chemical bonds.

Examples of such graft-crosslinking monomers are monomers containing allyl groups, in particular allyl esters of ethylenically unsaturated carboxylic acids such as allyl acrylate, allyl methacrylate,

Diallyl maleate, diallyl fumarate, diallyl itaconate or the corresponding monoallyl compounds of these dicarboxylic acids. There are also a large number of other suitable graft-crosslinking monomers; for further details, reference is made here, for example, to US Pat. No. 4,148,846. In general, the proportion of these crosslinking monomers in component F) is up to 5% by weight, preferably not more than 3% by weight, based on F). Some preferred emulsion polymers are listed below. First of all, graft polymers with a core and at least one outer shell are to be mentioned, which have the following structure:

Instead of graft polymers with a multi-layer structure, homogeneous, i.e. single-shell elastomers

Buta-1,3-diene, isoprene and n-butyl acrylate or their copolymers can be used. These products can also be prepared by using crosslinking monomers or monomers with reactive groups.

The elastomers F) described can also be produced by other conventional methods, e.g. by suspension polymerization. Of course, mixtures of the rubber types listed above can also be used.

The molding compositions according to the invention can also contain other conventional additives and processing aids. Additives for trapping formaldehyde (formaldehyde scavenger), plasticizers, lubricants, adhesion promoters, light stabilizers and pigments are only mentioned here as examples. The proportion of such additives is generally in the range from 0.001 to 5% by weight. It goes without saying that these stabilizers should be different from B) to D) and optionally E).

According to a preferred embodiment, the molding compositions according to the invention can contain a maleic-formaldehyde condensate as nucleating agent. Suitable products are e.g. in the

DE 25 40 207 described. Corresponding compounds are known to the person skilled in the art and are described, for example, in EP-A 327 384.

The thermoplastic molding compositions according to the invention are produced by mixing the components in a manner known per se, which is why detailed information is unnecessary here. The components are advantageously mixed in an extruder.

The thermoplastic molding compositions according to the invention are distinguished by a balanced spectrum of properties, in particular by the very good weather stability. Accordingly, they are suitable for the production of moldings of any kind, in particular for applications in the automotive sector, such as, for example, external handles, fuel caps or bumpers.

Examples

The following components were used: component A)

Polyoxymethylene copolymer from 97.3 wt .-% trioxane and

2.7% by weight butanediol formal. The product still contained approximately 3% by weight of unreacted trioxane and 5% by weight of thermally unstable components. After the thermally unstable portions had broken down, the copolymer had a melt index of 9 g / 10 min. (190 ° C, 2.16 kg support weight according to ISO 1133).

Component B)

B / 1

2- (4,6-diphenyl- (1,3,5-triazin-2-yl-5- [hexyl) oxy] phenol)

B / 2 Araldite ^® PT 810 from Ciba Geigy AG. Triglycidyl

Component D

D / 1 Tinuvin ^® 622 LD by Ciba Geigy AG: dimethyl succinate polymer piperidineethanol 4-hydroxy-2,2,6,6-tetramethyl-1 with D / 2 Tinuvin ^® 770 from Ciba Geigy AG DF: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate

D / 3 Chimasorb ^® 944 from Ciba Geigy: poly [[6- [1,1,3,3-tetramethylbutyl) amino] -1,3,5-triazine-2,4-diyl] [(2,2, 6,6-tetramethyl-4-piperidinyl) iminol] 1,6-hexanediyl [(2,2,6,6-tetra-methyl-4-piperidinyl) imino]]

D / 4 Uvinul ^® 4049 from BASF AG H from the company..

Component E

E / l

Tinuvin ^® 234 from Ciba. 2- (2'-hydroxy-3 ', 5DI (1,1-dimethylbenzyl) phenyl) benzotriazole

E / 2

TTiimnuvin ^® 329 from Ciba. 2- (2H-benzotriazol-2-yl) -2,4- (tert-butyl) phenol

E / 3

Uvasorb MET ^® of Sigma 3V. 2-Hydroxy-4-methoxy-benzophenone

Component F

F / 1 Epikote ^® from Shell

F / 2 Araldit ^® PY 284 of Messrs. Ciba Geigy

To produce the molding compositions, component A) was compounded, each with 0.4% by weight of components B) to F), on a twin-screw extruder at 220 ° C., degassed, and extruded and pelletized as a strand.

The UV stability was tested as follows: Injection molded bodies (round disks, thickness 2 mm, diameter 60 mm) produced at 200 ° C. were weathered in an Atlas Weather Ometer according to the guidelines of the Society Automotive Engineers (SAE) according to J 1885 for 700 h . Every 100 h during the weathering, the surface of the round disks was examined for cracks using a light microscope at 60 × magnification.

The results of the measurements can be found in the tables.

In the examples listed in Table 1 and Table 2, Ex. 21V-24V, it should be shown that regardless of the sterically hindered amine in the presence of antioxidants that cause cracking, cracking during weathering by using 2- (4 , 6-Diphenyl-1,3,5-triazin-2-yl) -5- [hexyl) oxy] phenol is significantly delayed. The sterically hindered amines apparently have no influence on the crack formation. The results in Table 2 show that even when B / 2 (Araldit ^® PT 810) is increased, cracking is significantly delayed in addition to the antioxidant, UV absorber and sterically hindered amines. The epoxy groups have no influence on the crack formation.

(see comparison components F / 1 and F / 2 examples 29V to 36V).

Claims

claims

1. Thermoplastic molding compositions containing

A) 10 to 99% by weight of a polyoxymethylene homo- or copolymer,

B) 0.05 to 2 wt. -% of an isocyanurate of formula I.

in which

R ¹ , R ² , R ^{3 are the} same or different radicals

and R ⁴ , R ^{5 are} independently hydrogen or one

Represent C ₁ -C ₄ alkyl group and

n is an integer from 1 to 3,

or a triazine derivative of the formula II or mixtures thereof

in which R ^{a is} hydrogen, an aliphatic radical having 1 to 12 carbon atoms, a phenyl radical,,

, where R ^{6 represents} a C ₁ -C ₄ alkyl group,

where R ⁷ , R ^{8 are the} same or different radicals hydrogen or

, C ₁ -C ₄ alkyl,

where R ^{9 is} hydrogen or a

Is methyl group and m is an integer from 0 to 20,

.

R ^b , R ^c independently of one another hydrogen, halogen, a

Represent cyano group or a C ₁ - to C ₄ -alkyl group,

C) 0.05 to 2% by weight of at least one sterically

hindered phenol compound

D) 0.05 to 2% by weight, at least one steric

hindered amine compound E) 0 to 2 wt .-% of at least one stabilizer selected from the group of

Benzotriazole derivatives or

Benzophenone derivatives or aromatic benzoate derivatives,

F) 0 to 80% by weight of conventional processing aids and additives, the weight percentages of components A) to F) giving 100%.

2. Thermoplastic molding compositions according to claim 1, containing as triazine derivative B) 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5 [(hexyl) oxy] phenol.

3. Thermoplastic molding compositions according to claims 1 or 2, in which the isocyanurate compound B) is triglycidyl isocyanurate.

4. Thermoplastic molding compositions according to claims 1 to 3, in which component C) contains at least 2 sterically hindered OH groups per molecule.

5. Thermoplastic molding compositions according to claim 4, in which the component C)

or

or their mixtures is built up. 6. Thermoplastic molding compositions according to claims 1 to 5, containing as component D) a dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol or

To (2,2,6,

6-tetramethyl-4-piperidyl) sebazate or their

Mixtures.

7. Use of the thermoplastic molding compositions according to claims 1 to 6 for the production of fibers, films and moldings.

8. Moldings obtainable from the thermoplastic molding compositions according to claims 1 to 6.