DE19912600A1 - Acid and oxidation-resistant molded parts - Google Patents

Abstract

The invention relates to the use of thermoplastic molding material consisting of A) 10 to 99 wt.- % of a polyoxymethylene homo- or copolymer, B) 0.1 to 2 wt.- % of at least one sterically hindered amine compound, C) 0 to 2 wt.- % of at least one stabilizer from the group of the benzotriazole derivatives or benzoate derivatives or benzophenone derivatives, D) 0 to 80 wt.- % of other additives and auxiliary processing agents, the sum of the weight percentages of components A) to D) being in any case 100 %, for producing stable molded parts in acidic and/or oxidative media.

Description

The invention relates to thermoplastic molding compositions

• A) 10 to 99 wt .-% of a Polyoxymethylenhomo- or -copolymeri sates,
• B) 0.1 to 2 wt .-% of at least one sterically hindered amine connection,
• C) 0 to 2 wt .-% of at least one stabilizer from the group the benzotriazole derivatives or benzoate derivatives or benzo photoinitiators,
• D) 0 to 80 wt .-% of other additives and processing aid medium,

the sum of the percentages by weight of components A) to D) being 100% in each case,
for the production of stable moldings in acidic and / or oxidative media.

Furthermore, the invention relates to the according to the invention Use available moldings.

Polyacetals have a good because of their high crystallinity Resistance to many chemicals, the high Resistance to fuels (including the methanolhal special), fats, oils, brake and cooling fluids is highlighted. Polyacetal shows only a slight swelling and consequently a high dimensional stability. The high processing shrinkage of polyacetal (compared to other techni rule thermoplastics) is z. B. in the production of power used in these applications integrated plug connections and piping a high Must have tightness. At the same time is a high breakage Expansion for automotive parts in the fuel sector necessary to meet the requirements of Law to meet required crash requirements. Also for this Polyacetal is the material of choice as well as the desired one high heat resistance in the field of Kraftstoffzu- and -rückführungssysteme.  

However, POM has the disadvantage that it is poorly resistant to acids or to oxidative agents. In the effect of such chemicals is expected in a short time with a molecular degradation. In the case of motor vehicles too, the action of acidic or oxidatively acting agents is to be expected (eg when so-called sour gasolines (fuel with acid constituents), SO ₂ gas from exhaust gas recirculation systems, F ₂ during fluorination of tanks and tank components, zinc chloride, eg from spreading salts, acid cleaning agents).

Acidic or oxidative agents are also outside of the Car building in use (descaling agent for parts in coffee and Espresso machines, disinfectant chlorine, bleach, ozone for applications in the drinking water or sanitary sector). It was now found that polyacetals containing sterically hindered amines are more resistant to acids and acids oxidative agents are.

Sterically hindered amines (HALS compounds), optionally with benzotriazole derivatives, are commonly used to increase UV stability in POM compositions, which can be combined with other UV stabilizers, depending on the application:
see, for. EP-A 448 038, EP-A 171 941, EP-A 586 988, DE-A 33 15 115 and DE-A 44 04 081.

Object of the present invention was therefore, from moldings To provide polyacetals, which are acidic and / or oxidative media (reduced molecular weight) large-scale degradation, retention of elongation at break), with the good ones above as far as possible should.

Accordingly, the use defined by Polyaceta found. Preferred embodiments are the sub to extract claims.

As component A) the inventively used Molding compounds 10 to 99, preferably 30 to 99 wt .-% and ins particular 90 to 99 wt .-% of a Polyoxymethylenhomo- or Copolymer.

Such polymers are known in the art and in of the literature.

In general, these polymers have at least 50 mole percent of recurring units -CH ₂ O- in the polymer backbone.

The homopolymers are generally prepared by polymerization of Formaldehyde or trioxane prepared, preferably in the counter were of suitable catalysts.

In the context of the invention, polyoxymethylene copolymers are preferred as component A, in particular those which, in addition to the recurring units -CH ₂ O-, are still up to 50, preferably 0.1 to 20, in particular 0.3 to 10 mol% and very particularly preferably 1 to 6 mol% of recurring units

where R ¹ to R ⁴ 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 of 0 to 3. Advantageously, these groups can be introduced into the copolymers by ring opening of cyclic ethers. Preferred cyclic ethers are those of the formula

wherein R ¹ to R ⁵ and n have the abovementioned meaning. For example, ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane and 1,3-dioxepane are called cyclic ethers and linear oligo- or Polyformals such as polydioxolane or polydioxepan called comonomers.

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

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

Preferred monomers of this type are ethylene diglycid, 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 C-Ato 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.

Process for the preparation of the above-described homo- and Copolymers are known in the art and be in the literature wrote, so that here further information is unnecessary.

The preferred polyoxymethylene copolymers have melting points of at least 150 ° C and weight average molecular weights M _W in the range of 5,000 to 200,000, preferably 7,000 to 150,000.

End-group stabilized polyoxymethylene polymers which are attached to the Chain end C-C bonds are particularly preferred.

In particular, products may also be used as component A) which still have a relatively high share (in general. <0.1% by weight) of thermally unstable portions. The Components C) and D) in particular, if they are before mixing with are premixed to the polyoxymethylene, stabilize such Crude polyoxymethylene very good.

As component B), the molding compositions according to the invention contain 0.05-2, preferably 0.1-1.5 and in particular 0.2-1.0 wt .-% of at least one sterically hindered Aminver bond, preferably z. B. Compounds of the formula

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 B) 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.

Further 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 ethane (2,2,6,6-tetramethyl-4-piperidyloxy)
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
suitable.

In addition, higher molecular weight piperidine derivatives such as Dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-7-pipe ridinethanol or Poly-6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-tri azine-2,4-diyl (2,2,6,6-tetramethyl-4-piperidinyl) imino-1,6-hexane diyl (2,2,6,6-tetramethyl-14-piperidinyl) imino  suitable such as bis (2,2,6,6-tetramethyl-4-piperidyl) sebazate are particularly well suited.

Such compounds are called Tinuvin © or Chimasorb® (registered trademark of Ciba-Spezialitä tenchemie GmbH) are commercially available.

Another particularly preferred amine compound B) which may be mentioned is Uvinul © 4049 H from BASF AG:

The molding compositions according to the invention can be used as component C) 0-2, preferably 0.1-1 and in particular 0.2-0.6 wt .-% at least a stabilizer from the group of benzotriazole derivatives or Benzophenone derivatives or aromatic benzoate derivatives.

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 known as Tinuvin® (a trademark of Ciba-Spezialitätenchemie GmbH) available in the stores.

Preferred benzophenone 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.

As aromatic benzoate derivatives are exemplified p-t-butylphe nylsalicylate and p-octylphenylsalicylate.

As component D) molding compositions of the invention can 0 to 80, preferably 0 to 50 wt .-% and in particular 0 to 40 wt .-% of conventional additives and processing aids ent hold.

As reinforcing fillers in amounts of up to 50% by weight, preferably up to 40% by weight, for example, potassium titanate Whiskers, called carbon and preferably glass fibers, wherein the glass fibers z. B. in the form of glass fabrics, mats, nonwovens and / or glass silk rovings or chopped glass silk of alka Luminous E glass with a diameter of 5 to 200 μm, preferably wise 8 to 50 microns can be used, wherein the fiber shaped fillers after their incorporation preferably one average length of 0.05 to 1 .mu.m, in particular 0.1 to 0.5 .mu.m point.

Other suitable fillers are, for example, wollastonite, Calcium carbonate, glass beads, quartz powder, Si 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 preferred are.

As further additives, in amounts up to 50, preferably 0 to 45 wt .-%, impact modifying polymers (hereinafter also as rubber-elastic polymers or elastomers be draws) called.

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

EPM rubbers generally have virtually no double bonds, whereas EPDM rubbers have 1 to 20 double bonds / 100 C atoms may have.

As diene monomers for EPDM rubbers are konju greedy dienes such as isoprene and butadiene, non-conjugated dienes with 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, cycloocta and dicyclopentadiene and Alkenylnorbornene such as 5-ethyl idene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5-norborne NEN, 2-isopropenyl-5-norbornene and tricyclodienes such as 3-methyl tricyclo (5.2.1.0.2.6) -3,8-decadiene or mixtures thereof. Preference is given to hexa-1,5-diene-5-ethylidene-norbornene and dicyclo pentadiene. The diene content of the EPDM rubbers is preferred Example 0.5 to 50, in particular 1 to 8 wt .-%, based on the Total weight of the rubber.

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

Another group of preferred rubbers are copolymers of ethylene with esters of (meth) acrylic acid. In addition, the rubbers may still contain epoxy group-containing monomers. These epoxy group-containing monomers are preferably incorporated into the rubber by adding epoxy group-containing monomers of the general formulas I or II to the monomer mixture

wherein R ⁶ -R ^{10 represent} hydrogen or alkyl groups having 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 preferably denote 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 formula II are epoxy group ent tende esters of acrylic acid and / or methacrylic acid, such as Gly cidyl acrylate and glycidyl methacrylate.

Advantageously, the copolymers consist of 50 to 98 wt .-% Ethylene, 0 to 20 wt .-% of epoxy-containing monomers so such as the residual amount of (meth) acrylic esters.  

Particularly preferred are copolymers of
50 to 98, in particular 55 to 95 wt .-% of ethylene, in particular 0.3 to 20 wt .-% glycidyl acrylate and / or
0 to 40, especially 0.1 to 20 wt .-% glycidyl methacrylate, and
1 to 50, in particular 10 to 40 wt .-% 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 may also be used as comonomers be set.

The ethylene copolymers described above can according to are prepared by known methods, preferably by random copolymerization under high pressure and elevated tem temperature. Corresponding methods are generally known.

Preferred elastomers are also emulsion polymers whose Her position z. As in Blackley in the monograph "Emulsion Polymeri The usable emulsifiers and kata Lystoren are known per se.

Basically, homogeneously constructed elastomers or those with a shell structure are used. The shellar The structure is determined by the order of addition of each mono determined; also the morphology of the polymers is from this order of addition affects.

Only representative are here as monomers for the production the rubber part of the elastomers acrylates such. For example, n-butyl acrylate and 2-ethylhexyl acrylate, corresponding methacrylates, Butadiene and isoprene and their mixtures called. This mono mers can with other monomers such. Styrene, acrylonitrile, Vinyl ethers and other acrylates or methacrylates such as methyl methacrylate, methyl acrylate, ethyl acrylate and propyl acrylate copo be lymerisiert.

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

Are in addition to the rubber phase still one or more Hartkompo nents (with glass transition temperatures of more than 20 ° C) on the structure involved in the elastomer, they are generally by Polymerization of styrene, acrylonitrile, methacrylonitrile, α-methylstyrene, p-methylstyrene, acrylic acid esters and methacrylic acid esters such as methyl acrylate, ethyl acrylate and methyl methacrylate produced as major monomers. In addition, 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 for. Example, epoxy, amino or amide groups and functional groups by Mitver use of monomers of the general formula

can be introduced
where the substituents may have the following meanings:
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 ^{15 is} a C ₁ - to C ₈ -alkyl or C ₆ - to C ₁₂ -aryl group which may optionally be substituted with 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

Also, the graft monomers described in EP-A 208 187 are suitable for the introduction of reactive groups on the surface.

Other examples are 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-diethyl amino) called ethyl acrylate.

Furthermore, the particles of the rubber phase can also be crosslinked his. Crosslinking monomers are, for example Buta-1,3-diene, divinylbenzene, diallyl phthalate and dihydrodicyclo pentadienyl acrylate and those described in EP-A 50 265 Links.

Furthermore, so-called graft-crosslinking monomers (graft linking monomers), d. H. Monomers with two or more polymerizable double bonds, in the Polymerisa tion at different speeds. virtue wise, such compounds are used in which at least a reactive group with about the same speed as the the remaining monomers polymerized while the other reactive Group (or reactive groups) e.g. B. significantly slower polymeri siert (polymerize). The different Polymerisationsge speeds bring a certain amount of unsaturated Double bonds in rubber with it. Is then on egg NEN such gum grafted another phase, so reactie At least part of the double bonds present in the rubber wise with the grafting monomers to form chemical Bindings, d. H. the grafted phase is at least partially linked via chemical bonds with the graft base.

Examples of such graft-linking monomers are allyl groups containing monomers, in particular allyl esters of ethylenically un saturated carboxylic acids such as allyl acrylate, allyl methacrylate, Diallyl maleate, diallyl fumarate, diallyl itaconate or the like ing monoallyl compounds of these dicarboxylic acids. There are also there are a variety of other suitable graft-linking monomials rer; for more details, for example, on the U.S. Patent 4,148,846.  

In general, the proportion of these crosslinking monomers to the component D) up to 5 wt .-%, preferably not more than 3% by weight, based on D).

Below are some preferred emulsion polymers leads. First, graft polymers with a core and to name at least one outer shell, the following structure to have:

Monomers for the core Monomers for the shell Buta-1,3-diene, isoprene, n-butyl acrylate, ethylhexyl acrylate or mixtures thereof, optionally together with crosslinking monomers Styrene, acrylonitrile, (meth) acrylates, optionally with reactive groups as described herein

Instead of graft polymers having a multi-shell structure can also be homogeneous, d. H. single-shell elastomers Buta-1,3-diene, isoprene and n-butyl acrylate or their copolymers be used. These products can also be used by others of crosslinking monomers or monomers having reactive groups getting produced.

The elastomers D) described may also be other customary Method, for. B. by suspension polymerization become.

Of course, mixtures of the above can be added led rubber types are used.

The molding compositions according to the invention can still further customary additives and processing aids. Only example Here are additives for trapping formaldehyde (Formalde hyd scavenger), plasticizers, lubricants, adhesion promoters, Called light stabilizers and pigments. The proportion of such Zu In general, rates are in the range of 0.001 to 5 wt .-%. It It goes without saying that these stabilizers are different of B) and, if appropriate, C).

As nucleating agents, the molding compositions of the invention according to a preferred embodiment, a melamine-formaldehyde Contain condensate. Suitable products are z. B. in the DE 25 40 207 described.  

Corresponding compounds are known to those skilled in and at For example, in EP-A 327 384 described.

The preparation of the thermoplastic form according to the invention Mass is done by mixing the components in per se known Way, which is why detailed information is unnecessary here. benefit The mixing of the components takes place on an extruder.

The thermoplastic molding compositions which can be used according to the invention are distinguished by a balanced property spectrum. Moldings produced therefrom are resistant to acidic and / or oxidative media. Therefore, such moldings are particularly suitable for use as moldings for

• - irrigation systems (resistance to acidic fertilizers)
• - Parts for sanitary applications, swimming pools z. B. cisterns, Floats, valves (resistance to acid and oxidative acting detergents, such. Zinc chloride, chlorine, ozone)
• - Parts for tank installations, which together with the PE tank fluo (resistance to fluorine)
• - petrol pump housing, stowage housing, parts for petrol pumps, Roll-over valves (resistance to sour gasoline and acid components in fuels)
• - Parts for coffee and espresso machines (resistance to acid descaling agent)
• - Check valves (eg in vacuum lines for brake booster), parts for exhaust gas recirculation, parts for desulphurisation catalysts (resistance to SO ₂ or diluted sulfuric acid).

Examples

The following components were used:

Component A)

Polyoxymethylene copolymer of 98.8% by weight of trioxane and 1.2% by weight of butanediol formal. The product still contained about 3 wt .-% unreacted trioxane and 5 wt .-% thermally insta ble shares. After degradation of the thermally unstable components, the copolymer had min a melt volume rate of 11 ^cm3 / 10 min. (190 ° C, 2.16 kg weight according to ISO 1133).

Component B)

Tinuvin® 622 LD from Ciba Geigy AG: dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol

Components D

D / 1 Irganox® 245 from Ciba-Geigy:

D / 2
Polyamide oligomer having a molecular weight of about 3000, prepared from caprolactam, hexamethylenediamine, adipic acid and acetic acid (as a molecular weight regulator) according to Ex. 5-4 of US Pat. No. 3,960,984 ("PA-dicapped")
D / 3
Synthetic Mg silicate (Ambosol® from Société Nobel, Bozel, Puteaux) having the following properties:

D / 4
A melamine-formaldehyde condensate according to Example 1 of DE-A 25 40 207 used.

Each POM mixture contained as a processing aid 0.4% by weight of component D / 1, 0.04% by weight of component D / 3, 0.05 wt% D / 3 and 0.2 wt% D / 4. For the production of Blends were Component A with 0.8 wt .-% of component B ge mixed and compounded in a twin-screw extruder at 220 ° C, degassed and extruded as a strand and granulated. Subsequently were prepared at 190 ° C specimens.

The specimens were stored under the conditions in the table specified conditions and media, with a measure of the Stabi mold quality, the elongation at break according to ISO 527-2 as per 2, 4,  8, 12, 21 and 42 days or 50 to 1000 hours storage measured has been.

In the table, the values for the elongation at break in percent of Initial value and the respective storage time specified.

As a comparison, a POM mixture was used, which the o. Amounts of components D / 1 to D / 4 contained, but no Kompo term B) (figures in brackets).

Results of the measurements are shown in the table.

The following agents were tested:
descaling:

• - citric acid
• - formic

Vehicle Application:

• Sulfuric acid (battery acid or dilute sulfuric acid, the in the engine compartment or exhaust system due to combustion of sulfur-containing fuel constituents can form)

table

Claims (4)

1. Use of thermoplastic molding compositions

• A) from 10 to 99% by weight of a polyoxymethylene homo- or copoly merisate,
• B) 0.1 to 2% by weight of at least one sterically hindered amine compound,
• C) 0 to 2% by weight of at least one stabilizer from the group of the benzotriazole derivatives or benzoate derivatives or benzophenone derivatives,
• D) 0 to 80% by weight of other additives and processing aids;

the sum of the percentages by weight of components A) to D) being 100% in each case,
for the production of stable moldings in acidic and / or oxidative media. 2. Use according to claim 1, in which the component C) 2- (2'-hydroxy-3 ', 5'-bis (1,1-dimethylbenzyl) phenyl) -benzotri azole or 2- (2H-benzotriazol-2-yl) -2,4-tert-butyl) phenol or whose mixtures are built up. 3. Use according to claims 1 or 2, wherein as a component B) a dimethyl succinate polymer with 4-hydroxy-2,2,6,6-tetra methyl-1-piperidineethanol or bis (2,2,6,6-tetramethyl- 4-piperidyl) sebazate or mixtures thereof is used. 4. sprinkler system components, moldings for sanitary applications, Cisterns, floats, valves, tank components, gasoline pump pen housing, storage enclosure, gasoline pump parts, roll-over ven tile, components for coffee-espresso tea makers, setback valves, parts for exhaust gas recirculation, components for desulphurisation Catalysts obtainable according to claims 1 to 3.