DE1802659B2 - Stabilisation of pigmented vinyl fluoride polymers - Google Patents

Abstract

Stabilised vinyl fluoride polymers are obtained by mixing a vinyl fluoride polymer contg. at least 75% wt. vinyl fluoride with a stabilising system contg. (I) an aliphatic polyol with 2-8 OH groups per 2-15C atoms, (II) an alkylphenol of formula (II), and (III) a tris(hydrocarbyl)phosphite of formula (III). R1 = H, alkyl or -SR; R = alkyl; R2 = alkyl, or an alkylhydroxyaromatic or thio-hydroxyaromatic gp; R3, R4 and R5 = C1-13 hydrocarbyl.

Description

Vinyl fluoride polymers have many excellent properties, particularly in the form of films and coatings Properties such as weather resistance (resistance to degradation under external environmental conditions) and good flexibility and strength (flexural, tensile and tensile strength) within the desired ranges. As a result the fact that vinyl fluoride polymers decompose when heated, before the formation of a film or coating are reached, it has been considered necessary to To disperse stabilizer particles and vinyl fluoride polymer in the form of individual particles and then either dry blending the particles or mixing them by blending on ball mills. However, vinyl fluoride polymers are still subject to strong degradation and corresponding discoloration, when they are exposed to the high temperatures required to fuse the polymer are. This insufficient stability is an obstacle to the commercial application of these Polymers.

One has already made great efforts to improve the thermal stability of vinyl fluoride polymers. There are also numerous Compounds have been proposed and investigated as additives that are incorporated into Vinylrlaaridpolymerisate to prevent or reduce their degradation. Since so far the desired success has not yet been achieved, there is a need for further improved heat resistance in molding compositions based on vinyl fluoride polymers, in particular in pigment-based molding compounds. It was found that the known stabilizers or rod isator systems, mi; de.be effective, inhibit the dismantling of Vir »ylf'zondpoiymerisaien that do not contain any other 1 additives, then ineffective s> d, wef..t sin vinyl fluoride polymer Pigments. When to do the numerous various stabilizers or stabilizer systems * .eme, which so far become known ün'i, for Vinyl polymerizates containing pigments are used, so these masses still discolor up to the melting temperatures that are generally used, UH ", the excitement and the training of the Accelerate mass on a substrate. So far there is still a lack of a stabilizer or stabilizer system, with the discoloration of both pure vinyl fluoride polymers as well as Vinyifluoridpoiymerisatert, cüis pigments can be effectively prevented.

The invention is based on the task of this Disadvantages of the previously known stabilization of Vinyl fluoride polymers to remedied x »d such Molding compounds of this type to schaifw, the bsi increased Temperatures improved thermal stability exhibit.

The invention also relates to a stabilized thermoplastic FowTiasse, consisting of

A. lOOGewichisieiien Vinyifiüoiidpolymerisat with at least 75 percent by weight vinylfluoridanieil,

B. 0.3 to 22 parts by weight of a stabilizer mixture

a) an aliphatic polyhydric alcohol Ttiu at least two to about eight hydroxyl groups 2 to about! 5 carbon atoms each ",

b) an alkylated phenol of the general formula

in which R ¹ and R ^{2 are} identical or different and each in ortho or meta position to the hydroxyl group is a hydrogen atom, an alkyl radical or an R - S group in which R is an alkyl radical and R ^{3 is} a hydrogen atom, an alkyl - or hydroxyalkyl radical, an R - S group in which R is an alkyl radical, a 2,4,6-trimethyl-bis-3,5- (3 ', 5'-di-tert-butyl-4-hydroxybenzyl) - benzyl group, or an alkylhydroxyaryl or thiohydroxyaryl radical,

C. an organic phosphite of the general formula

R ⁵ - O - P - O - R ⁶
O
R ⁴

in which R ⁴ , R ⁵ and R ⁶ , which can be identical or different, denote hydrocarbon radicals having 1 to 13 carbon atoms, and

D. optionally 5 to 50 parts by weight of a pigment and other customary additives.

The molding compositions according to the invention have disregarded their improved thermal stability has the further advantage that they are much more stable against discoloration as a result of degradation or decomposition, especially when processing at elevated levels Temperatures.

Examples of particularly effective aliphatic polyhydric alcohols in the stabilizer mixture contained in the molding compositions according to the invention are: trimethylolethane, trimethylolpropane, pentaerythritol and its oxyalkylated derivatives, dipentaerythritol, tripentaerythritol, sorbitol, mannitol, methyl glucoside, sucrose, hydroxypropyl saccharose and mixtures thereof with a carboxylic acid , polyhydroxy-substituted acids such as gluconic acid, arabonic acid and glucoheptonic acid, their lactones and salts such as the sodium, potassium and ammonium salts, and esters such as the C ₄ - to Q 6 -alkyl esters. Combinations of the abovementioned polyhydric alcohols can also be used in the molding compositions according to the invention. These polyhydric alcohols are e.g. B. described in U.S. Patent Reissue 25,451.

For the purposes of the invention suitable alkylated phenols are, for. B. 2,2'-bis (p-hydroxyphenol) propane, 4,4'-thiobio £ - (6-tert.-butyl-m-creso!), F, 3.5-trimethyl-2,4,6 -tris- (3 ₉ S-di-tert-butyl-4-hydroxybenzyl) -bepzol, the 2,6-Diaikyiphenols, the Alkykhioäther-

phenols, the 2,4,6-triacylphenols, 2,6-di-tert.-butyl-4-hydroxymethylphenol and combinations of such compounds.

Examples of the organic phosphites suitable for the purposes of the invention are trimethyl phosphite, Dimethyl ethyl phosphite, diethyl methyl phosphite, triethyl phosphite, diethyl propyl phosphite, trinony phosphite, Tridecyl phosphite, dipropyl ethyl phosphite, dipropyl butyl phosphite, tributyl phosphite, methyl ethyl propyl phosphite, Methyl ethyl butyl phosphite, ethyl propyl butyl phosphite, dibutyl ethyl phosphite, dibutyl propyl phosphite, Dibutylmethylphosphii, Methyldivinylphosphit.Dimethylvinylphosphit.Trivinylphosphit, Methyldipropenyl phosphite, propenyl dimethyl phosphite, butenyl methyl ethyl phosphite, propenyl ethyl methyl phosphite, tripropenyl phosphi ^ tributenyl phosphite, Tripentenylphosphite, Trihexenylphosphite, Triheptenylphosphite, Trioctenylphosphite, Trinonenylphosphite, Tridecenylphosph; t, triundecenylphosphite, Tridodecenyl phosphite, triiridecenyl phosphite, tribenzyl phosphite, Methyläthylbenzylphosphit, Merhylbenzylpropenylphospb.it, Dipentylpropenyl phosphite, dihexylpropenyl phosphite, diheptylpropenyl phosphite, Dioetylpropenylphosphite, divinylpropenylphosphite, didecylpropenylphosphite, diundecylpropenylphosphite, Didodecylpropenyl phosphite, ditridecenyl propenyl phosphite, Tristearyl phosphite, phenyldidecyl phosphite. Triisooctoyl phosphite, triallyl phosphite, and combinations of the aforementioned compounds.

The term "polymer" in the present description and in the claims includes homo- and copolymers of vinyl fluoride. "The carbon polymers should contain at least 75 to 80 weight percent vinyl fluoride units. Examples of suitable comonomers are ethylene, propylene, isobutylene and styrene, halogen-substituted hydrocarbons with a double bond, such as vinyl chloride, vinyl bromide,!,! - dichloroethylene, 1, 1-Difluoroethylene, l.2-diet: uoroethylene, difluorochloroethylene, tetrachlorethylene, trifluoropropylene, difluoroisobutylene, vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl pivalai, vinyl stearaethyl, acids, vinyl fluoroethers such as vinyl fluoroethers, such as vinyl fluoroethers, such as vinyl fluoroethers, acids, vinyl salicyl ethers, such as vinylsalyl ethylacetates, vinylsalyl ethylacetates, vinylsalicyl ethers, trifluoropropylene, vinylsalicyl ethers and Vinyldicxoia-i, vinyl ketones, such as methyl vinyl ketone, N-vinyl imides, such as N-vinyisucrinimide and N-vinylphthalimide, acrylic and methacrylic acids and their derivatives, such as ethers, nitriles, amides, anhydrides and their halides, including methyl methacrylate, / f -Hydroxyäthylmethacrylat, Allybieihacrylat, Acrylonitril, N-Butylmeihacryiamid, derivatives of maleic and Fumaric acid, such as diethyl maleate and dimethyl fumarate, propsnyl ester, such as allyl acetate and sopropenyl acetate. Di-; Using this Copo'ymerisate, even if they contain only small amounts Comonomerbausteiae causes da3 the Verarbeilungseigenschifts ^"1, for example, the Scrmeizbarkeit the molding composition:..!; Τ> ratio zj = d r>Homopolymer'säten verbsssft-i and characterized the Ai.Tjringen is emitted on a substrate.

Suitable Vinyi ^ 'iDrid ^ oi'ymftfisatR approach a GrenzvissLC & iiaiszih! > / on '.venigsisrks 0,.'; 5, Preferably Weiiigs'ms ■ :. The Potymerisaiteilchen can diameter up to za e. * va? 3ΰ · μ have '· * »-cz'jp ,: ve ^: s'i lies he unisr \ 5Q u .. 3is Gr ⁵ SBe -iet Poly r ensat · aggregate kanr sn hsrk'Jnr. r.ücbe? VvV'v ·. 2 B. ii> rcb treatment in Κϋ ^ ηπαΛίνι, he «khg5« e'2 "« "ί-den Prefer" are Tfttlr.hen with 75 bs \? S μ Ιτιπϊγ-half of a dispersion, the particle size does not have to be uniform.

Most of the numerous known white pigments have so far been used together with plastics processed of a quality suitable for extrusion. Among these, titanium dioxide has the most am found widespread use as an inorganic white pigment because of its various beneficial properties Properties in combination are peculiar,

ίο z. B. high refractive index, no discoloration (whiteness), physical and chemical stability and a relatively low specific weight. The titanium dioxide pigments are divided into "chalking" and "non-chalking" types. The pigments of the chalking Type are characterized by the fact that when they are used in paints, the paint subject to gradual degradation, being pulveriormige Chalk is produced, which is removed as a result of the eroding effect of wind and rain, so that the underlying layer is exposed to the atmosphere and further attacked, resulting in a leads to continued wear and tear and eventual destruction of the coating. That in the anatase modification occurring titanium dioxide has this chalking property. For the reasons given above, for many paints and coatings pigments of the chalking type are not used.

When titanium dioxide m the form of the rutile modification is present, particularly when the rutile crystals with oxides of silicon, aluminum or zinc have been treated, it has no chalking properties. However, as with the chalking modifications such as anatase, discoloration also occurs with rutile during extrusion. In contrast to extrusion-quality molding compositions which contain pigments of the chalking type, it is difficult to obtain extrusion-quality molding compositions which contain pigments of the iiich; have chalking type to stabilize fluorine-containing polymers. The compounds which have been found to be suitable for stabilizing molding compositions containing pigments of the chalking type are by no means necessarily effective when it comes to stabilizing molding compositions with pigments of the non-chalking type.

The erfindungsgernäßeri molding compounds with the new However, stabilizer systems are in each, which is a further advantage of the present invention The case remains stable, regardless of which crystal modification of the titanium dioxide or pigment is used.

Oje rr> ii tifandioxyf any crystal modification pigmented.!? Molding compounds according to the invention show no discoloration during extrusion -m ^ during subsequent aging.

In the most reactive Ft & nsnt one can in the Dispcrsior-ssysten? auzh λο ^ Λ other finely comminuted solid P'gi-r.ebite, wis'Ariiimoatrioxyd, Pigmentstreck-; rui? e. \ FürSiciT ?, ν, ηά other usually in pig- (n2 .'-;'. tertfs! Missen used additives such as barium sulfa! ', ZitfkcTiifH, An'itmaEnraxyd, Chrcmoxyd, Eisen-So axy <i. Ofin.-ser, Kaoiin, Minerafsilikate and farbg? ly5r> .is M'Vrf. /.asetzerr. Man tcann also Schutzko 'iotds uiid ¹ the Pigmsrf Jispefgieiwide or defiocken-fe Miü ^ i, wfc Tsiranatriusipyrophosphat or K3i>uLTiv.rip'"ifyphosphat, mk use.

$ 5 i ». -ij-if * '.' 'Igeif Mangen art VitiyMuoridpoiymerisat, F'-i'T'-in.' ^ xi. Scabiinat'-r ki> rtn «n depending on the type of Λ.Τ * md» ng and the intended type of application ν &;."ίΐ.ίΐ * τ: One can integrate the SiabEisaiorsystem into the

5 6

Molding compound in concentrations from about 0.3 to generally at a pressure of the order of magnitude

22 weight percent, preferably from about 0.7 to about 1.4 kg / cm ² or more and at one temperature

5.5 percent by weight, per 100 parts by weight of vinyl fluo- of about 30 ° C or higher, applies. A typical one

Incorporate ridpolymerisat. A preferred coating method is that one on the

Embodiment contains the stabilizer system 5 with the substrate in contact polymer

applying at least two of the three ingredients at 10 weight pressure using hot rollers. One achieves

percent, based on the total weight of the stabilizer - the coating formation even if the vinyl

satorsystems. If, for example, 0.7 parts by weight per fluoride polymer with the help of suitable adhesives,

100 parts by weight of vinyl fluoride polymer of stabilizers such as acrylic or epoxy resins on the to be coated

sensor are present, the proportionate amount of 10 applies the object, at least two of the three components of the stabilizer

at least 0.07 part by weight. The pigment is in the B e 1 s ρ 1 e 1 1 molding compound in an amount of about 5 to 50 parts by weight A number of white pigmented vinyl fluoride parts, preferably 10 to 20 parts by weight, per 100 gel polymer molding compounds which contain vinyl fluoride polymer from various parts by weight. The 15 gel sources contained titanium dioxide and molding compositions according to the invention based on vinyl, in which various stabilizers and stabilizer fluoride polymers can also other additives, systems were used, were added according to the following, as they are usually prepared in coating compositions based on a recipe: based on polymers are used. Examples of such additives are thickeners, 10 Component weight siciic

such as polymethyl methacrylate, methyl methacrylate-co-polyvinyl fluoride 100

polymers with acrylonitrile, vinyl resin, carboxyvinyl antimony trioxide 15

compounds, cellulose acetates and neutralizing titanium dioxide 30

agents such as amines. Stabilizer system 0 to 12

The molding compositions according to the invention can be reduced to 2 seconds

Basis of vinyl fluoride polymers in such a way that the polyvinyl fluoride used had a limit manufacture that the pigment-containing or viscosity number of 0.50. The polyvinyl fluoride was unpigmented Vinylfluoridpolymerisat and Stabili · together with the stabilizer and pigments sator system in powder or particulate form mixed milled at 154 ^C C on a roll mill. If ground or in the heat. To do this, you can use a mixer, two-roll mills, colloid mills available in a ball mixer, two-roll mills, colloid mills up to the desired size, which are used in this mill or sand mills. In the example it was 50 to 60 μ for the polyvinyl fluoride, a typical production method the vinyl is shredded. The Polyvinylfluoridformmasse ^c was in fluoridpolymerisat at about 150 to 180 C on hot .15 a twin-screw extruder processed and milled as rollers, while the stabilizer is extruded film. The dried film had an added and uniformly dispersed strength in the polymer of about 25.4;

yaws, whereby, depending on the recipe, pigment may be present. For test purposes, a dry film with may or may not You can also heat the vinyl fluoride with a thickness of about 1 to 2.5 mm in a hot polymer at temperatures between room temperature and air circulation oven to 260 ° C. This Zersetzungsratur and mix dry 180 ⁰ C for about, the test at 260 C is considerably more stringent than the stabilizer also incorporated and can be dispersed in the poly requirements at normal Verarbeitungstempemerisat and wherein it re raturcn 150-205 C. The specimens decompose only depends on the desired approach, whether exothermic and split off hydrogen fluoride as soon as pigment is present or not. The vinyl fluoride 45 they achieve thermal instability. The reaction polymer, in which the stabilizer and that is autocatal) table, d. H . Once the decomposition has been incorporated into the pigment, it is started in extruders. then it continues without there being any injection molding machines. as twin-screw extruder requires further exposure to heat, so that the ventilated extruder can be removed from the furnace with a vacuum or with a sample. Extruders working on these pressurized feed hoppers. 50 way can be the disintegration time by which the or processed in screw molding machines. The thermal stability of the samples measured by the polymer can be determined at such a high temperature. The Stabili- used (about 165 to 205 ° C) processed so that it can be extruded in the satoren and the results of the thermal Slabilig the desired shape and dimensions. Tests of effectiveness are given in Table I. Table I You can also extrude foils and add «/ cigt. that the total amount of door orient the stabilization stretching. 3 parts per 100 parts of polymer. That with the

A large number of substrates can be produced using the organically extruded moldings used from the experiments listed in Table 1 and made from the inventive phosphite. Phosphite is a commercially available product. Upper drawing molding compounds. For example, which has the empirical formula C ₃₃ He ₃ PO ₃ and IbI-Leder, Textilstoff ^, resins, wood, stone, concrete, cement Agende composition: trinonyl phosphite and what is of particular interest. Metals such as 90 percent by weight, nonyl alcohol 2.5 percent by weight steel, aluminum, iron. Magnesium and nickel / ent. p-Butylphenol 4.5 percent by weight, the remainder inert as well as their alloys, with an upper layer of filler. See the stabilizing properties of this. The coating is made in such a way as a product derived from trinonyl phosphite. on. that one freshly extruded moldings from the ⁶ ^ The in the experiments listed in Table I ver vinyl fluoride polymer, the shape of which was about that used aliphatic polyhydric alcohol Trides corresponds to the object to be coated, under pcntaenthritol (TPE) as essentially pure sufficient pressure and sufficient heat , in bond. 2.6-Di-tcrt-

butyl-p-cresol is used. Apparently that exists Function of organic phosphite is that it decomposes to form free radicals, while

the aliphatic polyhydric alcohol as the acid acceptor and the alkylated phenol for the trapping serve the free radicals.

Table I.

attempt Stabilizer system and connection without lot
(Parts per 100 parts resin) Decomposition time at 260 ° C
in minutes 1 2,6-di-tert-butyl-p-cresol 1.5 2 C ₃₃ H ₆₃ PO ₃ 3 1.0 3 Tripentaerythritol 3 2.0 4th Tripentaerythritol 3 4.0 5a C ₃₃ H ₆₃ PO, 2.0 7.5 5b 2,6-di-tert-butyl-p-cresol 1.0 6a C ₃₃ H ₆₃ PO ₃ 1.5 3.0 6b Tripentaerythritol 1.5 7a 2,6-di-tert-butyl-p-cresol 2.0 5.0 7b Tripentaerythritol 1.0 8a 2,6-di-tert-butyl-p-cresol 0.5 7.5 8b C ₃₃ H ₆₃ PO ₃ 0.5 Kc Tripentaerythritol 2.0 9a 2,6-di-tert-butyl-p-cresol 0.5 10.0 9b C ₃₃ H ₆₃ PO ₃ 0.5 9c Tripentaerythritol 2.0 I Oa 2,6-di-tert-butyl-p-cresol 2.0 8.5 praise C ₃₃ H ₆₃ PO ₃ 0.5 10c Tripentaerythritol 0.5 lla 2,6-di-tert-butyl-p-cresol 1.0 7.0 Man C ₃₃ H ₆₃ PO ₃ 1.0 lic Tripentaerythritol 1.0 12a 2,6-di-tert-butyl-p-kreso! 1.0 15.0 I2b C ₃₃ H ₆₃ PO ₃ 0.5 12c 1.5

Example 2

The procedure was as in Example I, but now a stabilizer system was used which consists of a combination of the aforementioned organic phosphite, tripentaerythritol (TPE) and 2,6-di-tert-butyl-p-cresol, but existed in other proportions. The one in the thermal decomposition test The values obtained are shown in Table II.

Table II

attempt Stabilisa (ors> Mem
Parts per 100 parts pole) vm> fluoride 2.6-Di-lcri -
but) l-
p-krcsol C ₃₃ H ₁₁ PO ₁ Decomposition / express
at 260 C
in minutes 13th
14th
15th
16 ·
P. TPE 0.0
0.0
0.5
0.5
0.5 0.0
0.5
0.0
0.5
0.5 1.5
5.5
4.0
16.0
19.0 0.0
0.5
0.5 ·
3.5
5.0

55

6o

attempt Sfabilisalorsyslem
Parts per 100 parts of polyvinyl fluoride 2,6-di-tert-
butyl
p-kretol CjJH ₁ JPO ₃ Decomposition time
at 260 ° C
in minutes 18th
19th TPE 5.0
0.5 0.5
5.0 10.5
19.0 0.5
0.5

B e i s ρ i e 1 3

The procedure was as in Example 1, but a stabilizer system was used, which is a combination of three other ingredients. As an aliphatic polyhydric alcohol, an im Commercially available oxypropylated pentaerythritol or the tripentaerythritol used in the previous examples (TPE) are used. As the alkylated phenol, it became one of the following commercially available compounds used: 2,6-di-tert-butyl-p-cresol or 2,6-dioctadecyl-p-cresol (hereinafter referred to as DOPC). As the organic phosphite, the product mentioned in the above examples or a commercially available tridecyl phosphite used. When performing the thermal stability tests Data obtained with each of the stabilization systems are summarized in Table III.

009 513 190

Table III

10

attempt Stabilizer system
Parts per 100 parts of polyvinyl fluoride alcohol alkylated phenol organic phosphite Decomposition
Time
at 260 ° C
in minutes 20th
21
22nd
23 1.5 PEP-450 *)
1.5 PEP-450
1.0 PEP-450
1.0 TPE 0.5 B **)
0.5 DOPC
0.5 DOPC
0.5 B 1.0A ***)
1.0 A
1.5 A
1.5 tridecyl phosphite 8.0
13.5
13.5
35.0

*) PEP-450 corresponds to an oxypropylated pentaerythritol *) B corresponds to 2,6-di-tert-butyl-p-cresol. ** ♦) A corresponds to the product of Example I containing _{C 33} H _{63 POj}

Example 4

The procedure was as in Example I, but in these experiments the polyvinyl fluoride dispersion no titanium dioxide pigment added. In addition, such a stabilizer system was used that a combination of three components in different proportional amounts per 100 parts of polyvinyl fluoride mass contained. In addition, the commercially available alkylated phenol was used in this experiment 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene used. The values obtained in performing the thermal resistance tests for each of these stabilizer systems are listed in Table IV.

Table IV

attempt Stabilizer system
Parts per 100 parts of polyvinyl fluoride alcohol alkylated phenol organic phosphite Decomposition time
at 260 ° C
in minutes 24
25th
26th 1.5 PEP-450 *)
1.5 PEP-450
1.5 PEP-450 0.5 B **)
0.5 C ****)
0.5 DOPC 1.0 A ***)
l, 0A
l, 0A 10.0
10.0
11.0

·) PEP-450 corresponds to an oxypropylated pentaerythritol *) B corresponds to 2,6-di-tert-butyl-p-cresol

***) A corresponds to the _{product containing C 33} H ₆₁ PO ₃ from Example I. * ♦ *) C corresponds to 1,3,5-trimethyl-2,4,6-tris- (3,5-di-tert - butyl-4-hydroxybenzyD-benzene.

It can be seen from the values given in the tables above that the thermal stability of the molding compositions according to the invention compared to the known use of only one stabilizer or a combination of two stabilizers is significantly improved when one in these according to the invention Molding compounds made up of three components, d. H. an aliphatic polyhydric alcohol, an alkylated phenol and an organic phosphite, existing stabilizer system uses, such as Experiments 8 to 12 and 16 to 25 make this clear.

b) an alkylated phenol of the general formula

Claims (1)

Claim: Stabilized thermoplastic molding compound, consisting of 55 A. 100 parts by weight of vinyl fluoride polymer with at least 75 percent by weight of vinyl fluoride, B. 0.3 to 22 parts by weight of a stabilizer mixture a) an aliphatic polyhydric alcohol * 5 with at least two to about eight hydroxyl groups per 2 to about 15 carbon atoms, in which R ¹ and R ^{2 are} identical or different and each in ortho or meta position to the hydroxyl group is a hydrogen atom, an alkyl radical or an R — S group in which R is an alkyl radical and R ^{3 is} a hydrogen atom, an alkyl radical or Hydroxyalkyl radical, an R - S group in which R is an alkyl radical, a 2,4,6-trimethyl - bis - 3,5 - (3,5 '- tert - butyl - 4 - hydroxybenzyl) benzyl group , or an alkylhydroxyaryl or thiohydroxyaryl radical, C. an organic phosphite of the general formula R ⁵ - O - P - O - R ⁶ O
R ⁴ in which R ⁴ , R ⁵ and R \, which can be the same or different, denote hydrocarbon radicals having 1 to 13 carbon atoms, and D. optionally 5 to 50 parts by weight of a pigment and other customary additives.