Thermoplastics stablized against the action of light

Di-(2,2,6,6-tetramethyl-4-piperidinyl) succinate and glutarate are very effective light stabilizers for thermoplastics, particularly for polyolefins.

The invention relates to thermoplastics, in particular polyolefins, which 
have been stabilized against the action of light. The stabilization is 
effected in this case by adding the succinic acid ester or glutaric acid 
ester of 2,2,6,6-tetramethylpiperidin-4-ol. 
It is known that most thermoplastics are damaged by the action of light, in 
which respect the short-wave component (UV) of light is particularly 
prominent. Damage by light is particularly severe in the case of 
polyolefins, especially in the case of polypropylene. Polymers of this 
type must be stabilized against the action of light for external uses. 
Nowadays a number of effective commercial light stabilizers are available 
for this purpose, for example hydroxybenzotriazoles, hydroxybenzophenones, 
nickel compounds, oxanilides or aryl benzoates. The most effective light 
stabilizers known today are, however, sterically hindered amines, amongst 
which the 2,2,6,6-tetramethylpiperidine derivatives are the best known. An 
example of these is di-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, which 
is available commercially under the name Tinuvin.RTM.770. 
It has now been found that the succinic acid ester and the glutaric acid 
ester of 2,2,6,6-tetramethylpiperidin-4-ol are particularly suitable for 
use as light stabilizers for thermoplastics. In some substrates these 
compounds are more effective than comparable known light stabilizers, for 
example than the corresponding sebacic acid esters. These compounds have 
the formula 
##STR1## 
in which n is 2 or 3. 
The invention therefore relates to thermoplastic polymers which have been 
stabilized against the action of light and contain, as the light 
stabilizer, di-(2,2,6,6-tetramethyl-4-piperidinyl) succinate or 
di-(2,2,6,6-tetramethyl-4-piperidinyl) glutarate. The polymers preferably 
contain the succinate (n=2). 
The use of di-(2,2,6,6-tetramethyl-4-piperidinyl) succinate as a light 
stabilizer for synthetic rubber latices containing TiO.sub.2 is suggested 
in Japanese Patent A-84/53545. The compound is mentioned there, but is not 
described in detail. Both compounds can be prepared process of U.S. 
application No. 3,840,494 by transesterifying 
4-hydroxy-2,2,6,6-tetramethylpiperidine with a dialkyl succinate or 
glutarate, respectively. The homologous 
di-(1,2,2,6,6-pentamethyl-4-piperidinyl) succinate is also mentioned in 
U.S. application No. 3,840,494. Owing to its low melting point, however, 
this compound is not very suitable for use as a stabilizer for 
thermoplastic polymers. In contrast, 
di-(2,2,6,6-tetramethyl-4-piperidinyl) succinate melts at 118.degree. C. 
and di-(2,2,6,6-tetramethyl-4-piperidinyl) glutarate melts at 
83.degree.-84.degree. C., as a result of which dry mixing with the 
powdered or granulated thermoplastic polymer is possible. 
The following are examples of thermoplastic polymers which can be 
stabilized by means of these compounds: 
1. Polymers of monoolefins, for example polyethylene, polypropylene, 
polyisobutylene, polybut-1-ene, polymethylpent-1-ene and polymers of 
cycloolefins, for example those of cyclopentene or norbornene. 
2. Mixtures of the polymers mentioned under 1 for example mixtures of 
polypropylene with polyisobutylene, with polyethylene or with EPDM. 
3. Copolymers of monoolefins with one another or with other vinyl monomers, 
for example ethylene/propylene copolymers, propylene/but-1-ene copolymers, 
propylene/isobutylene copolymers, ethylene/but-1-ene copolymers, 
ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate 
copolymers, ethylene/vinyl acetate copolymers or ethylene/acrylic acid 
copolymers and salts thereof (ionomers). 
4. Polystyrene, poly-(p-methylstyrene) and styrene copolymers with other 
vinyl monomers, for example styrene/acrylonitrile, styrene/alkyl 
methacrylate, styrene/maleic anhydride and 
styrene/acrylonitrile/methylacrylate. 
5. Polymers containing halogens, for example polychloroprene, chlorinated 
rubber, chlorinated or chlorosulfonated polyethylene, epichlorohydrin 
homopolymers and copolymers, and especially polymers formed from vinyl 
compounds containing halogens, for example polyvinyl chloride, 
polyvinylidene chloride, polyvinyl fluoride and polyvinylidene fluoride; 
and also copolymers thereof, such as vinyl chloride/vinylidene chloride, 
vinyl chloride/vinyl acetate or vinylidene chloride/vinyl acetate. 
6. Polymers derived from .alpha.,.beta.-unsaturated acids and derivatives 
thereof, such as polyacrylates and polymethacrylates, polyacrylamides and 
polyacrylonitriles. 
7. Copolymers of the monomers mentioned under 6 with one another or with 
other unsaturated monomers, for example acrylonitrile/alkyl acrylate 
copolymers, acrylonitrile/alkoxyalkyl acrylate copolymers or 
acrylonitrile/vinyl halide copolymers. 
8. Polymers derived from unsaturated alcohols and amines or acyl 
derivatives or acetals thereof, such as polyvinyl alcohol, polyvinyl 
acetate, stearate, benzoate or maleate, polyvinyl butyral, polyallyl 
phthalate and polyallylmelamine. 
9. Homopolymers and copolymers of cyclic ethers, such as polyalkylene 
glycols, polyethylene oxide or polypropylene oxide, or copolymers thereof 
with bisglycidyl ethers. 
10. Polyacetals, such as polyoxymethylene, and polyoxymethylenes containing 
comonomers, for example ethylene oxide. 
11. Polyphenyl oxides and sulfides and mixtures thereof with styrene 
polymers. 
12. Polyurethanes derived, on the one hand, from polyethers or polyesters 
containing terminal hydroxyl groups and, on the other hand, from aliphatic 
or aromatic polyisocyanates, and also precursors thereof. 
13. Polyamides and copolyamides derived from diamines and dicarboxylic 
acids and/or from aminocarboxylic acids or the corresponding lactams, such 
as polyamide 4, polyamide 6, polyamide 6/6, polyamide 6/10, polyamide 11, 
polyamide 12, poly-2,4,4-trimethylhexamethyleneterephthalamide or 
poly-m-phenyleneisophthalamide and block copolymers thereof with 
polyethers, for example polyethylene glycol, polypropylene glycol or 
polytetramethylene glycol. 
14. Polyureas, polyimides, polyamide-imides and polybenzimidazoles. 
15. Polyesters derived from dicarboxylic acids and dialcohols and/or from 
hydroxycarboxylic acids or the corresponding lactones, such as 
polyethyleneterephthalate, polybutyleneterephthalate, 
poly-1,4-dimethylolcyclohexane terephthalate, polyhydroxybenzoates and 
block polyether-esters derived from polyethers containing hydroxyl end 
groups. 
16. Polycarbonates and polyester-carbonates. 
17. Polysulfones, polyether-sulfones and polyetherketones. 
The stabilization of polyolefins and olefin copolymers such as are 
enumerated above under 1-3 is of particular importance, especially, 
however, the stabilization of polypropylene and propylene copolymers. The 
amount of light stabilizer added is appropriately 0.01 to 5% by weight, 
preferably 0.025 to 2% by weight, relative to the polymer to be 
stabilized. 
Additions can be carried out before, during or after polymerization, but 
before or during shaping. The stabilizer can, for example, be mixed with 
the polymers in powder form or can be added to the melt of the polymer by 
methods customary for this purpose. The stabilizer can also be mixed in in 
the form of a master-batch containing, for example, 5-25% of the 
stabilizer. 
In addition to the stabilizer according to the invention, it is also 
possible to add other known stabilizers to the polymer. The following 
classes of stabilizers are examples of these: 
1. Antioxidants 
1.1. Alkylated monophenols, for example 2,6-ditert.-butyl-4-methylphenol, 
2-tert.-butyl-4,6-dimethylphenol, 2,6-ditert.-butyl-4-ethylphenol, 
2,6-ditert.-butyl-4-n-butylphenol, 2,6-ditert.-butyl-4-i-butylphenol, 
2,6-di-cyclopentyl-4-methylphenol, 
2-(.alpha.-methylcyclohexyl)-4,6dimethylphenol, 
2,6-di-octadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol or 
2,6-ditert.-butyl-4-methoxymethylphenol. 
1.2. Alkylated hydroquinones, for example 
2,6-ditert.-butyl-4-methoxyphenol, 2,5-ditert.-butylhydroquinone, 
2,5ditert.amylhydroquinone or 2,6-diphenyl-4-octadecyloxyphenol. 
1.3. Hydroxylated thiodiphenyl ethers, for example 
2,2'-thiobis-(6-tert.butyl-4-methylphenol), 2,2'-thiobis-(4-octylphenol), 
4,4'-thiobis-(6-tert.-butyl-3-methylphenol) or 
4,4'-thiobis-(6-tert.butyl-2-methylphenol). 
1.4. Alkylidene bisphenols, for example 
2,2'-methylenebis-(6-tert.butyl-4-methylphenol), 
2,2'-methylenebis-(6-tert.butyl-4-ethylphenol), 
2,2'-methylenebis-[4-methyl-6-(.alpha.-methylcyclohexyl)-phenol], 
2,2'-methylenebis-(4-methyl-6-cyclohexylphenol), 
2,2'-methylenebis-(6-nonyl-4-methylphenol), 
2,2'-methylenebis-(4,6-ditert.butylphenol), 
2,2'-ethylidenebis-(4,6-ditert.butylphenol), 
2,2'-ethylidenebis-(6-tert.butyl-4-isobutylphenol), 
2,2'-methylenebis-[6-(.alpha.-methylbenzyl)-4-nonylphenol]. 
2.2'-methylenebis-[6-(.alpha.,.alpha. dimethylbenzyl)-4-nonylphenol], 
4,4'-methylenebis-(2,6-ditert.butylphenol), 
4,4'-methylenebis-(6-tert.butyl-2-methylphenol), 
1,1-bis-(5-tert.butyl-4-hydroxy-2-methylphenyl)-butane, 
2,6-di-(3-tert.butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol, 
1,1,3-tris-(5-tert.butyl-4-hydroxy-2-methylphenyl)-butane, 
1,1-bis-(5-tert.butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane, 
ethylene glycol bis-[3,3-bis-(3'-tert.butyl-4'-hydroxyphenyl)-butyrate], 
di-(3-tert.-butyl-4-hydroxy-5-methylphenyl)-dicyclopentadiene or 
di-[2-(3'-tert.butyl-2'-hydroxy-5'-methylbenzyl)-6-tert.butyl-4methylpheny 
l] terephthalate. 
1.5. Benzyl compounds, for example 
1,3,5-tri-(3,5-ditert.-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene, 
di-(3,5-ditert.butyl-4-hydroxybenzyl)-sulfide, isooctyl 
3,5-ditert.-butyl-4-hydroxybenzylmercaptoacetate, 
bis-(4-tert.butyl-3-hydroxy-2,6-dimethylbenzyl)-dithiol terephthalate, 
1,3,5-tris-(3,5-ditert.butyl-4-hydroxybenzyl) isocyanurate, 
1,3,5-tris-(4-tert.butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, 
dioctadecyl 3,5-ditert.butyl-4-hydroxybenzylphosphonate or the calcium 
salt of monoethyl 3,5-ditert.butyl-4hydroxybenzylphosphonate. 
1.6. Acylaminophenols, for example 4-hydroxylauranilide, 
4-hydroxystearanilide, 
2,4-bisoctylmercapto-6-(3,5-ditert.-butyl-4-hydroxyanilino)-s-triazine or 
octyl N-(3,5-ditert.-butyl-4-hydroxyphenyl)-carbamate. 
1.7. Esters of .beta.-(3,5-ditert.butyl-4-hydroxyphenyl)-propionic acid 
with monohydric or polyhydric alcohols, for example with methanol, 
octadecanol, 1,6-hexanediol, neopentylglycol, thiodiethylene glycol, 
diethylene glycol, triethylene glycol, pentaerythritol, trishydroxyethyl 
isocyanurate or dihydroxyethyloxamide. 
1.8. Esters of .beta.-(5-tert.butyl-4-hydroxy-3-methylphenyl)-propionic 
acid with monohydric or polyhydric alcohols, for example with methanol, 
octadecanol, 1,6-hexanediol, neopentylglycol, thiodiethylene glycol, 
diethylene glycol, triethylene glycol, pentaerythritol, trishydroxyethyl 
isocyanurate or dihydroxyethyloxamide. 
1.9. Amides of .beta.-(3,5-ditert.butyl-4-hydroxyphenyl)-propionic acid, 
for example N,N'-di-(3,5-ditert.butyl- 
4-hydroxyphenylpropionyl)-hexamethylenediamine, 
N,N'-di-(3,5-ditert.-butyl-4-hydroxyphenylpropionyl)-trimethylenediamine 
or N,N'-di-(3,5-ditert.butyl-4-hydroxyphenylpropionyl)-hydrazine. 
2. UV Absorbers and Light Stabilizers 
2.1. 2-(2'-Hydroxyphenyl)-benzotriazols, for example the 5'-methyl-, 
3',5'-ditert.butyl-, 5'-tert.butyl-, 5'-(1,1,3,3-tetramethylbutyl)-, 
5-chloro-3',5'-ditert.butyl-, 5-chloro-3'-tert.butyl-5'-methyl-, 
3'-sec.butyl-5'-tert.butyl-, 4'-octoxy-, 3', 5'-ditert.amyl- or 3', 
5'-bis-(.alpha.,.alpha.-dimethylbenzyl)-derivative. 
2.2. 2-Hydroxybenzophenones, for example the 4-hydroxy-,4-methoxy-, 
4-octoxy-, 4-decyloxy-, 4-dodecyloxy-, 4-benzyloxy-, 4,2',4'-trihydroxy- 
or 2'-hydroxy-4,4'-dimethoxyderivative. 
2.3. Esters of substituted or unsubstituted benzoic acids, for example 
4-tert.butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, 
dibenzoylresorcinol, bis-(4-tert.butylbenzoyl)-resorcinol, 
benzoylresorcinol, 2,4-ditert.butylphenyl 
3,5-ditert.butyl-4-hydroxybenzoate or hexadecyl 
3,5-ditert.butyl-4-hydroxybenzoate. 
2.4. Acrylates, for example ethyl or isooctyl 
.alpha.-cyano-.beta.-.beta.-diphenylacrylate, methyl 
.alpha.-carbomethoxycinnamate, ethyl or butyl 
.alpha.-cyano-.beta.-methyl-p-methoxycinnamate, methyl 
.alpha.-carbomethoxy-p-methoxycinnamate or 
N-(.beta.-carbomethoxy-.beta.-cyanovinyl)-2-methylindoline. 
2.5. Nickel compounds, for example nickel complexes of 
2,2'-thiobis-[4-(1,1,3,3-tetramethylbutyl)-phenol], such as the 1:1 or the 
1:2 complex, if appropriate containing additional ligands, such as 
n-butylamine, triethanolamine or N-cyclohexyldiethanolamine, nickel 
dibutyldithiocarbamate, nickel salts of monoalkyl 
4-hydroxy-3,5-ditert.butylbenzylphosphonates, such as the methyl or ethyl 
ester, nickel complexes of ketoximes, such as 2-hydroxy-4-methylphenyl 
undecyl ketone oxime, or nickel complexes of 
1-phenyl-4-lauroyl-5-hydroxypyrazole, if appropriate containing additional 
ligands. 
2.6. Sterically hindered amines, for example 
bis-(2,2,6,6-tetramethylpiperidyl) sebacate, 
bis-(1,2,2,6,6-pentamethylpiperidyl) sebacate, 
bis-(1,2,2,6,6-pentamethylpiperidyl) 
n-butyl-3,5-ditert.butyl-4-hydroxybenzylmalonate, 
tris-(2,2,6,6-tetramethyl-4-piperidyl) nitrilotriacetate, 
tetrakis-(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate 
or 1,1'-(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone). 
2.7. Oxamides, for example 4,4'-dioctyloxyoxanilide, 
2,2'-dioctyloxy-5,5'-ditert.butyloxanilide, 
2,2'-didodecyloxy-5,5'-ditert.butyloxanilide, 2-ethoxy-2'-ethyloxanilide, 
N,N'-bis-(3-dimethylaminopropyl)-oxamide, 
2-ethoxy-5-tert.-butyl-2'-ethyloxamide and a mixture thereof with 
2-ethoxy-2'-ethyl-5,4'-ditert.butyloxanilide and mixtures of 
o-methoxy-substituted and p-methoxy-substituted and of 
o-ethoxy-disubstituted and p-ethoxy-disubstituted oxanilides. 
3. Metal deactivators, for example N,N'-diphenyloxamide, 
N-salicylal-N'-salicyloylhydrazine, N,N'-bissalicyloylhydrazine, 
N,N'-bis-(3,5-ditert.butyl-4-hydroxyphenylpropionyl)-hydrazine, 
3-salicyloylamino-1,2,4-triazole or bisbenzylideneoxalic acid dihydrazide. 
4. Phosphites and phosphonites, for example triphenyl phosphite, diphenyl 
alkyl phosphites, phenyl dialkyl phosphites, tri-(nonylphenyl) phosphite, 
trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythrityl 
diphosphite, tris-(2,4-ditert.butylphenyl) phosphite, diisodecyl 
pentaerythrityl diphosphite, di-(2,4-ditert.butylphenyl) pentaerythrityl 
diphosphite, tristearyl sorbitol triphosphite, 
tetrakis-(2,4-ditert.butylphenyl) 4,4'-biphenylenediphosphonite or 
3,9-bis-(2,4-ditert.butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5 
]undecane. 5. Compounds which destroy peroxides, for example esters of 
.beta.-thiodipropionic acid, for example the lauryl, stearyl, myristyl or 
tridecyl ester, mercaptobenzimidazole, the zinc salt of 
2-mercaptobenzimidazole, zinc dibutyldithiocarbamate, dioctadecyl 
disulfide or pentaerythrityl tetrakis-(.beta.-dodecylmercapto)-propionate. 
6. Polyamide stabilizers, for example copper salts in combination with 
iodides and/or phosphorus compounds and salts of divalent manganese. 
7. Basic co-stabilizers, for example melamine, polyvinylpyrrolidone, 
dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine 
derivatives, amines, polyamides, polyurethanes, alkali and alkaline earth 
metal salts of higher fatty acids, for example Ca stearate, Zn stearate, 
Mg stearate, Na ricinoleate or K palmitate, antimony pyrocatecholate or 
tin pyrocatecholate. 
The concomitant use of known stabilizers can result in particularly 
advantageous stabilizing effects, which is particularly the case when UV 
absorbers and/or phenolic antioxidants are concomitantly used. The 
concomitant use of phenolic antioxidants, of phosphites or phosphonites 
and of alkaline earth metal salts of higher fatty acids is of particular 
importance in the stabilization of polyolefins. Similarly, the amount of 
the various costabilizers added is appropriately 0.01 to 5% by weight, 
preferably 0.025 to 2% by weight, relative to the polymer. 
It is also possible to add other additives which are customary in plastics 
technology, for example pigments, fillers, reinforcing agents, lubricants, 
flame-retarding agents, antistatic agents, blowing agents or plasticizers. 
The plastics thus stabilized can be used in a very wide variety of forms, 
for example as films, fibres, tapes, sheets, containers, tubes or other 
profiles. 
The following examples describe the preparation of the compounds mentioned 
and their use in thermoplastics. In these examples, parts and % are by 
weight, unless stated otherwise.

EXAMPLE 1 
Preparation of di-(2,2,6,6-tetramethyl-4-piperidinyl) succinate. 
322.3 g (2.05 mol) of 4-hydroxy-2,2,6,6-tetramethylpiperidine and 146.1 g 
(1 mol) of dimethyl succinate in 300 ml of xylene are heated to 80.degree. 
C. 1.2 g of lithium amide are added to the reaction mixture at this 
temperature, and the temperature is raised to 120.degree.-125.degree. C. A 
mixture of methanol and xylene is then distilled off slowly under a slow 
stream of nitrogen. After approx. 10 hours virtually no more methanol 
distills off, which indicates the end of the transesterification. The 
contents of the flask are diluted with 500 ml of petroleum ether (boiling 
range 110.degree.-140.degree. C.) and are washed in the separating funnel 
while still warm (60.degree.-70.degree. C.) with three times 100 ml of 
water. The reaction product crystallizes from the organic phase on cooling 
as colourless crystals. The di-(2,2,6,6-tetramethyl-4-piperidinyl) 
succinate obtained melts at 118.degree. C. 
EXAMPLE 2 
Preparation of di-(2,2,6,6-tetramethyl-4-piperidinyl) glutarate. 
The procedure is as in Example 1, using 160.2 g (1 mol) of dimethyl 
glutarate instead of the succinic acid ester. The crude product (residue 
from evaporation of the organic phase) is crystallized from 1200 ml of 
petroleum ether, boiling range 110.degree.-140.degree. C. The crystals 
melt at 83.degree.-84.degree. C. 
EXAMPLE 3 
Light stabilizing action in polypropylene tapes. 
100 parts of polypropylene powder [melt index 2.4 g/10 minutes (230.degree. 
C., 2160 g)] are mixed in a drum mixer with 0.05 part of pentaerythrityl 
tetrakis-[.beta.-(3,5-ditert.-butyl-4-hydroxyphenyl)-propionate], 0.05 
part of tris-(2,4-ditert.butylphenyl) phosphite, 0.1 part of Ca stearate 
and 0.05 part of the light stabilizer, and are then granulated in an 
extruder at a temperature of 180.degree. to 220.degree. C. 
The resulting granules are processed in a second extruder equipped with a 
sheeting die (temperature 220.degree. to 260.degree. C.) to give a film, 
which is cut into tapes, which are then stretched in a ratio of 1:6 at an 
elevated temperature and are wound up (titer of the tapes: 700 to 900 den; 
ultimate tensile strength: 5.5 to 6.5 g/den). 
The polypropylene tapes thus prepared are mounted on sample carriers 
without tension and are exposed to light in a Weather-O-Meter WRC 600. 
Groups of 5 specimens are taken out after various times and their ultimate 
tensile strength is determined. The exposure time after which the ultimate 
tensile strength of the tapes has deteriorated to 50% of the starting 
value is taken as a measure of the protective action of the various light 
stabilizers. The values obtained are listed in Table 1. 
TABLE 1 
______________________________________ 
Exposure time until ultimate 
Light stabilizer tensile strength is 50% 
______________________________________ 
none 560 hours 
0.05% of di-(2,2,6,6- 
2820 hours 
tetramethyl-4-piperidinyl) 
succinate 
______________________________________ 
EXAMPLE 4 
Light stabilization of polypropylene tapes 
The procedure is as in Example 3, but the polypropylene tapes are exposed 
in a Weather-O-Meter Ci 65 at a black-panel temperature of 
63.degree..+-.3.degree. C. 
TABLE 2 
______________________________________ 
Exposure time until ultimate 
Light stabilizer tensile strength is 50% 
______________________________________ 
none 560 hours 
0.05% of di-(2,2,6,6- 
&gt;1400 hours 
tetramethyl-4-piperidinyl) 
glutarate 
______________________________________ 
EXAMPLE 5 
Light stabilizing action in small polypropylene injection-moulded sheets 2 
mm thick. 
100 parts of polypropylene powder [melt index 2.4 g/10 minutes (230.degree. 
C./2160 g)] are mixed in a drum mixer with 0.05 part of pentaerythrityl 
tetrakis-[.beta.-(3,5-ditert.butyl-4-hydroxyphenyl)-propionate], 0.05 part 
of tris-(2,4-ditert.butylphenyl) phosphite, 0.1 part of Ca stearate, 0.1 
part of phthalocyanine blue and 0.2 part of light stabilizer, and are then 
granulated in an extruder at a temperature of 200.degree.to 220.degree. C. 
The resulting granules are injection-moulded, at a temperature of 
190.degree. to 220.degree. C., in an injection-moulding machine to give 
small sheets 2 mm thick. 
The small polypropylene sheets thus prepared are exposed to light in a 
Weather-O-Meter 65 WR at a blackpanel temperature of 
63.degree..+-.3.degree. C. (ASTM G 26-77). The samples are examined 
visually for chalking at regular intervals. The exposure time up to 
incipient chalking is taken as a measure of the protective action of the 
various light stabilizers. The results are shown in Table 3. 
TABLE 3 
______________________________________ 
Light stabilizer Exposure time up to 
(0.2%) incipient chalking 
______________________________________ 
Di-(2,2,6,6-tetramethyl- 
6100 hours 
piperidin-4-yl) succinate 
none 510 hours 
______________________________________ 
EXAMPLE 6 
Light stabilization of small polypropylene injection-moulded sheets. 
The procedure is as in Example 5, but only 0.05 part of phthalocyanine blue 
and only 0.05 part of light stabilizer are used for 100 parts of 
polypropylene. Processing to give small sheets is carried out in an 
injection-moulding machine at 250.degree.-260.degree. C. The small sheets 
are exposed in a Weather-O-Meter Ci 65. Assessment is carried out as in 
Example 5. 
TABLE 4 
______________________________________ 
Exposure time up to 
Light stabilizer incipient chalking 
______________________________________ 
0.05% of di-(2,2,6,6-tetramethyl- 
&gt;1400 hours 
4-piperidinyl) glutarate 
none 475 hours 
______________________________________