4-Aminomethylpolyalkylpiperidines useful as light stabilizers

Compounds of formula I ##STR1## where R.sub.1, R.sub.2 and R.sub.3 are defined in the text, are useful as light stabilizers for polymeric materials, particularly for thermoplastic polymers and automotive finishes. Preferred compounds are those in which R.sub.1 is hydrogen and R.sub.2 and R.sub.3 are identical (C.sub.8-17 alkyl)carbonyl groups.

This invention relates to 4-aminomethylpolyalkylpiperidines, which are 
useful as light stabilizers for polymeric materials. 
The invention provides compounds of formula I 
##STR2## 
in which R.sub.1 is hydrogen or C.sub.1-8 alkyl; 
R.sub.2 is hydrogen, (C.sub.1-22 alkyl)carbonyl, phenyl (C.sub.1-4 
alkyl)carbonyl, cyclohexylcarbonyl, phenylcarbonyl in which the phenyl 
ring is unsubstituted or substituted by 1 or 2 C.sub.1-12 alkyl groups 
having a total of not more than 18 carbon atoms, or a group of formula (a) 
EQU --CONHR.sub.4 (a) 
where 
R.sub.4 is C.sub.1-18 alkyl unsubstituted or substituted by a 
--N.dbd.C.dbd.O group, cyclohexyl, benzyl, phenyl, or (C.sub.1-12 
alkyl)phenyl; and 
R.sub.3 has one of the significances of R.sub.2 provided that R.sub.3 may 
be hydrogen only when R.sub.2 is hydrogen, or is a group of formula (b) or 
(c) 
##STR3## 
where R.sub.5 is C.sub.1-20 alkylene or phenylene and 
R.sub.6 is a group of formula (d) or (e) 
EQU --NR.sub.7 R.sub.8 (d) 
##STR4## 
in which R.sub.7 is hydrogen, C.sub.1-18 alkyl or .beta.-hydroxyethyl, and 
R.sub.8 is C.sub.1-18 alkyl, .beta.-hydroxyethyl or phenyl or 
R.sub.7 and R.sub.8 together with the nitrogen atom to which they are 
attached form a morpholine or piperidine group. 
In compounds of formula I, wherever the same symbol appears more than once 
it may have the same or different significances, unless otherwise stated. 
All C.sub.3 or higher alkyl groups may be either straight chain or 
branched. 
R.sub.1 is preferably R.sub.1 ' where R.sub.1 ' is hydrogen or methyl, and 
more preferably R.sub.1 is hydrogen. 
R.sub.2 and R.sub.3 as alkylcarbonyl preferably contain a C.sub.1-17 alkyl 
group, more preferably a C.sub.8-17 alkyl group most preferably a 
C.sub.11-17 alkyl group. When R.sub.3 is other than a group (b) or (c), 
R.sub.2 and R.sub.3 are preferably identical. R.sub.2 preferably has one 
of the significances of hydrogen, alkylcarbonyl or a group of formula (a) 
and is preferably R.sub.2 ' where R.sub.2 ' is hydrogen, (C.sub.1-17 
alkyl)carbonyl or a group of formula (a) in which R.sub.4 is R.sub.4 ' 
where R.sub.4 ' is C.sub.1-17 alkyl or phenyl. More preferably R.sub.2 is 
R.sub.2 " where R.sub.2 " is hydrogen or (C.sub.8-17 alkyl)carbonyl. Where 
R.sub.3 is a group of formula (b) or (c) then R.sub.2 is preferably 
hydrogen. 
R.sub.3 preferably has one of the significances of alkylcarbonyl, a group 
of formula (a) or a group of formula (b). 
R.sub.3 is preferably R.sub.3 ' where R.sub.3 ' is (C.sub.1-17 
alkyl)carbonyl, a group of formula (a) in which R.sub.4 is R.sub.4 ' or a 
group of formula (b) in which R.sub.1 is hydrogen, R.sub.2 is R.sub.2 ' 
and R.sub.5 is R.sub.5 ' where R.sub.5 ' is C.sub.1-8 alkylene or 
p-phenylene. More preferably, R.sub.3 is R.sub.3 " where R.sub.3 " is 
(C.sub.8-17 alkyl)carbonyl or a group of formula (b) in which R.sub.1 is 
hydrogen, R.sub.2 is hydrogen and R.sub.5 is R.sub.5 '. Most preferably 
R.sub.3 is R.sub.3 '" where R.sub.3 '" is (C.sub.11-17 alkyl)carbonyl and 
R.sub.2 and R.sub.3 preferably have the same significance. 
Where R.sub.3 is a group of formula (b), the compound is preferably a 
symmetrical compound of formula I.sub.s 
##STR5## 
where R.sub.5 is preferably R.sub.5 '. 
Where R.sub.3 is a group of formula (c), this preferably contains either 0 
or 2 groups of formula (e). In group (d), R.sub.7 and R.sub.8 are 
preferably C.sub.1-18 alkyl or together with the nitrogen atom to which 
they are attached, form a morpholine or piperidine ring. More preferably 
R.sub.7 and R.sub.8 together form one of these two ring systems. 
Preferred compounds of formula I are those of formula Ia 
##STR6## 
where R.sub.1 ', R.sub.2 ' and R.sub.3 ' are defined above, and 
particularly preferred compounds are those of formula Ib 
##STR7## 
where each group R.sub.9 is C.sub.8-17 alkyl and both groups R.sub.9 are 
preferably the same. 
Compounds of formula Ic 
##STR8## 
that is, compounds of formula I in which both R.sub.2 and R.sub.3 are 
hydrogen, may be prepared by reduction of a compound of formula VII 
##STR9## 
in known manner. Reduction may be carried out for example by catalytic 
hydrogenation or by the use of metal hydrides, e.g. lithium aluminium 
hydride. 
Compounds of formula Ic are themselves light-stabilizers, but are primarily 
of use as intermediates in the preparation of other compounds of formula 
I. Thus, where R.sub.2 is hydrogen and R.sub.3 is a group other than (a), 
(b) or (c), the compound of formula Ic may be reacted with 1 mole of a 
compound of formula III 
EQU R.sub.3a --OH III 
where R.sub.3a has any of the significances of R.sub.3 other than hydrogen 
(a), (b) or (c); or with a functional derivative thereof. 
Compounds of formula I in which R.sub.2 is hydrogen and R.sub.3 is a group 
of formula (a) may be prepared by reacting a compound of formula Ic with 1 
mole of a compound of formula IV 
EQU R.sub.4 --N.dbd.C.dbd.O IV 
in which R.sub.4 is defined above. 
Where R.sub.2 is hydrogen and R.sub.3 is a group of formula (b), 2 moles of 
the compound of formula Ic is reacted with 1 mole of a compound of formula 
V 
##STR10## 
in which R.sub.5 is defined above, or with a functional derivative 
thereof. 
Where R.sub.2 is hydrogen and R.sub.3 is a group of formula (c), from 1 to 
3 moles of compound of formula Ic is reacted with 1 mole of a compound of 
formula VI 
##STR11## 
in which R.sub.6a has one of the significances of R.sub.6 or is chlorine. 
Compounds of formula I in which R.sub.2 is other than hydrogen may be 
obtained by reacting the product of any of the above reactions with a 
further mole of a compound of formula III or a functional derivative 
thereof, or of formula IV. The compounds of formulae III, IV, V, VI and 
VII are known or may be prepared by known methods from available starting 
materials. 
Compounds of formula I are useful as stabilizers to protect polymeric 
materials against degradation by light. The compounds have particularly 
good solubility and miscibility in solvent systems and in liquid polymers 
and prepolymers, which makes them useable in a wide range of polymeric 
materials. 
The concentration of compound of formula I employed in the polymeric 
material is suitably 0.01 to 5% by weight, preferably 0.02 to 1% by 
weight. The compound may be added before, during or after the 
polymerization step, and may be added in solid form; in solution, 
preferably as a liquid concentrate containing from 20-80% by wt. of 
compound of formula I; or as a solid master-batch composition containing 
20-80% by wt. of compound of formula I and 80-20% by wt. of a solid 
polymeric material which is identical with or compatible with the 
polymeric material to be stabilized. 
Suitable polymeric materials include plastics materials for example 
polyethylene, polypropylene, ethylene/propylene copolymers, polyvinyl 
chloride, polyester; polyamide, polyurethane, polyacrylonitrile, ABS, 
terpolymers of acrylates, styrene and acrylonitrile, styrene/acrylonitrile 
and styrene/butadiene. Other plastics materials such as polybutylene, 
polystyrene, chlorinated polyethylene, polycarbonate, 
polymethylmethacrylate, polyphenylene oxide, polypropylene oxide, 
polyacetals, phenol/formaldehyde resins and epoxy resins may also be used. 
Preferred plastics materials are polypropylene, polyethylene, 
ethylene/propylene copolymers and ABS. Natural polymers for example 
natural rubber may also be stabilized, as may lubricating oils containing 
polymeric material. 
The compounds of formula I may be incorporated by known methods into the 
polymeric material to be stabilized. Of particular importance is blending 
of the compounds with thermoplastic polymers in the melt, for example in a 
melt blender or during the formation of shaped articles, including foils, 
tubes, fibres and foams by extrusion, injection moulding, blow moulding, 
spinning or wire coating. 
It is not essential for the polymeric material to be fully polymerised 
before mixing with the compounds according to the invention. The compounds 
may be mixed with monomer, prepolymer or precondensate, and the 
polymerisation or condensation reaction carried out subsequently. This 
will of course be the preferred method of incorporation of the compounds 
into thermosetting polymers, which cannot be melt blended. 
The compounds of formula I may be used alone or in combination with other 
stabilizers, for example antioxidants. Examples include sterically 
hindered phenols, sulphur or phosphorus-containing compounds or mixtures 
of these. Examples are benzofuran-2-ones; indolin-2-ones and sterically 
hindered phenols such as 
.beta.-(4-hydroxy-3,5-ditert.-butylphenyl)-propionyl stearate, methane 
tetrakis-[methylene-3(3', 5'-ditert.-butyl-4-hydroxyphenyl-)-propionate], 
1,3,3-tris-(2-methyl-4-hydroxy-5-tert.-butylphenol)-butane, 
1,3,5-tris(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazin-2,4,6 
(1H, 3H, 5H)-trione, 
bis(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)dithiolterephthalate, 
tris(3,5-ditert.-butyl-4-hydroxybenzyl)isocyanurate, the triester of 
.beta.-(4-hydroxy-3,5-ditert.-butylphenyl)propionic acid with 
1,3,4-tris-(2-hydroxyethyl)-5-triazin-2,4,6(1H, 3H, 5H)-trione, 
bis[3,3-bis-(4'-hydroxy-3-tert.-butylphenyl)-butyric acid]glycol ester, 
1,3,5-trimethyl-2,4,6 tris-(3,5-ditert.-butyl-4-hydroxybenzyl)benzene, 
2,2'-methylene-bis-(4-methyl-6-tert.-butylphenyl)terephthalate, 
4,4-methylene-bis(2,6 ditert.-butylphenol), 
4,4'-butylidene-bis-(tert.-butylmeta-cresol), 
4,4-thio-bis-(2-tert.-butyl-5-methylphenol), 
2,2'-methylene-bis-(4-methyl-6-tert.-butylphenol. 
Sulphur-containing antioxidative co-stabilizers which may be used include 
for example distearylthiodipropionate, dilaurylthiodipropionate, methane 
tetrakis(methylene-3-hexylthiopropionate), methane 
tetrakis(methylene-3-dodecylthiopropionate) and dioctadecyldisulphide. 
Phosphorus-containing co-stabilizers include for example trinonylphenyl 
phosphite, 4,9-distearyl-3,5,8,10-tetraoxadiphosphaspiroundecane, 
tris-(2,4-ditert.-butylphenyl)phosphite and 
tetrakis(2,3-ditert.-butylphenyl)-4,4'-biphenylylene diphosphonite. 
Further additives such as aminoaryl compounds and UV-absorbers and light 
stabilizers e.g. 2-(2'-hydroxyphenyl)-benzotriazole, 
2-hydroxybenzophenone, 1,3-bis-(2'-hydroxybenzoyl)benzene, salicylates, 
cinnamates, benzoates and substituted benzoates, sterically hindered 
amines and oxolic acid diamides may be used. Other known types of 
additives, e.g. flame retardants and antistatic agents, may also be added. 
The compounds of formula I are especially suitable for use in organic 
polymer-containing coatings, particularly automotive finishes. 
Automotive finishes are generally solutions or dispersions of organic 
polymers or polymer precursors in organic solvents. The majority are 
stoving finishes, which require the application of heat, generally above 
100.degree. C., in order to harden the finish in an acceptable time once 
it has been applied to the primer-coated metal surface. The effect of this 
heating may be to accelerate the chemical reaction between polymer 
precursors in a thermosetting system, or to bring about fusion of 
particles of a thermoplastic polymer. 
Many automotive finishes are metallic finishes, which contain flakes of 
metal, usually aluminium, in order to provide optical effects due to 
reflection. Such finishes are often two-coat finishes, in which a clear 
top coat is applied over a base coat containing the pigment and metal 
flakes. Such two-coat metallic finishes have particular need of UV 
stabilizers in the top coat, since the polymer in this coat is not 
protected by light-absorbing pigments, and it is subjected to almost 
double the normal amount of radiation because of reflection of light from 
the lower metallic layer. 
The compounds of formula I are particularly useful in stoving finishes, 
particularly in the top coat of two-layer metallic finishes. 
The compounds of formula I are suitable for use as UV stabilizers in a wide 
range of liquid finishes, for example those base on combinations of 
melamine-formaldehyde resins with oil-modified polyester resins, 
polyacrylate resins with added crosslinkers, or saturated polyesters; or 
on self-crosslinked polyacrylate or polyacrylate resin copolymerised with 
styrene. 
Further examples are two-component finishes based on an aliphatic or 
aromatic di-isocyanate and a hydroxy-group-containing polyacrylate, 
polyester or polyether resin. Thermoplastic polyacrylate resins may also 
be used, the latter being particularly useful in metallic finishes, as are 
also polyacrylate resins with added crosslinkers in combination with 
melamine-formaldehyde resins etherified with butanol and, further, 
hydroxy-group-containing polyacrylate resins hardened with aliphatic 
di-isocyanates. 
The compound of formula I may be added to the finish at any stage in its 
manufacture, and may be added in solid form or in solution, preferably in 
the form of a liquid concentrate in a suitable solvent. 
The addition of from 0.02-5% by weight, preferably 0.2-2% by weight of one 
or more compounds of formula I gives a clear improvement in the light- and 
weather-stability of organic pigments in stoving finishes as well as 
reducing the tendency to hairline cracking and loss of gloss as the result 
of weathering. This is surprizingly also found for metallic finishes, and 
excellent long-term stability of the clear top coat of two-layer metallic 
finishes is obtained. In such finishes, the compound of formula I may be 
added to the metallic undercoat, the clear top coar or both, preferably 
only to the clear top coat. 
The following Examples, in which all parts are by weight and all 
temperatures in degrees Centigrade, illustrate the invention.

EXAMPLE 1 
To a suspension of 40 parts 4-hydroxy-4-cyano-2,2,6,6-tetramethylpiperidine 
in 400 parts ether is added gradually 16.6 parts lithium aluminium 
hydride, keeping the temperature at 0.degree..varies.10.degree.. The 
mixture is heated to reflux for 90 minutes, then cooled to 
0.degree.-15.degree. while 100 parts water are added dropwise. The solid 
precipitate is removed by filtration and the filtrate dried over sodium 
sulphate, filtered and the solvent evaporated. The residue is purified by 
chromatography on silica gel, eluting with a mixture of 
ethanol/concentrated aqueous ammonia in the volume ratio 5:1. The product 
is 4-hydroxy-4-aminomethyl-2,2,6,6-tetramethylpiperidine, m.p. 
87.degree.-89.degree.. (Compound of formula Ic, R.sub.1 =H.) 
EXAMPLE 2 
To a two-phase mixture of 1 part 
4-hydroxy-4-aminomethyl-2,2,6,6-tetramethylpiperidine, 50 parts ether and 
5.4 parts 1 N aqueous sodium hydroxide at room temperature is added 
dropwise 1.8 parts stearoyl chloride. The reaction mixture is shaken 
periodically until no more cloudiness appears in the ether layer. The 
organic phase is separated, dried over sodium sulphate, filtered and the 
solvent evaporated. The crude product is recrystallized from ethyl acetate 
and dried in a vacuum oven. The product consists of white crystals of the 
compound of formula 
##STR12## 
EXAMPLES 3-9 
The following compounds are obtained in analogous manner by reaction of the 
product of Example 1 with the appropriate reagent in the appropriate molar 
ratio: 
##STR13## 
TABLE I 
______________________________________ 
Compounds of formula 
Example 
No. R.sub.2 R.sub.3 
______________________________________ 
4 COC.sub.17 H.sub.35 
COC.sub.17 H.sub.35 
5 H 
##STR14## 
##STR15## 
##STR16## 
7 CONHC.sub.18 H.sub.37 
CONHC.sub.18 H.sub.37 
8 H CONH(CH.sub.2).sub.6NCO 
9 H 
##STR17## 
______________________________________ 
APPLICATION EXAMPLE (A) 
0.5% by wt. of the compound of Example 2 is worked into polypropylene 
(containing no UV stabilizer) in a kneading mixer at 180.degree.. The 
resulting mass is pressed into a 3 mm thick plate, and also into a 0.3 mm 
thick film. The film is illuminated in an Atlas Weatherometer WRC 600 with 
a xenon lamp, and the damage caused by UV light is measured by the growth 
in intensity of the IR carboxyl band absorption at 5.8.mu.. According to 
test method DIN 53453, the change in impact strength of samples cut from 
the 3 mm plate is measured after exposure in the Atlas Weatherometer. In 
both cases the results obtained are better than those using unstabilized 
polymer. 
APPLICATION EXAMPLE (B) 
A two-layer metallic finish is prepared having the following composition: 
(a) Base Coat 
12.6 parts commercial polyacrylate resin, with added cross-linking as 
defined in DIN 53 186 (Viacryl SC 344, Vianova, Vienna, supplied as 50% 
solution in xylene/butanol 4:1) 
2.19 parts commercial butanol-etherified melamine resin, medium reactive, 
prepared by condensation of 1 mol melamine with 3-6 mole formaldehyde, 
etherified with 3-6 mole butanol according to DIN 53 187 (Maprenal MF 800, 
Casella, supplied as 72% solution in isobutanol) 
0.96 parts butanol 
0.26 parts colloidal silicic acid 
7.05 parts xylene 
52.0 parts of a 20% cellulose acetate butyrate solution of the following 
composition by weight: 
20% cellulose acetate butyrate: acetyl content 13.6%, butyryl content 
38.7%, hydroxyl content 1.25%, viscosity of 20% solution in acetone=200 cp 
10% butanol 
35% xylene 
35% butyl acetate 
6.80 parts non-leafing aluminium paste, supplied as 65% suspension in 
alkylglycol acetate according to DIN 55 923 
18.14 parts butyl acetate 
0.3 parts copper phthalocyanine blue (C.I. Pigment Blue 15:1) 
(b) Top Coat 
80.00 parts polyacrylate resin (as in the base coat) 
13.75 parts melamine resin (as in the base coat) 
4.50 parts butyl glycollate 
7.50 parts aromatic hydrocarbon solvent, b.p. 186.degree.-212.degree. 
6.00 parts aromatic hydrocarbon solvent, b.p. 155.degree.-178.degree. 
(c) Application 
The base coat is applied to primer-coated metal plates by spraying, giving 
a layer approx. 20 .mu.m thick, without UV stabilizer. After drying of the 
base coat, the plates are sprayed with 
(i) top coat as in (b) above, without UV stabilizer or (ii) top coat as in 
(b) above, containing 1 part (i.e. 1% by wt.) of the compound of Example 
2, added as an 80% solution in xylene, and stoved at 140.degree. for 30 
minutes. Exposure tests (1 year in Florida) show superior results for the 
plates coated with top-coat (ii). 
The compounds of Examples 1 and 3-9 can be used in analogous manner to 
Application Examples A and B.