CA1130489A - Light stabilisation of metallic lacquers - Google Patents

Abstract

Abstract of the Disclosure Use of 2,2,6,6-tetraalkylpiperidine compounds, of their acid addition salts or complexes with metal compounds, optionally together with further stabilisers, for stabilising metallic stoving lacquers based on hot-crosslinkable alkyd or acrylic resins against the action of light, moisture and oxygen.

Description

~o4~39 LIGHT STABILISATION OF METALLIC LACQUERS
The present invention relates to the stabilising of metallic stoving lacquers based on hot-crosslinkable alkyd resins or acrylic resins against the action of light and moisture by the addition of polyalkylpiperidine derivatives, and also to the metallic lacquers stabilised in this manner.
It has been found that the problems repeatedly occuring in the case of metallic lacquering, especially with regard to cracking and loss of lustre, with use of stoving lacquers based on hot-crosslinkable alkyd resins or acrylic resins can be satisfactorily solved by the addition of light stabilisers based on polyalkylpiperidine derivatives, optionally together with further stabilisers.
The present invention relates therefore to the use of 2,2,6,6-tetraalkylpiperidine compounds, of their acid addition salts or complexes with metal compounds, optionally together with further stabilisers, for stabil-ising metallic stoving lacquers based on hot-crosslinkable alkyd resins or acrylic resins against the action of light, moisture and oxygen.
The 2,2,6,6-tetraalkylpiperidine compounds to be used according to the invention are generally known, and are e~

1~3~)4~39

- 2 -already being used to combat light degradation. They are for example compounds which contain a group of the formula (I) RCH ~ R
- N ~ (I) in which R is hydrogen or methyl.
The light stabilisers to be used according to the invention include in particular the following classes of compounds:
a) Light stabilisers of the formula (II) RC~2~R

Rl ~ -R2 (II) RC~2 CX3 n in which n is a number from 1 - 4 inclusive, preferably 1 or 2; R is as defined under the formula (I); Rl is hYdrgen~ oxyl~ Cl-C18 alkYl~ C3-C8 alkenyl, C3-C8 alkynyl, C7-C12 aralkyl, Cl-C8 alkanoyl, C3-C5 alkenoyl, glycidyl, a group -CH2CH(OH)-Z wherein Z is hydrogen, methyl or phenyl, with Rl preferably being hydrogen, Cl-C12 alkyl, allyl, benzyl, acetyl or acryloyl; and R2 when n is 1 is hydrogen, Cl-C18 alkyl optionally interrupted by one or more oxygen atoms, cyanoethyl, benzyl, glycidyl, a mono-valent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acid, or of carbamic acid or of a phosphorus-containing acid, or a monovalent silyl radical, preferably a radical of an aliphatic carboxylic acid having 2 - 18 C atoms, of a cycloaliphatic carboxylic acid having 5 - 12 C atoms or of an aromatic carboxylic acid having ll;~U4 7 - 15 C atoms; R2 when n is 2 is Cl-C12 alkylene, C4-C12 alkenylene, xylylene, a bivalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic dicarboxylic acid, of dicarbamic acid or of a phosphorus-containing acid, or a bivalent silyl radical, preferably a radical of an aliphatic dicarboxylic acid having 2 - 36 C atoms, of a cycloaliphatic or aromatic dicarboxylic acid having 8 - 14 C atoms, or of an aliphatic, cycloaliphatic or aromatic dicarbamic acid having 8 - 14 C atoms; R2 when n is 3 is a trivalent radical of an aliphatic, cyclo-aliphatic or aromatic tricarboxylic acid, of an aromatic tricarbamic acid or of a phosphorus-containing acid, or a trivalent silyl radical; and R2 when n is 4 is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid.
If any substituents are Cl-C12 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.
As Cl-C18 alkyl, Rl or R2 can be for example the groups given above, and in addition for example n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
When Rl is C3-C8 alkenyl, it can be for example l-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl or 4-tert-butyl-2-butenyl.
As C3-C8 alkynyl, Rl is preferably propargyl.
Rl as C7-C12 aralkyl is in particular phenethyl or especially benzyl.
As Cl-C8 alkanoyl, Rl is for example formyl, propionyl, butyryl, octanoyl but preferably acetyl, and as C3-C5 alkenoyl, Rl is particularly acryloyl.

il304~9 If R2 is a monovalent radica:L of a carboxylic acid, it is for example a radical of acetic acid, stearic acid, salicylic acid, methacrylic acid, maleic acid, benzoic acid or ~-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid.
If R2 is a bivalent radical of a dicarboxylic acid, it is for example a radical of adipic acid, suberic acid, sebacic acid, phthalic acid, dibutylmalonic acid, dibenzyl-malonic acid or butyl-(3,5-di-tert-butyl-4-hydroxybenzyl)-malonic acid, or bicycloheptenedicarboxylic acid.
If R2 is a trivalent radical of a tricarboxylic acid, it is for example a radical of trimelli,ic acid or of nitrilotriacetic acid.
If R2 is a tetravalent radical of a tetracarboxylic acid, it is for example a radical of pyromellitic acid.
If R2 is a bivalent radical of a dicarbamic acid, it is for example a radical of hexamethylenedicarbamic acid or of 2,4-toluylenedicarbamic acid.
The following compounds are examples of polyalkyl-piperidine light stabilisers of this class:
1) 4-hydroxy-2,2,6,6-tetramethylpiperidine, 2) 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine,

3) 1-benzyl-4-hydroxy-2,2,6,6-tetramethylpiperidine,

4) 1-(4-tert-butyl-2-butenyl)-4-hydroxy-2,2,6,6-tetra-methylpiperidine,

5) 4-stearoyloxy-2,2,6,6-tetramethylpiperidine,

6) 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine,

7) 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine,

8) 1,2,2,6,6-pentamethylpiperidin-4-yl-~-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate,

9) 1-benzyl-2,2,6,6-tetramethyl-4-piperidinylmaleinate,

10) (di-2,2,6,6-tetramethylpiperidin-4-yl)-adipate

11;~048'9 11) (di-2,2,6,6-tetramethylpiperidin-4-yl)-sebacate,

12) (di-1,2,3,6-tetramethyl-2,6-d:iethyl-piperidin-4-yl)-sebacate,

13) (di-1-allyl-2,2,6,6-tetramethyl-piperidin-4-yl)-phthalate,

14) 1-propargyl-4-~-cyanoethyloxy-2,2,6,6-t:etramethyl-piperidine,

15) 1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate,

16) trimellitic acid-tri-(2,2,6,6-tetramethylpiperidin-4-yl) ester,

17) 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine,

18) dibutyl-malonic acid-di-(1,2,2,6,6-pentamethyl-piperidin-4-yl) ester,

19) butyl-(3,5-di-tert-butyl-4-hydroxybenzyl)-malonic acid-di-(1,2,2,6,6-pentamethylpiperidin-4-yl) ester,

20) dibenzyl-malonic acid-di-(1,2,2,6,6-pentamethyl-piperidin-4-yl) ester,

21) dibenzyl-malonic acid-di-(1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) ester,

22) hexane-1',6'-bis-(4-carbamoyloxy-1-n-butyl-2,2,6,6-tetramethylpiperidine),

23) toluene-2',4'-bis-(4-carbamoyloxy-1-n-propyl-2,2,6,6-tetramethylpiperidine),

24) dimethyl-bis-(2,2,6,6-tetramethylpiperidine-4-oxy)-silane,

25) phenyl-tris-(2,2,6,6-tetramethylpiperidine-4-oxy)-silane,

26) tris-(1-propyl-2,2,6,6-tetramethylpiperidin-4-yl)-phosphite,

27) tris-(1-propyl-2,2,6,6-tetramethylpiperidin-4-yl)-phosphate, and

28) phenyl-[bis-(1,2,2,6,6-pentamethylpiperidin-4-yl)]-phosphonate.

11304~3c~

b) Light stabilisers of the formula (III) ~R4 (Ill) CH2 C~3 n in which n is the number 1 or 2; R is as defined under the formula I; Rl is as defined under a); R3 is hydrogen, Cl-C12 alkyl, C5-C7 cycloalkyl, C7-C8 aralkyl, C2-C18 alkanoyl, C3-C5 alkenoyl or benzoyl; and R4 when n is 1 is hydrogen, Cl-C18 alkyl, C5-C7 cycloalkyl, C2-C8 alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or it is glycidyl, a group of the formula -CH2-CH(OH)-Z or of the formula -CONH-Z wherein Z is hydrogen, methyl or phenyl; or R4 when n is 2 is C2-C12 alkylene, C6-C12 arylene, xylilene, a -CH2-CH(OH)-CH2 group, or a group -CH2-CH(OH)-CH2-0-X-O-CH2-CH(OH)-CH2-C2 C10 alkylene, C6-C15 arylene or C -C
cycloalkylene; or, provided that R3 is not alkanoyl, alkenoyl or benzoyl, R4 can also be a bivalent radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbamic acid, or can be the group -CO-; or R3 and R4 together when n is 1 can be the cyclic radical of an aliphatic or aromatic 1,2- or 1,3-dicarboxylic acid.
If any substituents are Cl-C18 alkyl, they are as already defined under a).
If any substituents are C5-C7 cycloalkyl, they are in particular cyclohexane.
As C7-C8 aralkyl, R3 is particularly phenethyl or above all benzyl.
As C2-C18 alkanoyl, R3 is for example propionyl, butyryl, octanoyl, dodecanoyl, hexadecanoyl, octadecanoyl 11304~9 but preferably acetyl; and as C3-C5 alkenoyl, R3 is in particular acryloyl.
If R4 is C2-C8 alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, it is ror example l-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl, 2,2-dicyanovinyl, 1-methyl-2-cyano-2-methoxycarbonyl-vinyl or 2,2-diacetylaminovinyl.
If any substituents are C2-C12 alkylene, they are for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.
If any substituents are C6-C15 arylene, they are for example o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
As C6-C12 cycloalkylene, X is especially cyclohexylene.
The following compounds are examples of polyalkyl-piperidine light stabilisers of this class:

29) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylene-1,6-diamine,

30) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-hexamethylene-1,6-diacetamide,

31) 1-acetyl-4-(N-cyclohexylacetamido)-2,2,6,6-tetramethyl-piperidine,

32) 4-benzylamino-2,2,6,6-tetramethylpiperidine,

33) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-N,N'-dibutyl-adipamide,

34) N,N'-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-N,N'-dicyclohexyl-(2-hydroxypropylene),

35) N,N`-bis-(2,2,6,6-tetramethylpiperidin-4-yl)-p-xylylene-diamine, - ~ -

36) the compound of the formula ~ f 3 ~ ~ 2-CX(OL~) C-L2 ~, 3 ~ ~-C~-2-CE(OX)-CE2 0 3 3 C4Hg

37) 4-(bis-2-hydroxyethyl)-amino-1,2,2,6,6-pentamethyl-piperidine,

38) 4-(3-methyl-4-hydroxy-5-tert-butyl-benzoic acid-amido)-2,2,6,6-tetramethylpiperidine,

39) 4-methacrylamido-1,2,2,6,6-pentamethylpiperidine, and

40) a-cyano-~-methyl-~-[N-(2,2,6,6-tetramethylpiperidin-4-yl)]-amino-acrylic acid methyl ester.
c) Light stabilisers of the formula (IV) RCE2~-~RO~
~ ~ 5 (IV) RCH2 CH3 ~n in which n is the number 1 or 2; R ls as defined under the formula (I); Rl is as defined under a); and R5 when n is 1 is C2-C8 alkylene or hydroxyalkylene or C4-C22 acyloxyalkylene; and R5 when n is 2 is the group (-CH2)2C(CH2 )2 If R5 is C2-C8 alkylene or hydroxyalkylene, it is for 11304~9 example ethylene, l-methyl-ethylene, propylene, 2-ethyl-propylene or 2-ethyl-2-hydroxymethylpropylene.
As C4-C22 acyloxyalkylene, R5 is for example 2-ethyl-2-acetoxymethyl-propylene.
The following compounds are examples of polyalkyl-piperidine light stabilisers of this class:

41) 9-aza-8,8,10,10-tetramethyl-1,5-dioxaspiro-[5.5]
undecane,

42) 9-aza-8,8,10,10-tetramethyl-3-ethyl-1,5-dioxaspiro [5.5]decane,

43) 8-aza-2,7,7,8,9,9-hexamethyl-1,4-dioxyspiro[4.5]
decane,

44) 9-aza-3-hydroxymethyl-3-ethyl-8,8,9,10,10-penta-methyl-1,5-dioxaspiro[5.5]undecane,

45) 9-aza-3-ethyl-3-acetoxymethyl-9-acetyl-8,8,10,10-tetramethyl-1,5-dioxaspiro[5.5]undecane, and

46) 2,2,6,6-tetramethylpiperidine-4-spiro-2'-(1',3'-dioxane)-5'-spiro-5"-(1",3"-dioxane)-2"-spiro-4"'-(2"', 2"', 6"', 6"'-tetramethylpiperidine).
d) Light stabilisers of the formula (V) RC~ R6 2 ~ ~ =0 (V) ~------N _ RCH2 CH3 0 _ n in which n is the number 1 or 2; R is as defined under the formula (I); Rl is as defined under a); R6 is hydrogen, Cl-C12 alkyl, allyl, benzyl, glycidyl or C2-C6 alkoxyalkyl; and R7 when n is 1 is hydrogen, Cl-C12 alkyl, C3-C5 alkenyl, C7-C9 aralkyl, C5-C7 cycloalkyl, 4~19 C2-C4 hydroxyalkyl, C2-C6 alkoxyalkyl, C6-C10 aryl, glycidyl, a group of the formula -(CH)-COO-Q or of the formula -(CH2)m-0-CO-Q wherein m is 1 or 2, and Q is Cl-C4 alkyl or phenyl; or R7 when n is 2 is C2-C12 alkylene, C6-C12 arylene, a group -CH2-CH(OH)-CH2-0-X-O-CH2-CH(OH)-CH2- wherein X is C2-C10 alkylene, C6-C15 arylene or C6-C12 cycloalkylene, or a group -CH2CH(OZ') CH2-(OCH2-CH(OZ')CH2)2- wherein Z' is hydrogen, Cl-C18 alkyl, allyl, benzyl, C2-C12 alkanoyl or benzoyl.
If any substituents are Cl-C12 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.
As Cl-C18 alkyl, Z' can be for example the groups stated above, and in addition for example n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
If any substituents are C2-C6 alkoxyalkyl, they are for example methoxymethyl, ethoxymethyl, propoxymethyl, tert-butoxymethyl, ethoxyethyl, ethoxypropyl, n-butoxy-ethyl, tert-butoxyethyl, isopropoxyethyl or propoxypropyl.
If R7 is C3-C5 alkenyl, it is for example l-propenyl, allyl, methallyl, 2-butenyl or 2-pentenyl.
As C7-C9 aralkyl, R7 is in particular phenethyl or above all benzyl; and as C5-C7 cycloalkyl, R7 is especially cyclohexyl.
If R7 is C2-C4 hydroxyalkyl, it is for example 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxy-butyl or 4-hydroxybutyl.
As C6-C10 aryl, R7 is in particular phenyl, or a- or ~-naphthyl which is unsubstituted or substituted by halogen or Cl-C4 alkyl.

11~304~39 If R7 is C2-C12 alkylene, it is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexa-methylene, octamethylene, decamethylene or dodecamethylene.
If R7 is C6-C12 arylene, it is for example o-, m-or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
If Z' is C2-C12 alkanoyl, it is for example propionyl, butyryl, octanoyl, dodecanoyl or preferably acetyl.
As C2-C10 alkylene, C6-C15 arylene or C6-C12 cyclo-alkylene, X has the meaning given under b).
The following compounds are examples of polyalkyl-piperidine light stabilisers of this class:

47) 3-benzyl-1,3,8-triaza-7,7,9,9-tetramethylspiro [4.5]decane-2,4-dione,

48) 3-n-octyl-1,3,8-triaza-7,7,9,9-tetramethylspiro [4.5]decane-2,4-dione,

49) 3-allyl-1,3,8-triaza-1,7,7,9,9-pentamethylspiro ~4.5]decane-2,4-dione,

50) 3-glycidyl-1,3,8-triaza-7,7,8,9,9-pentamethylspiro [4.5]decane-2,4-dione, or the compounds of the following formulae:

4~3~3 V I V
~ l' ~, V J V
\/ ~ ~
~T= v~
o ~ V~ ~
X = o I ~ o o V ~TV ~ -V 2; ~
X

,1 ~=o 1 1=o ~ 1=o r<~ X ~ ~ X
V~ ~V V~, kV V~ , <v V I ~ V V I ~ V ~ ~ V
V V

n n ~n 113048C~

e) Light stabilisers of the formula (VI) ) (VI) ~ Rlo in which n is the number 1 or 2, and R8 is a group of the formula R~ 2R

--Y--( A) m~ ~ R

oH3 ~H2R

in which R is as defined under the formula (I), Rl is as defined under a), Y is -O- or -NRll-, A is C2-C6 alkylene; and m is the number O or l; R9 is the g P 8' RllR12' OR13~ -NHCH20R13 or -N(cH2oRl3)2;
Rlo when n is 1 is the groups R8 or Rg~ and Rlo when n is 2 is the group -Y-Q-Y- wherein Q is C2-C6 alkylene optionally interrupted by -N(R14)-; Rll 1 12 cyclohexyl, benzyl or Cl-C4 hydroxyalkyl, or a group of the formula R CH3 >~:H2R
~--21 R12 is Cl-C12 alkyl, cyclohexyl, benzyl or Cl-C4 hydroxy-alkyl; R13 is hydrogen, Cl-C12 alkyl or phenyl; and R14 is hydrogen or the group -CH20R13; or Rll and R12 together are C4-C5 alkylene or oxaalkylene, or Rll and R12 are each a group of the formula 113U~89 H~ ~ N ~ ~ ~ ~ - A-CX3 CH3 y 13 l CH ~ CX3 C~3 C~3 If any substituents are Cl-C12 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.
If any substituents are Cl-C4 hydroxyalkyl, they are for example 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxy-propyl, 2-hydroxybutyl or 4-hydroxybutyl.
If A is C2-C6 alkylene, it is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene or hexamethylene.
If Rll and R12 together are C4-C5 alkylene or oxa-alkylene, this is for example tetramethylene, penta-methylene or 3-oxapentamethylene.
The compounds of the following formulae are examples of polyalkylpiperidine light stabilisers of this class:

113~4~91 5 4 )CH H CH3 3>"<

3 y 3 /~ .

~ N /L}~>

S5) ~(C4H9)2 CH3 CH3 J, 3~ 3 ~; Q~} --c2qs G2~ Cq 5 6 ) 2-- CH3 CH2--CH ~I.q CI~ ~ ~F.~3 ~CH2~H2 J~ ~H2~.~2~,H

Ch-3 CE3 3 3 ~ - ~
V~
~ l' ~
) V

T
D--~ ~D

I -V~/z~V I V ~ ' ~a ~ ~ O~ ~a T
V- ~0~ V
æ~ æ~
v l ~ v v ~o 04~39 59) ~CH3 H17C8~ H

NoM C~3 CH3 H17C8--N N NH( CH2) 3 _ C~ CH3 3 H3 _ 2 f) Light stabilisers of the formula (VII) R ~ CH2R
_ ~ -R14 (VII) ~H3 CH2 n in which n is the number 1 or 2; R is as defined under the formula (I); and R14 when n is 1 is C4-C18 alkyl, C7-C12 aralkyl, the group -CO-R15, or Cl-C4 alkyl which is substituted by -CN, -COOR16, -OH, -OCOR17 or 2 ( ) \ / wherein R15 is Cl-C12 alkyl, C -C
alkenyl or phenyi, R16 is Cl-C18 alkyl, R17 is Cl-C18 alkyl, C2-C10 alkenyl, cyclohexyl, benzyl or C6-C10 aryl;
or R14 when n is 2 is C4-C12 alkylene, 2-butenylene-1,4S
xylylene, the group -(CH2)2-OOC-R18-COO-(CH2)2 or the CH OOC-R -COO-CH2- wherein R18 2 10 1~3V4 phenylene or cyclohexylene, and R19 is C2-C10 alkylene, xylylene or cyclohexylene.
If any substituents are Cl-C12 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl or n-dodecyl.
Any substituents which are Cl-C18 alkyl can be for example the groups mentioned above, and in addition for example n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
If any groups are C2-C10 alkylene, these are in particular ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene or deca-methylene.
As C4-C18 alkyl, R14 is for example n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, l,l-dimethyl-2-tert-butylethyl, n-nonyl, n-decyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
If R14 is a Cl-C4 alkyl group substituted by -CN, it is for example cyanomethyl, cyanoethyl, 3-cyano-n-propyl or 4-cyano-n-butyl.
If R14 is C4-C12 alkylene, it is for example 2,2-dimethylpropylene, tetramethylene, hexamethylene, octa-methylene, decamethylene or dodecamethylene.
If R14 is C7-C12 aralkyl, it is in particular phenethyl, p-methyl-benzyl or especially benzyl.
As C2-C4 alkenyl, R15 is for example vinyl, l-propenyl, allyl, methallyl or 2-butenyl.
As C2-C10 alkenyl, R17 is for example the groups mentioned for R15 as alkenyl, and in addition for example crotyl, 2-hexenyl, 2-octenyl or 2-decenyl.

1131~489 If R17 is C6-C10 aryl, it is for example phenyl which is unsubstituted or substituted in the o- or p-position by methyl, ethyl, isopropyl, n-butyl or tert-butyl.
The following compounds are examples of polyalkyl-piperidine light stabilisers of this class:
60) bis-[~-(2,2,6,6-tetramethylpiperidino)-ethyl]-sebacate, 61) a-(2,2,6,6-tetramethylpiperidino)-acetic acid-n-octyl ester, and 62) 1,4-bis-(2,2,6,6-tetramethylpiperidino)-2-butene.
g) Light stabilisers of the formula (VIII) 2\/ H3 /R
Rl-N Q-E-C0-NH-CH2-OR2 (VIII) RCH /\CH
in which Q is -N(R3)- or -0-; E is Cl-C3 alkylene, the group -CH2-CH(R4)-0- wherein R4 is hydrogen, methyl or phenyl, the group -(CH2)3-NH- or a single bond; R is hydrogen or methyl; Rl is hydrogen, Cl-C18 alkyl, C3-C8 alkenyl, C3-C8 alkynyl, C7-C12 aralkyl, Cl-C8 alkanoyl, C3-C5 alkenoyl or glycidyl; R2 is hydrogen or Cl-C18 alkyl; R3 is hydrogen, Cl-C18 alkyl, C5-C7 cycloalkyl, C7-C12 aralkyl, cyanoethyl, C6-C10 aryl, the group -CH2-CH(R4)-OH wherein R4 has the meaning defined above, a group of the formula RCH2 ~ R
R -N~

or a group of the formula )489 ~ R
CH3 ~ ~ CH3 Rl wherein G can be C2-C6 alkylene or C6-C12 arylene; or R3 is a group -E-C0-NH-CH2-OR2.
If any substituents are Cl-C18 alkyl, they are for example methyl, ethyl, n-propyl, n-butyl, sec-butyl, tert-butyl, n-hexyl, n-octyl, 2-ethyl-hexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
If any substituents are C7-C12 aralkyl, they are for example phenethyl or in particular benzyl.
If Rl is C3-C8 alkenyl, it can be for example 1-propenyl, allyl, methallyl, 2-butenyl, 2-pentenyl, 2-hexenyl, 2-octenyl or 4-tert-butyl-2-butenyl.
As C3-C8 alkynyl, Rl is preferably propargyl. As Cl-C8 alkanoyl, Rl is for example formyl, propionyl, butyryl, octanoyl but preferably acetyl; and as C3-C5 alkenoyl, Rl is especially acryloyl.
As C5-C7 cycloalkyl, R3 is in particular cyclohexyl.
As C6-C10 aryl, R3 is particularly phenyl, or - or ~3-naphthyl which is unsubstituted or substituted with halogen or Cl-C4 alkyl. As Cl-C3 alkylene, E is for example methylene, ethylene or propylene.
As C2-C6 alkylene, G is for example ethylene, propylene, 2,2-dimethylpropylene, tetramethylene or hexamethylene;
and as C6-C12 arylene, G is o-, m- or p-phenylene, 1,4-~i304~9 naphthylene or 4,4'-diphenylene.
The following compounds are examples of polyalkyl-piperidine light stabilisers of this class:
63) N-hydroxymethyl-N'-2,2,6,6-tetramethylpiperidin-4-yl-urea, 64) N-methoxymethyl-N'-2,2,6,6-tetramethylpiperidin-4-yl-urea, 65) N-methoxymethyl-N'-n-dodecyl-N'-2,2,6,6-tetramethyl-piperidin-4-yl-urea, and 66) 0-(2,2,6,6-tetramethylpiperidin-4-yl)-N-methoxy-methyl-urethane.
f) Polymeric compounds of which the recurring structural unit contains a polyalkylpiperidine radical of the formula (I), especially polyesters, polyethers, polyamides, polyamines, polyurethanes, polyureas, polyaminotriazines, poly(mèth)acrylates or poly(meth)acrylamides, and copolymers thereof which contain such radicals.
The compounds of the following formulae, wherein m is a number from 2 to about 200 inclusive, are examples of polyalkylpiperidine light stabilisers of this class.

li~O489~

~ =,L
=
~ o = y r z O=~
N

U~ V L
T N r N
~, V I V
~ ~ ~ \,/Z~ /
X~X ,~ V~

V ~ ~
o 0=~

O X O -~
o =
V N V O
~ ~N ~ N
Vl ~ ~V

N ~ I ~ V~\ V
v m ~

v 1~
o=~ ~ ~

CO
~D

.. . . . . .. . ... . . . . . .... .. _ . _ . _ _ _ . . . .. . .. ~ . . . .

V
o= I

V-- _V
o=l ~ V I V
r~ `
~Z ~ ~ V 1~ V
V I ~
O ~
, V
~ V ~ V
:~ I ~ ~ ~ ~ ~ V
V--V--V ~ ~: ~ X
5~ ~ ~Z~ V V
V--V--V I ~ ~< V I V
~Z~ V V I ~<Z ~ ~
/ ~ ~
~ ~ ~V .V ~ ~

O _I ~
r r~ 1-.. . . .. ~

48'9 e o=~ ~' C`J
m o = b Yz ~ m~\ I m m m 5:
b ~e o = ~ 1 0=, a ~Y~

7r. ~<r à ~ "

r r r 11304~

76) ~ ~ CH2 ~
O=C ~ CH3 77) CH3 ~2 ~
O~C ~ 3 6 13 ~ H

It is also possible to use polyalkylpiperidine derivatives of the classes a) - f) which form chemical bonds with the binder of the lacquer. This is the case when the polyalkylpiperidine derivative possesses a reactive group suitable for this purpose, for example a glycidyl group or a methylol group.
Examples of such compounds are the polyalkylpiperidine derivatives of the class g) containing methylol or methylol ether groups.
Provided the polyalkylpiperidine derivatives are basic compounds, they can form salts with acids. Suitable acids are for example inorganic acids or organic carboxylic, sulfonic, phosphonic or phosphinic acids, such as hydro-chloric acid, boric acid, phosphoric acid, acetic acid, salicylic acid toluenesulfonic acid or benzenephosphonic acid.

il30489 The polyalkylpiperidine compounds can form complexes with comp]ex-forming metal compounds, for example with zinc-II-acetate, cobalt-II-acetylacetonate, nickel-II-acetylacetonate, aluminium-III-acetylacetonate, nickel-II-benzoate or aluminium-III-benzoylacetonate.
The acrylic resin lacquers which according to the invention can be stabiLised against light, moisture and oxygen are the customary acrylic resin stoving lacquers, such as are described for example in H. Kittel's 'Lehrbuch der Lacke und Beschichtungen' (Textbook of Lacquers and Coatings), Volume 1, part 2 on pages 735 and 742 (Berlin, 1972), and in H. Wagner, H.F. Sarx, 'Lack-kunstharze' (Synthetic resins for Lacquers), on pages 229 - 235.
of particular interest is the stabilisation, according to the invention, of metallic lacquers based on hot-crosslinkable polyacrylate resins which contain styrene incorporated by polymerisation. It would be possible with these resins to produce metallic lacquers having excellent physical and chemical properties if it were not for the formation of cracking on weathering, depending of the content of incorporated styrene. An outstanding stabil-isation against the formation of cracking mentioned is however possible by the addition according to the invention of polyalkylpiperidine derivatives, especially in combi-nation with a conventional light stabiliser of the UV-absorber type.
The stabilisation of metallic lacquers based on alkyd resins, in accordance with the invention, is likewise of particular interest. The stabilisation of metallic lacquers based on alkyd resin with the customary light stabilisers of the UV-absorber type is also problematic, and offers no satisfactory technical solution. It is il30489 however now possible by the addition according to theinvention of light stabilisers based on polyalkyl-piperidine derivatives, optionally together with other stabilisers, to fully satisfactorily stabilise also metallic lacquers based on alkyd resin against light and moisture, particularly against the formation of cracking.
The alkyd resin lacquers which can be stabilised according to the invention against the action of light and moisture are the customary stoving lacquers, which are used especially for the lacquering of motor cars (so-called motor car lacquers), for example lacquers based on alkyd-melamine resins and alkyd-acrylic-melamine resins.
Also metallic lacquers based on oil-free polyesters can be successfully stabilised according to the invention.
For obtaining the metallic effect, there are used the aluminium pigments normally employed for this purpose in an amount of 1 to 10 per cent by weight, relative to the solvent-free binder (lacquer resin). The application of the metallic lacquers stabilised according to the invention is effected preferably, in the usual manner, by one of two processes: either by the single-layer process or by the two-layer process. In the latter case, the layer containing the aluminium pigment is firstly applied, and then over this is applied a covering clear-lacquer layer.
The amount of polyalkylpiperidine derivative added is 0.01 to 5 per cent by weight, relative to the solvent-free binder, preferably 0.5 to 1 per cent by weight. The lacquers can contain the customary organic solvents, or they can be dissolved or dispersed in water, or they can be free from solvent.
In the case of application in two-layer lacquering, the ~i31)4~i19 polyalkylpiperidine derivative to be used for stabil-isation according to the invention can be incorporated either solely into the unpigmented surface lacquer, or both into the unpigmented surface lacquer and into the initially applied lacquer containing the aluminium pigment. In the production of acrylic resins or of acrylic-modified alkyd resins, polymerisable polyalkyl-piperidine derivatives (for example compounds 7 and 39) can be incorporated into the resin by polymerisation.
Incorporation into the lacquer binder can however also be effected by way of polycondensation in the production process, or possibly during stoving of the melamine, alkyd or polyester resins. Examples of polyalkyl-piperidine derivatives which can be incorporated by condensation are the compounds 1, 26, 27 and also 1-hydroxyethyl-4-hydroxy-2,2,6,6-tetramethylpiperidine.
Incorporation by way of polyaddition can be effected for example by way of the reaction of free carboxyl groups in the acrylic resin with glycidyl groups of the polyalkyl-piperidine derivative. These carboxyl groups can be incorporated by polymerisation of acrylic acid or of derivatives thereof.
In these cases, there is the additional advantage that the light stabilisers cannot be removed by extraction or migration, so that their action is retained for a very long time.
To obtain maximum stability to light, the concomitant use of other customary stabilisers can be advantageous.
Examples of these are W absorbers of the benzophenone, oxalanilide or benzotriazole type, or acrylic acid derivatives, or metal-containing light stabilisers, such as organic nickel compounds.

1130~8'9 In the case of such combinations, the sum of all light stabilisers is 0.02 to 5 percent by weight, preferably 0.5 to 2 percent by weight, relative -to the lacquer resin.
Further additives which can be contained in the lacquer are antioxidants, for example those of the sterically hindered phenol derivative tvpe, organic phosphorus compounds, for example phosphites, phosphonites or phosphines, plasticisers, levelling agents, curing accelerators, for example organic Co, Mn or Zr salts, thickeners, dispersing agents or agent improving adhesion.
The following Examples illustrate the use according to the invention of polyalkylpiperidine derivatives in metallic lacquers based on binder systems containing alkyd resin. The term 'parts' in the Examples denotes parts by weight, and percent-ages are given as percent by weight.
In the accompanying drawings, Figure 1 compares graphically variation in gloss values plotted against weathering time for a stabilised and unstabilised specimen of lacquered sheet metal;
Figure 2 compares graphically the variation in gloss values gainst weathering time for additional unstabilised and stabilised specimens; and Figure 3 compares graphically weight loss against weathering time for unstabilised and stabilised specimens.

1~04~9 EXAMPLES
Example 1 Li~ht stabilisation of a two-laver metallic lacquerin~
based on binder systems containin~ alkyd resin (crackin~ test) Basic recipe of the lacquers a) Metallic first-coat lacquer Alftalat~VAN 21/1 13.15 parts (Hochst) CAB 381.01/18% in butylacetate 55 parts (Eastman Chemical Corp.) Uresin~B 2.5 parts (Hochst) Maprenal~VM~ 80/15 3.45 parts (Hochst) Alcoa~726 6.5 parts (Aluminium Corp of America) 15% solution of BYK 300 (BYK
Mallinckrodt) in butylacetate/xylene 2 parts xylene 6 parts butyl glycol 5 parts butylacetate/xylene = 1/1 6.4 parts b) Unpi~mented surface lacquer (second-coat lacquer) Alftalat AC 451 n 28.5 parts (Hochst) Synthacryl~SC 303 30.7 parts (Hochst) Maprenal VMF 80/15 22.8 parts (Hochst) butyl glycol 4.3 parts butyl glycol acetate 1.7 parts Solvesso~150 (Esso) 8.5 parts Solvesso 100 (Esso) 3.5 parts f f " J~

113048g The first-coat lacquer (base lacquer) was sprayed (15-20 ~u) onto aluminium sheet coated with a coil coat.
After a short airing time, the surface lacquer (top layer) was sprayed on wet on wet with a coating thickness of 30-40 ~u and, after an airing time of 15 minutes, the coated sheet was stoved for 20 minutes at 135C.
Before application, there was added to the surface lacquer the polyalkylpiperidine compound given in column 2 (numbered according to the examples mentioned in the specification) in the amount given in per cent in each case in column 1 of the following Table I.
After storage for 4 weeks in an air-conditioned chamber (23C/50% relative humidity), the lacquered sheets were weathered according to test method ASTM G-53/77 in a QUV Tester for 930 hours. The specimens in this test were in each case moistened for 4 hours at 50C, and irradiated for 4 hours in a moist atmosphere at 60C
with UV light.
The evaluation of the weathered lacquer specimens was made according to the TN0 cracking scale, Type 353, with the pattern of cracking being compared with stan-dardised samples. The capital letters give the nature and form of cracking. The numbers give the intensity of cracking. Ten levels are chosen for designation of the intensity; the level of maximum intensity is always given as 10. The small letters are a measure for the depth of cracking: a denotes superficial damage of the top layer;
b and c denote cracking in top layer and top and base layer, respectively; d indicates the case where the base layer is cracked but not the top layer. The respective pattern of cracking is shown in column 3 of Table I.

113048~

Table _ Polyalkylpiperidine compound r :t- n 1 compound 1 no crack 1 compound 3 J 2 a 1 compound 4 J 3 a 1 compound 11 no crack 1 compound 19 no crack 1 compound 20 no crack 1 compound 67 no crack 1 compound 70 no crack 1 compound 75 no crack Comparative test Metallic lacquers which are bases on binder sYstems containin~ alkyd resin and which contain a UV absorber as a li~ht stabiliser In a comparative test, the procedure was carried out exactly as described for Example 1 with the single exception that a W absorber was used instead of the polyalkylpiperidine compound. In the following Table II, the amount of light stabiliser in per cent (relative to the lacquer resin) is given in column l; the light stabiliser used is given in column 2; and the pattern of cracking is shown in column 3.

~1~0~9 Table II

IPattern o~
% Light stabiliser cracking 1 2-(2-hydroxy-3,5-di-tert-amyl-phenyl)-benzotriazole J 10 b 3 2-(2-hydroxy-3,5-di-tert-amyl-phenyl)-benzotriazole J 9 b 1 2-(2,4-dihydroxyphenyl)-benzo-triazole J 9 b 3 2-(2,4-dihydroxyphenyl)-benzo-triazole . J 4 a 1 2,4-dihydroxybenzophenone J 7 a 3 2,4-dihydroxybenzophenone J 2 a 1 2-hydroxy-4-octylbenzophenone J 8 b 3 2-hydroxy-4-octylbenzophenone J 7 a 1 2-hydroxy-4-dodecylbenzophenone J 9 b 3 2-hydroxy-4-dodecylbenzophenone J 9 b 1 2-(2-hydroxy-5-isooctylphenyl)-benzotriazole J 4 a 3 2-(2-hydroxy-5-isooctylphenyl)-benzotriazole J 2 a 1 2-ethoxy-2'-ethyl-oxalanilide J 4 b 3 2-ethoxy-2'-ethyl-oxalanilide J 7 b 1130~8~

Example 2 Combination of polyalkylpiperidine derivative and W absorber for stabilising a two-layer metallic lacquering based on a binder system containing alkyd resin Metallic lacquerings were produced and tested exactly as described in Example 1 with the single exception that with the polyalkylpiperidine derivative was incorporated also a UV absorber. In the following Table III, the amount of light stabiliser in per cent (relative to the lacquer resin) is given in column l; the light stabiliser used is given in column 2; and the pattern of cracking is shown in column 3.

Table III

% Light stabiliser crack g 0.5 compound 1 J 1 a 0.5 2-(2-hydroxy-3,5-di-tert-amyl-phenyl)-benzotriazole .
0.5 compound 20 no crack 0.5 2-(2-hydroxy-3,5-di-tert-amyl-phenyl)-benzotriazole 0.5 compound 67 no crack 0.5 2-(2-hydroxy-5-a-methyl-styryl-phenyl)-benzotriazole ~3(~489 Example 3 Combination of polyalkylpiperidine derivatives with a metal compound for stabilising a two-layer metallic lacquering based on binder systems containing alkyd resin (cracking test) Metallic lacquerings were produced and tested exactly as described in Example 1 with the single exception that together with the polyalkylpiperidine derivative was incorporated also a metal salt. In the following Table IV, the amount of light stabiliser and of metal compound in per cent (relative to the lacquer resin) is given in column l; the light stabilisers and metal compounds used are given in column 2; and the pattern of cracking is shown in column 3.
Table IV

_ Light stabiliser Pattern of 0 metal compound cracking 0.5 compound 11 no 0.2 nickel acetylacetonate crack 0.5 compound 11 no 0.2 aluminium acetylacetonate crack Example 4 A metallic lacquering was produced and tested exactly as described in Example 1 with the single exception that together with the polyalkylpiperidine derivative were incor-porated both a W absorber and a metal compound. To 0.5%
of the compound 11 were added 0.5% of 2-hydroxy-3,5-di-tert-amyl-phenylbenzotriazole and 0.2% of aluminium acetylacetonate (% values are relative to the lacquer resin).
No cracking was observed after weathering.

3~ ~8 Example 5 Light stabilisation of a two-layer metallic lacquering based on binder systems containing acrylic resin (gloss retention test) Basic recipe for the lacquers a) Metallic first-coatin~ lacquer polyester resin L 1850 (Dynamit Nobel AG) 27.0 parts melamine resin Maprenal RT
(Farbwerke H~chst AG) 3.0 parts cellulose acetobutyrate CAB 531 (Eastman Chem. Corp.) 2.0 parts Alcoa 726 (Aluminium Corp. of America) 8.0 parts toluene 10.0 parts xylene 7.0 parts butanol 3.0 parts butylacetate 25.0 parts armatic solvent Solvesso 150 (Esso) 15.0 parts b) Unpigmented surface lacquer (second-coat lacquer) Synthacryl SC 303 59.0 parts (Hochst) Maprenal MF 590 (Hochst) 17.4 parts butyl glycol acetate 2.0 parts Solvesso 150 (Esso) 2.0 parts Solvesso 100 (Esso) 2.0 parts xylene 6.6 parts silicone oil AL / 1% in xylene 0.2 part 1~3~)4~9 A commercial primer and also a commercial intermediate filler were firstly applied to 0.4 mm thick aluminium sheet, and the specimen was then stoved. An approximately 15 /u thick layer of first-coat lacquer containing the aluminium pigment was sprayed onto this lacquer foundation, and an approximately 30 - 40 ~ thick layer of unpigmented surface lacquer was subsequently applied wet-on-wet over the first-coat lacquer. After a brief airing time, the lacquers were stoved in a lacquer drying oven at 125 for 30 minutes. Two specimens were produced: the first one without any addition of stabiliser, the second one with an addition of 1 % (relative to the lacquer resin) of the compound 11 in the surface lacquer. The specimen sheets obtained in this manner were then stored for four weeks under standard climatic conditions (23 C / 5% relative humidity), and afterwards subjected to weathering in a Q W apparatus according to ASTM G 53 - 77. The attached Diagram I shows the gloss values (ASTM D 523) obtained on the stabilised specimen (0) and on the unstabilised specimen (X) plotted against the weathering time.
Example 6 Light stabilisation of a two-layer metallic lacquering based on hot-crosslinkable polyacrylate resins containing styrene incorporated by polymerisation -Basic recipe of the lacquers a) Metallic first-coat lacquer polyester resin L 1850 (Dynamit Nobel AG) 27.0 parts melamine resin Maprenal RT
(Farbwerke Hochst AG) 3.0 parts cellulose acetobutyrate CAB 531 (Eastman Chem. Corp.) 2.0 parts Alcoa 726 (Aluminium Corp. of America) 8.0 parts ~304819 toluene 10.0 parts xylene 7.0 parts butanol 3.0 "
butylacetate 25.0 "
aromatic solvent Solvesso 150 ~Esso) 15.0 "
b) Unpi~mented surface lacquer commercial acrylic resin containing styrene incorporated by polymerisation (60%) 59.0 "
Maprenal MF 590 (Hochst) 17.4 "
butyl glycol acetate 2.0 "
Solvesso 150 (Esso) 2.0 "
Solvesso 100 (Esso) 2.0 "
xylene 6.6 "
silicone oil OL / 1% in xylene 0.2 "
An aluminium sheet coated with a coil coat was sprayed with the first-coat lacquer containing the aluminium pigment to give a layer thickness of about 15 ,u; onto this layer was then sprayed wet-on-wet the unpigmented surface lacquer to give a layer thickness of about 30 - 40 ,u. After a short airing time, the lacquers were stoved in a lacquer drying oven at 140C for 30 minutes. The sheets obtained were stored for 4 weeks under standard climatic conditions (23C / 50% relative humidity), and were subsequently subjected to weathering in a Q W apparatus according to ASTM G 53-77, in the manner already mentioned in Example 1.
Into the unpigmented surface lacquer, there had been incorporated beforehand the light stabilisers listed in column 2 of the following Table V in the amount given in each case in % (relative to the lacquer resin) in column 1.
In column 3 of Table V is given the weathering time, and in column 4 the pattern of cracking occurring.
, 1~3048C~

Table V

__ .
% Light stabiliser Weathering time Pattern of _ g _ _ 1400 h J 10 b 1compound 11 2800 h no crack ....
0.5compound 11 2800 h no crack O.S 2-(2-hydroxy-3,5-di-tert-amyl-phenyl) benzotriazole l .

Comparative test Metallic lacquers based on hot-cross-linkable polyacrylate resins containing styrene incorporated by polymerisation, stabilised with a W absorber -In a comparative test, the procedure was carried out exactly as described in the case of Example 6, with the single exception that a W absorber was used in place of the polyalkylpiperidine compound. In the following Table VI, the amount of light stabiliser in % (relative to the lacquer resin) is given in column 1, the employed light stabiliser in column 2, the weathering time in column 3 and the pattern of cracking in column 4.
Table VI
% Light stabiliser W ath ing time ¦Pattkrin cf _ _ _ 1400 h J 10 b 1 2,4-dihydroxy- 2800 h J 10 a benzophenone 1 2-(2-hydroxy-3,5-di 2800 h J 10 a tert-amyl-phenyl)-benzotriazole It is shown from Table V that with an addition of apolyalkylpiperidine compound as stabiliser there is still no cracking even with double the weathering time in the QW apparatus, in contrast to the cracking in the specimen containing no polyalkylpiperidine compound as stabiliser.
As is shown by Table VI, this surprisingly good stabil-ising effect was not obtained with the W absorbers tested by way of comparison.
It can be seen from the attached Diagrams II and III
that there is obtained by combination of a polyalkyl-piperidine compound with a UV absorber a synergistic stabilising effect, which is manifested in a clearly better retention of gloss (determined according to ASTM D 523) and in a distictly lower loss of weight.
Example 7 Light stabilisation of a single-layer metallic lacquering based on binder systems containing acrylic resin (gloss retention test) -Basic recipe of the lacquer aluminium paste Mobil R superfine (Eckhart-Werke, Furth/Bay, D) 1.29 parts xylene (to form a slurry of the aluminium paste) 1.29 "
Synthacryl SC 300 (50% strength) (Hochst) 59.35 t Maprenal M~ 650 (55% strength) (Cassela-Hochst) 25.22 "
Polysolfan 0 (Hochst) 3.97 "
ethyl glycol acetate 1.98 "
xylene 6.90 "

1~30489 The lacquerwas adjusted with 29.7 parts of a DKH
synthetic resin thinner (Dr. K. Herberts, Wuppertal, D) to give a spray viscosity of 19 seconds according to DIN 53211.
A commercial primer and also a commercial intermediate filler were firstly applied to a 0.4 mm thick aluminium sheet, and the specimen was then stoved. Onto this lacquer foundation was then sprayed, in 3 cross-coatings with 15 seconds airing for each, the lacquer containing the aluminium pigment to obtain a layer thickness of about 40 ~. After being exposed to the air for 20 minutes, the lacquer was stoved in a lacquer drying oven at 120~C
for 25 minutes.
Before the lacquer was applied, there was added to it the stabiliser(s) shown in column 2 of the following Table VII in the amount given in each case in column 1 in % (relative to the lacquer resin) (polyalkylpiperidine compounds numbered according to the examples mentioned in the specification~. The sheets obtained were stored for four weeks under standard climatic conditions (23C /
5% relative humidity), and they were then subjected to weathering in a Q W apparatus according to ASTM G-53/77.
In the following Table VII are given the gloss values (ASTM D 523) as a function of the weathering time (before weathering, after 350, 480 and 570 hours, respectively).

11304~9 Table VII

% Light stabiliser ¦ 20 gloss after weathering 0 h350 h 480 h 570 h _ _ 70 25 19 17 1 compound 3 76 64 57 47 1 compound 11 75 60 55 52 1 compound 19 75 63 51 48 0.5 compound 11 0.5 2-(2-hydroxy-3,5-di- 75 60 59 59 tert-amyl-phenyl)-benzotriazole 0.5 compound 19 0.5 2-(2-hydroxy-3-~- 77 70 71 71 methylbenzyl-5-methyl-phenyl)-benzotriazole Analogous results are obtained also with the use of polyalkylpiperidine derivatives in combination with 2-(2-hydroxy-3,5-di-,~-dimethylbenzyl-phenyl)-benzotriazole or with 2-[2-hydroxy-3,5-di-(1,1,3,3-tetramethyl-butyl-phenyl)-benzotriazole.
Example 8 Li~ht stabilisers which can be incorporated by addition Light stabilisation of a two-layer metallic lacquering with the compound A of the formula (gloss retention test) 3~ ><C--h-CH -CH-CH (A) Incorporation of compound A into the unpi~mented surface lacquer Compound A was added to a comrnercial clear lacquer based on acrylic resin which can be cross-linked with melamine/formaldehyde resins and which contains acrylic acid besides acrylic acid esters and styrene incorporated by polymerisation, and the wholewas stirred overnight at 40C. Thereoccured during this stage the incorporation of the light stabiliser by reaction of the glycidyl group of the light stabiliser with the acid groups in the acrylic resin. Further light stabilisers can if necessary be subsequently added (see following Table VIII, column 2).
Preparation of the test specimens The surface lacquer produced as described above was sprayed wet-on-wet onto an aluminium sheet to which had previously been applied a commercial filler-primer and the metallic first-coat lacquer, and the specimen was then stoved at 130C for 30 minutes. The layer thickness of the first-coat lacquer was about 15 ,u, and that of the surface lacquer about 35 ,u.
Weatherin~ tests After 2 weeks' storage of the sheets under standard climatic conditions, the specimens were weathered according to test method ASTM G53-77 in a QUV Tester for 1000 hours.
To the unpigmented surface lacquer had been added the light stabilisers given in column 2 of the following Table VIII in the amounts shown in % (relative to the lacquer resin) in column 1 of the Table. The gloss of the lacquer surface was subsequently measured according to test method ASTM D 523, the values obtained being listed in column 3:

11304~9 Table VIII

20 gloss (averaged) % Light stabiliser after 1000 hours unweathered of weatherlng _ 98 43 1 compound A 96 80 0.5 compound A 99 92 0.5 2-(2-hydroxy-3,5-di-a,a-dimethylbenzyl-phenyl)-benzotriazole 1 compound A 99 98 1 2-(2-hydroxy-3,5-di-a,a-dimethylbenzyl-phenyl)-benzotriazole Example 9 Li~ht stabilisers incorporated by polymerisation Light stabilisation of a two-layer metallic lacquering with the compound B of the formula C 3\ / 3 CH3-N~ = ~ -C-CH=CH2 (B) CH / \CH o Incorporation of compound B into the unpi~mented surface lacquer The compound of the formula B was incorporated, at a concentration of about 30 per cent by weight (relative to the lacquer resin), into an acrylic resin (copolymer from acrylic acid esters and styrene). In this case, the 1130~89 compound of the formula Bwas used along with other (meth)-acrylic acid esters and styrene as comonomers, with the solution being introduced into boiling xylene, and polymerisation initiated with the aid of di-tert-butyl-peroxide. The reaction time was about 4 hours. The acrylic resin produced in this manner was used as a stabiliser concentrate for producing the surface lacquer.
For this purpose, the stabiliser concentrate, optionally together with other light stabilisers (see Table IX), was added to a commercial clear lacquer (acrylic/melamine-resin mixture).
Preparation of the test specimens The surface lacquer produced in the manner described abovewas sprayed wet-on-wet onto an aluminium sheet onto which had been previously applied a commercial filler-primer and the metallic first-coat lacquer, and the specimentwasstoved at 130C for 30 minutes. The layer thickness of the first-coat lacquerwas about 15 ,u, and that of the surface lacquer about 35 ,u.
Weatherin~ tests After 2 weeks' storage of the sheets under standard climatic conditions, the specimenswere weathered in a Xenotest 1200 apparatus, and the time until cracking in the surface lacquer commenced was determined.
To the unpigmented surface lacquerwere added the light stabilisers shown in column 2 of the following Table IX in the amounts given in each case in % (relative to the lacquer resin) in column 1. The time in hours until cracks commencedto form is shown in column 3.

Table IX

% Light stabiliser Hours until cracks commenced to form _ _ 1300 1 2-(2-hydroxy-3,5-di-tert- 1600 amyl-phenyl)-benzotriazole 0.5 compound B 1900 0.5 2-(2-hydroxy-3,5-di-tert-amyl-phenyl)-benzotriazole

Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of stabilislng metallic stoving lacquers based on hot-crosslinkable alkyd resins or acrylic resins against the action of light, moisture and oxygen, which comprises adding to said alkyd or acrylic resin a stabilizing amount of a 2,2,6,6-tetraalkylpiperidine compound, an acid addition salt thereof or a complex thereof with a metal compound.

2. A method according to claim 1 wherein the 2,2,6,6-tetraalkylpiperidine stabiliser is used in conjunction with one or more further stabilisers.

3. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (II) (II) in which n is a number from 1-4 inclusive; R is hydrogen or methyl;

R1 is hydrogen, oxyl, C1-C18 alkyl, C3-C8 alkenyl, C1-C8 alkynyl, C7-C12 aralkyl, C1-C8 alkanoyl, C3-C5 alkenoyl, glycidyl or a group -CH2-CH(OH)-Z wherein Z is hydrogen, methyl or phenyl; and R2 when n is 1 is hydrogen, C1-C18 alkyl optionally interrupted by one or more oxygen atoms, cyanoethyl, benzyl, glycidyl, a mono-valent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acid, or of carbamic acid or of a phosphorus-containing acid, or a monovalent silyl radical; R2 when n is 2 is C2-C12 alkylene, C4-C12 alkenylene, xylylene, a hivalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic dicarboxylic acid, of dicarbamic acid or of a phosphorus-containing acid, or a bivalent silyl radical; R2 when n is 3 is a trivalent radical of an aliphatic, cycloaliphatic or aromatie tricarboxylic acid, of an aromatic tricarhamic acid or of a phosphorus-containing acid, or a trivalent silyl radical; and R2 when n is 4 is a tetravalent radical of an aliphatic, cycloaliphatic or aromatic tetracarboxylic acid.

4. A method according to claim 3 wherein a light stabiliser of the formula (II) is employed in which n is the number 1 or 2;
R is hydrogen or methyl; R1 is hydrogen, C1-C12 alkyl, allyl, benzyl, acetyl or acryloyl; and R2 when n is 1 is a radical of an aliphatic carboxylic acid having 2-18 C atoms, of a cycloaliphatic carboxylic acid having 5-12 C atoms or of an aromatic carboxylic acid having 7-15 C atoms; and R2 when n is 2 is a radical of an aliphatic dicarboxylic acid having 2-36 C atoms, of a cycloaliphatic or aromatic dicarboxylic acid having 8-14 C atoms, or of an ali-phatic, cycloaliphatic or aromatic dicarbamic acid having 8-14 C
atoms.

5. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (III) (III) in which n is the number 1 or 2; R is hydrogen or methyl; R1 is hydrogen, oxyl, C1-C18 alkyl, C3-C8 alkenyl, C3-C8 alkynyl, C7-C12 aralkyl, C1-C8 alkanoyl or C3-C5 alkenoyl; R3 is hydrogen, C1-C12 alkyl, C5-C7 cycloalkyl, C7-C8 aralkyl, C2-C18 alkanoyl, C3-C5 alkenoyl or benzoyl; and R4 when n is 1 is hydrogen, C1-C18 alkyl, C5-C7 cycloalkyl, C2-C8 alkenyl which is unsubstituted or sub-stituted by a cyano, carbonyl or carbamide group, or it is glycidyl, a group of the formula -CH2-CH(OH)-Z or of the formula -CONH-Z
wherein Z is hydrogen, methyl or phenyl; or R4 when n is 2 is C2-C12 alkylene, C6-C12 arylene, xylilene, a-CH2-CH(OH)-CH2-group or a group -CH2-CH(OH)-CH2-O-X-O-CH2-CH(OH)-CH2- wherein X is C2-C10 alkylene, C6-C15 arylene or C6-C12 cycloalkylene; or, provided that R3 is not alkanoyl, alkenoyl or benzoyl, R4 can also be a bi-valent radical of an aliphatic, cycloaliphatic or aromatic dicarbox-ylic acid or dicarbamic acid, or can also be the group -CO-; or R3 and R4 together when n is 1 can be the cyclic radical of an ali-phatic or aromatic 1,2- or 1,3-dicarboxylic acid.

6. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (IV) (IV) in which n is the number 1 or 2; R is hydrogen or methyl; R1 is hydrogen, oxyl, C1-C18 alkyl, C3-C8 alkenyl, C3-C8 alkynyl, C7-C12 aralkyl, C1-C8 alkanoyl or C3-C5 alkenoyl; and R5 when n is 1 is C2-C8 alkylene or hydroxyalkylene or C4-C22 acyloxyalkylene; and R5 when n is 2 is the group (-CH2)2C(CH-2-)2.

7. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (V) (V) in which n is the number 1 or 2; R is hydrogen or methyl; R1 is hydrogen, oxyl, C1-C18 alkyl, C3-C8 alkenyl, C3-C8 alkynyl, C7-C12 aralkyl, C1-C8 alkanoyl or C3-C5 alkenoyl; R6 is hydrogen, C1-C12 alkyl, allyl, benzyl, glycidyl or C2-C6 alkoxyalkyl; and R7 when n is 1 is hydrogen, C1-C12 alkyl, C3-C5 alkenyl, C7-C9 aralkyl, C5-C7 cycloalkyl, C2-C4 hydroxyalkyl, C2-C6 alkoxyalkyl, C6-C10 aryl, glycidyl, a group of the formula -(CH2)m-COO-Q or of the formula -(CH2) -O-CO-Q wherein m is 1 or 2, and Q is C1-C4 alkyl or phenyl; or R7 when n is 2 is C2-C12alkylene or C6-C12 arylene, a group -CH2-CH(OH)-CH2-O-X-O-CH2-cH(OH)-cH2- wherein X is C2-C10 alkylene, C6-C15 arylene or C6-C12 cycloalkylene, or a group -CH2CH(OZ')-CH2-(OCH2-CH(OZ')CH2)2- wherein Z' is hydrogen, C1-C18 alkyl, allyl, benzyl, C2-C12 alkanoyl or benzoyl.

8. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (VI) (VI) in which n is the number 1 or 2; and R8 is a group of the formula in which R is hydrogen or methyl, R1 is as defined in claim 3, Y
is -O- or -NR11-, A is C2-C6 alkylene; and m is the number 0 or 1; R9 is the groups R8, NR11R12, -OR13, -NHCH2OR13 or -N(CH2OR13)2;
R10 when n is 1 is the groups R8 or R9; and R10 when n is 2 is the group -Y-Q-Y- wherein Q is C2-C6 alkylene optionally inter-rupted by -N(R14)-; R11 is C1-C12 alkyl, cyclohexyl, benzl or C1-C4 hydroxyalkyl, or a group of the formula R12 is C1-C12 alkyl, cyclohexyl, benzyl, C1-C4 hydroxyalkyl;
R13 is hydrogen, C1-C12 alkyl or phenyl; and R14 is hydrogen or the group -CH2OR13; or R11 and R12 together are C4-C5 alkylene or oxaalkylene, or R11 and R12 are each a group of the formula

9. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (VII) (VII) in which n is the number 1 or 2; R is hydrogen or methyl; and R14 when n is 1 is C4-C18 alkyl, C7-C12 aralkyl, the group -CO-R15, or C1-C4 alkyl which is substituted by -CN, -COOR16, -OH, -OCOR17 or -CH2-CH(OH) wherein R15 is C1-C12 alkyl, C2-C4 alkenyl or phenyl, R16 is C1-C18 alkyl, R17 is C1-C18 alkyl, C2-C10 alkenyl, cyclohexyl, benzyl or C6-C10 aryl; or R14 when n is 2 is C4-C12 alkylene, 2-butenylene-1,4, xylylene, the group -(CH2)2-OOC-R18-COO-(CH2)2- or the group -CH2-OOC-R19-COO-CH2-wherein R18 is C2-C10 alkylene, phenylene or cyclohexylene, and R19 is C2-C10 alkylene, xylylene or cyclohexylene.

10. A method according to claim 1 wherein the stabiliser is a light stabiliser of the formula (VIII) (VIII) in which Q is -N(R3)- or -0-; E is C1-C3 alkylene, the group -CH2-CH (R4) -O- wherein R4 is hydrogen, methyl or phenyl, the group -(CH2)3-NH- or a single bond; R is hydrogen or methyl; R1 is hydrogen, C1-C18 alkyl, C3-C8 alkenyl, C3-C8 alkynyl, C7-C12 aralkyl, C1-C8 alkanoyl, C3-C5 alkenoyl or glycidyl; R2 is hydrogen or C1-C18 alkyl; R3 is hydrogen, C1-C18 alkyl, C5-C7 cycloalkyl, C7-C12 aralkyl, cyanoethyl, C6-C10 aryl, the group -CH2-CH(R4)-OH wherein R4 has the meaning defined above, a group of the formula or a group of the formula wherein G can be C2-C6 alkylene or C6-C12 arylene; or R3 is a group -E -CO-NH-CH 2 -OR2 .

11. A method according to claim 1 wherein the stabiliser is a light stabilizing polymeric compound of which the recurring structural unit contains a 2,2,6,6-tetraalkylpiperidine radical.

12. A method according to claim 11 wherein said polymeric compound is a polyester, polyether, polyamide, polyamine, poly-urethane, polyurea, polyaminotriazine, poly(meth)acrylate, poly-(meth)acrylic amide, or copolymer thereof.

13. A method according to claim 1 wherein an acid addition salt of a 2,2,6,6-tetraalkylpiperidine compound is used as stabiliser.

14. A method according to claim 1 wherein a complex of a 2,2,6,6-tetraalkylpiperidine compound with a metal compound is used as stabiliser.

15. A method according to claim 1 wherein the 2,2,6,6-tetraalkylpiperidine compound is used in an amount of 0.01 to 5 percent by weight, based on the solvent-free binder (lacquer resin).

16. A method according to claim 15, wherein there are additionally used one or more other light stabilisers, the amount of which is so chosen that the sum of all the light stabilisers is 0.02 to 5 percent by weight, based on the solvent-free binder (lacquer resin).

17. A method according to claim 15 or 16 wherein one or more antioxidants, plasticisers, levelling agents, curing accelerators, thickeners, dispersing agents or agents improving adhesion are used as further additives.

18. A method according to claim 1 wherein a metallic lacquer based on a binder system containing alkyd resin is stabilised.

19. A method according to claim 1 wherein a metallic lacquer based on a hot-crosslinkable polyacrylate resin containing styrene incorporated by polymerisation is stabilised.