CA1263096A

CA1263096A - Process for the electron beam curing of coating compositions

Info

Publication number: CA1263096A
Application number: CA000445782A
Authority: CA
Inventors: Godwin Berner
Original assignee: Ciba Geigy AG
Current assignee: Ciba Geigy Investments Ltd
Priority date: 1983-01-20
Filing date: 1984-01-20
Publication date: 1989-11-21
Also published as: EP0114784A3; EP0114784B1; EP0114784A2; JPS59138205A; US4511596A; DE3471595D1

Abstract

Process for the electron beam curing of coating compositions Abstract:
The electron beam curing of ethylenically unsaturated coating compositions can be accelerated by the addition of sterically hindered amines. These amines are at the same time light stabilisers for the cured coating. 2,2,6,6-Tetra-alkylpiperidine derivatives are examples of such amines. If a UV absorber is added to the coating compositions in addi-tion, a synergistic increase in the light-stabilising effect occurs.

Description

~r~

3-'1 4287/=

Process for the electron beam curing of coating compos;tions The invent;on relates to a process for curing ethylen-;cally unsaturated coating compositions by electron beam irradiation with the addit;on of sterically h;ndered amines as cur;ng accelerators~ and to the coat;ng compositions cur-able in this way.
The curing of f;nishes, print;ng ;nks, graphic pro-duc~s, printed circuits and other coating compositions by electron beam curing ;s ga;ning ;ncreas;ng ;mportance in industr;al product;on, where a large number of items is to be cured w;thin a short time. If a further shortening of the curing times in electron beam cur;ng, which per se are very short~ is accomplished, the economics of this curing pro-cess can be substantially improved, in spite of the high costs of the irradiation equipment, and a lower radiation dose can be appl;ed.
H;therto, no accelerators for electron beam cur;ng have been disclosed. It has no~ been found that the curing of ethylenically unsaturated coating compos;t;ons can be sub-stantially accelerated by an addition of sterically hindered am;nes. In contrast to other amines, th;s does not cause any significant yellowing of the coating compositions or pre-mature gelling on storage. A further advantage is the known fact that the ster;cally h;ndered amines generally possess a l;ght-stabilising action. After curing, these compounds thus act as light stabilisers for the coating compositions.
The subject of the invention is therefore a process for curing coating compositlons, which contain ethylenically ~63~

unsatu~ated compounds, by electron beam irradiation with the addition of a curing accelerator, which process comprises using at least one compound from ~he clas~ of s~erically hindered amines as the curing accelerator, in which process in a first step the hindered amine is added to ~he coatlng material which is in a second step coated onto substra~e and in a third step irradiated by electron beams.
The coating composition can consist of an individual radiation-curable compound, for exa~ple an acrylate or methacrylate of a polyol. Preferably, however, mixtures of at least one low-molecular and one hiyher-molecular radiation-curable compound are used. Examples of low-molecular compounds are t~e~h)acrylates o~ monools, dlols, triols or tetraols, for example methyl, ethyl, butyl, 2-ethylhexyl, 2-hydroxyethyl or 2-hydroxypropyl acrylate, isobornyl acrylate, methyl, ethyl or isopropyl methacrylate, dicyclopentadienyl (meth)acrylate~
dicyclopentadienyloxyethyl (meth)-acrylate, ethylene glycol, propylene glycol, hexamethylene glycol di(~eth)acrylate, bisphenol-A diacrylate, trimethylolpropane triacrylate, tris-(2-acryloxyethyl) isocyanurate and pentaerythrltol triacrylate orte~ra(meth)acrylate. Further low-molecular monomers are acrylonitrile, acrylamide, methacrylamide, N-substituted (~eth~acrylamides, vinyl acetate, vinyl acrylate, vinyl alkyl ethers, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, styrene, alkyl- or halogenostyrenes, divinylbenzene, divinyl succina~e, diallyl phthalate, triallyl i~ocyanurate or triallyl phosphate.

~,... . . ....
~. ~. . .~. .

~3~9~i

2~4~9-~462 E~amples of hiyher-molecular (oligomeric) ra~iation-curable compounds are acrylated or methacrylated epoxide resins, polyurethanes, polyethers or polyestexs, unsaturated polyester resins, oligomers of alkyl (meth)acrylates or corresponding co-oligomers. Such ollgomers are also called p:repolymers. Their molecular weight can range from about 400 to 4,000, and the number of double bonds per molecule can be 1 up to about 20.
The viscosity of the mixtures and the properties of the cured coatings can be varied by appropriate mixing of low-molecular components with higher-molecular components. In general, the mixtures are solvent-free, but in certain cases the addi~ion of a small amount of solvent may be necessary 2a .,, ~.: .. ' ;

for settin~ the correct v;scosity. To increase the viscosity, it is also possible to dissolve limited amounts of a polymer in the mixture.
The coating composition can also be a mixture of ethylenically unsaturated, rad;ation-curable binders and thermally or catalytically-thermally curable binders. Such a hybrid system can be cured in two stages; for example, pre-curing can be effected by electron irradiation and final cur~
ing can be effected by supply;ng heat; for certain appLic-a~ions, this can have advantages. As the catalysts for the thermal curing, preferably masked (capped) acid curing agents can be used here, which are ineffective in normal storage and are converted into the active form only by the supply of heat~
The coatings can be transparent or pigmented, and they can also contain conventional add;tives, for example flow assistants~ thixotropic agents or wetting agents. For spe-cial applicat;ons, the coating compositions can also have been mixed with fillers or reinforcing agents~ Examples of f;llers are kaolin, talc, gypsum or silicate-type fillers.
Examples of reinforcing agents are in particular fibres, for example glass fibres, metal fibres or carbon fibres.
Further possibLe additives are stab;l;sers, for example antioxidants, metal deactivators or light stabilisers.
Of particular importance is the addition of light stabilisers of the UV absorber type and of organic compounds of trivalent phosphorus, for example ~f phosphites, phosphonites or phos-phines.
The cu~;ng accelerators, used according to the in-vent;on, from the class of stericaLly hindered am;nes are compcunds which are known as light stab;lisers. Preferably, these are cyclic am;nes, ;n particular der;vat;ves of 5-membered, 6-membered or 7-membered heterocyclic ring systems with 1 or 2 N atoms ~hich ring systems have tertiary C atoms in both ortho-posit;ons relat;ve to the N atom, whereby steric h;ndrance of the N atom is effected.
Examples of such ring systems are the 2~2,5,5-tetrasubstituted pyrrol;dines~ imida~ol;dones and oxa~
~ol;dines of the formulae , ~ 263~6 R -- RR - -R Rl~ 1/ 3 R2 \NI 4 RY I \~R 2 1 4 X X X
or the 2,2,6,6-tetrasubstituted piperazinones~ piperaz;ne-diones and hexahydropyrimidines of ~he formulae y R6

3 ~ ~ R2 \11/ R~, X X

or the diazacycloheptanones of the -formula R5~ ~ Y
~=o 7 ~.~ ~3 in which R1, R2, R3 and R4 are aliphat;c hydrocarbon radicals which may be linked to form spiro rings, Rs, R6 and R7 are hydrogen or aLkyl, and X and Y are hydrogen, oxide oxygen, OH or a monovalent organic radical. Decahydro-quinolines disubstituted in the 2-position are also represent-atives of sterically hindered amines~
Compounds of particular importance from amongst the sterically hindered amines are the 2~2,6,6-tetraalkylpiper-idine derivativesu These are compounds which, in their mole-cule, contain at least one group of the formula I
:

~Z~3C)~6 \ / 3~
_~ \./ (I) RC~ / \CH

in which R is hydrogen or methyl~ The curing accelerators can contain one or more such groups of the formula I, and these can, for example, be a mono-, b;s-~ tris~, tetra- or ol;go-piperidine compound. Those piperidine deriva~;ves are preferred which contain a group of the formula I ;n which R ;s hydrogen, and those ;n ~Ih;ch there ;s no hydrogen atom on the r;ng n;trogen.
Most of these piperidine light stabilisers carry polar subst;tuents ;n the 4-pos;tion of the piperidine ring, or carry a spiro ring in this position.
Of particular ;mportance are the follow;ng classes of piperidine compounds:
a) Compounds of the formula II

RCH2\ /C~l3~ 1 R ~~, \-~ ~ R2 R~ / \CH ~ (II) ;n wh;ch n ;s a number from 1 to 4, preferably 1 or 2, R is hydrogen or methyl, R1 is hydrogen, O, ~OH, ~O~C1-Cg-alkanoyl, C1-C18-alkyl, -CH2CN, C3 C8 alkenyl, C3 C8 a~kynyl, C7-c12-aralkyl~ C1-C8-alkanoyl, C3-C5-alkenoylp glycidyl or a group -CH2CH(OH)-Z, in which Z is hydrogen~ methyl or phenyL, R1 preferably being C1-C1~-alkyl, allyl, benzyl, acetyl or acryloyl and R2, ;f n = 1, being hydrogen, C1-C18-alkyl wh;ch may be interrupted by one or more oxygen atoms, cyanoethyl, benzyl~ glycidyl, a monovalent radical of an aliphatic~ cycloaliphat;c, aral;phatic or aromat;c carboxylic acid, carbamic acid or phosphorus-ii3~

containing acid or a monovalent silyl radical, preferably aradical of an aliphatic carboxylic acid hav;ng 2 to 18 C
atoms, a cycloaliphat;c carboxyl;c acid having 7 to 15 C atoms or an aromatic carboxylic acid having 7 to 15 C atoms, or, if n 2~ R is C1-C12-alkYLene, C~-c1z-alkenylene~
xylylene, a divalent radical of an aliphatic, cycloaliphatic, araliphatic or aromatic d;carboxylic acid, dicarbamic acid or phosphorus-containing acid or a divalent silyl radical, preferably a radical of an aliphatic dicarboxylic acid having 2 to 3~ C atoms, a cycloaliphatic or aromatic dicarboxylic acid having 8 to 14 C atoms or an aliphatic, cycloaliphatic or aromatic dicarbamic acid having ~ to 14 C atoms, or, if n = 3, R2 is a trivalent radical of an aliphatic, cyc loaliphatic or aromatic tricarboxyl;c ac;d, an aromat;c tr;carbam;c acid or a phosphorus-containing acid or a trivalent silyl radical, or, if n = 4, R2 is a tetravalent radical of an aliphatic, cycloaliphatic or aromat;c tetracarboxylic acid.
Any C1-C12-alkyl substituents 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.
C1-c18-Alkyl R1 or R2 can be, for example, one of the groups listed above and additionaLly also, for example, n-tr;decyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
C3-c~-Alkenyl R1 can, for example, be prop-l-enyl, allyl, methallyl, but-2-enyl, pent-2-enyl, hex-2-enyl, oct-2-enyl and 4-tert.-butyl-but-2-enyl.
C3-cg-Alkynyl R1 is pre~erably propargyl.
C7-C12-Aralkyl R1 ;s in part;cular phenethyl or especially benzyl.
C1-C8-Alkanoyl R1 ;s~ for example, ~ormyl~ pro-pionyl, butyryl, octanoyl and preferably acetyl, and C3~C5-alkenoyl R1 is especially acryloyl.
A monovalent carboxylic ac;d radical R2 is, for example, an acetic acid, stearic acid, salicylic acid, meth-acryl;c ac;d, benzo;c ac;d or l~-(3,5-di-tert.-butyl-~-hydroxy-phenyl)-~prop;on;c ac;d rad;cal.

~Z~3~6 A d;valent dicarboxylic acid radical R2 is, for example, an ad;pic acid, suberic acid~ sebacic acid, maleic acid, phthalic acid, dibu~ylmalon;c acid, dibenzylmalonic acid, butyl-(3,5-di-tert.-butyl-4-hydroxybenzyl) malonic acid or bicycloheptenedicarboxylic acid radical.
A ~rivalent tricarboxylic acid radical R2 is, for example, a trimellitic acid or a nitrilotriacetic acid radi-cal~
A tetravalent tetracarboxylic acid radical R2 is, for example, the tetravalent radical of butane 1,2,3,4~tetra-carboxylic acid or of pyromellitic acid.
A divalent dicarbamic acid radical R2 is, for example, a hexamethylenedicarbamic acid or a 2,4-toluene-dicarbamic acid radical.
The ~ollowing compounds are examples of piperidine compounds from this class:
1) 4-hydroxy-2,Z,6,6-tetramethylpiperidine 2) 1-allyl-4-hydroxy-2,Z,6,6-tetramethylpiperidine 3) 1-benzyl-4-hydroxy-2,2,6,6-tetramethylpiperidine

4) 1-(4-tert~-butyl-but-2-enyl)-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) prop;onate

9) di-~1-benzyl-2,2,6,6-tetramethylpiperidin-4-yl) maleate

10) d;-(2,2,6,6-tetramethylpiperidin-4-yl) adipate

11) di-(2,2,6,6-tetramethylpiperidin-4-yl) sebacate

12) d;-~1,2,3,6-tetramethyl-2,6-diethyLpiperidin-4-yl) sebacate

13) d;-(1-allyl-2,2,6,6-tetramethylpiperidin-4-yl) phthalate

14) 1-propargyl-4-~-cyanoethoxy-2,2,6,6-tetramethylpiperidine

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

16) tri-(2,2,6~6~tetramethylpiperidin-4-yl) trimellitate

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

18) di-(1,2,2,6,6-pentamethylpiperid;n-4-yl) d;butyl-malonate ~6~ [)~Ç;

19) di-(1,2,2,6,6-pentamethylpiperidin-4-yl~ butyl-(3,5-di-tert.-butyl-4-hydroxybenzyl)-malonate

20) di-~1,2,2,6,6-pentamethylpiperidin-4-yl) dibenzyl-malonate

21) d;-(1,2,3,6-tetramethyl-2,6-diethylpiperidin-4-yl) dibenzyl-malonate

22) hexane-1',6'-bis-(4-carbamoyloxy-1-n-butyl-2,2,6,6-tetra-methylpiperidine~

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

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

25) phenyl-tris-(2,2,6,6-te~ramethylpiperidin-4-oxy)-silane

26) tris~ propyl-2,2,6,6-tetramethylpiperidin-4-yl) phos-phite

27) tris-(1-propyl-2,2,6,6-tetramethylpiperid;n-4-yl) phos-phate

28) phenyl Cbis-(1,2,2,6,6-pentamethylpiperidin-4-yl)] phos-phonate

29) di-~1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate b) Compounds of the formula (III) PCH2 CH3 / R ~3 1 : R1- N ~ l~i I R4 ~ I I I ) /\
_R~H2 CH3 _ ~

in which n is the number 1 or 2, R and R1 are as defined under a), R3 is hydrogen, C1-C12-alkyl, C2-Cs-hydroxy-alkyl, C5-C7-cycloalkyl, C7 Cg~aralkylr C2-C18-alkanoyl~ C3-C5-alkenoyl or benzoyl and R4, if n = 1 ;s hydrogen, C1-C18-alkyl, C3-C8 alkenyl~ C5 7 cycloalkyl, C1-C4-alkyl substituted by a hydroxy~ cyano, alkoxycarbonyl or carbamide group, glycidyl, a group of the formula -CH2-CH~OH)-Z or of the formula -CONH-Z, in which Z lS hydrogen, methyl or phenyl, or, if n = 2, R4 is C2-C1~~
alkylene, C~-c12-arylene~ xylylene, a -CH~-CH(OH)-CH2-group or a group -CH2-CH(OH)-CH2-0-D-O-CH2-CH(OH~-CH2-, ~2~3~

in which D is c2-c10-alkylene~ C6-C15-arYlene' C6-C12-cycloalkylene or, provided that R3 is not alkanoyl, alken-oyl or benzoyl, R4 can also be a divalent radical of an aliphatic, cycloaliphatic or aromatic dicarboxylic acid or dicarbam;c acid or also the group -CO-, or, if n = 1, R3 and ~4 together can be the divalent radical of an aliphatic, cycloaliphatic or aromatic 1~2- or 1,3-dicarboxylic acid~
Any C1-C12- or C1-C1g-alkyl substituents are as already defined under a).
Any Cs-C7-cycloalkyl substituents are especially cyclohexyl.
C7-c8-Aralkyl R3 is in particular phenylethyl or especially ben~yl.
Cz-C18-Alkanoyl R3 is, for example, propionyl, butyryl, octanoyl, dodecanoyl, hexadecanoyl, octadecanoyl or preferably acetyl, and C3-C5-alkenoyl R3 is especially acryloyl.
C2-C8-Alkenyl R~' is, for exampLe, allyl, meth-allyl, but-2-enyl, pent-2-enyl, hex-2-enyl or oct-2-enyl.
C2-C4-Alkyl R4, which is substituted by a hydr-oxyl, cyano, alkoxycarbonyl or carbamide group, can be~ for example, 2-hydroxyethyl, 2-hydroxypropyl, 2-cyanoethyl, meth-oxycarbonylmethyl, 2-ethoxy-carbonylethyl, Z-aminocarbonyl propyl or 2-tdimethylaminocarbonyl)-ethyl~
Any c2-c1z-alkYlene substituents are, for example, ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethyl-ene.
Any C6-c15-arylene substituents are, for example, o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
C6-C12-Alkylene ~ ;s espec;ally cyclohexylene.
The following compounds are examples of piperid;ne compounds from this class:

30) N~N'-bis-(2,2,6,6-tetramethylp;perid;n-4-yl~ hexamethyl-ene-1,6 d;amine

31) N~N' b;s-~2,Z,6,6-tetramethylpiperid;n-4 yl)-hexamethyl-ene-1,6-diacetamicle

32) 1-acetyl-4-(N-cyclohexylacetamido)-2,2,6,6-tetramethyl-pip~ridine

33) 4-benzylamino-Z,2,6,6-tetramethylpiperidine

34) N,N'-bis-(2,2,6,6-tetramethyLpiperidin-4-yl)-N,N'-dibutyl-adipamide

35) N,N'-bis-(2,2,6,~-tetramethylpipericlin-4-yl)-N,N'-d;-cy.clohexyl-2-hydroxypropylene-1,3-diamine

36) N,N'-bis-~2,2,6,6-~etramethylp-iperidin-4-yl)-p-xylylene-diamine

37) the compound of the formula cx !~ f ;~

C-~3- N ~ ;2-C~-(0~C~2---0 /\ 1 CH C'~ (~) CH --C--CX

3 ~ ~ C~2-5U(o-~)-C-~2___0 : CX3 CX3 4~9

38) 4-(b;s-Z-hydroxyethyl-amino)-1,2,2,6,6-pentamethyl-piperidine

39) 4-~3-methyl-4-hydroxy-5-tert.-butyl-benzam;do)-2,2,6,6-tetramethylpiperidine

40~ 4-methacrylam;do-1,2,2,6,6-pentamethylp;per;dine : c~ Compounds of the formula (IV7 Rt~ CE R
~ ~ r 1 ~ ~< ~5 ~ C'~2 C'~ J

3~

in which n is the number 1 or 2, R and R1 are as defined under a) and R5, if n = 1, is c2-c~-alkYlene or -hydroxy-alkylene or C~-C22-acyloxyalkyLene and, if n = 2, ;s the group (-cH2)2c(cH2-)2-C2-Cg-Alkylene or -hydrcxyalkylene R5 is, for example, ethylene, 1-methyl-ethylene, propylene, 2-ethyl-propylene or 2-ethyl-2-hydroxyme~hylpropylene.
C4-C22-AcYloxyalkylene R5 is, for example, 2-ethyl~2-acetoxymethylpropylene.
The following compounds are examples of piperidine compounds from this class:

41) 9-a~a-8,8,10,10~tetramethyl-1,5-dioxaspiro[5.5~undecane

42) 9-aza-8,8,10,10-tetramethyl~3-ethyl-1,5-dioxaspiroC5.5]-undecane

43) 8-aza-2,7,7,8,9,9-hexamethyl-1,4-dioxaspiroC4.5]decane

44) 9-aza-3-hydroxymethyl-3-ethyl-8,8,9,10,10-pentamethyl 1,5-dioxaspiroC5.5~undecane

45) 9-aza-3-ethyl-3-acetoxymethyl-9-acetyl-8,8,1û,10-tetra-methyl-1,5-d;oxaspiroCS.5]undecane

46) 2,2,6,6-tetramethylpiperidine-4-spiro-2'-t1',3'-dioxane)-S'-sp;ro-5"-(1",3"-d;oxane)-2"-spiro-4"'-t2"',2"',6"',6"1-tetramethylpiperid;ne).
d) Compounds of the formulae VA, VB and VC

~6 RCH2~ R il- C=O

/\~ ,~,~ 7 ~ V A ) RCH2 C~I ~; ;l n Z\~ ~ ~ o--C - ~
R--N~._~N _ ¦ = O (VB) : RCH2 CH3 H

~2~i3~

~ICH2 (~H R 'rl ~ O C - T2 Rl- ~ C_-_N_R (VC) ~CH2 ~3 ll o ;n which n is the number 1 or 2, R and R1 are as defined under a)~ R6 is hydrogen, C1-c12-aLkyl~ allyl, ben2yl~
glyc;dyl or c2-c6-alkoxyalkYl, R7, if n = 1, ;s hydrogen, C1-C12-3lkYl~ C3-Cs-alkenyl, C7-Cg-aralkyl~ C~-C7-cyc loa lky l, C2-C4-hydroxya lky l, C2-C6-a lkoxya lky l, C6-C10-arYl, glycidyl or a group of the formula -(CH~)p-COO-Q or of the formula -(C~2)p-û-CO-Q, ;n which p is 1 or 2 and Q is C1-C4-alkyl or phenyl, and, ~ R iS C2-C1Z-alkYlene~ C6-C12-arylene, a group -cH2-cH(oH)-cH2-o-D-o-cH2-cH(oH)-cH2-~ ;n wh;ch D ;5 C2-C10-alkYlene, C6-C1s-arylene, Cb-C12-cyclo-alkylene or a group -CH2cH(oz'~cH2-(ocH2-cH(oz')cH2)2-in which Z' is hydrogen, C1-C1~-alkyl, allyl~ benzyl, C2-C12-alkanoyl or benzoyl, R7a is hydrogen, C1-C12-alkyl, C3-C5-alkenyl, C7-Cg-aralkYl, Cs-C7-cYclo-alkyl, C2-C4-hydroxyalkyl, C2-C6-alkoxyalkyl, glycidyl, C2-C12-alkanoyl, C7-C11-aroyl or a group -CH2-COOQ', -CHzcH2-cooQ~ or -CH2CH(CH3)-COOQI, in which ~' is C1-C20-alkYl~ c3-c14-alkoxyalkyl~ Cs-C7-cycloalkyl or phenyl, and T1 and T2 independently of one another are hydrogen, c1-c1g-alkYl or C6 C10 ary~ or 7 9 aralkyl which are unsubstituted or substituted by halogen or C1-C4-alkyl, or T1 and T2, together with the C atom linking them, form a C5-C12-cycloalkane ring.
Any C1-C12-alkyl substituents 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.
Any C1-cl8-alkyl substituents can, for example~
be the groups listed above and in addition also, for example, ' ~263~

n-tridecyl, n-tetradecyl, n-hexadecyl or n-oct3decyl~
Any c2-c6-alkoxyalkyl substituents are, for ex-ample, methoxymethyl, ethoxymethyl, propoxymethyl, tert7-butoxymethyl, ethoxyethyl, ethoxypropyl, n-butoxyethyl, tert.-butoxyethyl, isopropoxyethyl or propoxypropyl.
Alkenyl R7 or R7a ;5~ for example, prop-1-enyl, allyl, methallyl, but-Z-enyl or pent-2 enyl.
C7-C9-AralkYl R7, R7a, T1 and T2 is in particular phenethyl or especially benzyl. If T1 and T2~
together with the C atom, form a cycloalkane ring, this can be, for example, a cyclopentane, cyclohexane9 cyclooctane or cyclo-dodecane ring.
C2-c4-Hydroxyalkyl R7 or R7a is, for example, 2-hydroxyethyl, 2-hydroxypropyl, 2 hydroxybutyL or 4-hydroxy-butyl.
C6-C10-Aryl R7, T1 and T2 is in particular phenyL, ~-naphthyl or ~ naphthyl, which are unsubstituted or substituted by halogen or C1-C4-alkyl.
C2-C12-Alkylene R7 is, for example, ethylene, propylene, 2,2-dimethylpropylene, tetramethylene, hexame~hyl-ene, octamethylene, decamethylene or dodecamethylene.
C4-C12-Alkenylene R7 is in particular but-2-enylene, pent-2-enylene or hex~3-enylene.
C6-C12-Arylene R7 is, for example, o-, m- or p-phenylene, 1,4-naphthylene or 4,4'-diphenylene.
C2-C1~-Alkanoyl R7a or Z' is, for example, pro-pionyl, butyryL, octanoyl, dodecanoyl or preferably acetyl.
Aroyl R7a can especially be benzoyl~
C2-C1~-Alkylene~ C6-C1s-arylene or C6-C12-cycloalkylene ~ is as defined under b).
The followin3 compounds are examples of piperid;ne compounds from this class:

47~ 3 benzyl-1,3,8~triaza-7,7,9,9-tetramethylspiroC4.5]decane-2,4-dione

48) 3-n-octyl-1,3,8-triaza-7,7,9,9-tetramethylspiroC4.5]-decane-2,~-dione

49) 3-alLyl-1,3,8-triaza-1,7,7,9,9-pentamethylspiroC4.5]-~263~

decane-2,4-dione

50) 3-glycidyl 1,3,8-triaza-7,7,8~9,9-pentamethylspiro[4.5]-decane-2,4~dione

51) 2-iso propyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro[4.5]decane

52) 2,2-dib~tyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiroC4.5~decane

53) 2,2,4,4-tetra~ethyl-7-oxa-3,ZO-diaza-21 oxo-dispiro-C5~1.11.2]heneicosane

54) 2-butyl-7,7,9,9-tetramethyl-1-oxa-4,8-d;aza-3-oxo--spiro-C4.5]decane or the compounds of the following formulae:

3L2~3 _1~
V I V
'I 1 n ~AV = o V-- V
o~
o N V I V
N _ \ /
v ~ v ~ A
_ ~ = o ~ \~
o ~, ~ W~

V --I
~ 3 1 1 O ~ A ~1 V N
C~l V \~

, = o Z~ = o Z.~ = o o\ . = o ~\ t~ Y~ A
o~ <cr~ ko~ ~\ `3' <-~ 3k~

V ~ ~ ~ V V
V V

~3~

e) Compounds of -the formula VI

~ R (Vl) in which n is the number 1 or 2 and R8 ;s a group of the formula R~ 2R
- E~ R 1 C~3 C~2R

in which R and R1 are as defined under a), E is -O- or -NR11-, A is Cz-C6-alkylene or -(CH2)3-0- and x is the nu~ber O or 1, R9 is identical to R8 or is one of the groups -NR11R12, -oR13, -NHCH20R13 or -N(CH20R13)2, R1~
;s, if n = 1, identical to R8 or R9 and, if n = 2, is a group -E-B-E-, in which B is c2-c6-alkYlene which m~y be ;nterrupted by -N(R~ R11 is C1-C1~-alkyl~ cyclo-hexyl, benzyl or c1-c4-hYdroxyalkyl or a group oF the formula ~ ~li ~ / C~2R

R
3 CH2~
R ;s C1~C12 alkyl, cyclohexyl, benzyl or C1-C4-hydroxyalkyl and R13 is hydrogen, c1-c12-alkYl or phenyl, or R11 and R12 together are C~-C5-alkylene or -oxa-alkylene or R11 and R12 are each a group of the Forlnula - .

~L263~

CX 3~ C ~ H 9 N
n--A--N

CH3 CH3 y C ~ --~J
~''9 1 CH3 N CE~3 Any C1-C12-alkYl substituents 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.
Any C1-C4-hydroxyalkyl substituents are, for example, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl or 4-hydroxybutyl.
C2-C6-Alkylene A is, for example, ethylene, pro-pylene, 2J2-dimethylpropylene, tetramethylene or hexamethyl-ene~
If R11 and R12 together are C4-C5-alkylene or -oxaalkylene, this is, for example, tetramethylene, penta-methylene or 3-oxapentamethylene~
The compounds of the follow;ng formulae are examples of piper;dine compounds from this class:

:: .

~i3~

CH~ a~ ,I<C~3 CH3 ~ C 3 <~ ~T ~

~T( a~ 9) 2 CH~ ~ G 1~, 0113 59) C'I~ 2 /\ C2'~7 C2~5 CH3CH~;

,~ 3 fE2--CH2 ~7 O ' C-~
60) C~_CH3 ~\ C,~CH3 C-~ -C~ ~C-~-2-C'~-2 ~'~

: ,~

~63~

o ~ v X~ o~
~- ~ V V
$~1~

.. . , o~ ~ ~ `

~ o~ o o V V

o o , V V . V

i3~

63) _ C8H1 ~ 3 loM C~3 CH3 C8H17--N iiH(CH2) 3 --_ CH~CH3 CH3 N CH3 ~ 2 CH2CH=C~2 64) C1~3~,, N CH3 N-C H
4 g CH2=CH2-C~ -N \~ N~ N-CH2CH =CH2 C~3CH3 c4~l9 4 9 CH3 C1~3 .

::

~2~i;3~

-f) Compounds of the formula VII

'2?1 7 \ I (V I I ) C~; 5'-~2~' ~

in which n is ~he number 1 or 2, R is as defined for formula I
and R14, i~ n = 1, is C4-c1g-alkyl~ C7-~12 aralkyl~
the group -Co-R15, c1-c~-alkYl substituted by -CN, -COOR16, -OH or -oCoR17, or ;s -CH2-CH(OH)~
.=.
being C1 C12-alkyl~ C2-C4-alkenyl or phenyl, R16 bein~ C1-C18-alkyl, R17 being C1-C1~-alkyl, Cz-ClO-alkenyl, cyclohexyl, benzyl or c6-C1û-aryl, and, if n = 2, R14 is C4-C12-alkylene, but-2-en-1,4-ylene, xyLylene, the group -(CH2)~-OOC-R18-COO-(CH2)2- or the group -CH2-ooc-R19-COO-CH2-, R18 being C2-C10-alkyl~
ene, phenylene or cyclohexylene and R19 being C2-C10-alkylene, xylylene or cyclohexylene.
Any c1-c12-alkYl subst;tuents 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.
Any C1-c18-alkyl substituents can, for example, be the groups listed above and in addition also, for example, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl.
Any C2-C10-alkylene groups are, for example, ethyLene, propylene, 2,2-dimethylpropylene, tetramethylene, hexamethylene, octamethylene or decamethylene.
C4-C18-Alkyl R14 is, for example, n-butyl, sec.-butyl, tert.-butyl, n-hexyl, n-octyl, 2-ethylhexyl, 1,1-di~
methyl-2-tert~-butylethyl, n nonyl, n-decyl, n-dodecyl, n-tridecyl~ n~tetradecyl, n-hexadecyl or n-octadecyl.
-CN-Substituted C1-C4-alkyl R14 j5, for example, ~Z6~
- ~2 -cyanomethyl, cyanoethyl, 3-cyano-n-propyl or 4-cyano-n-butyl.
C4-c12-Alkylene R14 is, for example, 2,2-di-methylpropylene, tetramethylene, hexamethylene, octamethylene, decamethylene or dodecamethylene.
C7-C12-Aralkyl R14 is in particular phenethyl, p-methylbenzyl or especially benzyl.
C2-C4-Alkenyl R15 is, for example, vinyl, prop-1-enyl, allyl, methallyl or but-2-enyl.
Cz-C10-Alkenyl R17 is, for example, one of the groups as defined for alkenyl R15 and add;tionally also, for example~ crotyl, hex-2-enyl, oct-2-enyl or dec-2-enyl.
C6-c10-Aryl R~7 is, for example, phenyl which is un-substituted or substituted in the o-position or p-position by methyl, ethyl, isopropyl, n-butyl or tert.-butyl.
The following compounds are examples of p;peridine co0pounds from this class:
65) bis-CI~-2,2~6,6 tetramethylpiperidino)-ethyl~ sebacate 66) n-octyl ~-(2,2,6,6-tetramethyl-piperid;no)-acetate 67) 1~4-b;s-(2,2,6,6-tetramethylp;per;dino)-but-2-ene.
g) Compounds of the formula VIII

~X CH~ R
2 ~
R --lY \~C00--~ 21 ( V I I I ) ~ \~20 P'~2 CH3 n in wh;ch n ;s a number from 1 to 4, preferably 1 or 2, R and R1 are as defined under a), R20 ;s hydrogen, hydroxyl or c1-c8-alkoxY and R21, if n = 1, ;s c1-C20-alkyl, C3-cl4-alkoxya~kyl~ Cs-C12-cycloalkyl or C7-C14 aralkyl and, ;f n = 2, ;s C2-C12-alkylene, C4-Cg-alkYl-ene which is interrupted by one or two -O , C6-C12-cyclo-alkylene, Cg-C16-cycloalkylene-dialkylene or C~-C1~~
aralkylene and, if n = 3, is C3-C12-alkanetriyl and, if n = 4~ ;s C4-C12-alkanetetrayl.
Examples of monovalent rad;cals R21 are ethyl, ~;3~6 - 2~ -2-ethylbuty~, n-octyl, n-dodecyl, n-octadecyl, 2-isopropoxy-ethyl, 2-dodecyloxyethyl, 2-butoxypropyl, cyclohexyl, cyclo-octyl, benzyl or Z~phenylethyl. Examples of divalent radicals R21 are 1,2-ethylene, tetramethylene, hexamethylene, octa-methylene~ dodecamethylene, 3-oxa-pentamethylene, 3,6~dioxa~
octamethylene, 1,4-cyclohexylene, 1,5-cyclooctylene, 1,4-cyclohexylene-dimethylene, 1,4-cyclohexylene-diethylene and m- or p-xylylene. ExampLes of trivalent radicals R21 are propane-1,2,3-triyl, 1,1,1-trimethyleneethane or 1,1r1-tri-methylenepropane. Examples of tetravalent radicals R21 are butane-1~2,3,4-tetrayl or tetramethylenemethane.
h) Polymeric compounds, the recurring structural unit of which contains a tetraalkylpiper;dine radical of the formula I, in particular polyesters, polyethers, polyamides, polyamines, polyurethanes, polyureas, polyaminotriazines, poly~meth)acryl-ates, poly~meth)acrylamides and copolymers thereof, which contain such radicals.
The compounds of the following forrnulae are examples of piperidine compounds from this class, m being one of the numbers from 2 to about ZOO.

~L2~3~

1 3o=l 0=~ ~> .

o = ~
o=
Q
_ ~1' ~ ~
~ o=o ~>

v I ~ o = ~ ~

0=~
v ~ X
o=l . c~ ~
L~

CO ~D

~3~

o =V

~ I
V~ V
o =1, o~ ~
I
,r ) C) '~
~O ~ 11 O V
~ ~ ~ V C
_~ I
V--V--V V ~ V C~ ~ V
V ~ ~ _~ <
V--1--V ~ ~ /y r ) t~ I V
v- v ~ ~ \1/
~; " ~ ~ O
~ Jv .v :

,~ ,~ ,_ _. . ~ ~
~;

~ ~3~

I
~ ~ I i I
~ ~V

~ ~ i V C~ I
. I ~ 1~
~<~

kw~
~W ~ V

{< Z ~ 7(rr~
r~ C) I

.

~3~1~6 ~ 27 --c~3 77) lC
L 1 2 m O=C CH~ C~13 ~<iT--CH3 7' C~3 CH3 78) ~C--CU2l O~C ~<CH3 C'-Y-13~

;) Compounds which, in the;r molecule, conta;n at least one 2-tZ'-hydroxyphenyl)-benzotriazole group or 2-hydroxybenzo-phenone group and at least one tetraalkylpiperidine group.
The compounds of the following formulae are examples of piperid;ne compounds from this class:

79) ~ ¦ ~, f 80) ~ 1/ ~ ~ H3 CH2CH2co ~- CH3 CH3 C~3 .

~L2~3~

0~1 C~2 C~ CH3 .3 CE~3 C~T C~
~ 3 To the extent that the tetraalkylpiperidine compounds are basic compounds, they can form salts with acids. Examples of such acids are inorganic acids or organic carboxylic, sulfonic, phosphonic or phosphinic acids, for example hydro-chloric acid, boric ac;d, phosphor;c acid, acet;c acid, sali-cyLic ac;d, toluenesulfonic acid or benzenephosphon;c ac;d.
To the extent that the tetraalkylpiper;dine compounds are basic compounds, they can form complexes ~ith metal chel-ates, which complexes can also be used for pu~poses of the inventionO The metal chelates can~ for example, be those of zinc, cadm;um, cobalt, aluminium or chromium, and those of nickel are particularly preferred. Examples oF suitable chelate formers are 1,3-dicarbonyl compounds or 2-acylphenols, for example ethyl acetoacetate~ acetylacetone, benzoylacetone~
o-hydroxyacetophenone or o-hydroxybenzophenone. Complexes having a piperidine : metal chelate ratio 1 : 1 and 2 : 1 are preferred. The polymeric piperid;ne derivatives of class h) can also form such complexes with metal chelates, which can be used accord;ng to the inventionO
For certain f;elds of application, it can be desir-able that the curing accelerator copolymerises with the ethylenically unsaturated compounds. For this purpose~ those sterically hindered amines are seLected which possess ethylen-ically unsaturated groups~ for example allyl~ vinyl or ~i3~

maleate groups, and in particular acrylic or methacrylic groups. Examples of such compounds are the compounds 2, 7, 9, 17 and 49, l;sted above, and the following compounds:
83) 1,2,2,6,6-pentamethyl-~-acryloyloxy-piperidine 84) 1-acetyl-2,2,6,6-tetramethyl-4-acryloyloxy-piperidine 85) 1-benzyl-2,2,6,6-tetramethyl-4-acryloyloxy-piperidine 86) 1,2~2,6,6-pentamethyl-4 methacrylamido-p;peridine 87) 1,2,2,6,6-pentamethyl-~-(N-butyl)-acrylamido-piperidine 88) 1,2,2,6,6~pentamethyl-4-maleimido-piperidine 89~ 1,3,8 tria~a-2,4-dioxo-3-acryloyloxyethyl-7,7,8,9,9-pentamethylspiro~4.5~decane 90~ (2-methacryloyloxy)-ethyl]-2,2,6,6-tetramethyl-piper-idine.
The advantage of the accelerators copolymerised in this way is that they cannot be lost from the cured coating by migration or extraction and can therefore act as light stabilisers for a long period.
In special cases, it can be an advantage to use a m;xture of sterically hindered amines. The total of added curing accelerator is 0.1 to 20 % by weight, preferably 0.5 to 10 % by weight, relative to the total of the unsaturated curable compounds.
The accelerator is added to the coating compositions in a simple manner by dissolving it in one of the monomeric components or in the mixture. These solutions are stable, since the accelerators are not polymerisation init;ators.
However, the mixtures can also contain inhibitors, such as are known for ethylenicaLly unsaturated compounds, for ex-ample hydroc~uinone and derivatives thereof, ~-naphthols, copper compounds, phenothiazine derivatives or hydroxylamine derivatives.
Due to their light-stab;lisation act;v;ty, the accel-erators according to the invention, of the sterically hindered amine type, effect a stabilisat;on of the coat;ng compos;tions against light-induced damage. This light-stabilisation effect can be cons;derably enhanced if a light stabiliser from the UV absorber class ;s also added to the coating compos;tions.

i3~

The following classes of compounds are examples of known UV
absorbers:
1. 2-(2l-Hydroxyphenyl)~benzotriazoles, for example the 5'-methyl, 3',5'-di-tert.-butyl, 5'-tert.-butyl, S'~ J1~3~3-tetramethylbutyl), 5-chloro-3',5'-di-tert.-butyl, 5-chloro-3'-~ert.-butyl-5'-methyl, 3'-sec.-b~tyl-5'-tert.-butyl, 31_ ~-methylber,zyl-5'-methyl, 3'~X-methYlbenzYl-5'-methYl-5-chloro, 4'-hydroxy, 4'-methoxy, 4'-octyloxy, 3l,5'-d;-tert.-amyl, 3'-methyl-5'-carbomethoxyethyl, 3l',5'-b;s-(~C~-d;methyl-benzyl), 3',5'-b;s-~&~-dimethylben~yl~5-chloro, 3',5'-di-tert.-octyl, 3',5'-di-tert.-octyl-5-chloro and 5-chLoro-3'~5'-di-tert.-amyl derivatives. The 1,2,3-triazoles described in U.S. Patent 3,642,813 can also be used.
2. 2,4-~;s-(2'-hydroxyphenyl)-6-alkyl-s-triaz;nes, for ex-ample the 6~ethyl, 6-heptadecyl and 6-undecyl derivatives.
3. 2-Hydroxybenzophenones, for example the 4-hydroxy, 4-meth-oxy, 4-octoxy, 4-decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-tr;hydroxy or 2'-hydroxy-4,4l-dimethoxy derivatives.
4. 1,3-(?'-Hydrox_benz_yl?-benzenes, for example 1,3-bis-~2'-hydroxy-4'-hexyloxy-benzoyl)-benzene, 1,3-bis-(2'-hydroxy-4'-octyloxy-benzoyl)-benzene and 1,3 bis-t2'-hydroxy-4'-do-decyloxy-benzoyl)-benzene.
5. Esters of substituted or unsubst;tuted benzoic acids~ for example 4-tert.-butyl-phenyl salicylate, phenyl salicylate, octylphenyl sal;cylate, d;benzoylresorcinol, bis-(4-tert.-butylbenzoyl)-resorcinol, benzoylresorcinol and 2,4-di-tert.-butyl-phenyl 3~5-di-tert.-butyl-4-hydroxybenzoate.
6. Acrylates, for example ethyl or isooctylC~-cyano-r~, ~di-phenylacrylate, methyl ~-carbomethoxy-cinnamate, me-thyl ~-cyano- ~ methoxy-p-methoxy-cinnamate and N-(~-carbomethoxy-~-cyanovinyl)-2-methyl-indoline.
7. Oxal;c acid _ am;des, for example 4,4~-di-octyloxy-oxanil-ide, 2,2'-di-octyloxy-5~5'-d;-tert.-butyl-oxanilide, 2,2'-di-dodecyloxy-5~5'-d;-tert.-butyl-oxanilide, 2~ethoxy Z'-ethyl-oxanil;de, N,N'-b;s-(3-dimethylaminopropyl)-oxalamide, 2-~; ethoxy-5-tert. butyl-Z'-ethyl-oxanilide, Z-ethoxy-2'-ethyl-5,4' di-tert.-butyl-oxanilide and mixtures of ortho- and para-methoxy and o- and p-ethoxy-disubstituted oxanilides.
Amongst the UV absorbers used according to the inven~
tion, those of classes 1, 3 and 7 are preferred, and in parti-cular those of class 1 (benzotriazoles). Such benzotriazoles are described, for example, in U.S. Patent Specifications 3,0û4,~96, 3,189,615, 3,320,194, 4,127,586 and ~,283,327.
The UV absorbers are added in a quantity of 0.1 to 5 % by weight, pre-ferably 0.5 to 2 J~ by weight, relative to the total of the radiation-curable compounds.
In a preferred embodiment of the invention, an organic compound of trivalent phosphorus is added to the radiation-curable mixtures. Examples of these are phosphites, phos-phonites and phosphines. Such compounds are known as co-stab;lisers for polymers. Examples of phosphites are tri-alkyl, triaryl and alkylated triaryl phosphites as well as mixed pl1osphites, such as trilauryl, triphenyl, phenyl di-~decyl), tris-(nonylphenyl) and tris-t2,4-di-tert.-butyl-phenyl) phosphites or pentaerythritol b;s-~octadecyl phos-ph;te). Examples of phosphonites are tetra-(2,4-cli-tert.-butylphenyl) diphenyl-~,4'~diphosphonite and di-(2,4-di-tert.-butylphenyl) phenylphosphonite. Examples of phosphines are especialLy tertiary phosphines, for example triphenyl-phosphine, tritolylphosphine or trilaurylphosphine. Prefer ably, phosphites are used.
These phosphorus compounds effect a stabil;sation of the cured coating to discolouration, in particular in the presence of UV absorbers, and to therrnal-oxidative ageing.
The quantity of the phosphorus compounds added is in general 0.1 to 5 æ by weightr relative to the total of the rad;at;on-curable compounds.
The radiation-curable m;xtures can contain further stabilisers, such as are conventional in coating technology.
Examples of these are antioxidants and metal deactivators.
The radiation-curable coatings can be applied to the most diverse substrates, for example to wood, metal, plastic, paper, glass or ceramic masses. The appl;cation can be carr;ed out continuously or d;scontinuously by the conventional ~3~316 methods of the technology, for example by brushing, spraying, dipp;ng or by electrostatic processes. Application in several layers is also possible.
Curing is effected by irradiation with electron beams, for which purpose the conventional types of equipment for the radiation curing of coatings are suitable. These operate predominantly in a continuous process, the object to be coated being transported through an irradiation chamber. At voltages of 100 to 400 KV and at about 10 to 10~ mA, curing of the coatings takes place in less than one second. P~eferably, the irradiation is carried out in an inert gas atmosphere.
In a variant of the curing process according to the invention, the coating composition is f;rst pre-cured by electron ;rrad;ation and then finally cured by ;rradiation with UV l;ght. In this case, a photoin;tiator, such as is known for the UV cur;ng of ethylenically unsaturated systems, is advan-tageously added to the composition to be cured.
Examples of such photoinitiators are benzophenone and ;ts derivatives, acetophenone derivat;ves and other aromat;c-al;phatic ketones, benzo;n and benzoin ethers, benzil and benzil ketals or acylphosph;ne oxides.
Such a two-stage process can be of advantage ;n spe-cial cases, for example ;f particularly rapid curing on the surface is important or ;f the electron irradiation is not carried out under an inert gas.
The fields of application of electron beam curing are wide-ranging, for example the coating of furniture, of vehi~le components or of machine components, coil coat;ng, the coat;ng of packaging material, ;n particular films, wire enamelling, the application of insulating layers for printed circuits or other electronic components, or the appl;cation of adhesives to films or other substrates.
The examples which follow illustrate the ;nvent;on ;n more detail. In the examples, parts are parts by weight and ~ are per cent by weight.
Example 1: A m;xture o~
.
parts of EbecrylR 584 tsolution of a polyester , acrylate in hexanediol diacrylate, manufacturer: UCs Belgium) parts of thinner QM 672 (dicyclopentadienyloxyethyl acrylate, manufacturer: Rohm ~ Haas Co., USA) 6.3 parts of Byk 300*tflow assistant based on a poly-siloxane~ manufacturer: Byk-Mallinckrodt, Federal Republic of Germany) and 1 part of the curing accelerator listed in Table 1, are homogenised in a high-speed stirrer. *Trade mark The clear mixture is applied by means of an applicator coil in a layer thickness oF 40 ~m to steel sheet coated beforehand with a primer and a metal-effect finish.
These samples are subjected in an electro-curtain apparatus from Messrs. Charm;lles, ~eneva, to electron beam cur;ng in an ;nert gas atmosphere (N2). The rad;at;on dose ;s 6 megarad. 24 hours af-ter the ;rrad;at;on, the Koenig pendulum hardness (DIN 53,157) is measured, wh;ch ;s a cr;-terior; of the degree of curing reached.
Table 1 Added curing acceleratorPendulum hardness (1 % relative to finish resin) ~seconds) none 129 - Di-(1,2,2,6,6-pentamethyl-piper;d;n-4 yl) sebacate l52 Di-(1-allyl-2,2,6,6-tetra-methyl-piper;d;n-4-yl) sebacate 150 2~4,b-Tris~ -butyl-1-allyl-2,2,6,6-tetramethylpiper;din-4-yl-amino)-1,3,5-triazine 151 (compound No. 64) This shows that the sterically hindered piperidine light stabilisers accelerate the curingO
Example 2: The procedure ;s as ;n Example 1. The following compounds are used as the additives according to the invention:

3~6 ~ I : di-(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate B II: 1,2,2,6,6-pentamethylpiperidin-4-yl) acrylate UV ~: UV absorber of the formula 0~ ~ (CH3)3 CH2cH2cOO-(cH2)8-cH=cH--(cH2)7cH3 P I : trilauryl phosphite The samples are electron beam-cured, as described in Example 1, with an irradiation dose of 6 megarad. The Koenig pendulum hardness of the cured samples is determ;ned~ The cured samples are also subjected for 300 hours to accelerated weathering in the QUV apparatus, and the gloss retention and crack formation are then determ;ned. The results are given ;n Table ~.
Table 2:
_ Accele- UV absorber Phosphorus Pendulum Gloss ~Crack rator compound hardness reten- form-(seconds tion ation _ ., _ . ~
~ ~ _ 129 26 extensive 1,0% B I _ _ 152 25 extensive _ 1,5~ VV I _ 88 72 none _ _ 005% P I105 20 extensive 1,0% U I 1,5% UV I _ 120 80 none _ 1,5% W I0~5%P I 40 75 none 1~0% B I 1D5% uv I 0,5% P I 120 78 none ¦ i,G~ B 1- ¦ l,5~ W I l4l ~ none ~3~

This shows tha~ both the UV absorber and the phos-phorus compound delay curing, whilst the piperidine light stabilisers accelerate curing. On the other hand, the UV
absorber leads to a substantial ;mprovement in the weathering resistance. I~hen all three components are cornbined~ the best weathering resistance is obtained, without having to accept a delay in curing.
Example 3: This example demonstrates the accelerating effect of a hindered am;ne ;n the presence of various UV absorbers.
A mixture of the following compos;tion was used:
39.7 parts of a polyester acrylate (EbecrylR 810, Messrs. UCB) 29 parts of a polyurethane acrylate tActylanR AJ 20, SNPE, France) parts of hexanediol diacrylate 9 parts of dicyclopentenyloxyethyl acrylate (QM 672, Messrs. Rohm ~ Haas, USA) 4.5 parts of trimethylolpropane triacrylate 2.5 parts of 2-ethylhexyl acrylate and 0.3 part of a flow assistant (BykR 300, Messrs. Byk-Mallinckrodt~ Federal Republic of ~ermany) The follow;ng additives were added to this m;xture, in the quantity indicated in Table 3:
B I di-(1,2,2,606-pentamethylpiperidin-4-yl) sebacate UV II :2-C2-hydroxy-3,5-di-(tert.-amyl)-phenyl~-benzotriazole UV III:2~ethoxy-4 -dodecyl-oxaldianilide UV IV :2-hydroxy-4-~Z~acryloyloxyethoxy)-benzophenone P II :tris-(2~4-di-tert.-butyl-phenyl) phosphite.
The samples are prepared as described in Example 1 and ;rradiated w;th a radiation dose of 5 megarad. The pen-dulum hardnesses (DIN 53,157) thus obtained for the coating film are indicated in Table 3:

~263~

Table 3 UV absorber Phosphite Accelerator Pendulum hardness (seconds) 3 % of UV II -- -- 45 2 % of UV II --1 % of B I 53 3 æ of UV II 0.5 % of P II -- 39 2 % of UV II 0.5 % of P II 1 % of B I 56 3 X of UV III -- -- 5?
2 % of UV III --1 % of B I 70 3 % of UV IV ~ 56 2 % of UV IV --1 % of B I 69 Example 4: The procedure ;s as ;n Example 1, but a m;xture of the following composit;on is used:
75.2 parts of a polyether acrylate (PlexR 6631, Messrs.
Rohm GmbH, Federal Republic of Germany) 24.0 parts of hexanediol diacrylate 0.5 part of a flow assistant based on silicones (BykR
300, Messrs. Byk-Mallinckrodt, Federal Republic of Germany) 0.3 part of a flow ass;stant based on silicones (Blister-freeR, Messrs. B. Schwegmann, Federal Republic of Germany~
The curing accelerator used is di-1,2,2,6,6-penta-methylpiper;din-4-yl sebacate (= B I) in quantities of 1 %
and 2 %, relative to the finish of the above composition.
The samples are ;rradiated with a radiation dose of 4 and 5 megarad. The results are listed in Table 4:

::

~63~

-- 37 ~
Tab le 4:

Curing accelerator Pendulum hardness according to DIN 53~157 (seconds) Radiation dose 4 Mrad 5 Mrad none 6088 1% of B I 92103 3X of B I 100128 Example 5: The procedure is as in Example 4, but a mixture of the follow;ng composition is used:
67.? parts of a polyether acrylate (PlexR 6673, Messrs.
Rohm GmbH) 32.0 parts of hexanediol diacrylate O.S part of a flow assistant based on silicones (BykR
300, Messrs. Byk-Mall;nckrodt, Federal Republic of Germany) 0.3 part of a flow ass;stant (Bl;sterfreeR, Messrs.
B. SchwegmannO Federal Republic of Germany) Table 5 ' AcceleratorPendulum hardness (seconds) at radiation dose of 10 Mrad 20 Mrad none 39 73 1 ~ of B I 66 112 3 ~ of B I 102 127 Example 6: The proçedure is as in Example 4, using the following mixture:
65.2 parts of an epoxide acrylate (SetaluxR UV Z280, Messrs~ Synthese B.V.~ Holland~
34.0 parts of hexanediol diacrylate 0.5 part of BykR 300 flow assistant 0.3 part of ~listerfreeR flow assistant ~2~;3~
- 3~ -Table 6 Accelerator Pendulum hardness (seconds) at radiation dose of 1 Mrad 1.5 Mrad none 65 81 1 % of B I 83 83 3 % of B I 87 106 Example 7: The procedure is as in Example 4~ using the foLlow-;ng mixture:
3942 parts of a polyacrylate resin (EbecrylR 754, Messrs.
UCB, Belgium) 56.0 parts of hexanediol diacrylate 0.5 part of BykR 300 flow assistant 0.3 part of BlisterfreeR flow assistant Table 7 Accelerator Pendulum hardness (seconds) at radiation dose of 5 Mrad 7.5 Mrad none 57 72 1 % of B I 60 76 3 XD of B I 84 83 Example 8: The procedure ;s as ;n Example 4~ us;ng the follow-;ng mixture:
49~Z parts of a polyurethane acrylate (ActylanR AJ, 18 MessrsO SNPE, France) 40uO parts of hexanediol diacrylate 10.0 parts of N vinylpyrrolidone 0.5 part of BykR 300 fLow ass;stant 0.3 part of Bl;sterfreeR flow ass;stant - 3~ -Table ~

Accelerator Pendulum hardness (seconds) at radiation dose of 0.75 Mrad 1 Mrad none 65 85 1 X of B I 90 9Z
3 % of B I 98 1 û8

Claims

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

1. A process for curing coating compositions, which contain ethylenlcally unsaturated compounds, by electron beam irradiation with the addition of a curing accelerator, which comprises using at least one compound from the class of sterically hindered amines as the curing accelerator, in which process in a first step the hindered amine is added to the coating material which is in a second step coated onto substrate and in a third step irradiated by electron beams.

2. A process according to claim 1, wherein the curing accelerator used is a 2,2,6,6-tetraalkylpiperidine derivative which, in its molecule, contains at least one group of the formula I
(I) in which R is hydrogen or methyl.

3. A process according to claim 2, wherein the curing accelerator used is a piperidine derivative which, in its molecule, contains at least one group of the formula I, in which X
is hydrogen and there is no hydrogen on the ring nitrogen.

4. A process according to claim 1, wherein the curable coating composition contains a light stabilizer from the class of UV absorbers.

5. A process according to claim 4, wherein the curable coating composition contains a light stabilizer from the class of 2-(2'-hydroxyphenyl)-benzotriazoles.

6. A process according to claim 1, wherein the curable coating composition contains an organic phosphite.

7. A process according to claim 1, wherein the curable coating composition is applied as an automotive finish or a coil coating finish or a film finish or a wire enamel.

8. A process according to claim 1, wherein the coating composition is a constituent of a multi-coat finish.

9. A process according to claim 1, which is followed by an irradiation with UV light and wherein a photoinitiator is added to the coating composition.

10. A process according to claim 1 for curing coating compositions which do not contain any N-vinylpyrrolidone.