Accelerator compositions for the free radical polymerization of unsaturated polyesters and for the curing of unsaturated polyesters and polyurethanes are disclosed. More particularly, use is made of complexes of thiolic compounds with metal salts as the accelerators. In more preferred embodiments, the accelerators also include oxygen-containing compounds or phosphorus-containing compounds. Also disclosed are curable resin compositions comprising these accelerators and polymerization and curing processes employing these accelerators.

The present invention relates to thiol group-containing compositions useful 
as accelerators for the curing of unsaturated maleic, vinylic, allylic and 
epoxy-type polyester resins, epoxy resins and polyurethanes, as well as 
the polymerization of these materials. More particularly, the thiol 
group-containing materials are employed in the form of a complex with 
selected metal salts as accelerators for curing unsaturated polyester 
resins, epoxy resins and polyurethanes. 
Thiol compounds are known for use in curing unsaturated polyesters. For 
example, in U.S. Pat. No. 3,318,974 it is disclosed to cure unsaturated 
polyesters with peroxides in the presence of thioglycolic acid 
accelerators. 
Japanese patent application JA-7039468 discloses the curing of polyesters 
with a peroxytriazine in the presence of a mercaptan accelerator. As an 
example of the accelerator is given t-dodecylmercaptan. Japanese patent 
application J6-2257936 discloses the use of a polythiol compound such as 
pentaerythritol tetrathioglycolate for the curing of epoxy resins. 
U.S. Pat. No. 3,291,716 describes the use of a wide variety of --SH 
group-containing compounds for the curing of epoxide resins. More 
particularly, polymercaptans having at least two --SH groups are disclosed 
including monomeric polymercaptans, polymeric-type polymercaptans, 
polythiopolymercaptans and even organic sulfides. U.S. Pat. No. 3,214,490 
discloses the acceleration of the hydroperoxide initiated polymerization 
of ethylenically unsaturated materials with an organotin mercaptoester 
and, optionally, cobalt naphthenate in conjunction therewith. 
European patent application 0 329 093 discloses the use of polythiols as 
epoxy resin curing agents. These polythiols are obtained by the reaction 
of a polyglycidyl amine with hydrogen sulfide and are said to be useful as 
curing agents in the absence of a tertiary amine. 
Other thiol-containing materials disclosed in the prior art include the use 
of a poly-thiol such as glycerine tris(mercaptoacetate), glycerin 
tris(mercaptopropionate) and glycerine tris(mercaptobutylate), in the 
presence of an amine for the curing of epoxy resins which is described in 
Japanese patent application J6-3186727; thiol-diene adducts for epoxy 
resin curing described in U.S. Pat. No. 3,838,494; propoxylated ether 
polythiols for curing epoxy resins described in U.S. Pat. No. 4,092,293; 
and butyl thiostannic acid anhydride in combination with nadic methyl 
anhydride are known for epoxy curing from U.S. Pat. No. 4,120,875. 
A combination of a 2-mercaptoalcohol and a cobalt or vanadium compound are 
known for use in the curing of unsaturated polyester compounds from 
British patent 1,170,983. Typically this curing is carried out in the 
presence of a peroxide and a copolymerizable monomer. 
The hardening of polyesters with a vanadium compound and a polyol 
thioglycolate ester as accelerators is disclosed in Belgian patent 
767,644. Again, the hardening is carried out in the presence of a 
copolymerizable monomer. 
U.S. Pat. No. 4,380,605 discloses the use of mercaptobenzothiazole with an 
inorganic metal salt and a peroxyester initiators for the room temperature 
cross-linking of unsaturated polyester resin. The inorganic metal salt is 
selected from iron and copper salts and mixtures thereof. 
Also known as epoxy resin hardeners are triphenyl phosphine and triphenyl 
phosphite which are disclosed in Japanese patent applications J6-4001721, 
J6-2212418 and J5-7040524. In addition, Japanese patent application 
J5-9126430 discloses the use of quaternary phosphonium salts in 
combination with mercaptobenzothiazole for the hardening of epoxy resin 
compositions. 
European patent application 0 160 621 discloses the use of a combination of 
a polymercaptan and an organic phosphite for the hardening of an epoxy 
resin in the presence of a radically polymerizable compound and an organic 
peroxide. The mercaptan is preferably an ester of a mercaptocarboxylic 
acid with a 2 to 6 carbon polyol, a phenol or a novolac. 
Finally, Japanese patent application JO-1174518 discloses the reaction of 
an epoxy resin and a carboxylic acid anhydride in the presence of 
triphenylphosphine in combination with lithium chloride as a catalyst, 
among other listed catalyst materials. This epoxy resin is employed as a 
binder for an electrostatic toner for developing electrocharged images. 
In the field of curing accelerators/catalysts there exist very specialized 
requirements for each and every curing system. Thus, there remains a need 
for the development of new combinations of curing accelerators which 
exhibit specific advantageous properties and provide the ability to more 
completely control the parameters of the cure procedure. The present 
invention has for one of its objects to meet these demands. 
SUMMARY 
For the free-radical polymerization, in the presence of per-compounds, of 
unsaturated maleic and allylic polyesters, and in the polymerization of 
epoxy resins, use is made of thiolic compounds, and more preferably 
thiolic compounds carrying at least two SH-functions. 
In a further aspect of the invention, for the curing of epoxy resins and 
unsaturated resins--polyurethanes, polyesters, maleics, allylics, 
vinylics--activated or inhibited thiols are employed. Lastly, phosphines 
and/or phosphites may be employed to further enhance the activity of the 
thiol accelerators. 
DETAILED DESCRIPTION OF THE INVENTION 
According to a first aspect, the invention has its subject the utilization 
of a metal chosen from the group constituted of lithium, manganese, 
aluminium, magnesium, zinc and tin, for the curing of a resin or 
prepolymer chosen from the group consisting of the unsaturated, maleic, 
vinylic, allylic and epoxy-type polyester resins, epoxy resins and 
polyurethanes in the presence of a thiolic compound. 
The metal salt is able to form a complex with the thiolic compound. 
Consequently the scope of the invention includes a composition comprising 
a complex of a thiol, or its adduct, with a salt of a metal chosen from 
the above-mentioned group. 
The complexes of the above-mentioned metals can be utilized as accelerators 
in combination with conventional initiators of peroxide type, in processes 
of curing of unsaturated polyesters, epoxy resins and polyurethanes, as 
well as for enhancing the free radical polymerization reaction of 
unsaturated polyester resins and epoxy resins. Such complexes can 
furthermore be employed along with known conventional accelerators and 
peroxidic initiators. 
The salt employed for formation of the complex is preferably a halide, 
nitrate or acetate. Chlorides are especially preferred. 
According to the invention, the thiols employed in the formation of the 
accelerators are preferably compounds carrying at least two --SH functions 
and having advantageously a molecular weight greater than 400. By way of 
examples, the following compounds can be advantageously employed: 
dithiols such as: dipentene dimercaptan, ethylcyclohexyl dimercaptan, 
ethylene-1,2-bis-3-mercaptoacetate or propionate; 
trithiols such as: 1,2,3-propanetrithiol, 1,2,6-hexanetrithiol; 
tetrathiols such as: pentaerythritothiol, pentaerythritol 
tetramercaptoacetate or propionate; and 
polythiols such as thioesters of polyalcohols and sugars, and polythiol 
compounds of formula R--(R--COH--CH.sub.2 --SH).sub.n in which R is 
C.sub.3 -C.sub.30 alkyl and n is an integer from 2 to 6. 
Also suitable are adducts of di-, tri-, tetra- and polythiols with epoxides 
or anhydrides. By way of example, the adducts can be obtained by means of 
addition reactions between a polythiol and an anhydride chosen from among 
maleic, hexahydrophthalic, tetrahydrophthalic, methyltetrahydrophthalic, 
methylnadic (methyl endomethylenetetrahydrophthalic), succinic, 
dodecylsuccinic, pyromellitic, and chlorendic anhydrides. 
Useful epoxide compounds for the preparation of an adduct with the thiol, 
include alkyl (C.sub.3-18) diglycidyl ethers, polypropylenoxydiglycidyl 
ethers, polytetramethylenoxydiglycidyl ethers, butylglycidylether, 
2-ethyleneglycidylether, alkylglycidylether, phenylglycidylether, 
o-cresylglycidylether, p-tertiary butylphenyl glycidylether, 
glyceroldiglycidyl ether, hexanedioldiglycidyl ether, glycyldiglycidyl 
ethers, neopentenediglycidyl ether, Bisphenol-A diglycidyl ether, 
Bisphenol-F diglycidyl ether, and cycloaliphatic epoxides such as 
vinylcyclohexenediepoxide and cycloaliphatic epoxides of formula I: 
##STR1## 
in which R is chosen among alkylene, oxygen, --O--R.sub.3 --O, 
--O--CO--R.sub.3 --CO--O; R.sub.3 being alkylene; R.sub.1 is hydrogen or 
methyl; R.sub.2 is hydrogen or =0. 
In the procedure for the curing of the abovementioned resins, which is a 
further subject of the invention, the metal complex compound acting as the 
a-accelerator is typically employed in such a way as to furnish an amount 
of metal, expressed as the corresponding chloride, which comprises between 
20 and 400 ppm on the basis of the weight of the resin. 
More specifically the preferred concentrations are as follows: 
LiCl, from 20 to 100 ppm on the basis of the resin weight, 
AlCl.sub.3, from 20 to 150 ppm on the basis of the resin weight, 
MgCl.sub.2, from 40 to 250 ppm on the basis of the resin weight, 
ZnCl.sub.2, from 60 to 350 ppm on the basis of the resin weight, and 
SnCl.sub.4, from 70 to 400 ppm on the basis of the resin weight. 
It has been established that lithium chloride is particularly active. Zinc 
chloride, although exhibiting in itself an accelerating effect, can 
advantageously be used to slow down the accelerating effect of lithium 
chloride when used in combination therewith. Hence the scope of the 
invention includes the use of a combination of one or more of the salts, 
preferably the chlorides, with the thiolic compounds. 
In the procedure of curing, the accelerators that are the subject of the 
invention can be employed in the presence of conventional quantities of 
peroxidic initiators which comprise between 0.02 and 5 weight ? -. based 
on the resin. The accelerators permit the reduction, by a substantial 
extent, the quantity of the peroxides down to values of between 0.02 and 
0.7 weight ? ,. ,if desired. Standard peroxide initiators known for use 
with these resins, may be employed. Thus the procedure of curing for 
obtaining a cross-linked polymer, comprises the addition, to the resin or 
prepolymer, of a peroxidic initiator and the accelerator. The accelerator 
can be made of a thiol of the above-specified type, being at least in part 
present in the form of a coordination compound with a salt, preferably a 
chloride, of the above-specified metals and, optionally, one or more 
conventional accelerators. 
Another aspect of the invention is, therefore, a curable mixture comprising 
a resin or prepolymer chosen from among the group of unsaturated maleic, 
vinylic, allylic and epoxy-type polyester resins, epoxy resins and 
polyurethanes, possibly an ethylenically unsaturated reactive monomer, and 
an accelerator consisting at least in part of a complex as previously 
described. The ethylenically unsaturated reactive monomer may be selected 
from the group consisting of styrene derivatives such as .alpha.-methyl 
styrene, indene, divinyl benzene, stilbene, di benzal actone, propenyl 
benzene, isopropanyl benzene, triallyl cyanurate, triallyl isocyanurate 
and mixtures thereof. 
The present invention also relates to processes for the curing, by means of 
radical or ionic-radical catalysis, of unsaturated, maleic, vinylic and 
allylic polyester resins, epoxy resins and polyurethanes and to the 
polymerization of unsaturated polyester resins and epoxy resins, and 
provides compounds that are useful as cocatalysts or accelerators in the 
process of polymerization. 
A further object of the invention is, therefore, the use of thiolic 
compounds chosen from the group that consists of dipentene dimercaptan, 
ethylcyclohexyl dimercaptan, ethylene-1,2-bis-3-mercaptoacetate and 
-propionate, 1,2,3-propanetrithiol, 1,2,6-hexanetrithiol, 
pentaerythritothiol, pentaerythritol tetramercaptoacetate, and 
-propionate, thioesters of polyalcohols and sugars, and thiolic 
derivatives of formula: 
##STR2## 
in which R is linear or branched alkyl I of 3 to 30 carbon atoms, while n 
is an integer from 2 to 6; and their adducts with mono-epoxides and 
anhydrides, in the polymerization of resins chosen from the group that 
consists of unsaturated, maleic, vinylic, allylic and epoxy-type 
polyesters and epoxy resins. 
Tests have demonstrated that by using a cocatalyst selected from the 
abovementioned group, it is possible to obtain substantial advantages, in 
particular: 
a low degree of liberation of styrene or other reactive solvents in the 
polymerization of unsaturated polyester resins; 
a low degree of shrinkage; 
the possibility for conducting the polymerization reaction while 
maintaining the resin at almost ambient temperature, generally between 
25.degree. and 40.degree. C., which allows one to embed in the resin, 
thermo-sensitive and delicate items, especially electronic devices or 
objects of natural history; 
a high yield of polymerization; and 
interesting qualities of the polymerized resin, which is generally 
transparent, colourless, resistant to ageing, and mechanically rugged. 
A further advantage resides in the low levels of toxicity of these 
compounds. 
The thiolic compounds can be employed in the process of crosslinking or 
curing of the resins not only in combination with conventional peroxidic 
initiators but also with other peroxides and per-compounds such as 
carbonates, persulphates, perborates and per-salts, and moreover with 
oxidants whether organic or inorganic, such as salts of metals of more 
than one oxidation state. Typically the thiolic compound is added to the 
resin in 0.1 to 2.0 weight % based on the resin when used with resins 
other than epoxy resins and from 15-150 weight percent based on the resin 
when employed to cure epoxy resins. 
In the curing process of the present invention, one begins with the resin 
composition. To this there may optionally be added an ethylenically 
unsaturated reactive monomer. The accelerator composition may be added in 
several different manners. For example, the accelerator composition may be 
premixed to form the metal salt complex prior to it being added to the 
resin composition. Another possibility is to add the individual components 
of the accelerator composition to the resin and form the metal complex in 
situ. which of these methods is preferred will depend on the specific 
curing process being carried out. 
Other additives, such as the peroxide initiator, or other accelerator 
enhancing materials may be added directly to the resin without first 
mixing them with the accelerator composition. However, in some cases it 
may be desirable to premix the accelerator enhancing materials with one or 
more of the accelerator components prior to introduction to the resin 
composition. 
The temperature at which curing or polymerization is carried out can range 
from room temperature up to at least 250.degree. C. The curing temperature 
wi 1 1 depend on the polyester being cured, the peroxide initiator and the 
particular curing accelerator that is employed. 
The thiolic compounds of formula 
##STR3## 
can be obtained by a reaction of the corresponding epoxy compound, of 
formula 
##STR4## 
with thiols, thio compounds like urea or thiocyanates, hydrogen sulphide, 
and metal mercaptides. 
The thiolic compounds may be advantageously employed in the form of adducts 
with anhydrides or epoxides. The choice of adduct allows one to improve 
the activity of the cocatalyst and to obtain compounds which are more 
compatible with the resin, especially with regard to solubility. Also, the 
thus obtained cocatalysts are better manageable and less toxic, smelly and 
volatile. Furthermore the resin polymerized in the presence of an adduct, 
has better properties in terms of transparency and better mechanical 
properties. 
Examples of anhydrides suited to form an adduct, include maleic, 
hexahydrophthalic, methylhexahydrophthalic, tetrahydrophthalic, 
methyltetrahydrophthalic, methylendo(m)ethylenetetrahydrophthalic 
(methylnadic), succinic, dodecylsuccinic, pyromellitic and chlorendic. It 
is thought that the carboxyl group of the anhydride present in the adduct, 
plays an important part in the polymerization in the sense that it acts as 
an accelerator to the thiol, once it is bound to it. 
As mono-epoxides, or monoglycidylethers, use is advantageously made of 
compounds selected from among C.sub.3 -C.sub.18 alkyldiglycidyl ethers, 
polypropylenoxydiglycidyl ethers, polytetramethylenoxydiglycidyl ethers, 
glycerindiglycidyl ether, hexanediol glycidyl ether, glycoldiglycidyl 
pentene diglycidyl ether, Bisphenol-A diglycidyl ether, Bisphenol-F 
diglycidyl ether, butylglycidyl ether, diethyleneglycidyl ether, 
alkylglycidyl ether, phenylglycidyl ether, o-cresylglycidyl ether, 
p-tert.butyl phenyl glycidyl ether, and cycloaliphatic epoxides, more in 
particular compounds of formula: 
##STR5## 
in which R is chosen from alklene, oxygen, --O--R.sub.3 --O--, 
##STR6## 
in which R.sub.3 is alkylene; R.sub.1 is hydrogen or methyl; R.sub.2 is 
hydrogen or oxygen. A further example of a cycloaliphatic epoxide is 
vinylcyclohexenediepoxide. When making such adducts it is preferably to 
employ from 0.25-2.0 moles of anhydride or epoxide per --SH group. More 
preferably is 0.75-1.25 moles of anhydride or epoxide per --SH group. 
The present invention refers in general terms to processes of curing, by 
means of radical or ionic-radical catalysis, of epoxy resins and of 
unsaturated resins: polyesters, polyurethanes, maleics, allylics, 
vinylics; and furnishes products and systems that are particularly 
effective for the curing of the said resins. A specific purpose of the 
present invention is the complete control of the parameters of the curing 
of such resins; such as: time of gelation, time of hardening, exothermal 
peak; and to amplify the types of cocatalyst utilizable in association 
with the thiol, or to enable the application of UV, X and Gamma 
radiations, or the application solely of thermal treatments. 
Hence another object of the invention is the employment of thiols having 
within their molecule the following groups that activate the R--SH group; 
that is to say, 
##STR7## 
resulting in thiols "activated" inside their molecule, of structure: 
##STR8## 
where n is an integer from 1 to 6, and R, R' and R" are organic radicals 
which do not significantly hinder the accelerative activity of the --SH 
group. More particularly, R, R' and R" are aliphatic, aromatic, cyclic 
hydrocarbons which may be substituted or unsubstituted. Preferably, at 
least one of R and R is an electron-repelling group. 
Such products are obtained by esterification of an organic acid or polyacid 
with an alcohal substituted with an "SH "group (a nonexhaustive list of 
examples includes all di- or polybasic organic acids (examples include 
tartaric, malic, citric, oxalic, malonic, succinic, adipic, maleic, 
fumaric, benzenetricarboxylic acid, pyromellitic acid, formic acid)); a 
non-exhaustive list of thioalcohols includes 2-mercaptoethanol, 
2-mercaptopropanol, 3-mercaptopropanol, mercaptoterti-arybutanol, and 
mercaptomethanol. 
##STR9## 
where n is an integer from 1 to 6, and R, R' and R" are as stated above. 
Such products are obtained by esterification of an alcohol, polyalcohol, 
saccharide or polysaccharide with an acid substituted with an "SH" group. 
A (non-exhaustive list of polyalcohols includes glycols, 
1,2,3-propanetriol, 1,2,6-hexanetriol, pentaerythritol, erythritol, 
hexa-alcohols such as sorbitol, mannitol, and inositol, sugars such as 
glucose, fructose, and saccharose, polysaccharides (non-exhaustive list 
includes cellulose, starch, inulin, pentosans) . Other alcohols include 
fatty alcohols, benzyl alcohol, 2-ethylhexylalcohol or methanol , ethanol, 
propanol and butanol. 
Non-limitative examples of mercaptoacids are 2-mercaptoacetic acid, 
2-mercaptopropionic acid, 3-mercaptopropionic acid, mercaptotertbutyric 
acids and mercaptoformic acid. 
##STR10## 
which result in intramolecularly "activated" thiols of structure: 
##STR11## 
wherein n is an integer from 1 to 6 and R, R' and R" are as stated above, 
and which are obtained by opening-up of an aliphatic or cyclic organic 
anhydride. A non-exhaustive list of anhydrides includes succinic, 
dodecylsuccinic, maleic, hexahydrophthalic, methylhexahydrophthalic, 
tetrahydrophthalic, methyltetrahydrophthalic, 
methylendome-thylenetetrahydrophthalic (i.e. methylnadic), phthalic, 
chlorendic, pyromellitic; and a non-exhaustive list of thiols includes 
dipentenedimercaptan, ethylcyclohexyldimercaptan, all other dimercaptans, 
trimercaptans (e.g. 1,2,3-propanetrithiol, 1,2,6-hexanetrithiol), 
tetramercaptans (e.g. pentaerythritothiol), pentamercaptans, 
hexamercaptans (e.g. sorbitol, mannitol or sugars substituted with SH). 3) 
It is possible to effectively combine among them, the structures of 
sections 1)A) and B) on the one hand, with the structures of section 2) on 
the other hand, yielding by way of non-limitative examples: 
##STR12## 
where n is an integer from 1 to 6, N is an integer from 1 to 10 and R, R' 
and R" are as stated above. 
##STR13## 
The tertiary mercaptans, especially if group R' and/or R" is an "electron 
repulsor" e.g. --CH.sub.3, are capable of being activated even by 
"dibenzoylperoxide" in the cold; examples: 
##STR14## 
5) It is possible to effectively combine among them, the structures of 
sections 1 )A) , 1) B) and 2) on the one hand , with those of section 4) 
on the other hand, e.g.: 
##STR15## 
where n and N are integers from 1 to 6 and R, R' and R" are as stated 
above. 
The following compounds are external activators of the thiol molecule, in 
the curing of the aforespecified resins: 
1) all compounds that possess the following groups: 
A) R--S--R.sub.1 
especially if the --S--S-- group is close to "electron-repulsing" groups 
(e.g. ditertiarybutyl sulphide), wherein R and R.sub.1 are organic 
radicals, 
B) R--S--S--R.sub.1 
especially if the --S--S-- group is close to "electron-repulsor" groups 
(e.g. ditertiarybutyl disulphide), wherein R and R.sub.1 are organic 
radicals, and 
C) Some Cyclic Sulphides, as Also Sulpholane, Sulpholene, and Their 
Substitution Products 
These activators are employed in a quantity of 0.1-0.5% by weight, based on 
the weight of the resin. 
2) Some compounds capable of existing in enol or keto form: 
1) Vitamin C or ascorbic acid and its esters (e.g. ascorbyl acetate) 
2) esters of acetoacetic acid including methyl acetoacetonate, ethyl 
acetoacetonate, vinyl acetoacetonate, and allylic acetoacetonate; 
acetylacetone, benzoylacetone, dibenzoylmethane --diacetyl, glyoxal. 
3) The following salts: 
LiCl, 
AlCl.sub.3.6H.sub.2 O, 
AlCl.sub.3, 
MgCl.sub.2 and other salts of metals having a +3 or +4 oxidation state. 
These materials are employed in quantities of 0.1 to 2 weight percent based 
on the weight of the resin. 
Compounds are inhibitors of thiols during the curing of the afore-specified 
resins, include: 
the following organic compound: 
thiourea in an amount of 0.5 to 3.0 weight percent; 
and the following salts: 
ZnCl.sub.2 in an amount of 0.01 to 0.1 weight percent; 
and potassium salts--in particular K-ethylhexanoate in an amount of 0.1 to 
3 weight percent; all weight percentages being based on the weight of the 
resin. 
Tests, have shown that with polymerization cocatalysts chosen from the 
group of the afore-enumerated substances, it is possible to attain 
substantial advantages, in particular: 
complete control of: 
time of gelation 
time of hardening 
exothermal peak 
stability of mixture of thiolic activator with resin to be cured; 
the possibility of utilizing in the cold, as initiators for the curing of 
the aforementioned resins, almost all types of organic peroxides 
(including percarbonates and -dibenzoylperoxide), oxygenated water, 
per-salts, and many oxidant compounds and acids. Likewise, the possibility 
of employing, for the cold-curing of such resins, radiation in the UV, X 
or Gamma spectral region; and likewise the possibility of occasionally 
employing, for the curing of such resins, the thiolic products alone, at 
an elevated temperature between 40.degree. and 100.degree. C. 
Further advantages include only a slight release of styrene or other 
reactive solvents in polymerization of unsaturated polyester resins; 
slight dimensional shrinkage; the possibility of conducting the 
polymerization reaction while keeping the resin at almost ambient 
temperature, generally comprised between 25.degree. and 40.degree. C., 
allowing to embed into the resin heat-sensitive and delicate -objects such 
as electronic devices or objects of natural history; a high yield of 
polymerization; and the ability to obtain interesting qualities of the 
thus obtained polymerized resin which is generally transparent, 
colourless, resistant to ageing, and endowed with a high mechanical 
stability. A further advantage is in the low levels of toxicity of these 
compounds. 
The scope of this aspect of the invention includes a curable composition 
comprising a resin or a prepolymer chosen from the group that consists of 
epoxy resins and unsaturated resins--polyesters, polyurethanes, maleics, 
allylics and vinylics--, and a thiolic compound or its adduct. The scope 
of the invention furthermore includes a procedure for the curing of the 
above-cited resins, whether or not with the further addition of 
activators, or of retardants. 
The thiolic compounds and their adducts can be marketed in the form of the 
separate additive destined to be added to the resin at the moment of 
cross-linking, or they can be preadded to the resin and marketed in the 
form of compositions of resin plus thiolic compound. 
The invention also includes a curable composition comprising a resin or a 
prepolymer and a thiolic compound or its adduct. The scope of the 
invention also includes a procedure for the curing of the abovespecified 
resins comprising the addition, to the resin, of an accelerator or 
cocatalyst as specified above. 
Also utilizable within the scope of the invention, are complexes 
constituted of a metal salt, a thiol or its adduct, and a second organic 
compound which is an oxygenated one. In this case, the salts of lithium, 
magnesium and manganese have proved particularly active. 
Thus a further subject of the invention is the utilization of a salt of a 
metal selected from lithium, magnesium and manganese as the accelerator 
for the curing of a resin or prepolymer in the presence of a thiolic 
compound and an oxygenated organic compound carrying aldehyde, ketone, 
ether, ester or alcohol groups. In this case again, it is implied that the 
salt is able to form a complex with the thiol and the oxygenated compound. 
The preferred amount of oxygenated compound to be employed in the curing 
process is from 0.002-0.3% by weight, based on the weight of the resin. 
More preferably, the diethylene glycol is employed in the range of 0.01 to 
0.2% by weight and, when using ascorbic palmitate, 0.02 to 0.1% by weight 
is used. 
In particular, the following can be employed as the oxygenated compound: 
keto- and aldo-esters and ethers or alcohols, in particular 
methylacetoacetate, ethylacetoacetate, mono- and diesters of ketoglutaric 
acid, pyruvates, sugars such as glucose and fructose; and esters of 
ascorbic acid such as ascorbic palmitate; 
1,3-diketones and aldehydes, in particular acetyl-acetone, benzoylacetone, 
dibenzoylmethane; 
mono- and diesters more in particular diethylmalonate and succinates; 
1,2-diketones, in particular diacetyl and glyoxal 
certain polyalcohols and other alcohols such as diethyleneglycol, benzyl 
alcohol and alcohols of the fatty series. 
The thiols to be considered, are the same as those listed previously. 
In a further aspect of the present invention, organic phosphites and 
phosphines are employed, optionally, in the presence of lithuim chloride, 
to enhance the accelerating effect of the thiol accelerators. The 
substantial advantages that result are the following: 
the duration of the polymerization is considerably abbreviated, 
the reaction conditions become much milder; e.g., the temperatures are much 
lowered, enabling operation even below ambient temperature with a 
sufficient speed of reaction, 
an elevated yield of polymerization, 
better resistance to ageing (radiation, heat), 
a very good colour (absence of colour can also be realized), and 
a contribution to the flame-retardant and heat-resistant properties. 
Although mono- and diphosphites and -phosphines have an effect, the 
especially active and most preferred ones are the organic triphosphites 
and triphosphines, whether aliphatic, cycloaliphatic, heterocyclic, 
aromatic, or mixed. The type of substituent in the phosphite or phosphine 
influences the compatibility with the type of resin, and has a certain 
influence on the reactivity. More particularly, trisubstituted organic 
phosphites and phosphines are preferred. Among the most preferred 
materials are triphenylphosphine and triphenylphosphite. 
The phosphine or phosphite is generally employed in an amount sufficient to 
enhance the activity of the thiol accelerator. More particularly, from 
0.1-10.0 weight percent phosphine or phosphite is employed, and more 
preferably 0.2-4.0 weight percent, based on the weight of the resin. The 
use of the organic phosphites and phosphines is primarily for the curing 
of epoxy-type resins. 
In addition, to avoid undesirable side reactions, it is often necessary to 
employ a small quantity of a lithium salt in combination with the 
phosphine or phosphite. For this purpose, lithium chloride is the most 
preferred material. Enough lithium chloride is employed to reduce the 
undesirable side reactions. More particularly, 0.02 to 1 weight percent of 
lithium is employed, based on the weight of the resin. 
The organic phosphites and phosphines may themselves be further activated 
by the presence of an effective amount of sulphide materials to activate 
the organic phosphites and phosphines. If this is done then the curing 
step is carried out in the presence of a small amount of one or more of 
these sulphides. Such sulphide activators include ditertiary butyl 
sulphide, ditertiary butyl disulphide, sulpholane, sulpholene, substituted 
sulpholanes and substituted sulpholenes.

The invention is further illustrated by the following examples. 
A) Tests Relating to the Application of Accelerators Consisting of 
Complexes of Thiols with Metal Salts 
EXAMPLE 1 
This test was performed using a thiolic compound obtained by means of a 
reaction of addition between pentaerythritoltetramercaptoacetate and 
maleic anhydride, the adduct having been obtained from the reagents by a 
reaction at 80.degree. C. for 1 hour with fall-back. 
To 100 g of a commercially available unsaturated polyester resin --DSM NX 
170--were added 0.5 g of the thus obtained adduct and 0.2 g of a 10% 
ethanolic solution of aluminum chloride. To the mixture was added 2% by 
weight, of a peroxidic initiator in the form of 50% methyl ethyl ketone 
peroxide and 50% or acetylacetone peroxide. 
The curing tests were carried out in a bath at 25.degree. C. The 
crosslinking of the resin was followed with recording of the time of 
gelation (tg), the time for arriving at the exothermal peak (tpe), and the 
temperature of the exothermic peak (tpe). The yields of poly-merization 
were measured by means of DSC. The results pertaining to this test have 
been collected in Table I. 
EXAMPLES 2-8 
The test of example 1 was repeated with the same thiol adduct, unsaturated 
polyester resin and various peroxidic initiators, and using variously the 
chlorides of aluminium, lithium, magnesium and zinc, and varying the 
concentration of salt and the quantity of initiator. The results have been 
summarized in Table I. In all cases the polymerization yields achieved 
were in excess of 95%, attaining values close to 99%, as measured by means 
of DSC. 
In particular with the use of the accelerators according to the invention, 
the obtained advantages reside in the rapidity of the cross-linking, in 
the high yield of cross-linking, and in the very low volatilization of the 
reactive solvent--styrene in this specific case. Moreover the possibility 
has been created for a reduction of the conventional amount of peroxidic 
initiator, whose application is generally undesirable from the point of 
view of workplace environment. Also, colourless and transparent resins are 
obtained. 
EXAMPLES 9-14 
A thiol complex, of lithium chloride with 
pentaerythritol-4-mercaptoacetate, was employed for the curing of an epoxy 
resin--Araldit Y 64631. The tests were carried out using 100 g of the 
resin and working in the cold, in a bath at 25.degree. C. The tests were 
done using either the thiol complex alone, or in combination with curing 
agents for epoxy resins such as methylhexahydrophthalic anhydride, 
dimethylbenzylamine (DMBA) and isophorone diamine. Examples 11 and 12 are 
examples for comparison, effectuated in the absence of lithium chloride. 
The employed amounts of curing agents, and the results concerning the time 
of polymerization and temperature of exothermal peak, are reported in 
Table II. Essentially analogous results were obtained employing aluminum 
chloride instead of lithium chloride. 
B) Complexes of Thiol and Oxygenated Compound with Metal Salt 
EXAMPLE 15 
Preparation of Accelerator (Called Alpha-Accelerator in the Following) 
The accelerator was prepared by dissolving 2 g of lithium chloride in 18 g 
diethyleneglycol, and adding 25 g of acetylacetone and 12 g of a thiol 
adduct obtained by the addition reaction between methylnadic anhydride and 
pentaerythritoltetramercaptopropionate, in a mixed solvent of 8 g 
dimethylsulphoxide and 10 g tetrahydrofuran. The thus obtained accelerator 
possesses a very low toxicity, and the polymerization tests relative to 
its application yielded colourless transparent polymerization products. 
EXAMPLE 16 
The accelerator obtained in example 15 was modified by the further addition 
of 2 g of manganese acetate. This accelerator, containing the manganese 
salt in addition to the lithium salt, presented an enhanced effect of 
gelation. Analogous accelerators can be obtained by using not the acetate 
but the lactate, chloride or ethyl -hexanoate of manganese (bivalent). 
EXAMPLES 17-22 
Effective accelerators were obtained according to the procedure of example 
15 but using as the thiol a-ny one of the following: 
adduct of maleic anhydride with pentaerythritoltetramercaptoacetate; 
adduct of 1,2,3-propanetrithiol with propane diglycidyl ether; 
adduct of pentaerythritol-tetramercaptoacetate with butane diglycidyl 
ether; 
adduct of 1,2,3-propanetrithiol with glycerylglycidyl ether; and 
adduct of 1,2,3-propanetrithiol with Bisphenol-A glycidyl ether; 
adduct of dipentenedimercaptan with butanediglycidylether and 
pentaerythritoltetramercaptoacetate. 
EXAMPLES 23-29 
The alpha-accelerator obtained according to example 15, and the accelerator 
obtained according to example 16, were employed in tests of polymerization 
of the commercially available polyester resins DSM 530, DSM 170 and 
Alusuisse 5026. Samples of 100 g size were taken and were processed in a 
thermostat bath of 25.degree. C. The results of the polymerizations are 
reported in Table III. The polymerization tests have yielded satisfactory 
results even in the absence of conventional peroxidic initiators. The 
optimal quantities of peroxidic initiator proved to range from 0.02 to 
0.2%. All obtained samples were colourless and transparent, and none 
liberated styrene during cross-linking. After the cross-linking they did 
not smell of styrene, and showed high mechanical resistances. The yield of 
the polymerization after 10 hours, with 2% of added peroxidic initiator, 
is about 95%, while it is about 85% when the extent of added peroxidic 
initiator equals 0.02%, in which latter case it can be raised to 98% by 
post-curing for 2-4 hours at 50.degree. -80.degree. C. 
EXAMPLES 30-36 
Polymerization tests were effectuated using the following thiolic 
compounds, obtained by reactions of addition between thiol and epoxide or 
anhydride at 80.degree. C. for 1 hour with fall-back: 
Compound 30: adduct of pentaerythritoltetramercaptopropionate and 
methylnadic anhydride; 
Compound 31: adduct of -pentaerythritol tetramercaptoacetate and maleic 
anhydride; 
Compound 32: adduct of 1,2,3-propanetrithiol and C.sub.3 -C.sub.18 
-alkyldiglycidylether; 
Compound 33: adduct of pentaerythritoltetramercaptoacetate and 
dipentenedimercaptan with C.sub.3 -C.sub.18 -alkyldiglycidylether; 
Compound 34: adduct of 1,2,3-propanetrithiol and glyceringlycidylether; 
Compound 35: adduct of 1,2,3-propanetrithiol and Bis-phenol-A glycidyl 
ether, and 
Compound 36: adduct of 1,2,3-propanetrithio and 
pentaerythritolglycidylether. 
The tests were carried out on 100-g samples of DSM NX 170 unsaturated 
polyester resin, in a 25.degree. C. bath. A quantity of thiol adduct was 
employed equal to 0.5 weight % referred to the resin, and an amount of 
peroxide in the form of 75% methylethylketone peroxide in 
dibutylphthalate. In Table IV are reported the times of gelation, the time 
corresponding to the exothermic peak, and the temperature at the 
exothermic peak. 
In all cases the yields of cross-linking as measured by DSC, were between 
75 and 85% after 6 hours. The yields can be further enhanced to values 
comprised between 90 and 95%, by post-curing at 50.degree.-80.degree. C. 
for 2-4 hours. The thus obtained samples were generally quite colourless 
and transparent. 
EXAMPLES 37-45 
Polymerization tests have been carried out with the following thiolic 
compounds: 
37 di-1,2-propanedithiolmaleate, 
37a pentaerythritoltetramercaptoacetate, 
38 ethylene-1,2-bis-3-mercaptopropionate, 
39 ethylene-1,2-bismercaptotertiarybutyrate, 
40 serbityltetramercaptoacetate, 
41 an adduct realized by boiling at 80.degree. C. for one hour, under 
"fall-back" [reflux], pentaerythritoltetra-mercaptoacetate plus 
methylhexahydrophthalic anhydride, in 1:2 molar ratio. 
42 trimetcaptomethyl citrate, 
43 trimercaptoethyl citrate, 
44 trimercapto-2-propyl citrate, and 
45 tetramercaptopyromellitate. 
The tests with 37, 38, 39 and 40 were effectuated using 100 g of Alusuisse 
5119 unsaturated polyester resin, in a 25.degree. C. thermostat bath. Test 
41 was effectuated using 100 g of epoxy resin of the type as obtained from 
Bisphenol A+epichlorohydrin, of c. 970 molecular weight, together with 2% 
of dimethyl benzyl amine. In Table V are listed the times of gelation, the 
time corresponding to the exothermal peak, and the temperature in the 
exothermal peak. 
In all cases the yields of cross-linking, measured by DSC, proved to be 
comprised between 75% and 85% after 6 hours. Such yields may be further 
raised to values ranging from 90 to 95%, by post-curing for 2-4 hours at 
50.degree.-80.degree. C. The obtained samples were generally quite 
colourless and transparent. 
EXAMPLES 46-51 
In the Table VI there are summarized a number of examples--which are 
non-limitative--in which 100 parts of epoxy resin, of the type obtained 
from Bisphenol A and epichlorohydrin and of approx. 970 molecular weight, 
are reacted (at 25.degree. ambient temperature) with triphenyl-phosphine 
(selected from the phosphines by way of non-limitative example) or with 
triphenylphosphite (selected from the phosphites by way of non-limitative 
example) in the presence of a mercaptan (by way of non-limitative example 
pentaerythritylmercaptoacetate was chosen) and lithium chloride (in 
examples 48 and 49). Along with these examples, blank tests are presented 
for comparison: without lithium chloride (example 51), without mercaptan 
(example 47), without phosphorus compound (example 46). 
From the examples, the accelerating effect from the trisubstituted 
phosphorus compounds is evident, especially in combination with mercaptan 
and lithium chloride. The products obtained by the polymerization have 
excellent mechanical and electrical characteristics, and have very bright 
colours. 
TABLE I 
__________________________________________________________________________ 
Quantity of salt 
Quantity of peroxide 
Metal salt (weight %) 
(weight %) 
Tg (min) 
Tpe (min) 
Tpe (.degree.C.) 
__________________________________________________________________________ 
Ex. 1 
AlCl.sub.3 10% 
0,2 2 3 5 126 
in ethanol 
Ex. 2 
AlCl.sub.3 1% 
0,2 2 1 6 98 
in ethanol 
Ex. 3 
LiCl 10% in 
0,2 2 1 3 117 
diethyleneglycol 
Ex. 4 
LiCl 1% in 
0,2 2 1 9 81 
diethyleneglycol 
Ex. 5 
MgCl.sub.2 10% in 
0,2 2 2 5 98 
diethyleneglycol 
Ex. 6 
LiCl 1% in 
0,2 0,02 3 5 117 
diethyleneglycol 
Ex. 7 
AlCl.sub.3 1% 
0,2 0,02 4 8 102 
in ethanol 
Ex. 8 
ZnCl.sub.2 10% and 
0,1 2 30 25 95 
LiCl 1% in 
0,2 
in diethyleneglycol 
__________________________________________________________________________ 
TABLE II 
__________________________________________________________________________ 
Epoxide resin ARALDIT Y 64 631 
100 g 
Ex. 9 
Ex. 10 
Ex. 11 
Ex. 12 
Ex. 13 
Ex. 14 
Curing agent Quantity of curing agent 
__________________________________________________________________________ 
Pentaerythritol- 
20 20 20 20 30 20 
tetramercaptoacetate (g) 
LiCl (ppm) 50 30 -- -- 70 50 
Methylhexahydrophthalic 
40 -- 40 -- -- -- 
anhydride (g) 
DMBA (g) -- -- -- -- -- 7 
Isophorone diamine (g) 
-- 15 -- 15 -- -- 
Polymerization time 
24 h 
17' 7 days 
55' 81' 15' 
Temperature 38.degree. C. 
172.degree. C. 
25.degree. C. 
147.degree. C. 
123.degree. C. 
86.degree. C. 
__________________________________________________________________________ 
DMBA = dimethylbenzylamine 
TABLE III 
__________________________________________________________________________ 
Example 
23 24 26 27 28 29 
Polyester resin 
Polyester resin 
Polyester resin 
DSM 530 25 DSM 170 ALu Suisse 5026 
__________________________________________________________________________ 
Peroxides* weight % 
0,02% 
0,02% 
0,2% 
-- 0,02% 
-- -- 
to resin 
Other per-compounds, 
-- -- -- Sodium per- 
-- -- Percarbonate 
weight % to resin borate 0.2%-25% 
0.3%-5% 
Time of final 
11' 13' 6' 16' 8' 25' 
15' 
gelation 
Temperature at 
55.degree. 
56.degree. 
97.degree. 
58.degree. 
57.degree. 
37.degree. 
40.degree. 
exothermal peak (.degree.C.) 
Catalyst 1,5% 
+++ 1,5% 
1,5% -- -- 1,5% 
Example 15 
Catalyst -- 1,5% 
-- -- 1,5% 
1,5% 
-- 
Example 16 
__________________________________________________________________________ 
*Peroxides: methylethylketone peroxide or acetylacetone peroxide 
TABLE IV 
__________________________________________________________________________ 
Non-limitative examples of dosage and cross-linking behaviour of thiols 
and their adducts 
Quantity of 
Quantity of 
Type of Thiol 
thiol in weight 
peroxide % based 
Time of 
Time for arriving 
Temperature in 
(Example No.) 
% to resin 
on weight of resin 
gelation 
at exothermal peak 
exothermal peak 
Note 
__________________________________________________________________________ 
30 0,5% 1-2% 6' 5' 53.degree. 
Quite colour- 
less and 
transparent 
31 0,5% 1-2% 8' 8' 62.degree. 
Quite colour- 
less and 
transparent 
32 0,5% 1-2% 9' 8' 56.degree. 
Quite colour- 
less and 
transparent 
33 0,5% 1-2% 12' 10' 57.degree. 
Quite colour- 
less and 
transparent 
34 0,5% 1-2% 15' 12' 55.degree. 
Quite colour- 
less and 
transparent 
35 0,5% 1-2% 10' 9' 61.degree. 
Quite colour- 
less and 
transparent 
36 0,5% 1-2% 12' 10' 53.degree. 
Quite colour- 
less and 
transparent 
__________________________________________________________________________ 
TABLE V 
__________________________________________________________________________ 
Type of 
Quantity of 
peroxide, and Time from 
Temper- 
thiol, weight 
weight % K-ethyl- 
Time of 
gelation 
ature at 
Type of Thiol 
% to resin 
to resin LiCl 
ZnCl.sub.2 
hexanoate 
gelation 
to peak 
peak Note 
__________________________________________________________________________ 
37 0,5% Mekp 0,002% 
-- -- 4' 4' 148.degree. 
colourless and 
50%-0,2% transparent 
37 0,5% Dibenzoylper- 
0,004% 
-- -- 7' 6' 145.degree. 
colourless and 
oxide 0,4% transparent 
37A 0,5% Mekp 0,002% 
-- -- 3' 3' 150.degree. 
colourless and 
50%-0,2% transparent 
37A 0,5% Mekp 0,002% 
0,02% 
-- 20' 18' 130.degree. 
colourless and 
50%-0,2% transparent 
37A 0,5% Mekp 0,002% 
-- 0,1% 60' 58' 102.degree. 
colourless and 
50%-0,2% transparent 
37A 0,5% Mekp -- -- -- 15' 14' 70.degree. 
colourless and 
50-0,2% transparent 
37A 0,5% percarbonate 
0,002 
-- -- 7' 5' 145.degree. 
colourless and 
25%-0,4% transparent 
37A 0,5% H.sub.2 O.sub.2 20%-0,3% 
0,002 
-- -- 3' 3' 152.degree. 
colourless and 
transparent 
38 0,5% Mekp 50%-0,2% 
0,002 
-- -- 5' 4' 145.degree. 
colourless and 
transparent 
39 0,5% Dibenzoyl per- 
0,002 
-- -- 7' 6' 150.degree. 
colourless and 
oxide 0,4% transparent 
40 0,5% Mekp 50%-0,2% 
0,002 
-- -- 3' 3' 150.degree. 
colourless and 
transparent 
41 100% -- 0,002 
-- -- -- -- -- Time of hardening: 
5 days at 25.degree. 
C., 
1 hour at 80.degree. 
C. 
__________________________________________________________________________ 
TABLE VI 
__________________________________________________________________________ 
Amount of Amount of 
Duration of curing 
phosphorous Amount of 
lithium 
at 25.degree. ambient 
Example 
Phosphorous compound 
compound 
Mercaptan 
mercaptan 
chloride 
temperature 
__________________________________________________________________________ 
46 -- -- Pentaerythri- 
50% -- 5 days 
toltetramercapto- 
acetate 
47 Triphenylphosphine 
1% -- -- -- 2 days 
48 Triphenylphosphine 
1% Pentaerythri- 
50% 0,1% 3 hrs. 
toltetramercapto- 
acetate 
49 Triphenylphosphite 
1% -- -- -- 3 days 
50 Triphenylphosphite 
1% Pentaerythri- 
50% 0,1% 4 hrs. 
toltetramercapto- 
acetate 
51 Triphenlyphosphite 
1% Pentaerythri- 
50% -- 7 hrs. 
toltetramercapto- 
acetate 
__________________________________________________________________________ 
Note: The percentual amounts are weights added to 100 weight parts of the 
epoxy resin (which was obtained from BisphenolA and epichlorohydrin and 
had about 970 molecular weight).