Cross-linkable structurally colored polymers, their preparation and their use in compositions for coatings

Structurally colored polymers, formed by polymerizing monomers of the acrylic type, containing 0.5% to 20% by weight of dyestuff in copolymerized form or grafted form which have a number-average molecular weight between 1000 and 12,880 g. and contain m hydroxy functions and n groups of the formula: ##STR1## in which X.sub.1 is hydrogen, chlorine, bromine or methyl; PA1 and R.sub.1 and R.sub.2 are the same or different and represent hydrogen, chlorine, methyl, phenyl, substituted phenyl or carboxyl; PA1 m being a number from 0 to 49 PA1 and n being a number from 2 to 70 PA1 such that the sum m+n is from 7 to 70 PA1 and the ratio m/n is from 0 to 2.4. These polymers are used in particular for the formation of colored coating on various supports and surfaces.

INTRODUCTION 
The present invention relates to new cross-linkable structurally colored 
polymers, used especially for the production of colored coatings on 
various supports such as, but not limited to, metal, paper and textile 
materials. The invention also relates to a process for the preparation of 
these polymers, the coating compositions containing these polymers as a 
constituent and the coatings obtained by means of these compositions. 
BACKGROUND OF THE INVENTION 
The formation of colored coatings on various supports by application of a 
colored composition to these supports followed by drying and 
thermo-cross-linking has been known for a long time. This prior art 
technique has a number of disadvantages including bulky installations, a 
large energy consumption owing to the fact that it is necessary to remove 
the solvent and heat the support and the coating, possible deterioration 
of the support during the treatment or at least alteration of some of its 
properties, and problems of safety and toxicity connected with the use of 
certain solvents. 
It has also been proposed in the prior art to replace the 
thermo-cross-linking by photo-cross-linking; i.e. cross-linking under the 
influence of ultra-violet rays which considerably restricts the above 
disadvantages. 
However, whether photo-cross-linking or thermo-cross-linking is used, the 
colored compositions used so far in the prior art for coatings contain, in 
the form of different entities, a cross-linkable colorless polymer on the 
one hand and a pigmentary dye on the other hand, which exhibit the 
following disadvantages: 
the necessity to put the dye in pigment form, which is often difficult, 
lengthy and costly. 
during the storage of the compositions, the dispersed pigment can separate 
or undergo undesirable changes such as crystallization or alteration of 
physical form. 
the pigment remains chemically independent of the coating after the 
cross-linking and may then migrate, with resulting loss of quality of the 
coating and possibly problems of toxicity. 
during the photo-cross-linking, the solid particles of pigment absorb a 
considerable amount of light energy, which necessitates increase in the 
time of irradiation and/or the amount of photo-initiator in the 
compositions. The increase in the quantity of photo-initiator has a very 
unfavorable influence on the stability on storage of the compositions and 
somewhat reduces the quality of the coating as a result of heterogenity 
due to the photo-initiator residues. 
SUMMARY OF THE INVENTION 
It has now been found according to the present invention that it is 
possible to obtain colored compositions for coating which are not subject 
to the previous disadvantages and which are capable of producing coatings 
of better quality than those obtained with the prior art compositions. The 
new compositions of the present invention are characterized by the fact 
that they contain, as constituents, one or more polymers of low molecular 
weight referred to hereinafter as "oligomers," which are structurally 
colored; that is, containing as an integral part of their chemical 
structure, chromophor or color-carrying groups and which oligomers are 
cross-linkable. 
More particularly, the invention pertains to structurally colored polymers, 
based on monomers of the acrylic type, containing 0.5% to 20% by weight of 
dyestuff in the copolymerized or grafted form, wherein the polymers have a 
number-average molecular weight between 1000 and 12,880 g. and carry m 
hydroxy functions and n groups of the formula: 
##STR2## 
In this formula X.sub.1 is hydrogen, chlorine, bromine or methyl; 
and R.sub.1 and R.sub.2 are the same or different and represent hydrogen, 
chlorine, methyl, phenyl, substituted phenyl or carboxyl; 
m is a number from 0 to 49 and 
n a number from 2 to 70 
such that the sum m+n is from 7 to 70 
and the ratio m/n is from 0 to 2.4. 
A further feature of the invention resides in a process for the preparation 
of the polymers defined above which comprises: 
(a) the preparation of a structurally colored oligomer containing m+n+x 
hydroxy functions, m and n being such as defined above and x being between 
0 and m+n15, by free radical polymerization of one or more monomers of the 
formula: 
##STR3## 
in which X.sub.2 is hydrogen or methyl; 
R.sub.4 and R.sub.5 are the same or different and represent hydrogen, or 
methyl, phenyl or substituted phenyl; 
R.sub.3 is an aliphatic, linear or branched, hydrocarbon, possibly 
substituted by chlorine, containing from 2 to 7 carbon atoms or a 
polyethyleneoxy or polypropyleneoxy chain containing 1, 2 or 3 monomer 
units and p is equal to 1 or 2, 
in the presence of one or more dyestuffs containing one or two groups of 
the formula 
##STR4## 
in which X.sub.1 is as above; 
and R.sub.6 and R.sub.7 are the same or different and represent hydrogen, 
methyl, phenyl, substituted phenyl, cyano or carboxyl; and/or one or more 
groups reactive towards hydroxy functions; 
(b) the conversion of n hydroxy functions of the oligomer prepared in (a) 
into groups 
##STR5## 
by reaction of the said oligomer with a compound of the formula 
##STR6## 
in which Y is chlorine or bromine; 
and X.sub.1, R.sub.1, R.sub.2 have the same significance as above; 
optionally in the presence of one or more dyestuffs containing one or two 
groups reactive towards hydroxy functions, the amounts of compound of 
formula (II) or (II bis) and of dyestuff introduced being calculated so as 
to act respectively on n and x of the hydroxy functions of the oligomer 
formed in (a), 
the total amount of dyestuff used in the stages (a) and (b) representing 
0.5% to 20% by weight of the whole of the compounds used. 
DETAILED DESCRIPTION OF THE INVENTION 
The oligomers formed in accordance with the present invention are based on 
monomers of the acrylic type. They have a number-average molecular weight 
of between 1000 and 12,880 g., preferably between 2000 and 5000 g., and 
contain 0.5% to 20% by weight of a dyestuff, in copolymerized or grafted 
form. Further, they contain m hydroxy (OH) functions and n groups of the 
formula 
##STR7## 
in which X.sub.1 is hydrogen, chlorine, bromine or methyl; 
R.sub.1 and R.sub.2 are the same or different and represent hydrogen, 
chlorine, methyl, phenyl, substituted phenyl or carboxyl; 
m is a number from 0 to 49 
and n is a number from 2 to 70 
such that the sum m+n is from 7 to 70 
and the ratio m/n is from 0 to 2.4. 
Preferably both m and n are numbers from 2 to 49 such that the sum m+n is 
from 7 to 70 and the ratio m/n is from 0.4 to 2.4. 
The oligomers defined above are new and as such form part of the invention. 
Structurally colored polymers having contents of dyestuff identical with 
those of the oligomers according to the invention are known; see, for 
example, Encyclopedia of Polymer Science and Technology, 1971, 15, 
314-319, and French Patent Nos. 74/26846 and 74/26847 filed on Feb. 8, 
1974 in the name of the applicants. However, these prior known polymers, 
contrary to the oligomers according to the invention, do not contain 
groups with the structure 
##STR8## 
and are not cross-linkable. 
The oligomers according to the invention may be obtained by the following 
process, which has two successive stages. In the first stage (stage a), a 
structurally colored oligomer is prepared containing m+n+x hydroxy 
functions, m and n being as defined above and x being between 0 and m+n/5. 
The reaction is carried out by free radical polymerization of one or more 
colorless hydroxyacrylic monomers, in the presence of one or more 
dyestuffs containing in their molecule one or two groups having a 
polymerizable ethylenic double bond and/or one or more groups reactive 
with respect to the hydroxy functions of the colorless monomers. 
In a second stage (stage b), n of the OH functions of the colored oligomer 
prepared in stage (a) are converted into groups of the formula: 
##STR9## 
by reacting the said oligomer with an unsaturated compound containing a 
group reactive towards the OH functions, optionally in the presence 
possibly of one or more dyestuffs having in their molecule one or two 
groups reactive towards hydroxy functions. The amounts of unsaturated 
compound and dyestuff introduced in this stage being calculated so as to 
act respectively on the n and x hydroxy functions of the oligomer. The 
total amount of dyestuff used in the stages (a) and (b) represents 0.5% to 
20% by weight of the total of the compounds used. 
Although, according to the process described above, the dyestuff may be 
introduced into the structure of the oligomer either in stage (a) by 
copolymerization with the hydroxyacrylic monomers owing to the opening of 
the polymerizable ethylenic double bond, or during stage (a) or (b), by 
grafting through the means of the reaction between the groups reactive 
towards OH and the OH functions of the oligomer, or again by both methods 
at once; preferably the method of incorporation of the dyestuff in the 
oligomer by copolymerization with the hydroxyacrylic monomers is used. In 
this preferential method of incorporation, the dyestuff used then has 
necessarily one or two groups having a polymerizable ethylenic double 
bond, the hydroxylated oligomer formed in stage (a) only containing m+n 
hydroxy functions (x is equal to 0) and stage (b) is carried out in the 
absence of dyestuff. 
The free radical polymerization of stage (a) is a polymerization in 
solution. It is effected, according to the conventional techniques, in an 
inert solvent, in the presence of an initiator of free radical 
polymerization and possibly of a chain transfer agent. Although it is not 
absolutely necessary, the solvent and the initiator are preferably 
selected so that the medium obtained at the end of the polymerization is 
sutable for stage (b) of the process, which has the advantage of avoiding 
the isolation of the hydroxylated oligomer formed in stage (a). Examples 
of such preferred solvents are dimethylformamide, dimethylacetamide and 
N-methyl pyrrolidone. Examples of preferred initiators are 
azo-bis-isobutyronitrile and the organic peroxides. Lastly, examples of 
chain transfer agents include alkylmercaptans such as n-dodecyl-mercaptan. 
The colorless hydroxyacrylic monomers used in stage (a) correspond to the 
general formula: 
##STR10## 
in which X.sub.2 is hydrogen or methyl; 
R.sub.4 and R.sub.5 are the same or different and represent hydrogen, 
methyl, phenyl or substituted phenyl; 
R.sub.3 is an aliphatic, linear or branched, hydrocarbon, possibly 
substituted by chlorine, containing 2 to 7 carbons or else a 
polyethyleneoxy or polypropyleneoxy chain containing 1, 2 or 3 monomer 
units, 
and p is 1 or 2. 
Illustrative of the compounds of formula (I) are among others, 
2-hydroxyethyl acrylate; 2,3-dihydroxypropyl acrylate, diethyleneglycol 
monoacrylate, 3-chloro-2-hydroxypropyl acrylate, 6-hydroxyhexyl acrylate, 
and the corresponding derivatives of methacrylic acid. 
The unsaturated compounds containing a reactive group with respect to the 
hydroxy functions used in stage (b) correspond to one of the formulae: 
##STR11## 
in which Y is chlorine or bromine; 
and X.sub.1, R.sub.1, R.sub.2 have the same significance as above. 
Examples of the compounds of formula (II) are acryloyl, methacryloyl, 
.alpha.-bromo-acryloyl and .alpha.-chloro-acryloyl chlorides. 
Illustrative of the compounds of formula (II bis) are among others, maleic 
anhydride, chloromaleic anhydride and citraconic anhydride. 
The dyes having one or two polymerizable ethylenic double bonds and/or one 
or more groups reactive with respect to the hydroxy functions, which are 
used in the process of the invention, may belong to very diverse classes 
such as, for example, the azo, anthraquinone, perinone, 
perylene-tetracarboxylic acid derivatives, phthalocyanines, dioxazines, 
quinacridones and quinophthalones classes. These dyes contain as groups 
having a polymerizable ethylenic double bond, one or two groups of the 
general formula: 
##STR12## 
in which X.sub.1 has the same meaning as above and R.sub.6 and R.sub.7 are 
the same or different and represent hydrogen, methyl, phenyl, substituted 
phenyl, cyano or carboxylic. The groups of formula (III) are attached to a 
ring of the dye molecule either directly or through the bridge of a group 
such as, for example, 
##STR13## 
Examples of groups of formula (III) are the vinyl, .beta.-cyanovinyl and 
.alpha.-bromovinyl groups. 
Examples of groups reactive towards the OH functions contained by the dyes 
used in the process according to the invention are groups containing an 
activated halogen atom such as the groups 
##STR14## 
the carboxylic anhydride group, the isocyanate group and the epoxy group. 
The dyestuffs used in stage (a) may carry hydroxy groups. However, the 
hydroxy functions of the oligomer formed in this stage are preferably 
introduced by the intermediary of the hydroxyacrylic monomer or monomers. 
Numerous dyestuffs containing in their molecule one or more groups of 
formula (III), and/or one or more groups relative towards hydroxy 
functions are known. Illustrative of examples of dyestuffs are those 
described in French Patent Nos. 1,083,584; 1,118,705; 1,207,925; 
1,291,903; 1,295,638 1,394,020, 2,016,740 and 2,091,873 and the British 
Pat. Nos. 1,036,700 and 1,262,092, and German patent application No. 
1,056,580. These disclosures are relied on for exemplification of suitable 
dyestuffs. 
The choice of the dyestuff or dyestuffs used in the process depends upon 
the desired shade and the desired fastness and takes into account the 
compatibility of the physico-chemical and chemical characteristics of the 
dyestuff with the proposed use. Preferably dyestuffs are used which are 
soluble in the polymerization medium, copolymerize suitably with the 
hydroxyacrylic monomer or monomers, and have a high tinctorial power and a 
good fastness to light. These are matters well within the scope of the 
skilled worker in the art. 
The cross-linkable structurally colored oligomers according to the 
invention are solids which may be kept, after having stabilized them with 
an inhibitor of free radical polymerization, such as hydroquinone, in 
order to avoid any premature polymerization. They are compatible; that is, 
several oligomers, for example of different shades, may be mixed so as to 
obtain composite shades. 
The oligomers according to the invention may be used as coloring material 
for coloring inks, varnishes, paints or printing pastes. However, their 
preferred use resides in use as a constituent of compositions for 
cross-linkable coating, and more especially of photo-cross-linkable 
compositions. When incorporated in such compositions, the oligomers 
readily produce the filmogenic character, the properties of adhesiveness 
to the support, the color and its permanence. 
The coating compositions prepared by means of the oligomers according to 
the invention provide, for example, on aluminum, paper, pasteboard or 
fabric, coatings having a very great homogenity of coloration, a very 
great transparency and remarkable fastness; especially a remarkable 
fastness to solvents. They show also, with respect to the cross-linking 
compositions conventionally used, great advantages in the ease of 
preparation. Many surfaces or supports may be coated with the colored 
polymer compositions of this invention. 
Photo-cross-linkable compositions, like with conventional 
photo-cross-linkable inks, usually contain five types of constituents, 
namely: 
a colorless polymeric base containing polymerizable ethylenic double bonds 
mono or polyfunctional (i.e. having one or more polymerizable ethylenic 
double bonds) acrylic monomers 
one or more photo initiators 
one or more adjuvants 
a pigment. 
Now on the one hand the incorporation of the pigment is always a difficult 
operation to carry out and is delicate, since it may be accompanied by a 
degradation of the pigment; i.e. loss of coloring power, modification of 
shade or by a disturbance of the physico-chemical characteristics of the 
mixture; e.g. modification of the viscosity, etc. On the other hand, since 
the properties of the coatings obtained after cross-linking are frequently 
very sensitive to slight modifications of the formulation, it is necessary 
to carry out numerous tests to determine the optimum proportions of the 
various constituents. 
In the case of cross-linking compositions prepared with the oligomers 
according to the invention, the difficulties of preparation connected with 
the incorporation of a pigment are prevented, since the two-component 
colorless polymeric base-pigment is replaced by a single entity; i.e. a 
cross-linkable structurally colored oligomer according to the invention. 
The latter are very soluble in the mono or polyfunctional acrylic monomers, 
from which there is a very rapid homogenization of the compositions. In 
other respects, the properties of the coatings obtained by means of the 
compositions according to the invention are less sensitive to the 
variations of formulation than those of the coatings obtained with the 
conventional compositions. 
Further, the yield of the photo-cross-linking process is improved in the 
case of the photo-cross-linkable compositions according to the invention, 
which enables smaller quantities of photo initiator to be used than in the 
case of the conventional photo-cross-linkable compositions.

The following examples, in which the parts indicated are parts by weight, 
illustrate the invention without restricting it in anyway. The values for 
average molecular weight and intrinsic viscosity provided in these 
examples are given at about .+-.10% and about .+-.5%, respectively. The 
intrinsic viscosity has been determined in dimethylformamide at 25.degree. 
C. 
EXAMPLE 1 
250 parts of pure and anhydrous dimethyl formamide, 100 parts of 
2-hydroxy-ethyl methacrylate and 10 parts of the unsaturated dyestuff of 
the formula: 
##STR15## 
are introduced into a reactor provided with a stirring device, an inlet 
tube for nitrogen and a temperature regulator. 
Then 0.8 parts of n-dodecyl-mercaptan and 1.65 parts of 
azobisisobutyronitrile are introduced, and the solution is deoxygenized by 
a current of nitrogen. It is then brought rapidly to (80.+-.2).degree.C., 
while stirring, and this temperature is maintained for about 6 hours. 
It is then cooled and diluted with 100 to 200 parts of pure and anhydrous 
dimethylformamide, and then 0.5 parts of hydroquinone and 1.2 parts of 
triethylamine are added. 
The temperature is brought to 50.degree.-60.degree. C. and 34.8 parts of 
distilled acryloyl chloride which corresponds to the conversion of about 
50% of the OH of the polymer obtained in the previous stage are introduced 
in one hour to 11/2 hours. After the end of the introduction, this 
temperature is maintained for one to two hours. Then after cooling, the 
polymer obtained is precipitated by pouring the reaction medium into a 
non-solvent, for example, water. It is filtered off, washed and dried 
under vacuum at ordinary temperature, after stabilization by addition of 
200 to 1000 ppm of hydroquinone. 
The yellow product obtained has an average molecular weight of 4500 g. and 
an intrinsic viscosity [.eta.]=0.18 deciliter/g. 
EXAMPLE 2 
The process is as in Example 1, but the 34.8 parts of acryloyl chloride are 
replaced by 40.2 parts of methacryloyl chloride. The product obtained has 
physico-chemical characteristics similar to those of the product of 
Example 1. 
EXAMPLE 3 
The process is as in Example 1, but 200 parts of dimethyl formamide, 0.6 
parts of n-dodecyl-mercaptan and 1.3 parts of azobisisobutyronitrile are 
used in the first stage. 
The copolymer obtained has an average molecular weight of 5000 g. and an 
intrinsic viscosity [.eta.]=0.22 deciliter/g. 
EXAMPLE 4 
The first stage polymerization is effected as in Example 1, then the medium 
is cooled, diluted with 100 to 200 parts of pure and anhydrous dimethyl 
formamide and 0.5 parts of hydroquinone are added. 
The temperature of the solution is raised to 75.degree. C.-85.degree. C. 
and 30.8 parts of maleic anhydride (which corresponds to the conversion of 
about 40% of the OH) are gradually introduced. The copolymer is isolated 
as in Example 1. 
EXAMPLE 5 
The process is as in Example 1, but 2-hydroxy-ethyl acrylate is used as 
monomer instead of the 2-hydroxy-ethyl methacrylate. The colored copolymer 
obtained has an average molecular weight of 3500 g. and an intrinsic 
viscosity [.eta.]=0.17 deciliter/g. 
EXAMPLE 6 
The process is as in Example 1, but 5 parts of the dyestuff of the 
following formula are used: 
##STR16## 
EXAMPLE 7 
A photo-cross-linkable composition is prepared at a temperature 
.ltoreq.60.degree. C. by means of the polymer of Example 1. For this 
purpose, 28.5 parts of the polymer prepared in Example 1 are introduced 
into 30 parts of 2-hydroxy-ethyl acrylate, then 30 parts of 
trimethylolpropane triacrylate, 10 parts of pentaerythritol triacrylate 
and finally 1.5 parts of benzoin monobutyl ether are added. In a few 
minutes a homogeneous photo-cross-linkable composition is obtained. 
This composition, applied on an aluminum plate in a layer of thickness 
24.mu., is photo-cross-linked in less than one second. The intense yellow 
film obtained has a good adherence, is stable towards solvents and very 
transparent. It may be covered over with other layers without any 
migration between the layers occurring. 
EXAMPLE 8 
A photo-cross-linkable composition is prepared, at a temperature 
.ltoreq.60.degree. C., containing 30 parts of the colored polymer of 
Example 6, 15 parts of 2-hydroxy-ethyl acrylate, 15 parts of benzyl 
acrylate, 20 parts of hexane-diol diacrylate, 20 parts of pentaerythritol 
triacrylate and 1.5 parts of benzoin monoethyl ether. This composition, 
when applied on aluminum and photo-cross-linked, gives a blue film having 
good general characteristics and fastness. 
EXAMPLES 9 TO 13 
The operation is as in Example 1, but the dyestuffs of the following Table 
are used. 
The colored copolymers obtained are incorporated in photo-cross-linkable 
compositions prepared according to the process of Examples 7 or 8. These 
compositions, applied on paper, give prints of very good quality. 
__________________________________________________________________________ 
DYESTUFFS OBTAINED 
EX. 
__________________________________________________________________________ 
##STR17## Orange 9 
##STR18## Red 10 
##STR19## Violet 11 
##STR20## Yellow 12 
##STR21## Red 13 
__________________________________________________________________________ 
EXAMPLE 14 
The process is as in Example 1, but the 0.8 parts of n-dodecyl-mercaptan 
are replaced by 2 parts of the same product. The copolymer obtained has a 
number-average molecular weight of 3500 and an intrinsic viscosity 
[.eta.]=0.13 deciliter/g. 
EXAMPLE 15 
The process is as in Example 14, but the 34.8 parts of acryloyl chloride 
are replaced by 70 parts of the same product, so as to transform all OH 
groups of the polymer obtained in the first stage. The copolymer obtained 
has a number-average molecular weight of 4500 and an intrinsic viscosity 
[.eta.]=0.17 deciliter/g. 
EXAMPLE 16 
250 parts of pure and anhydrous dimethylformamide, 100 parts of 
2-hydroxyethyl methacrylate, 2 parts of n-dodecyl mercaptan and 1.65 parts 
of azobisisobutyronitrile are introduced into a reactor provided with a 
stirring device, an inlet tube for nitrogen and a temperature regulator. 
The solution is deoxygenized by a current of nitrogen, then brought rapidly 
to (80.+-.2).degree.C., while stirring. This temperature is maintained for 
about 6 hours. 
The solution is then cooled and diluted with 100 to 200 parts of pure and 
anhydrous N,N-dimethylformamide, and then are added 10 parts of the 
dyestuff of the formula: 
##STR22## 
The temperature is raised to 100.degree.-110.degree. C. This temperature is 
maintained for about 8 hours. 
The medium is then cooled to 50.degree.-60.degree. C. and 0.5 parts of 
hydroquinone are added. The condensation with acryloyl chloride is 
effected as in Example 1. 
The yellow copolymer obtained has a number-average molecular weight of 4000 
and an intrinsic viscosity [.eta.]=0.17 deciliter/g. 
EXAMPLE 17 
A photo-cross-linkable composition is prepared, at a temperature 
.ltoreq.60.degree. C., containing 40 parts of the copolymer of Example 15, 
15 parts of 2-hydroxyethyl acrylate, 40 parts of trimethylolpropane 
triacrylate, 5 parts of pentaerythritol triacrylate and 1 part of benzoin 
monobutyl ether. This composition when applied on a white cardboard in a 
layer of thickness of 12.mu., is photo-cross-linked in less than one 
second. The yellow film obtained feels dry and is stable towards solvents 
and very transparent. It may be covered over with other layers without any 
migration between the layers occurring. 
Further embodiments, variations and modifications of the present invention 
will be apparent from the foregoing specification to persons having 
ordinary skill in the art.