CH631476A5 - Use of unsaturated polyesters as radiation-curable binders, and process for their preparation - Google Patents

Description

The invention relates to the use of unsaturated polyesters as radiation-curable binders in systems which can be used in particular as solvent-free printing inks. These systems generally consist of a binder which mostly contains an ethylenic CC double bond, a reactive diluent which can be copolymerized with it, at least one sensitizer and, in the case of printing inks, optionally a pigment for the production of radiation-curable coatings, coatings, adhesives, fillers or printing inks.

Such a system is expected to dry quickly, i.e. Crosslinking under the influence of high-energy radiation, preferably UV light, in the case of printing inks the formation of a hard, well-adhering but flexible film with high gloss, good pigment wetting and thus high color strength. Furthermore, the inks should be easy to process on printing machines, especially on offset machines, and have sufficient storage stability.

The use of radiation-curable, ethylenically unsaturated resins in coating compositions, adhesives or printing inks is known. It is also known that these substances, especially when they are mixed with photosensitizers, polymerize under the influence of high-energy radiation. However, the commercially available products often give cause for concern regarding pigment wetting and storage stability by wetting the pigments too little or thickening them with storage. Furthermore, printing with colors made from it can be very difficult. For example, acrylated epoxy resins for «plucking», 35 i.e. the printing ink spoils the rollers or the rollers and paper, which may cause the paper to tear.

Curable synthetic resins in a mixture with acrylamide compounds often have the disadvantage that they have too high a viscosity. They must therefore be mixed with a lot of reactive thinner, which affects the drying speed. Crystallization phenomena and phase separation of the printing inks are also frequently observed, which makes processing difficult or impossible.

45 Systems based on acylated polyesters are also known which have been obtained by reacting polyhydric alcohols with dicarboxylic acids and further reacting with acrylic or methacrylic acid. These systems are generally easier to process and have a high gloss, but they have disadvantages in that the drying times are too long and therefore do not meet the requirements of modern practice.

The compounds used in the radiation-curable polyester systems described hitherto generally have at least one easily polymerizable C-C double bond, namely α, β-olefinically unsaturated bonds. However, unsaturated polyester resin systems are also known in which the double bond lies in an isocyclic ring. Resins of this type have a linear structure and have substituted-60 or unsubstituted unsaturated bicyclo- (2.2.1) -hepten-nyl-2 groups either in the polymer chain or on side chains. When it comes to radiation curing, however, it turns out that such systems are also insufficient in drying.

Furthermore, unsaturated polyesters are known which are curable by free radical polymerization and are composed of polyhydric alcohols and α, β-ethylenically unsaturated polycarboxylic acids, a proportion of these unsaturated acids also being obtained by saturated aliphatic and /

3 631476

or aromatic polycarboxylic acids can be replaced and a, ß-ethylenically unsaturated dicarboxylic acid or a radio

the additional di- or tricyclic dialcoholic compounds of the derivative thereof or one of the polycar-

have in which an endo-methylene group is contained. bonic acids or mixtures thereof are prepared. The po-

These are, for example, dimethyloldicyclopenta- lycyclic compounds contain at least one diene or dicyclodicarboxylic acid, which also has an endo-Me- 5 carboxyl, hydroxyl or primary amino group, however, each

have ethylene group, e.g. Hexachloroendomethylenetetrahy- Weils only with one type of functional groups, and are drophthalic acid. Unsaturated polyesters are also known, to which the compounds used for the production of the polyester are added, not the acid component, but the diol component in accordance with their reactive group. The polyester

are partially replaced by di- or tricyclic diols. Resin can contain excess hydroxyl groups or carboxyl group

These are dimethylolbicyclo- (2.2.1) -heptane and io pen as reactive groups. Such a hydroxyl or

Dimethyloltricyclo- (5.2.1.02 6) decane. The presence of these carboxyl-containing, optionally unsaturated di- or tricyclic endo-methylene groups containing polyester resin is in a second stage with at least one

Compounds in the unsaturated polyester cause an increased acrylic compound to react, with ester formation, i.e. Sales

cure speed and thus a reduction esterification or transesterification of the excess reactive group

time that leads to a tack-free state. 15 pen can occur.

Instead of the unsaturated di- or tricyclic compo- Suitable acids that are free from aliphatic multiple

Polyester can also be used. saturated aliphatic or cycloaliphatic

Reaction from a saturated dicyclopentadiene derivative, e.g. see polycarboxylic acids with 4 to 13 carbon atoms, e.g. Amber-

the 3 (4), 8 (9) -dihydroxymethyltricyclo- (5.2.1.02-6) -decane with acid, dimethylsuccinic acid, adipic acid, azelaic acid, Se-

unsaturated dicarboxylic acids have been obtained. This po- 20ic acid, brassylic acid, hexahydrophthalic acid or aromatic

Lyers can also be used as styrene copolymers on solvent-containing polycarboxylic acids with 8 or 9 carbon atoms, such as the various

Tele-free, fast-drying lacquers of special hardness process isomeric phthalic acids and trimellitic acid. Suitable ones are processed, but are unsuitable for UV curing. unsaturated dicarboxylic acids are e.g. aliphatic unsaturated

Due to the action of high-energy rays, acids with 4 or 5 carbon atoms such as maleic acid, fumaric acid,

curable resin compositions have been described which consist of a mi 25 itaconic acid, mesaconic acid, citra acid and chloromaleine.

Schung A) an unsaturated polyester, B) a norbornene acid. The carboxylic acid derivatives and C) optionally a copolymer used for the production of the binders according to the invention can also be obtained by incorporating benzo

sizable vinyl monomers are constructed. The component phenones substituted with at least one carboxyl group

B) can also be via the acid group with a tricyclo- and then act as internal sensitizers, as well as with

(5.2.1.02,6) -dec-3-en group must be esterified. This mixture of modified oils and / or unsaturated fatty acids must be modified,

lymerises during the curing process, the copoly being preferred, those which use a conjugated diene

merizable monomers are incorporated into the resin. Own system, e.g. 9,11-ricinic acid and / or 10,12-linoleic

Although products based on the systems mentioned in the acid. In addition, a modification with saturated

In practice, attempts will be made to non-fatty acids, which act as internal plasticizers. The fact that the properties meet the increased requirements 35 proportion of the modification components should be appropriately adapted; so it is desirable to have the processability and not more than 30%, preferably up to 20% and in particular up to

Storage stability of the pigment-containing printing inks to improve 10%, based on the total weight of the acid com

and also to increase the gloss of the prints. component A).

The invention relates to the use of unsaturated polyesters from A) of at least one mono-, ß-olefinic alcohols used for the production of the polyester are, for example, di- to tetrafunctional, such as niche unsaturated dicarboxylic acid and / or a polycarbonate Ethanediol, the various propane, butane, pentane, hexanoic acid, which is free from polymerizable aliphatic multidiols or other polyhydric alcohols with saturated or specialist bonds, B) at least one polyhydric alcohol, C) olefinically unsaturated carbon chain with up to 15 C-Ato-at least one condensable acrylic compound and D) men, such as dimethylolcyclohexane, bis- (4-hydroxycyclohexyl) -at least one via a functional group from the series 45 methane or -propane, A-2,3-butenediol-1,4 , also glycerol, carboxyl, hydroxyl and primary amino group or via a trimethylolethane or propane, pentaerythritol or similar plurality of only similar funk tional groups from the polyhydric alcohols or mixtures of several polyvalent series bonded polycyclic compound with a ger alcohols. Preference is given to compounds which have only primary norbornane skeletons as binders in binder systems for the hydroxyl groups, especially trimethylolpropane and the preparation of radiation-curable coatings, coatings, such as ethanediol.

Adhesives, fillers or printing inks. As condensable acrylic compounds with which the object of the invention is also a process for the production of polyester resin in a second stage, such a position of a binder in the form of an unsaturated poly compound is used which is simple with the functional group esters from A) at least one a, ß-olefinically unsaturated polyester resin can react, preferably acrylic-dicarboxylic acid and / or a polycarboxylic acid which contains free 55 or methacrylic acid or its functional derivatives such as anist of polymerizable aliphatic multiple bonds, B) hydrides, acid chlorides etc., furthermore hydroxyalkyl acrylates or at least one polyhydric alcohol and C) at least methacrylates with up to 3 C atoms in the alkyl radical, such as ß-Hy-a condensable acrylic compound, thereby characterized- hydroxyethyl- or ß- or γ-hydroxypropyl acrylate or which shows that in the 1st stage components A) and B) and corresponding methacrylic acid derivatives and N-alkylol acrylic additionally D) at least one polycyclic compound with 60 amides (including the methacrylamides) with up to 4 C-ato-a norbornane skeleton and with a functional group in the alkyl radical such as N-methylolacrylamide. The Einkondensa - from the series carboxyl and hydroxyl group or a group of the acrylic compound can also be reacted with one another by transesterification of only identical functional groups from this group of hydroxyl group-containing polyesters with suitable esters to form an ester, and acrylic or methacrylic acid done, e.g. with the alkyl that thereupon in the 2nd stage the reaction product obtained with the or hydroxyalkyl esters. This means that in this case component C) is also reacted with ester formation. alcoholic group is split off. This mode of operation is. Such polyesters can e.g. by implementing naturally less preferred. The proportion of these unsaturated polyhydric alcohols with at least one saturated or saturated compound is generally 10 to 50, preferably

631 476 4

to work more than 20% by weight, based on the p-toluenesulfonic acid, methanesulfonic acid, etc. in the second stage. The polyester resin obtained. Catalysts are preferred in amounts of 0.1 to 5

As polycyclic compounds which are used in the production of 0.5 to 2% by weight, based on the total amount of the reactive

Polyesters to be condensed in are suitable with ion components, added and are suitable both for the esterification

Carboxyl, hydroxyl and amino groups substituted endocy- 5 rang as well as suitable for etherification.

cical compounds, such as tricyclo- (5.2.1.02,6) -decane-3 (4) - in the second process step, it is also advantageous

carboxylic acid (formula I, see formula sheet), use tricyclo entraining agents such as cyclohexane, benzene, toluene, xy-

(5.2.1.02-6) -decane-3 (4), 8 (9) -dicarboxylic acid (II), tricycloloi, gasoline fractions in the same boiling range, e.g. n-hexane,

(5.2.1.02-6) -decane-2-carboxylic acid (III), 8,8'-di- (tricyclo-further trichlorethylene, isopropyl ether and the like.

(5.2.1.02-6) -decyl) -ether-4,4'-dicarboxylic acid (IV), 8-hydroxy- reaction temperatures are between 70 and 120 ° C

4 (5) -hydroxymethyl-tricyclo- (5.2.1.02-6) -decane (V), 8 (9) -Hy- and are dependent on the type and amount of towing used.

droxytricyclo- (5.2.1.02 <5) -decane (VI), 8 (9), 3,4-trihydroxytricy- dependent. Sometimes it is advisable to

clo- (5.2.1.02 6) -decane (VII), 3,4-dihydroxytricyclo- (5.2.1.02-6) - pressure to work. The course of the reaction can be followed by decane (VIII), 3 (4) -hydroxymethyltricyclo- (5.2.1.02 6) -decane determination of the amount of water formed, where-

(IX), 3 (4), 8 (9) -dihydroxylmethyltricyclo- (5.2.1,02,6) -decane 15 can be regarded as ended in the reaction if

(X), 3 (4) -aminomethyl-tricyclo- (5.2.1.02-6) -decane (XI), more than 95% of the theoretical amount of water separated 3 (4), 8 (9) -diaminomethyl-tricyclo- (5.2 .1.02-6) Dean (XII). has been.

But also polycyclic norboman ring compounds, To polymerize in the reaction in the second stage,

in which a C-C double bond is present in a fused in the unsaturated compounds

5-ring is like 8 (9) -hydroxytricyclo- (5.2.1.02 6) -dec-3-ene 20dem, is generally a polymerization inhibitor,

(XIII) and 5-hydroxy-tricyclo- (5.2.1.02-6) -dec-3-ene (XIV), advantageously in amounts of 0.1 to 5, preferably 0.5 to 2

are for the production of the polyesters of the% by weight according to the invention, based on the total amount of the reaction compo-

Suitable binder. nenten, added. As inhibitors e.g. Hydroquinone,

The polycyclic compounds are generally obtained in the case of p-benzoquinone, alkylated phenols such as p-tert-butylphenol from their industrial preparation as mixtures of isomers, and 25 and catechol, 2,6-di-tert-butyl-cresol, and also diphenyl-

are usually used as such for the preparation of the amine, thiosemicarbazide, sulfur, phenothiazine and p-meth-

used polyester. oxyphenol can be used.

The content of polycyclic compounds is at least. After the reaction, the azeotropic dewatering agent is at least 0.5, preferably 3 to 30% by weight, based on that in under reduced pressure, preferably in a thin

polyester resin obtained in the second stage. 30 layer or rotary evaporator distilled off.

The binders according to the invention are, for example, reacted with the acrylic compounds, preferably hydroxyls with reactive diluents, suitable sensitizers and numbers (determined according to DIN standard 53240) between 100 and pigments to form a binder system and as pressure -1000, preferably between 200 and 800, best used between dyes, which, in addition to good storage stability, impart a high 400 and 600 and the carboxyl group-containing polyester 35 curing rate when irradiated with UV light acid numbers (determined according to DIN 53402) between 100 and . For example, drying speeds of 800, preferably between 200 and 600, can be used. For application speeds of more than 400 m / min. The polyester resins in which the reactive prints have a high gloss and color density are best suited. But groups of the base resin have not been completely reacted with acrylic compound, even in unpigmented form, such a mixture has been brought to fertilization, but at least 40 production of radiation-curable coatings, coatings 2%, preferably 10 to 35% of the reactive groups does not change and glue suitable. If fillers have been added, this may have been used. The resin is then easier to manufacture and can also be used as a filler.

because it does not cause crosslinking reactions so quickly, although UV light is already used to achieve high drying

prone to undesirable premature gelation; furthermore, if the application speed is sufficient, the irradiation can thereby increase the pigment wetting ability. 45 naturally also with higher-energy radiation, e.g.

The viscosities of the finished polyester resins lie in the general electron beam.

mean between 100 and 800 P (20 ° C, roto-viscometer); it The visco required for the respective purpose

However, polyesters with higher viscosities can also be used.

for example, those with up to 1500 P can be used. At least one of a reactive diluent must be set, the low viscosity of which is generally up to 60% by weight for further processing, based on the binder system.

tion of the polyester but particularly advantageous. stem, can be. As reactive diluents are advantageous

The polyester resins are expediently prepared from acrylic and methacrylic acid esters of mono- and / or polyvalent

according to the usual working technique for polycondensation resins, alcohols such as 2-ethylhexanol, ethane and various

e.g. by condensation in the melt, by esterification of which propane and butanediols, trimethylolpropane, pentaery

with azeotropic distillation of the ss thritol formed in the reaction or mixtures thereof.

Water or by transesterification. It is recommended that in the end the sensitizers have the task of

esterification, which generally increases at 160 to 250 ° C. through the speed of the binder system. Expedient

is carried out, at least briefly under reduced pressure, this is done by admixing the compounds to work to water, such as unreacted volatile from the binder system. Suitable are e.g. Benzoin, benzoin starting materials and low-molecular reaction products - 60 esters, ethers, ketals, benzophenone or Michler's ketone (al-

breastfeed. This resin is then mixed with at least one linen or in combination), chlorinated aromatic compounds.

Acrylic compound added and described below and ketones, anthraquinone derivatives, combinations of which give a further, if necessary partial, combination of benzophenone and Michler's ketone, e.g. in a ratio of 1: 1,

esterification of free hydroxyl or carboxyl groups. to be favoured. The amount of sensitizers is in

While in the first stage generally no polycon 65 to 2, preferably 3 to 10% by weight, based on condensation catalysts are used, in the two it is based on the binder system. The addition of the sensitizers ten stage appropriately, in the presence of catalysts such as can be omitted in whole or in part, if already in the

Sulfuric acid, hydrochloric acid, benzenesulfonic acid, production of the starting polyester so-called internal sensitization

631476

ren have been added. As already mentioned, the benzophenones substituted with carboxyl groups are preferably suitable for this chemical incorporation.

For the production of printing inks and pigmented lacquers, the pigment portion can e.g. 5 to 40, preferably 8 to 20% by weight, based on the finished product, e.g. Printing ink or varnish. Suitable pigments are the known compounds commonly used in the paint and printing ink industry, such as organic pigments, e.g. Pigment dyes from the azo series, complex pigment dyes, anthraquinone dyes and quinacridone pigments, carbon black, inorganic pigments such as titanium dioxide, iron oxide or cadmium sulfide selenide. The addition of pigments can be carried out on any of the devices customary in the paint or printing ink industry, e.g. with a three-roll mill.

The binders according to the invention can also be combined with other resins in the binder system to achieve certain special properties, these being added in amounts of up to 60% by weight, preferably 3 to 20% by weight, based on the total binder containing the other resins can be. Suitable resins are e.g. acrylated epoxy resins, unsaturated polyesters, acrylamide-containing systems, alkyd resins, cyclo rubber, hydrocarbon resins e.g. based on cyclo- or dicyclopentadiene, rosin, acrylic and / or maleate resins and rosin resins modified with phenolic resin, insofar as they are high-melting, aliphatic-compatible types, and phenolic resins. For example, maleate resins improve the processing of printing inks on offset machines without having a negative impact on drying.

The binders described in the following examples are made as follows.

1st stage:

The carboxylic acid and the alcohol components are intimately mixed together with the polycyclic compound and optionally further additives and kept in a flask equipped with stirring, thermometer and water separator with stirring at approx. 160 to 250 ° C until the theoretical amount of water has separated Has.

2nd stage:

The polyester resin formed in the 1st stage is dissolved in an azeotropic dewatering agent and the acrylic compound, inhibitor and catalyst are added. The mixture is heated to 70 to 120 ° C., the azeotropic dewatering agent is distilled off - if appropriate under reduced pressure - and, after the azeotropically distilled water has been separated off, it is returned to the reaction mixture. The catalyst can be washed out of the resin solution in a known manner, whereupon the solvent is distilled off at 50 to 70 ° C. under reduced pressure.

To produce a printing ink for printing testing, the resin is adjusted to a viscosity of about 200 P with trimethylolpropane triacrylate and mixed with 15% pigment and 8% by weight of a mixture of benzophenone and Michler's ketone as a sensitizer. The increase in viscosity due to the incorporation of the additives is compensated for by a further addition of trimethylolpropane triacrylate to a viscosity of 400 P.

To determine the drying speed of the individual printing inks, test prints were made on white paper with an average print run of 1.5 g / m2 of printing ink and irradiated with a mercury vapor lamp of 80 watts / cm at different throughput speeds. The irradiation time which is necessary to dry an irradiated print in this way, i.e. to network so that when a white paper is placed on and with a contact pressure of 130 kp / cm2 there is no ink transfer to the white paper (so-called "smear test" - carried out on a test printer from Dürner, Peis-senberg, Federal Republic of Germany). The gloss was assessed visually (see table)

The binders according to the invention are distinguished by high storage stability, i.e. they show no gel formation, no thickening and no change in viscosity within a period of 6 months. The storage stability of the batches made with the îo binder is also excellent.

In the following examples, T always means parts by weight.

example 1

348 parts of trimethylolpropane are condensed with 292 parts of adipic acid i5 and 36 parts of a compound of the formula I at 200 ° C. under the specified conditions, 75 parts of water separating out. 100 T of this resin (OH number 330) are dissolved in 150 T toluene and 36.7 T acrylic acid, 0.75 T 2,6-di-tert-butyl cresol and 1 T conc. Added sulfuric acid and reacted at 95 ° C under slightly reduced pressure. After the water separation, the solvent is distilled off, whereupon a yellowish resin with a viscosity of 647 P is obtained (determined at 20 ° C. using a Roto viscometer from Gebrüder Haake).

25th

Comparison 1:

Example 1 is repeated, but without the addition of compound I (ÖH number of the polyester 350). A colorless resin with a viscosity of 250 P is obtained.

30th

Comparison 2:

Example 1 is repeated with the replacement of compound I by an equimolar amount of benzoic acid. (OH number of polyester 340). A pale resin with a viscosity 35 of 470 P is obtained.

Comparison J. Example 1 is repeated, replacing the compound I with an equimolar amount of acetic acid (OH number of the Po-40 lyte ester 340), 200 T of toluene being used in the second process stage. A colorless resin with a viscosity of 157 P is obtained.

Example 2

450 parts of trimethylolpropane are condensed with 263 parts of adipic acid 45 and 54 parts of compound I at 200 ° C., with 70 parts of water being split off. 100 g of this resin (OH number 490) are dissolved in 150 T toluene and 43.8 T acrylic acid with the addition of 0.75 T 2,6-di-tert-butyl-cresol and 1 T concentrated sulfuric acid and as in Example 1 implemented. After the azeotropic separation of the water formed in this way, the solvent is distilled off under reduced pressure, a slightly yellowish resin having a viscosity of 753 P being obtained.

55 Example 3

450 parts of trimethylolpropane, 263 parts of adipic acid and 58 parts of compound XII are condensed at 200 ° C., with 65 parts of water being split off. 100 T of this resin (OH number 560) are dissolved in 150 T toluene and 43.8 T acrylic acid and after 60 addition of 1 T 2,6-di-tert-butyl-cresol and 1.5 T concentrated sulfuric acid as in Example 1 implemented. When the water separation is complete, the solvent is distilled off and a slightly yellowish resin with a viscosity of 725 P is obtained.

65

Example 4

472 parts of 1,6-hexanediol are condensed with 876 parts of adipic acid and 80 parts of a compound of the formula I under the stated conditions at 200 ° C., with 132 parts of water

631 476

separate. 100 T of this resin (SZ 210) are dissolved in 150 T toluene and 43.4 T 2-hydroxyethyl acrylate, 0.75 T 2,6-di-tert-butyl-cresol and 1.5 T conc. Added sulfuric acid and reacted at 95 ° C under slightly reduced pressure. After the water has been separated off, the solvent is distilled off under reduced pressure, a pale yellowish resin having a viscosity of 720 P being obtained.

Example 5

118 parts of 1,6-hexanediol are mixed with 124 parts of ethylene glycol,

292 parts of adipic acid and 36 parts of a compound of formula I condensed at 200 ° C., 75 parts of water separating out. 100 parts of this resin (OH number 450) are dissolved in 150 parts of toluene, 60 parts of N-methylolacrylamide, 1.5 parts of 2,6-di-tert-butyl-cresol and 52.0 parts of conc. Added sulfuric acid and reacted at 95 ° C under slightly reduced pressure. After water separation, the mixture is worked up as in Example 1, giving a pale yellowish resin with a viscosity of 850 P.

table

example

pigment

Drying speed

shine

C.I. Number approx. M / min.

1

Pigm. Yellow 126

180

excellent

Pigm. Blue 15

270

very well

Comparison 1

Pigm. Yellow 126

40

Good

Pigm. Blue 15

40

Good

Comparison 2

Pigm. Yellow 126

80

satisfying

Pigm. Blue 15

80

mediocre

Comparison 3

Pigm. Yellow 126

20th

not very good

Pigm. Blue 15

20th

Bronze the prints

2nd

Pigm. Yellow 126

240

Good

Pigm. Blue 15

300

Good

3rd

Pigm. Yellow 126

190

very well

Pigm. Blue 15

210

Good

Example 1 shows a system with a particularly high gloss and good drying properties, while systems according to Example 2 have very good drying and good gloss. In contrast, the comparative resins dry much worse and sometimes have a much poorer gloss. It does not matter whether they are not (comparison 1) or modified with an aromatic (comparison 2) or aliphatic (comparison 3) acid. Example 3 has a high gloss with good drying properties.

Formula sheet

3 cooh

(I)

cooh hooc

(II)

cooh

(III)

hooc cooh

(iv)

ho ch, oh

(V)

ho

(VI)

ho oh oh (vii)

Oh oh

(viii)

ch2oh

(ix)

hoh2c ch2oh

(x)

ch, nh,

(xi)

h2nch2

ch2nh2

(xii)

ho

(xiii)

?

Oh

(XIV)

Claims (12)

631 476 PATENT CLAIMS 1. Use of unsaturated polyesters from A) at least one mono-, β-olefinically unsaturated dicarboxylic acid and / or a polycarboxylic acid which is free from polymerizable aliphatic multiple bonds, B) at least one polyhydric alcohol, C) at least one condensable acrylic compound and D) at least one polycyclic compound bonded via a functional group from the series carboxyl, hydroxyl and primary amino group or via a plurality of only identical functional groups from this series with a norbornane skeleton as a binder in binder systems for the preparation of radiation-curable systems Coatings, coatings, adhesives, fillers or printing inks. 2. Use according to claim 1, characterized in that the binder system contains at least one reactive diluent in amounts up to 60 wt .-%, based on the binder system. 3. Use according to claim 1 or 2, characterized in that the binder system contains sensitizers in amounts of 2 to 20, preferably 3 to 10 wt .-%, based on the binder system. 4. A process for the preparation of a binder in the form of an unsaturated polyester from A) at least one mono-, β-olefinically unsaturated dicarboxylic acid and / or a polycarboxylic acid which is free from polymerizable aliphatic multiple bonds, B) at least one polyhydric alcohol C) at least one acrylic compound , which is condensed into the polyester by forming ester bonds, and the component D) mentioned below, characterized in that in the 1st stage components A) and B) and additionally D) at least one polycyclic compound with a norbornane skeleton and with a functional group from the series carboxyl and hydroxyl group or a plurality of only similar functional groups from this series are reacted with one another with ester formation, and that in the second stage the reaction product obtained with component C) is also reacted with ester formation. 5. The method according to claim 4, characterized in that the polycyclic compound D) has a C-C double bond in a fused 5-ring. 6. The method according to claim 4 or 5, characterized in that the polycyclic compound D) in amounts of at least 0.5, preferably 3 to 30% by weight, based on the polyester resin obtained in the second stage, is condensed into the polyester. 7. The method according to any one of claims 4 to 6, characterized in that acrylic acid or methacrylic acid is used as the acrylic compound C). 8. The method according to any one of claims 4 to 6, characterized in that the acrylic compound C) is N-alkylolacrylic amide having up to 4 carbon atoms in the alkyl-ol group. 9. The method according to any one of claims 4 to 8, characterized in that the reaction is carried out in the 1st stage at 160 to 250 ° C and in the 2nd stage at 70 to 120 ° C. 10. The method according to any one of claims 4 to 9, characterized in that catalysts are added in the second reaction stage. 11. The method according to any one of claims 4 to 10 with the exception of claim 8, characterized in that the polyester resins have an OH number between 100 and 1000, preferably between 200 and 800, before the reaction with the acrylic compounds. 12. The method according to any one of claims 4 to 10 with the exception of claims 7 and 8, characterized in that the polyester resins have an acid number between 100 and 800, preferably between 200 and 600 before the reaction with the acrylic compounds and in the second stage with hydroxyal alkyl acrylates or methacrylates are implemented.