CH631478A5 - Low-solvent baking finishes - Google Patents

Description

The present invention relates to low-solvent stoving lacquers which contain acrylate resin, epoxy resin, solvent and optionally pigment, catalyst and other customary auxiliaries.

Stoving lacquers which contain mixtures of acidic acrylate resin and epoxy resin, as well as pigment, solvent and, if appropriate, catalyst as binder, have long been known and are described, for example, in US Pat. Nos. 3,301,801, 3,196,120, GB Pat. No. 943,217 and US Pat FR-PSen 1 250 867, 1 315 679 and 1 352 572.

Such stoving lacquers result in coatings with good mechanical properties and good chemical resistance. They are therefore used, for example, for painting equipment.

A disadvantage of the stoving enamels on this basis, however, is that they can only be processed with a relatively high proportion of volatile organic solvents and thus make a significant contribution to environmental pollution.

The object of the present invention is therefore to provide stoving lacquers which contain acrylate resins, epoxy resins, solvents and, if appropriate, pigment and catalyst, 20 which process with significantly lower proportions of organic solvent, such as e.g. can be sprayed without adversely affecting their other processing properties and the level of properties of the baked coatings of the corresponding known prior art. The present invention relates to low-solvent stoving enamels containing

(A) an acrylic resin,

(B) an epoxy resin as well

(C) a mixture of organic solvents,

30 which are characterized in that the acrylate resin (A) is a copolymer which contains 10 to 35% by weight, based on copolymer (A), of a, β-olefinically unsaturated carboxylic acid, in polymerized form, according to a K value Fikentscher, under 15 and an acid number between 70 and 250 mg KOH / g, the 35 epoxy resin (B) contains at least two oxirane groups per molecule and the mixture of organic solvents (C) is a mixture of 20 to 80% by weight of a solvent or a solvent mixture with a boiling point between 100 and 280 ° C and a dielectric constant between 2 and 40 4.99 and 80 to 20 wt .-% of a solvent or a solvent mixture, with a boiling point between 80 and 200 ° C and a dielectric constant between 5 and 27, wherein the weight ratio of components (A) :( B) is between 9: 1 and 6: 4, the weight ratio of components 45 (A + B) :( C) is between 7: 3 and 5: 5, or Stoving lacquers a solids content of over 70% by weight.

Preference is given to such stoving lacquers which, as acrylate resin (A), are a copolymer of 12 to 25% by weight of acrylic or methacrylic acid, 5 to 70% by weight of at least one ester of acrylic 50 or methacrylic acid with 1 to 8 carbon atoms containing monoalkanols , 5 to 40 or 5 to 70 wt .-% styrene and 0 to 20 wt .-% of an allcandiol monoester of acrylic or methacrylic acid.

Particularly preferred are those stoving enamels whose 55 acrylate resin (A) has an average molecular weight Mn of 1500 to 300 and a non-uniformity (Mw / Mn) between 1.5 and 2.0 measured by gel permeation chromatography.

Those acrylate resins (A) which are obtainable from the monomers at temperatures of 170 to 280 ° C. and pressures of 1.5 to 60 30 bar, optionally in the presence of a free radical initiator and / or an organic solvent, are particularly preferred.

The stoving enamels according to the invention can surprisingly be processed with a very low solvent content. These stoving enamels can be sprayed with solids contents> 70, preferably 75 to 85% by weight, can be processed on vertical surfaces, show good flow and, after stoving, give coatings with good mechanical properties

631 478

Properties, good chemical and solvent resistance and good corrosion protection.

The following is to be stated with regard to the individual components making up the stoving enamels according to the invention.

(A) The acrylic resin (A) contains 10 to 35% by weight, based on the copolymer, of a, β-olefinically unsaturated carboxylic acids polymerized in, has a K value, measured by the Fikentscher method (cf. Cellulose Chemistry 13, 58; 1932) below 15 and an acid number between 70 and 250 mg KOH / g. In addition to dicarboxylic acids such as e.g. Maleic acid, fumaric acid and itaconic acid, preferably monocarboxylic acids, such as e.g. Acrylic acid and / or methacrylic acid, which are preferably copolymerized in amounts of 12 to 25% by weight.

The copolymer (A) may contain, in copolymerized form, as comonomers:

a) esters of acrylic and / or methacrylic acid with 1 to 8 carbon atoms containing straight-chain or branched monoalkanols, such as e.g. Ethyl acrylate, n-, iso- and tert-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, preferably in amounts of 5 to 70% by weight, based on the copolymer (A),

b) vinyl aromatics, e.g. Styrene and / or vinyl toluene, preferably in amounts of 5 to 40% by weight, based on copolymer (A), and c) optionally in amounts of up to 20% by weight of acrylic acid and / or methacrylic acid monoesters of Alkanediols with 2 to 6 carbon atoms, where the alkanediols can also contain one or more oxa groups, for example Hydroxypropyl acrylate, butanediol monoacrylate, hydroxyethyl methacrylate, diethylene glycol and triethylene glycol monoacrylate or monomethacrylate,

d) optionally in minor amounts of up to 10% by weight of further copolymerizable monomers, such as e.g. Acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methyl (meth) acrylamide, N-alkoxymethyl (meth) acrylamide, vinyl esters, e.g. Vinyl acetate, vinyl propionate, maleic and fumaric acid dialkyl esters, maleic and fumaric acid monoalkyl esters, acrolein and allyl alcohol.

Particularly preferred as acrylate resin (A) are, for example, copolymers of 12 to 25% by weight of acrylic or methacrylic acid, 10 to 40% by weight of ethyl acrylate, n-butyl acrylate or 2-ethylhexyl acrylate, 0 to 30% by weight of t-butyl acrylate and 10 to 40 or 30 to 70% by weight of styrene.

The acrylate resins (A) to be used according to the invention are preferably prepared as solution polymers in higher-boiling solvents with boiling ranges from 100 to 280 ° C. and dielectric constants between 2 and 5. The polymerization is advantageously carried out at the reflux temperature of the solvent without a regulator.

Likewise, the acrylate resins to be used according to the invention can also be prepared as solution polymers in solvents with boiling points between 80 and 200 ° C. and dielectric constants between 5 and 27. In some cases it is also expedient to work with solvent mixtures from the solvent groups indicated.

The polymerization for the production of the acrylic resin (A) can, however, also be carried out in other customary paint solvents, if appropriate in the presence of regulators.

The acrylic resins (A) to be used according to the invention can also be prepared by the bulk polymerization process and then dissolved.

The acrylic resins to be used according to the invention with a K value below 15 have as 60% solutions in ® Solvesso 100 (= aromatic hydrocarbon, boiling range 155 to 168 ° C, aromatic content> 95%) / n-butanol, viscosities at 23 ° C of generally 10 to 30 poise, preferably 15 to 25 poise. This corresponds to expiry times (spout cup with

6 mm nozzle / 23 ° C) from 70 to 200 sec, preferably 90 to 150 sec.

However, it is particularly preferred to use the acrylate resins (A) to be used according to the invention by radical oligomerization under pressures from 1.5 to 30 bar at temperatures from 160 to 280 ° C., in bulk, in particular at temperatures from 170 to 250 ° C. or in solution at 160 to 250 ° C. This radical oligomerization is then advantageously carried out without a regulator.

io The oligomerization can optionally in the presence of free radical initiators such as peroxides or hydroperoxides, e.g. Di-tert-butyl peroxide, t-butyl perbenzoate, butyl hydroperoxide, pinane hydroperoxide, cumene hydroperoxide, and organic solvents such as aromatic hydrocarbons, e.g. Solls vesso 100 from Esso (boiling range 155 to 178 ° C, aromatic content> 95%), xylene, alcohols, e.g. n-propanol, n-buta-nol, ethylene glycol monoalkyl ethers, e.g. Methyl glycol, ethyl glycol, butyl glycol, alkyl glycol ether acetate, e.g. Methyl glycol acetate, ethyl glycol acetate, butyl glycol acetate, esters e.g. Butyl-20 acetate and / or ketones, e.g. Methyl siobutyl ketone or methyl ethyl ketone can be carried out.

The acrylate resins to be preferably used according to the invention with molecular weights Mn from 1500 to 3000 have as 60% solutions in ®Solvesso 100 (= aromatic carbon-25 hydrogen, boiling range 155 to 168 ° C., aromatic content> 95%) / n-butanol in the ratio 6: 4, discharge times (discharge cup with 6 mm nozzle / 23 ° C.) from 15 to 150 seconds, preferably 20 to 90 seconds; the non-uniformity (Mw / Mn) measured by gel permeation chromatography is 1.5 to 2.0. 30 The gel permeation chromatographic determination of the non-uniformity (Mw / Mn) is carried out according to the in Journal of Applied Polymer Science, Vol. 19, 1975, pp. 629-631 or at the 5th International Seminar of the Waters Company in London, 1968 and the 6th International Siminar from Waters, method described in 1968 in 35 Miami Beach / Florida. Tetrahydrofuran is used as the solvent, cross-linked polystyrene gel (TSKG 3000 H8 and TSKG 4000 H8) as the separation column. The measurement is carried out at 23 ° C. 0.2 ml of a 0.25% solution are injected. The flow rate is 40 0.8 ml / minute.

(B) Particularly suitable epoxy resins with at least 2 oxirane groups per molecule are those with epoxy values of approximately 0.2 to 0.7 moles of epoxy / 100 g of substance. Suitable components (B) are, for example, reaction products of epichlorohydrin and bisphenol A, epichlorohydrin and polyalcohols such as trimethylolpropane or pentaerythritol or epichlorohydrin and aliphatic, cycloaliphatic or aromatic polycarboxylic acids. However, low molecular weight acrylate resins with pendant oxirane groups, for example glycidyl methacrylate homo- and copolymers, can also be used as epoxy resins (B).

The ratio of acrylate resin (A) to epoxy resin (B) is variable within wide limits, but carboxyl / epoxy ratios of 0.3: 1 to 3: 1 are preferably chosen. 55 (C) Component C is a mixture of 20 to 80% by weight of a solvent or a solvent mixture with a boiling point between 100 and 280 ° C and a dielectric constant between 2 and 4.99, and 80 to 20% by weight of one Solvent or a solvent mixture with 60 a boiling point between 80 to 200 ° C and a dielectric constant between 5 and 27.

Suitable solvents with a boiling point between 100 and 280 ° C and a dielectric constant between 2 and 4.99 are as follows:

65 Solvesso 100 (aromatic hydrocarbon from Esso with an aromatic content> 95%), Solvesso 150 (aromatic hydrocarbon from Esso with aromatic content> 95%), ®Shellsol R (aromatic hydrocarbon from the company

631 478

4th

Shell with aromatic content> 80%), toluene and xylene, as well as mixtures of these solvents.

Suitable solvents with a boiling point between 80 and 200 ° C and a dielectric constant between 5 and 27 are e.g. n-propanol, i-propanol, n-butanol, i-butanol, pentanol, amyl alcohol, 2,2-dimethylpropanol, hexanol, 2-ethylhexanol, cyclohexanol, ethylene glycol monomethyl ether ("methyl glycol"), ethylene glycol monoethyl ether ("ethyl glycol"), ethylene glycol monobutyl ether ( "Butylgly-kol"), diethylene glycol monomethyl ether ( "methyl diglycol"), diethylene glycol monoethyl ether ( "Äthyldiglykol"), diethylene glycol monobutyl ether ( "diglycol"), propylene glycol mono-methyl ether, Äthylenglykolmonoacetat, propylene glycol mono-acetate, Äthylenglykolmonoäthylätheracetat, Äthylenglykolmo-nomethylätheracetat, butyl acetate, Diacetone alcohol, 2-ethyl-mercaptoethanol, methyl isobutyl ketone, and mixtures of these solvents.

Solvent mixtures of 30 to 70% by weight of aromatic hydrocarbons with boiling ranges between 150 and 270 ° C. and aromatic contents> 80% by weight and 70 to 30% by weight of alcohols, which may contain glycol monoalkyl ether and / or glycol monoalkyl ether acetate, are preferred.

Suitable pigments are the inorganic and organic pigments customary in the paint industry, for example titanium dioxide, inorganic and organic colored pigments, carbon black, talc, Aerosil, rust protection pigments.

The solvents already described are preferably used to dilute the pigmented lacquers to spray viscosity. However, other customary paint solvents, such as aromatics, alcohols, esters, ketones, can also be used.

If appropriate, the low-solvent stoving enamels according to the invention can also be crosslinked using customary catalysts. Suitable catalysts of this type are e.g. tert. Amines such as 1,2-dimethylimidazole, 1-phenylimidazole or quaternary ammonium salts such as tetrabutylammonium iodide.

In addition, the solvent-poor stoving lacquers can be used in the lacquer industry with common auxiliaries, such as leveling agents, anti-panic agents, dispersing aids, such as e.g. Silicone oils, e.g. finely divided silica can be added as a thixotropic agent.

The stoving enamels according to the invention are suitable e.g. for the production of household appliance lacquers and automotive primer lacquers.

It is particularly advantageous that they can be processed on vertical surfaces without the addition of thixotropic agents with a layer thickness of 40 to 50 yes.

The parts and percentages given below and in the example relate to the weight.

Production of the acrylic resin I

376 parts of aromatic hydrocarbon with boiling range 155 to 178 ° C and an aromatic content> 95% (e.g. ®Solvesso 100 from Esso) and 94 parts of ethyl glycol acetate are placed in a round bottom flask and heated to reflux temperature (-155 ° C). A mixture of 300 parts of 2-ethylhexyl acrylate, 300 parts of styrene, 200 parts of t-butyl acrylate, 200 parts of methacrylic acid and 27 parts of t-butyl perbenzoate is added in 2 hours under N 2. 30 minutes after the end of the feed, another 13 parts of t-butyl perbenzoate are added and polymerization is continued for 1 hour at the reflux temperature. Solids content = 70.0%, K value (according to Fikentscher) = 13.5 (measured 3% in acetone).

The resin solution is diluted to 60% solids content with n-butanol.

Viscosity / 23 ° C 17.2 poise

Run-out time 120 sec

(Outlet cup with 6 mm nozzle / 23 ° C)

If the acrylic resin I is diluted to 50 or 40% solids content with n-butanol, the following viscosity values are obtained:

Solids content 50% by weight 40% by weight

Viscosity / 23 ° C 2.71 poise 1.25 poise

Flow time 62 sec 21 sec ok (flow cup with 6 mm nozzle / 23 ° C)

Production of the acrylic resin II

175 parts of aromatic hydrocarbon with a boiling range of 155 to 178 ° C and an aromatic content> 95% (e.g. ®Solvesso 100) are placed in a round bottom flask and heated to reflux (~ 160 ° C) under i5N2. A mixture of 210 parts of 2-ethylhexyl acrylate, 210 parts of styrene, 140 parts of t-butyl acrylate, 140 parts of methacrylic acid and 19 parts of t-butyl perbenzoate is then added in 2 hours. 30 minutes after the end of the feed, a further 9 parts of t-butyl perbenzoate are added and polymerization is continued for 1 hour.

Solids content = 81.0%, K value (according to Fikentscher) = 13.2 (measured 3% in acetone).

Acrylate resin II is mixed with an aromatic hydrocarbon (boiling point 155 to 178 ° C, aromatic content> 2595%, e.g. Solvesso 100), n-butanol, or mixtures of this aromatic hydrocarbon (= KW) and n-butanol to a solids content of 65 % diluted. The following viscosity values resulted:

Solvent at 65% solids viscosity

30 100 parts aromatic KW> 800 P

62 parts aromatic KW 104 P

38 parts of n-butanol

50 parts of aromatic KW 72 P

50 parts of n-butanol 35 38 parts of aromatic KW 53 P

62 parts of n-butanol If the acrylic resin II is diluted with aromatic hydrocarbon (boiling range 155 to 178 ° C, e.g. Solvesso 100) to a solids content of 50%, the viscosity is 40 of 220 poise.

An acrylate resin III produced analogously to acrylate resin II gives a solids content = 82.0% and a K value (according to Fikentscher) of 14.8.

Acrylate resin III is diluted to 65% solids with different polar solvents. The following viscosity values result:

Thinner viscosity n-butanol 127 poise

Ethyl glycol 121 poise

50i-butnaol 208 poise

Butyl glycol 288 poise

Butyl diglycol 500 poise

Ethyl glycol acetate 796 poise

55 Production of the acrylic resin (A) IV:

In an oil-heated steel kettle, 1.5 parts of an aromatic hydrocarbon with a boiling range of 155 to 178 ° C and an aromatic content> 95% (e.g. ®Solvesso 100 from Esso) are heated to 200 ° C. The pressure in the boiler rises to approx. 1.6 bar. A monomer mixture of 1.575 parts of styrene, 1.313 parts of 2-ethylhexyl acrylate and 0.613 parts of acrylic acid, to which 0.070 part of di-tert-butyl peroxide had previously been added, is then added to the boiling solvent in 30 minutes under pressure. The pressure in the 65 boiler rises to 7 bar. After the end of the feed, the resin is stirred under pressure at 200 ° C. for a further 30 minutes, then the kettle is cooled to 120 ° C., the pressure is released and the resin is adjusted to a solids content of 60% with n-butanol.

631478

Expiry time

(Outlet cup with 6 mm nozzle / 23 ° C) 31 sec

Acid number (solid resin) 135 mg KOH / g average molecular weight Mn in toluene 2300

Inconsistency (Mw / Mn) GPC 1.78

Production of the acrylic resin (A) V:

60 parts of styrene, 25 parts of 2-ethylhexyl acrylate, 15 parts of acrylic acid and 2 parts of di-tert-butyl peroxide are heated in a continuous pressure autoclave at 210 ° C. at 24 bar for 10 minutes. The reaction mixture is then pressed through a static mixer for postpolymerization (approx. 15 minutes at 200 ° C.). The unreacted monomers are then distilled off at 230 ° C. and normal pressure. The resin is dissolved 60% in a solvent mixture consisting of 6 parts Solvesso 100 and 4 parts n-butanol. Expiry time

(Flow cup with 6 mm nozzle / 23 ° C) 26 sec acid number (solid resin) 113 mg KOH / g average molecular weight Mn in toluene 1800 inconsistency (Mw / Mn) GPC 1.86

example 1

124.0 parts of acrylic resin I (solids content = 60%) 26.4 parts of epoxy resin based on bisphenol A / epichlorethylene

inside, (epoxy value = 0.54)

140.0 parts TiOz 2.0 parts tetrabutylammonium iodide (10% in n-buta-

nol / xylene 1: 1)

6.0 parts of n-butanol 6.0 parts of xylene are on a vibratory mill, e.g. Rad De-vil, intensely dispersed.

The mixture is then diluted to a spray viscosity (DIN 53 211 = 60 sec) with about 15 parts of a solvent mixture (butylglycol / xylene 1: 1).

Solids content = 74.0%.

The paint is sprayed onto sheet steel and baked at 140 to 190 ° C for 30 minutes.

Testing the paint:

Layer thickness 50 [x

Gloss 60 ° (DIN 67 530) 95

Pendulum hardness (DIN 53 157) 160 sec

Erichsen cupping (DIN 53 156) 4.5 mm

Soapy water resistance 7 rounds

The resistance to wash liquor is determined by boiling a coated sheet in a 1% solution of a commercially available detergent (e.g. OMO) for 8 hours and leaving it in the cold solution overnight. This test is repeated until there are noticeable changes in the coating, e.g. Loss of gloss, blistering or detachment from the sheet is observed

The low-solvent stoving varnish can be processed without a thixotropic agent with a layer thickness of 40 to 50 µm on vertical surfaces.

Example 2

124.0 parts of acrylic resin IV (solids content = 60%) 26.4 parts of epoxy resin based on bisphenol A (epoxy value = 0.54)

s 140.0 parts Ti02

2.0 parts tetrabutylammonium iodide (10% in n-buta-

nol / xylene 1: 1)

6.0 parts of n-butanol 6.0 parts of xylene are intensively dispersed on a vibrating ball mill (e.g. Red Devil) for 30 minutes.

The mixture is then diluted to a spray viscosity (DIN 53 211 = 60 sec) with about 15 parts of a solvent mixture (butylglycol / xylene 1: 1).

15 solids content = 76.1%

The paint is sprayed onto sheet steel and baked at 150 ° C for 30 minutes.

Testing the paint:

Layer thickness 64 n

20 gloss 60 ° (DIN 67 530) 92

Pendulum hardness (DIN 53 157) 164 sec

Erichsen cupping (DIN 53 156) 2.6 mm

Detergent resistance 8 rounds

The resistance to washing water is determined by boiling a coated sheet in a 1% solution of a commercially available detergent (e.g. OMO) for 8 hours and leaving it in the cold solution overnight. This test is repeated until there are noticeable changes in the coating, e.g. Loss of gloss, blistering or detachment from the sheet can be observed.

Example 3

124.0 parts of acrylic resin V (solids content = 60%) 26.4 parts of epoxy resin based on bisphenol A, (epoxy-35 value = 0.54)

140.0 parts Ti02 2.0 parts tetrabutylammonium iodide (10% in n-buta-

nol / xylene 1: 1)

6.0 parts of n-butanol 40 6.0 parts of xylene are intensively dispersed on a vibrating ball mill (e.g. Red Devil) for 30 minutes.

Then it is diluted to about 15 parts of a solvent mixture (butylglycol / xylene 1: 1) to spray viscosity (DIN 53 211 = 60 45 sec).

Solids content = 78.5%

The paint is sprayed onto sheet steel and baked at 150 ° C for 30 minutes.

50

Testing the paint:

Layer thickness 62 jx

Gloss 60 ° (DIN 67 530) 96

Pendulum hardness (DIN 53 157) 144 sec

55 Erichsen cupping (DIN 53 156) 8.8 mm

Soapy water resistance 7 rounds

C.

Claims (8)

631 478 PATENT CLAIMS 1. Low-solvent stoving enamels, containing (A) an acrylic resin, (B) an epoxy resin as well (C) a mixture of organic solvents, characterized in that the acrylate resin (A) is a copolymer which contains 10 to 35% by weight, based on copolymer (A), of a, β-olefinically unsaturated carboxylic acids in copolymerized form, a K value, according to Fikentscher , below 15 and has an acid number between 70 and 250 mg KOH / g, the epoxy resin (B) contains at least two oxirane groups per molecule and the mixture of organic solvents (C) is a mixture of 20 to 80% by weight of a solvent or a solvent mixture with a boiling point between 100 and 280 ° C and a dielectric constant between 2 and 4.99 and 80 to 20 wt .-% of a solvent or a solvent mixture with a boiling point between 80 and 200 ° C and a dielectric constant between 5 and 27, wherein the weight ratio of components (A) :( B) is between 9: 1 and 6: 4, the weight ratio of components (A + B) :( C) is between 7: 3 and 5: 5, or the stoving lacquers have a solids content of more than 70% by weight . 2. Low solvent stoving enamels according to claim 1, characterized in that the acrylate resin (A) is a copolymer of 12 to 25 wt .-% acrylic or methacrylic acid, 5 to 70 wt .-% of at least one ester of aryl or methacrylic acid with 1 to Monoalkanols containing 8 carbon atoms, 5 to 40% by weight of styrene and 0 to 20% by weight of an alkanediol monoester of acrylic or methacrylic acid. 3. Low-solvent stoving enamels according to one of the preceding claims, characterized in that the epoxy resin (B) has an epoxy value of 0.2 to 0.7 mol epoxy / 100 g substance. 4. Low-solvent stoving enamels according to one of the preceding claims, characterized in that the carboxyl / epoxy ratio of acrylate resin (A) to epoxy resin (B) is 0.3: 1 to 3: 1. 5. Low solvent stoving enamels according to claim 1, characterized in that the acrylate resin (A) is a copolymer of 12 to 25 wt .-% acrylic or methacrylic acid, 10 to 40 wt .-% of at least one compound from the group consisting of ethyl acrylate, n -Butyl acrylate and 2-ethylhexyl acylate, 10 to 40% by weight of styrene and 0 to 30% by weight of t-butyl acrylate. 6. Low-solvent stoving enamels according to one of claims 1 to 4, characterized in that the acrylate resin (A) has an average molecular weight Mn of 1500 to 3000 and a non-uniformity (Mw / Mn) measured by gel permeation chromatography between 1.5 and 2.0 . 7. Low solvent stoving enamels according to claim 6, characterized in that the acrylate resin (A) is a copolymer of 12 to 25 wt .-% acrylic or methacrylic acid, 5 to 70 wt .-% of at least one ester of acrylic or methacrylic acid with 1 to Monoalkanols containing 8 carbon atoms, 5 to 70% by weight of styrene and 0 to 20% by weight of an alkanediol monoester of acrylic or methacrylic acid. 8. Low solvent stoving enamels according to claim 6 or 7, characterized in that the acrylate resin (A) is such as it is at temperatures from 170 to 280 ° C and pressures from 1.5 to 30 bar, optionally in the presence of a radical initiator and / or an organic solvent from which the monomers can be obtained.