DE2550740A1 - RADIANT COATING COMPOUNDS - Google Patents

Description

BASF Aktiengesellschaft

Our sign; O ₀ Z ₀ 31 673 Dd / MK 6700 Ludwigshafen, H ₀ 11.1975

Radiation-curable coating compositions

The invention relates to radiation-curable coating compositions which have a polymerizable, unsaturated binder as the binder Aminoplast resin with (meth) acrylic groups contain »

It is known that coating compositions, which act as binders, acrylate groups Contain load-bearing prepolymers that can be cured by high-energy rays and thereby coatings with good adhesion, smooth surface and good abrasion and impact resistance

According to DT-AS 1 745 540 polymerizable amino resins are produced by reacting melamine / formaldehyde condensates with hydroxyacrylates. As catalysts for this Implementation, cation exchange resins or silicates are used » The use of hydrochloric acid supposedly leads to gelling of the reaction mass during the reaction »In the DT-AS 2 132 318 are quite complex electron beam-curable paints and coatings based on acrylate described, which contain, among other things, a reaction product of an amine / formaldehyde condensate with a hydroxyacrylate » The reaction is carried out in a weakly alkaline or weakly acidic environment, e.g. in the presence of acrylic acid. The electron beam-curable acrylate-modified melamine / formaldehyde condensates according to SZ-PS 560 729 are also used by conversion in the weakly acidic range, ζ »Bo in the presence from formic acid, produced »

Experiments have shown that such reaction products of amine / formaldehyde condensates produced in the weakly acidic range have a relatively low reactivity with hydroxy (meth) acrylates, so that during curing Long exposure times with UV light or during curing high doses of radiation are necessary with electron beams.

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The invention was based on the object of radiation-curable Provide coating compositions that are easy to use as a binder polymerizable unsaturated amino resins with high reactivity which can be prepared contain =

It has been found that this object is achieved when in the preparation of the polymerizable unsaturated amino resins optionally completely or partially etherified amine / formaldehyde condensates with hydroxyl or amino groups containing (meth) acrylic! compounds in the presence of organic or inorganic acids with a pK value <3.0 are converted »

According to the explanations of DT = AS 1 7 ^ 5 540, it was not to be expected that this reaction with strong acids would even be feasible _{or similar}

The amine / formaldehyde condensates of component A are condensation products of aminoplast formers bearing amino, imino or amido groups with 1 to 2 moles of formaldehyde per amino, imino or amido group , Urea, benzoguanamine, acetoguanamine, acetylenediurea, ethylene urea, propylene urea, also carbamates and urons »These compounds are condensed with formaldehyde in a weakly alkaline range, whereby, depending on the reaction conditions, simple reaction products or higher condensed polymeric compounds can arise» They are characterized by the - N-CH ₂ -O group, where 1 or 2 -CHg-O groups can be located on a nitrogen »

These condensation products can now be used directly for the reaction according to the invention. However, it is preferred to use them in a wholly or partially etherified form. This etherification generally becomes acidic Medium carried out, being monoalcohols with 1 to 6 carbon atoms are used »Preference is given to condensation products of melamine with 3 to 6 molecules of form

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aldehyde, which are preferably partially etherified with monoalcohols, with methanol or butanol, ₀ The component A can be used neat or in aqueous or alcoholic solution.

The amine / formaldehyde condensates A are now with hydroxy I- or (meth) acrylic compounds bearing amino groups B implemented »Preference is given to monoesters of (meth) acrylic acid with alkanediols with 2 to 4 carbon atoms, such as Hydroxyäthy 1 (meth) acrylate, HydroxypropyKmeth-) acrylate and Butandxolmonoacrylatο Furthermore, N-MethyIo1 (meth -) - acrylamide, and N-methylol (meth -) acrylamide etherified with butanediol suitable “As amino group-bearing compounds acrylamide and methacrylamide come into consideration. Particularly good results are obtained when mixtures of hydroxyl and (meth) acrylic compounds containing amino groups can be used in a molar ratio of 4 s 1 to 1 s 4 »

The proportions in the reaction according to the invention are chosen so that for 1 equivalent -CHp-O- group of the amine / formaldehyde condensate 1/3 to 1 mol of acrylic compound is used «,

The essence of the invention is to be seen in the fact that the reaction is carried out in the presence of a strong organic or inorganic acid. The pK value of the acid in aqueous solution should accordingly be below 3.0, preferably below 2.0 (pK values tabulated Z ₀ B ₀ in Handbook of Chemistry and Physics, 48th edition, 1967/68, D9O- / D9D. The pK value is to be understood as the negative logarithm of the dissociation constant, with polybasic acids referring to the dissociation constant of the first stage » in question, for example, hydrochloric acid, sulfuric acid, para-toluenesulfonic acid, oxalic acid, maleic acid and phthalic acid. preferred is hydrochloric acid, the acids are m in amounts of 2 VaI to 60 m VaI, preferably from 3 m VaI to 40 m VaI per equivalent -CH ₂ -0 group of the amine / formaldehyde condensate used.

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The reaction is preferably carried out in the presence of 0.01 to 0.5 wt. ^, Based on the components A + B, D inhibitors, which are intended to prevent polymerization of the acrylic compounds suitable are ZOB = ₀ hydroquinone, Hydrochinonmonoalkylather, phenothiazine or Salts of N-nitrosocyclohexy! Amine ₀

The reaction temperature may be between 50 and 120 ⁰ C, preferably between 70 and 100 C. In the condensation water formed and / or volatile monoalcohols in the course of the reaction are distilled off "This can either be done by at reduced pressure, z _o B _o is carried out between 50 and 200 torr, or that the reaction in the presence of azeotropic entraining agents to as Z ₀ B ₀ cyclohexane · carried out The reaction generally lasts 10 minutes to 5 hours, "It is ended by neutralizing the catalyst acid with bases such as sodium hydroxide, soda or amines"

The obtained polymerisiertareη unsaturated amino resins generally have a viscosity from 400 to 10,000 mPas (20 ⁰ C) Low viscosity resins provide in itself useful coating compositions _o High-viscosity resins are diluted with copolymerizable organic compounds that are liquid, conveniently at room temperature. These reactive thinners can be used in amounts from 0 to 60, preferably from 10 to 50% by weight, based on the coating mass.

To achieve special effects, inorganic or organic pigments, such as Z ₀ B ₀ titanium dioxide or fillers, such as talc, can be added in amounts of from 0 to 80, preferably from 3 to 60, by weight, based on the coating mass.

Furthermore, the organic additives customary in the paint industry, such as thixotropic agents, leveling agents,

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ventilants or lubricants in amounts of up to IO GeWo # be present »

In addition to the polymerizable unsaturated aminoplastic resins according to the invention, the coating _{compositions can also contain 0} to 50% by weight of other polymerizable unsaturated binders, Z 0 B ₀ unsaturated polyesters or acrylate-modified epoxy resins, polyurethanes and saturated polyesters,

The coating compositions according to the invention can be used for painting substrates such as wood, metal, paper or plastic be used, also as fillers or as printing inks »

The curing takes place through the polymerisation of the acrylic groups. It can either be initiated with the help of electron beams with an energy between 50 and 500 KeV or with UV light are »In the latter case, the coating compositions are photoinitiators, expediently in amounts of 0.5 to 10 GewJ added.

The parts and percentages given in the examples are based on weight

Example Is

390.0 parts of hexamethoxymethyl melamine, 432.0 parts of butanediol monoacrylate

0.5 parts hydroquinone

4.7 parts of concentrated hydrochloric acid _o
240.0 parts of cyclohexane

The reaction mixture is heated to the boil. A mixture of water and methanol is removed via an azeotrope separator. The temperature rises from 70 to 85 ⁰ C. After neutralization with aqueous sodium hydroxide solution, the cyclohexane is removed by distillation or vacuum distillation to 90 ⁰ C. Approx. 700 g of resin with a viscosity of approx. 1,500 mPas remain in the flask. 709821/0809

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Hardening; **

a) electron beam hardening;

The resin was applied to sheet metal with a layer thickness of 120 / U applied and irradiated with 0.9 Mrad »The lacquer film is as hard as a nail and shiny»

b) UV curing:

The resin was mixed with 4% benzoin butyl ether and applied at a belt speed of 20 m / min in a layer thickness of 15 / rev under nitrogen with a high-pressure mercury tube with 80 watts / cm and a length of 20 cm (HOK 2 UV tube) irradiated »Here, too, the resulting film is as hard as a nail and shiny»

Example 2;

550.0 parts of hexabutoxymethyl melamine

71.0 parts of acrylamide
144.0 parts of butanediol monoacrylate
1.0 part oxalic acid
0.5 parts hydroquinone

About 135 g are distilled off in vacuo at 100 ^° C. in the course of an hour. After neutralization with sodium hydroxide solution, the viscous resin is diluted with 45 parts of 2-ethylhexyl acrylate »

Example 3s

350.0 parts of a 70% strength aqueous solution of a partially with

Methanol etherified tetramethylolmelamine 390.0 parts of hydroxypropyl acrylate

0.5 parts hydroquinone

2.4 parts of concentrated hydrochloric acid

In a vacuum at 70 to 80 ⁰ C in the course of ~ b> 5 hours about 125 g of distilled off. It is neutralized with sodium hydroxide solution.

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The resin mixed with 4 $ benzoin butyl ether results in a belt speed of 10 m / min and irradiation with a
UV lamp HOK 6 (tube length 60 cm) a nail-hard, shiny PiIm ₀

Example 4:

1,140.0 parts of an 80% methanolic solution of hexamethylolmelamine partially etherified with methanol, 426.0 parts of acrylamide
I ₀ 170.0 parts of hydroxypropyl acrylate
1 _S 5 parts hydroquinone
7.2 parts concentrated hydrochloric acid

In vacuum ° C in the course of 4.5 hours in total be approximately 410 g _o abdestillierto The residual resin is filtered after the neutralization from 70 to 120 »

The resin is mixed with 4% benzoin butyl ether and a 30 / rev film is irradiated at a belt speed of
7 m / min with access to air with a HOK 6 UV lamp, this gives a hard, glossy paint film, »

Comparative example according to DT-AS 1 745 540, example 5

390.0 parts of hexamethoxymethyl melamine
130.0 parts of hydroxypropyl acrylate

0.2 parts hydroquinone
26.0 parts of strongly acidic cation exchanger

It was heated to 97 ° C for 4 hours »This went against the
DT-AS no distillate over »

If the filtered resin is mixed with 4% benzoin butyl wire, even at a belt speed of only 2 m / min under a HOK 6 UV lamp, no curing occurs »

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Example 5

300 parts of an approx. 70 # strength aqueous solution of a urea-formaldehyde resin partially etherified with methanol (corresponding to approx. 2 mol of urea) 520 parts of hydroxypropyl acrylate
0.5 parts hydroquinone
1.7 parts hydrochloric acid conc "

Vacuum distillation rising from 60 to 90 ° for 2.5 hours

6 hours at 90 to 95 1 hour at 100 °

After adding 3 parts of 50 $ sodium hydroxide solution, approx. 670 g resin with a viscosity of 1 "120 mPas (at 20 °) <■

Example 6

a) According to the invention:

390 parts of hexamethoxymethylmelamine, 390 parts of hydroxypropyl acrylate, 0.5 part of hydroquinone

3.4 parts hydrochloric acid conc »

In a vacuum for about 90 minutes at 70 °, then for about 25 minutes at 90 ° (weight loss approx. “90 g). After the addition 6 parts of 50 # sodium hydroxide solution give 700 g of a resin with a viscosity of 2,480 mPas (at 20 °).

b) Comparative test according to SZ-PS 560 729, Example 2

390 parts of hexamethoxymethylmelamine, 390 parts of hydroxypropyl acrylate 0.65 parts hydroquinone

4.5 parts of formic acid

In the course of 4 hours at 110 °, approx. 40 g distilled off ο 745 g of resin with a viscosity of 200 mPas (at 20 °) obtained.

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Hardening:

The resin from Example 6a was diluted with approx. 20% hydroxypropyl acrylate to a viscosity of approx. 350 mPas (at 20 °). This solution and the resin according to Example 6b, after adding 3 % benzxldimethylketal, were applied to paper in a layer thickness of 100μ and irradiated with a HOK 6 UV lamp Film, while under these conditions the comparative resin did not show any hardening, _o

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Claims (1)

7RB074O Claims Radiation-curable coating compositions comprising acrylic groups bears as a binder, a polymerizable unsaturated aminoplast resin, the (meth), characterized _s that the polymerizable unsaturated aminoplast resin was prepared by reacting A) optionally completely or partially etherified amine / formaldehyde condensates, B) Acrylic or methacrylic compounds containing hydroxyl or amino groups, _{1/3 to 1 mol of the acrylic compound being used for 1 equivalent -CH 2} -O-GrUpPe of the amine / formaldehyde condensate, in the presence of C) an organic or inorganic acid with a pK value of <3 ₉ 0 as a catalyst in an amount of -2 m VaI to 60 m VaI per equivalent -CHg-O group of the amine / formaldehyde condensate, optionally in the presence of D) polymerization inhibitors » Coating compositions according to Claim 1, characterized in that component A is a condensation product of aminoplast formers bearing amino, imino or amido groups with 1 to 2 formaldehyde molecules per amino, imino or amido group " Coating compositions according to claim 1, characterized in that component A is an amine / formaldehyde condensation product which is completely or partially etherified with monoalcohols having 1 to 6 carbon atoms. Coating compositions according to claim 3, characterized in that component A ₃ is a condensation product of melamine and 3 to 6 molecules of formaldehyde, which is partially etherified with methanol or butanol " 709821/0809 - ii - .ο. ζ. yi 673 5ο coating compositions according to claim I _9, characterized in that component B is a monoester of (meth) acrylic acid with alkanediols having 2 to 4 carbon atoms or (meth) · acrylamide 6 "coating compositions according to claim _s l characterized in that component B is a mixture of Monoestern of (meth) acrylic acid with alkanediols having from 2 to 4 carbon atoms and (meth) acrylamide in a molar ratio 4: 1 to 1: 4o Coating compositions according to claim l characterized in _{Λ s} that component C is an acid having a pK value below 2.0 » δ »Coating compositions according to claim I ₃ , characterized by ₃ that component C is hydrochloric acid» 9. coating compositions according to claim 1, characterized in ₃ that the reaction of components A and B was carried out at temperatures between 50 and 120 C, thereby resulting water and volatile monoalcohols were distilled off under reduced pressure ,, 1Oo radiation-curable coating compounds, characterized in that they consist of 20 to 100 GeWo # of the polymerizable unsaturated Aminoplast resin according to claim 1 as a binder, 0 to 60 GewJ at room temperature liquid copolymer sizable organic compounds, 0 to 80 wt = # pigments or fillers, 0 to 10 GeWo $ of other common organic paint additives, 0 to 50% by weight of further polymerizable unsaturated binder
where the percentages add up to 100 = 7098? 1/0809 Use of the coating classes according to claim 1 for coating substrates, characterized in that the curing with electron beams of an energy
between 50 and 5 "000 KeV is carried out" BASF Aktiengesellschaft 709821/0809