DE102009040058A1 - Producing polyamines, comprises producing polyhydroxy compounds terminated with carboxylic acid ester, with acrylic acid alkyl esters, in presence of catalyst, removing acrylic acid alkyl ester and reacting product with aliphatic polyamine - Google Patents

Abstract

The invention relates to a process for preparing low-viscosity, hydrolysis-stable, amino-containing polyoxyalkylenes. The compounds thus obtained can be used for the preparation of polyurethane ureas, which in turn can be used for the production of coatings, adhesives and sealants or porous foams or non-porous moldings.

Description

The The invention relates to a process for the production of low-viscosity, hydrolysis-stable, amino-containing polyoxyalkylenes. The thus obtained compounds can be used for the production of polyurethane ureas, Which in turn for the production of coatings, adhesives and Sealants or porous foams or not porous moldings can be used, be used.

Amino-containing polyoxyalkylenes and processes for the conversion of OH groups into amino groups are known in principle. For example, describes DE-A 1 643 426 a process for the direct exchange of OH groups by amino groups by catalytic conversion of polyoxyalkylenes in an ammonia-hydrogen atmosphere under pressure to polyoxyalkyleneamines.

In addition to this, referred to as Direktaminierung process, multi-step process are known in which the end groups of polyoxyalkylenes are modified in the first step so that in the second step, the formation or introduction of an amino group is possible. So describes US Pat. No. 4,847,416 a 2-stage process in which polyoxyalkylenes are reacted with chloronitrobenzenes in the first stage to give nitro group-terminated polyoxyalkylenes. In the second stage, the nitro groups are reduced to amino groups under a hydrogen atmosphere.

In the US Pat. No. 5,072,020 NCO prepolymers are reacted with nitroalkanols and hydrogenated in the second step, the nitro group to the amino group.

US Pat. No. 3,799,986 describes a process for addition of acrylonitrile to polyether polyols and subsequent hydrogenation of the nitrile group to the amino group.

Of the Disadvantage of this method is that the reaction in a reactive gas atmosphere and partially performed under elevated pressure Need to become. This has the consequence that such procedures with an increased security risk and thus increased Investments and costs are associated. Therefore, as a rule preferred chemical processes in which the transfer an OH group in an amino group in pressureless process under an inert gas atmosphere can be performed.

In the DE-A 2 019 432 For example, a process for producing polyamines by reacting polyhydroxy compounds with isatoanhydride is claimed.

Of the Disadvantage of this method is that the attachment of the amino groups carrying residual is done by an ester group. However, to ensure that polymers resulting from the reaction of a polyamine and a polyisocyanate are obtained, are resistant to hydrolysis, the use of Raw materials that carry ester groups in their main chain are prohibitive.

The DE-A 10 2005 028 081 describes a process for the partial hydrolysis of NCO prepolymers to amino-containing polyurethane prepolymers.

In US Pat. No. 6,355,829 For example, a process is claimed in which NCO prepolymers are reacted with secondary diamines, in particular polyaspartic acid esters, to form polyamines.

Of the Disadvantage of the latter method is that the polyamines obtained have a high viscosity. This is especially so a disadvantage, because the production of polyurethane ureas under Use of polyoxyalkyleneamines and polyisocyanates by a high rate of polymerization, usually only a few seconds, is characterized. Therefore, such polyurethane ureas often be applied by spraying onto a substrate, wherein the viscosity of the usable polyamines to a few 1000 mPas is limited.

task The present invention was therefore an unpressurised process for the preparation of low-viscosity, amino-containing polyoxyalkylenes to develop, in which the amino groups on hydrolysis Groups are attached to the polyoxyalkylene skeleton.

It was found to be low viscosity, hydrolysis stable and amino groups having polyoxyalkylenes according to the following process according to the invention with good yield and selectivity can be made.

• A) Herstellung von mit Carbonsäurestergruppen terminierten Polyhydroxyverbindungen durch Umsetzung von Polyhydroxyverbindungen mit einer mittleren Funktionalität von mindestens 1,5
• a1) mit Acrylsäurealkylestern in einem molaren Verhältnis von OH-Gruppe zu Doppelbindung von 1:1 bis 1:10, bevorzugt 1:1 bis 1:5, besonders bevorzugt 1:1,8 bis 1:2,2 und ganz besonders bevorzugt 1:2,
• a2) in Anwesenheit eines Katalysators in einem molaren Verhältnis von OH-Gruppe zu Katalysator von 1:0,5, bevorzugt 1:0,05,
• a3) in einem Temperaturintervall von 0°C bis 100°C, bevorzugt 0°C bis 70°C und besonders bevorzugt 20°C bis 40°C,
• a4) ggfs. Entfernen eines Überschusses Acrylsäurealkylester aus a1) und Lösemittel aus a2) und
• B) Umsetzung des Produktes aus A)
• b1) mit aliphatischen Polyaminen im molaren Verhältnis von Estergruppe zu Aminogruppe von 1:1 bis 1:10, bevorzugt 1:1 bis 1:5, besonders bevorzugt 1:1,8 bis 1:2,2 und ganz besonders bevorzugt 1:2,
• b2) in einem Temperaturintervall von 20°C bis 200°C, bevorzugt 80°C bis 200°C und besonders bevorzugt 80°C bis 150°C und
• b3) ggfs. Entfernen eines Überschusses eingesetzter aliphatischer Polyamine aus Schritt b1).

The invention relates to a process for the preparation of aliphatic amino-containing polyamines from polyols

• A) Preparation of carboxylic acid ester-terminated polyhydroxy compounds by reacting polyhydroxy compounds having an average functionality of at least 1.5
• a1) with acrylic acid alkyl esters in a molar ratio of OH group to double bond of 1: 1 to 1:10, preferably 1: 1 to 1: 5, more preferably 1: 1.8 to 1: 2.2, and most preferably 1 : 2,
• a2) in the presence of a catalyst in a molar ratio of OH group to catalyst of 1: 0.5, preferably 1: 0.05,
• a3) in a temperature range from 0 ° C to 100 ° C, preferably 0 ° C to 70 ° C and especially preferably from 20 ° C to 40 ° C,
• a4) if necessary. Removing an excess of alkyl acrylates from a1) and solvents from a2) and
• B) reaction of the product from A)
• b1) with aliphatic polyamines in a molar ratio of ester group to amino group of 1: 1 to 1:10, preferably 1: 1 to 1: 5, more preferably 1: 1.8 to 1: 2.2 and most preferably 1: 2 .
• b2) in a temperature range of 20 ° C to 200 ° C, preferably 80 ° C to 200 ° C and particularly preferably 80 ° C to 150 ° C and
• b3) optionally removing an excess of aliphatic polyamines used from step b1).

For the preparation of carboxylic acid groups described in step A) terminated polyhydroxy compounds can be used as polyhydroxy compounds all compounds known to those skilled in the art are used, which an average OH functionality of at least 1.5, preferably of at least 1.7. This can be, for example low molecular weight diols (eg 1,2-ethanediol, 1,3- or 1,2-propanediol, 1,4-butanediol), triols (eg, glycerin, trimethylolpropane) and tetraols (For example, pentaerythritol), but also higher molecular weight polyhydroxy compounds such as polyether polyols, polyester polyols, polycarbonate polyols, and Polythioetherpolyols.

However, preference is given to polyether polyols having number average molecular weights M _{n of} from 300 to 20 000 g / mol, more preferably from 1000 to 12000 g / mol, very particularly preferably from 2000 to 6000 g / mol. Such polyether polyols are accessible in a conventional manner by alkoxylation of suitable starter molecules under base catalysis or use of Doppelmetallcyanidverbindungen (DMC compounds). Suitable starter molecules for the preparation of polyether polyols are, for example, simple, low molecular weight polyols, water, organic polyamines having at least two NH bonds or any mixtures of such starter molecules. Preferred starter molecules for the preparation of polyether polyols by alkoxylation, in particular by the DMC process, are in particular simple polyols such as ethylene glycol, 1,3-propylene glycol and 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-ethylhexanediol 1,3, glycerol, trimethylolpropane, pentaerythritol and low molecular weight, hydroxyl-containing esters of such polyols with dicarboxylic acids of the exemplified species mentioned below or low molecular weight ethoxylation or propoxylation of such simple polyols or any mixtures of such modified or unmodified alcohols. Alkylene oxides which are suitable for the alkoxylation are, in particular, ethylene oxide and / or propylene oxide, which can be used in any order or also in a mixture in the alkoxylation.

Particularly suitable polyether polyols are those of the abovementioned type with an unsaturated end group content of less than or equal to 0.02 meq / gram of polyol (meq / g), preferably less than or equal to 0.015 meq / g, more preferably less than or equal to 0.01 meq / g (determination method ASTM D2849-69 ). Such polyether polyols can be prepared in a conventional manner by alkoxylation of suitable starter molecules, in particular using double metal cyanide catalysts (DMC catalysis). This is z. B. in the US-A 5,158,922 (eg example 30) and EP-A 0 654 302 (P.5, Z. 26 to p.6, Z. 32).

Examples for the alkyl acrylates used in step a1) are methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate.

The Molar ratio of OH group to double bond is 1: 1 to 1:10, preferably 1: 1 to 1: 5, particularly preferably 1: 1.8 to 1: 2.2 and most preferably 1: 2.

In Step a2) of the method according to the invention can as catalysts basic compounds are used. The used Catalysts may be solid or liquid However, in the reaction mixture, a sufficient, preferably complete, Possess solubility. Not soluble in the reaction mixture Catalysts can be prepared by the addition of a suitable Solvent be brought into solution.

Basic catalysts are, for example, inorganic and organic salts which give an alkaline reaction in water. Particularly suitable are from this group hydroxides of alkali and alkaline earth metals, for example, sodium hydroxide and potassium hydroxide, also soluble aluminates such. As sodium aluminate, carbonates of alkali metals, especially soda and potash, bicarbonates of alkali metals, especially sodium and potassium bicarbonate, alkali and alkaline earth metal salts of mono- and polycarboxylic acids containing no NCO-reactive groups, preferably salts of aliphatic monocarboxylic acids with up to 18 C atoms, z. Sodium formate, sodium acetate, potassium octoate or potassium stearate. Alkali metal salts of phenols and thiophenols optionally substituted by non-NCO-reactive groups, soluble alkali metal and alkaline earth metal salts of weak, preferably inorganic, acids such as cyanic acid, isocyanic acid, thiocyanic acid, isothiocyanic acid, silicic acid, phosphorus III to V acids; Hydrocyanic acid, hydrazoic acid, etc., alkali metal mercaptides and sulfides or hydrogen (poly) sulfides, β-diketone compounds such as the Na, K, Mg acetylacetonates and acetoacetates. Alkali and alkaline earth metal salts can also be formed in situ by reaction of the corresponding alkali or alkaline earth metal with the polyhydroxy compound. In addition, in particular such quaternary ammonium hydroxides and quaternary phosphonium hydroxides in question, resulting in organic solvents such. As aliphatic and aromatic hydrocarbons, ethers, alcohols, tert. Dissolve amines, ketones, esters, nitriles, lactams or ureas well. Examples are tetramethylammonium hydroxide, tetraethylammonium hydroxide, Trimethylvinylammoniumhydroxid, tetrapropylammonium hydroxide, tetra-n-butylammonium hydroxide, Dimethylethyldodecylammoniumhydroxid, Trioctylmethylammoniumhydroxid, dimethyldiethylammonium, Triethylmethylammoniumhydroxid, Tributylmethylammoniumhydroxid, dodecyltrimethylammonium hydroxide, Didodedecyldimethylammoniumhydroxid, hexadecyltrimethylammonium, Octadecyltrimethylammoniumhydroxid, benzyltrimethylammonium hydroxide, benzyltriethylammonium hydroxide, Dibenzyldimethylammoniumhydroxid, N-Dodecylpyridiniumhydroxid, Tripropylmethylammoniumhydroxid, trimethylbenzylammonium hydroxide, triethylbenzylammonium hydroxide, 4-Dimethylamino-N-hexadecylpyridinium hydroxide, tetraethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, trioctylmethylphosphonium hydroxide, hexadecyltrimethylphosphonium hydroxide and triphenylmethylphosphonium hydroxide.

preferred However, catalysts are the hydroxides of alkali and alkaline earth metals, in particular NaOH and KOR, as well as quaternary ammonium hydroxides. Very particular preference is given to the use of benzyltrimethylammonium hydroxide (Triton B).

The Catalysts to be used according to the invention are technically easily accessible, cheap catalysts, which can be separated and reused if necessary, however, remain in the product in the preferred embodiment.

Prefers the catalyst is in a molar ratio of OH group to catalyst from 1: 0.01 to 1: 0.5, preferably 1: 0.02 to 1: 0.1 and most preferably 1: 0.05.

basic Catalysts may optionally be added by addition of acid partially or completely neutralized, which for example facilitate their separation or their activity at any Can reduce follow-up conversions.

As a solvent for the catalyst from step a2) can Carbonsäuredialkylamide, lactams, tetraalkylated aliphatic ureas having 4 to 12 carbon atoms, such as tetramethylurea or tetraethylurea, aliphatic or cycloaliphatic sulfones or sulfoxides having 2 to 10 carbon atoms, such as tetramethylsulfone or dimethyl sulfoxide, aliphatic or cycloaliphatic Phosphoric acid amides, eg. As hexamethylphosphoric triamide, dialkyl ketones such as acetone and alcohols and polyhydroxy compounds such as methanol, ethanol, n-propanol, iso-propanol or tert-butanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol. 1,3-butanediol, 1,2-butanediol, trimethylolpropane (TMP), polyalkylene oxides having number average molecular weights M _{n of} from 200 to 20,000 g / mol.

The mentioned solvents can also be used in any Mixing ratios are used to each other.

Preference is given to the use of isopropanol, propylene glycol, dipropylene glycol, 2,3-butanediol and polyalkylene oxides having number average molecular weights M _{n of} from 200 to 20 000 g / mol, more preferably of polyalkylene oxides having number average molecular weights M _{n of} from 200 to 20 000 g / mol.

Of the Step a3) is in a temperature range of 0 ° C to 100 ° C, preferably 0 ° C to 70 ° C and especially preferably carried out at 20 ° C to 50 ° C.

Under In special circumstances, it may also be necessary Reaction under pressure to sufficiently high To get temperatures.

fugitive Ingredients may be removed from the reaction mixture in step a4) be removed by distillation. In this case, the distillation be carried out batchwise or continuously. In any case, the distillation is preferably under reduced Pressure of less than 500 mbar, more preferably less than 250 mbar, most preferably less than 100 mbar. The Distillation temperature is in an interval of 20 ° C. to 100 ° C, preferably 20 ° C to 70 ° C and most preferably from 40 ° C to 70 ° C.

In step b1), all polyamino compounds known to those skilled in the art which have an average amine functionality of at least 2 and which have at least one aliphatically bonded amino group with at least one opposite to electrophilic reactive hydrogen can be used to convert the product from A) to polyamines. Examples of such compounds are ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 2,2-dimethyl-propane-1,3-diamine, hexamethylenediamine, 1,8-diaminooctane, isophoronediamine, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'diaminoddicyclohexanemethane, 3- (methylamino) propylamine, 3- (cyclohexylamino) propylamine, diethylenetriamine, 1,4,8-triazaoctane, dipropylenetriamine, N, N-bis (3-aminopropyl) methylamine, 1,5,8,12-tetraazadodecane, octahydro-4,7-methano 1H-indenedimethanamine (TCD-diamine); 1,3-bis (aminomethyl) cyclohexane, 1,3-bis (aminomethyl) benzene, 1-methyl-2,4-diaminocyclohexane, 1-methyl-2,6-diaminocyclohexane, 1,8-menthanediamine, 1,5- Diamino-2-methylpentane, 1,3-diaminopentane, 1,8-bisamino-4- (aminomethyl) octane, 1,2,3-triaminopropane, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,2- Diaminocyclohexane, and polyoxyalkyleneamines with number average molecular weights M _n from 150 to 6000 g / mol.

The Polyamine compound is in a molar ratio of Ester group to amino group of 1:10, preferably 1: 5 and especially preferably used of 1: 2.

Of the Step b2) is in a temperature range of 20 ° C to 200 ° C, preferably 80 ° C to 200 ° C and especially preferably carried out at 80 ° C to 150 ° C.

Under In special circumstances, it may also be necessary Reaction under pressure to sufficiently high To get temperatures.

In principle, the excess polyamine compounds in step b3) can be separated off by discontinuous distillation under reduced pressure. However, this procedure is not preferred. Preference is given to continuous distillation processes, such as short-path, falling film and / or thin-film distillation (see, for example, US Pat Chemical Engineering, Wiley-VCH, Vol. 1, 5th Ed., Pp. 333-334 ).

With sufficient attention paid to the process parameters, the method according to the invention permits a conversion of OH into NH ₂ groups of at least 80%.

To Completion of the method according to the invention the residual content of solvent in the polyamine produced less than 2% by weight, preferably less than 1% by weight.

As well is the residual content of monomeric polyamine compounds after carrying out the inventive Method preferably not more than 1 wt .-%, preferably not more as 0.50 wt .-%, based on the polyamine produced.

The Obtained according to the invention, preferably aliphatic Polyamines are preferred because of their low vapor pressure as a reaction partner for optionally blocked polyisocyanates or Epoxy resins used. The resulting polyepoxides and Polyurethaneureas can then be used, for example, as a coating, Adhesive and sealant or as porous (foams) or non-porous moldings are used. For the production of coatings as well as adhesives and sealants, non-porous Moldings or foams, the optionally also polyamines according to the invention with other low molecular weight (molecular weight 32 to 399) and / or higher molecular weight (molecular weight 400 to 12000 g / mol) Compounds with isocyanate-reactive groups be combined. Particularly suitable are polyhydroxy compounds, which already mentioned above in connection with the production of the Polyisocyanate prepolymer have been described.

The Reactive mixtures of the inventively prepared Polyamines, polyisocyanates, optionally further NCO-reactive Of course, compounds and / or polyepoxides can be used also the usual auxiliaries and additives such as pigments, (Paint) additives, thixotropic agents, leveling agents, emulsifiers and stabilizers are added.

The Preparation of the reactive mixtures is carried out by mixing the components in any order before or during their application, for example as a coating.

The Reactive mixtures can be prepared by the techniques known per se like spraying, dipping, flooding or pouring on surfaces be applied. After venting if necessary existing Solvent, wherein the reactive mixtures are preferably are free of solvents, harden the coatings then at ambient conditions, especially at minus 20 ° C up to 40 ° C, but also at higher temperatures of for example 40 to 200 ° C.

coatings such polyurethane ureas can be used, for example on metallic surfaces, eg. B. of iron, steel, aluminum, Bronze, brass or chrome are applied. But also the coating of mineral surfaces, e.g. Glass, ceramics, Stone or concrete, natural materials such as wood or also plastics, eg. B. in the form of existing coatings, is possible.

Examples:

Example 1:

a) Preparation of a carboxylic acid ester terminated polyoxyalkylene

To a mixture of 8200 g of a polyhy hydroxy compound with secondary OH groups (OH equivalent 56.1 mg / KOH) and 1640 g of ethyl acrylate are added 23 g of potassium hydroxide (20 wt .-% in isopropanol). The mixture is stirred for 20 h at room temperature. 44 g of 2-chloropropionic acid are added and volatile components are distilled off at 85 ° C. and 3 mbar.

b) Preparation of a Polyoxyalkyleneamines

1443 g of the product from a) are stirred at 140 ° C. for 29 hours with 557 g of a polyamine compound (NH content: 18.8% by weight). Volatile compounds are separated by thin film distillation at 180 ° C and <1 mbar. You get a product with the following characteristics:
NH content: 1.35% by weight
Viscosity (23 ° C): 3270 mPas
Content of monomeric polyamines: 0.01% by weight.

Example 2:

a) Preparation of a carboxylic acid ester terminated polyoxyalkylene

To a mixture of 8200 g of a polyhydroxy compound with secondary OH groups (OH equivalent 56.1 mg / KOH) and 1640 g of ethyl acrylate 23 g of potassium hydroxide (20% by weight in isopropanol) are added. The Mixture is stirred for 20 h at room temperature. It will 44 g of 2-chloropropionic acid added and volatile components distilled off at 85 ° C and 3 mbar.

b) Preparation of a Polyoxyalkyleneamines

2849 g of the product from a) are stirred at 120 ° C. for 74 h with 751 g of a polyamine compound (NH content: 27.5% by weight). Volatile compounds are separated by thin-layer distillation at 120 ° C and <1 mbar. You get a product with the following characteristics:
NH content: 1.39% by weight
Viscosity (23 ° C): 1760 mPas
Content of monomeric polyamines: 0.06 wt .-%.

Example 3:

a) Preparation of a carboxylic acid ester terminated polyoxyalkylene

To a mixture of 884 g of a polyhydroxy compound with primary OH groups (OH equivalent 56.1 mg / KOH) and 449 g of ethyl acrylate 1.7 g of potassium hydroxide (20% by weight in isopropanol) are added. The mixture is stirred for 20 hours at room temperature. 5 g of 2-chloropropionic acid are added and light Volatile components distilled off at 85 ° C and 3 mbar.

b) Preparation of a Polyoxyalkyleneamines

845 g of the product from a) are stirred for 24 hours at 120 ° C. with 254 g of a polyamine compound (NH content: 27.5% by weight). Volatile compounds are separated by thin-layer distillation at 120 ° C and <1 mbar. You get a product with the following characteristics:
NH content: 1.48% by weight
Viscosity (23 ° C): 755 mPas
Content of monomeric polyamines: 0.10 wt .-%.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 1643426 A [0002]
• - US 4847416 A [0003]
• - US 5072020 A [0004]
• US 3799986 A [0005]
• - DE 2019432 A [0007]
• - DE 102005028081 A [0009]
• - US 6355829 A [0010]
• - US 5158922 A [0017]
• EP 0654302 A [0017]

Cited non-patent literature

• ASTM D2849-69 [0017]
• - Chemical Engineering, Wiley-VCH, Volume 1, 5th Edition, pages 333-334 [0036]

Claims (10)

Process for the preparation of aliphatic amino groups having polyamines from polyols A) Preparation of with carboxylic ester groups terminated polyhydroxy compounds by reaction of polyhydroxy compounds with a middle one Functionality of at least 1.5 a1) with acrylic acid alkyl esters in a molar ratio of OH group to double bond from 1: 1 to 1:10, preferably 1: 1 to 1: 5, more preferably 1: 1.8 to 1: 2.2 and most preferably 1: 2, a2) in the presence a catalyst in a molar ratio of OH group to catalyst of 1: 0.5, preferably 1: 0.05 a3) in a temperature interval from 0 ° C to 100 ° C, preferably 0 ° C to 70 ° C and more preferably 20 ° C to 40 ° C a4) if necessary, remove an excess of alkyl acrylate from a1) and solvents from a2) and B) Implementation of the Product from A) b1) with aliphatic polyamines in molar Ratio of ester group to amino group of 1: 1 to 1:10, preferably 1: 1 to 1: 5, more preferably 1: 1.8 to 1: 2.2 and most preferably 1: 2, b2) in a temperature interval from 20 ° C to 200 ° C, preferably 80 ° C to 200 ° C, and more preferably 80 ° C to 150 ° C b3) if necessary, remove an excess of aliphatic used Polyamines from step b1). Process according to claim 1, characterized in that the polyhydroxy compounds have an average OH functionality of at least 1.7. Process according to claim 1, characterized in that the polyhydroxy compound is one or more Compounds selected from the group consisting of 1,2-ethanediol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, triols, tetraols, Polyether polyols, polyester polyols, polycarbonate polyols, polybutadiene polyols and Polythioetherpolyolen be used. A method according to claim 1, characterized in that polyether polyols having a number average molecular weight M _n of 300 to 20,000 g / mol, preferably 1000 to 12,000 g / mol, particularly preferably 1000 to 6000 g / mol are used as the polyhydroxy compound. Process according to claim 1, characterized in that the alkyl acrylate used in step a1) be selected from the group consisting of methyl acrylate, Ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate and tert-butyl acrylate. Process according to claim 1, characterized characterized in that it is the catalyst a2) hydroxides of alkali and alkaline earth metals. Process according to claim 1, characterized characterized in that the catalyst a2) is quaternary Ammonium hydroxides is. Process according to claim 1, characterized characterized in that the catalyst a2) is benzyltrimethylammonium hydroxide is. Process according to claim 1, characterized characterized in that the catalyst a2) is sodium hydroxide and / or potassium hydroxide. Process according to claim 1, characterized characterized in that the step a3) in a temperature range from 0 ° C to 100 ° C, preferably 0 ° C to 70 ° C and particularly preferably carried out at 20 ° C to 50 ° C. becomes.