DE10152680A1 - Pure higher (meth)acrylate ester preparation in high yield, for use as monomer, by carrying out esterification by adding reaction components to refluxing azeotrope-forming solvent in reactor with rotating evaporator - Google Patents

Abstract

Preparation of higher (meth)acrylate esters, by reacting (meth)acrylic acid with an alcohol in presence of acid catalyst(s), polymerization inhibitor(s) and a solvent forming an azeotrope with water is effected in a reactor with a rotating evaporator by heating to the boiling point (b.pt.) of the lowest boiling component, commencing rotation and dosing the remaining components. Preparation of higher (meth)acrylate esters (I), by reacting (meth)acrylic acid (II) with an alcohol (III) in presence of acid catalyst(s) (AC), polymerization inhibitor(s) (PI) and a solvent (SV) forming an azeotrope with water, distilling off the azeotrope and condensing to form aqueous and organic phases, is effected in a reactor with a rotating evaporator in presence of at least 10 wt. % SV based on the reaction mixture. At least part of SV and optionally at least of part of AC and/or PI is heated in the reactor to the b.pt. of the lowest boiling component, rotation is commenced and (II), (III) and if necessary the remainder of SV, AC and/or PI are supplied (together or separately). In variants, the components initially added to the reactor also include at least part of (II) and/or (III), provided that the presence of at least part of AC and at least part of PI is essential (rather than optional) if (II) is present. An Independent claim is included for reaction mixtures (A) comprising mainly trimethylol propane triacrylate (Ia) or alkoxylated trimethylol propane triacrylate (Ib), obtained by heating at least 10 wt. % SV (based on acrylic acid (IIa) and trimethylol propane (IIIa) or alkoxylated trimethylol propane (IIIb)) in a reactor with a rotating evaporator and supplying (IIa) and (IIIa/b) in ratio 3.3-4.5:1 (the necessary amount of AC being added before dosing of (IIa) and (IIIa/b)), adjusting the temperature to 70-110 deg C, reacting for less than 20 hours, optionally washing, neutralizing, optionally washing, and removing SV by distillation and stripping until the content of (A) is less than 0.5 wt. %.

Description

The present invention describes a method for Production of higher (meth) acrylic acid esters by esterification of (Meth) acrylic acid with the corresponding alcohols in the presence at least one acid catalyst, one Polymerization inhibitor / polymerization inhibitor mixture and one Solvent that forms an azeotrope with water.

The inventive method is for the production of higher Esters of (meth) acrylic acid with higher mono- or polyvalent Suitable alcohols, polyether or polyester alcohols. However, it is preferred for the production of higher (Meth) acrylic acid esters can be used which have a molecular weight of> 200 g / mol exhibit. Such esters can no longer be distilled getting cleaned.

Higher (meth) acrylic acid esters are because of their reactive Double bond valuable monomers z. B. as paint raw materials for the Electron beam hardening or as part of UV radiation-curable printing inks, topcoats, molding or potting compounds or find application in adhesives.

Colorless products without Own smell, with low acid number and high storage stability.

The production of higher (meth) acrylic acid esters by acid catalyzed esterification of (meth) acrylic acid with the corresponding Alcohols in the presence of an inhibitor / inhibitor system and optionally a solvent, such as. B. benzene, toluene, Cyclohexane is well known.

As a rule, sulfuric acid, aryl or Alkyl sulfonic acids or mixtures thereof are used.

As is known, the formation of the ester from (meth) acrylic acid and Alcohol is based on an equilibrium reaction, um to generate economic sales, usually a Input material used in excess and / or the formed Esterification water and / or the target ester out of balance away. Influencing the esterification balance by the However, using an excess of alcohol is disadvantageous because thereby u. a. the formation of ethers from the starting alcohols and is promoted by Michael addition products (see, for example, US 4,280,010, Column 1).

Michael addition products are the products that by adding alcohols or (meth) acrylic acid to the Double bond of (meth) acrylic compounds are formed, e.g. B. Alkoxypropionic acids or acryloxypropionic acids, as well as their esters.

Because the higher (meth) acrylic acid esters due to their high Boiling points cannot usually be cleaned by distillation, these by-products remain in the target ester and influence them Further processing and / or the quality of the subsequent products.

Therefore, in the manufacture of the higher (meth) acrylic acid esters usually the water of reaction removed and usually an excess used on (meth) acrylic acid. The esterification water is thereby usually by distillation, by stripping, e.g. B. with air, or with the help of a solvent that azeotropes with water forms, separated.

Since (meth) acrylic compounds in general and in particular polyfunctional (meth) acrylic acid esters easily become undesirable Polymerization, especially when exposed to heat, great efforts are generally being made to Polymer during esterification and isolation of the To avoid target testers.

As a rule, this polymer formation leads to one Allocation of the reactor walls, heat exchanger surfaces and column plates (Fouling) and clogging of lines, pumps, Valves etc. (EP-A 522 709, p. 2, lines 9-18; US 5 171 888, column 1, Z. 19-38). The result is expensive parking and complex Cleaning operations such as B. that in DE-A 195 36 179th described cooking with basic solutions, which is then expensive must be disposed of.

The polymer in the reaction mixture also hampers Refurbishment by having phase separation problems in the washings caused. There, as stated above, the higher (meth) acrylic acid esters cannot be cleaned by distillation, this remains Polymer in the target ester and influences further processing and Quality of the polymers or copolymers prepared (US Pat. No. 3,639,459, 1, lines 40-55).

In order to largely prevent undesired polymer formation, the use of polymerization inhibitors or inhibitor systems is generally recommended. In the case of the production of higher (meth) acrylates, the following are used, for example:
DE 38 43 854: α-substituted phenolic compounds
DE-A 29 13 218: Organic esters of phosphorous acid and mono- or dihydric phenols
DE 38 43 938: Unsubstituted phenol compounds and activated carbon
EP 449 919: hydroquinones, sterically hindered hydroquinones, e.g. B. 2,5-di-tert-butylhydroquinone, sterically hindered phenols, e.g. B. tocopherols.
Colorings can be removed with aluminum oxide or activated carbon
DE-AS 12 67 547: copper oxide / hydroquinone monomethyl ether
DE-OS 20 03 579: phenothiazine

Difficulties may arise in that the Inhibitors or inhibitor systems on the one hand the radical Must prevent polymerization during manufacture, and that they on the other hand, if the product remains in the end product must not disturb, d. H. that it must be possible, its effect when used through targeted radical reaction initiation to overcome. It may therefore be necessary "Manufacturing inhibitor" expensive to separate and by a "Application inhibitor" to replace (WO 91/08192).

US 3,639,459 describes a process for producing monomeric Diesters of glycols and α, β-unsaturated acids in one solvent free system with an excess of acid from at least 10% at a temperature below half the Boiling point of the acid and cleaning by washing with 20 to 30% aqueous alkali metal hydroxide solution.

A disadvantage of the method described there is that Reaction times are about 20 hours, the esterification water must be removed by an azeotrope with the acid in vacuo, what a complex vacuum control in the course of the reaction (Regulation from 100 mm Hg to 5 mm Hg depending on reaction progress) makes necessary, and the reaction mixture expensive, z. T. at Temperatures below 0 ° C are handled to cause ester cleavage to avoid by the highly concentrated alkali lye.

US 4 187 383 describes an esterification process of (Meth) acrylic acid with organic polyols at a Reaction temperature of 20 to 80 ° C in the presence of 50 to 5000 ppm one alkoxy-substituted phenol or alkylated alkoxyphenol as Polymerization inhibitor with which products with a color number 4.0 Gardner or less. In Example 1 of the above Scripture is presented while the polyol and a solvent the heating phase are acrylic acid, polymerization inhibitor and Catalyst added, after the reaction with 15% Washed sodium hydroxide solution and stripped the solvent. The Response times are up to 35 hours, the color numbers according to Gardner are at best <1 and it is mechanical stirring a technically simpler circulation evaporator (see below) is required Not insertable. 1.0 Gardner corresponds to about 160 APHA, 4.0 Gardner correspond to about 800 APHA, so those with this Process color numbers are unsatisfactory.

In order to shorten the esterification time, EP-A 331 845 proposes submit a starting material in a stirred reactor heat at least 100 ° C and then the other Starting material within the period necessary to at least Separate 65% of the water of reaction, add continuously and then until the reaction is complete heat. If necessary, a solvent can be added which with water an azeotrope with a boiling point above 100 ° C forms.

According to the examples, the Solvent concentration in the reaction mixture about 3.5% and the reaction temperature 118-135 ° C.

According to this document, temperatures slow down below 100 ° C the reaction rate considerably.

The reaction mixture should be worked up in the usual way Methods may be possible. However, a suitable workup will not disclosed.

The disadvantage is u. a. that get strongly colored products be that the reaction mixture is not cleaned by washing can and that the end products have an increased viscosity and have an increased salt content (see comparative examples).

A further disadvantage is that the total quantity is presented Alcohol when heating in the presence of the acidic catalyst leads to increased ether formation (by-product formation), presentation the total amount (meth) acrylic acid, however, to an increased Formation of Michael addition products and to an increased Risk of polymerization, since the (meth) acrylic acid then Form Michael addition products and in the worst case can polymerize in an uncontrolled manner (by-product formation and Security problem).

To spontaneous polymerization z. B. by local overheating to prevent, must be well mixed during the reaction be taken care of, which is expressly stated in EP-A 331 845 mechanical agitator (mechanical agitator, page 4, line 6) is to be provided. Such mechanically moving parts are however due to Avoiding their susceptibility to faults as far as possible, generally endeavors to technically less malfunctioning circulation evaporators, especially use natural circulation evaporators. Also are the reactor size is limited because of the heat transfer available wall area with increasing Reactor size decreases.

However, the method presented in EP-A 331 845 can be used Not presenting the highly viscous higher alcohols with one Natural circulation evaporators are carried out because of the circulation the viscosity of the alcohols is difficult or impossible to achieve. Safe mixing is, however, because of the described Security problems absolutely necessary.

The addition of a solvent, as in EP-A 331 845 or US 4 187 383, does not bring a solution here, since that Solvent with the higher alcohol before starting the reaction often forms two phases, the task of mixing Circulation evaporator would be the alcohol as a component with the higher However, density forms the lower phase, so that here too Circulation did not come about safely.

In general, there is the result of the esterification Reaction mixture essentially from the target ester, the Esterification catalyst, the inhibitors, the excess (meth) acrylic acid, optionally a solvent and high molecular weight by-products (e.g. Polymer, ether and Michael addition products).

The catalyst, the excess (meth) acrylic acid and possibly Parts of the inhibitors are usually treated with aqueous bases, e.g. B. alkali solutions and / or salt solutions (DE-A 198 36 788) or solid powdered oxides, carbonates or Hydroxides (DE-A 39 39 163, EP 449 919, EP 449 918, DE-OS 14 93 004) or ion exchangers separated.

The by-products are made during these cleaning operations in so far negatively noticeable that they the phase separation in the difficult or even prevent individual washing steps.

EP-A 890 568 therefore proposes a technical separation of the phases complex centrifuge.

EP-A 933 353 proposes the addition of organic, polymeric anionic water-soluble flocculants. The educated However, polymer is usually sticky and hindered or complicates the filtration steps.

The excess (meth) acrylic acid can also be treated with Epoxides are bound (rendered harmless), but the addition products formed remain in the end product (DE-C 38 36 370, DE-A 33 16 593).

The removal of any solvent present for removal the water of reaction is usually carried out by distillation.

Since the higher (meth) acrylic acid esters e.g. T. application in the paint sector color, as well as purity and viscosity a major role.

Since the higher (meth) acrylic acid esters were not purified by distillation Various measures have been proposed to to obtain colorless end products.

DE-A 38 43 938 suggests the addition of activated carbon during prior to esterification to prevent the formation of discolored reaction products to prevent (column 2, lines 63-68). Discoloration occurs anyway on, an additional treatment with an appropriate Decolorizing agents, e.g. B. aluminum oxide, recommended (column 5, line Z. 20-27).

EP-A 995 738 recommends the esterification in the presence of perform supercritical carbon dioxide to u. a. Discoloration too prevent.

The known methods have the disadvantage that they are technical are complex and / or complicated apparatus and / or require additional auxiliaries and are unsuitable on an industrial scale are.

The object of the present invention was a to develop an economic process which involves the production of largely colorless higher (meth) acrylic acid esters in high Purity and high yield in a simple way and without enables additional auxiliaries on a technical scale.

• a) die Veresterung in einem Reaktor mit Umlaufverdampfer und
• b) in Gegenwart von mindestens 10 Gew.-% Lösungsmittel, bezogen auf das Reaktionsgemisch, durchführt und entweder
  • 1. zumindest einen Teil des Lösungsmittels, gegebenenfalls einen Teil des Katalysator(gemisches) und gegebenenfalls zumindest einen Teil des Polymerisationsinhibitor(gemisches) im Veresterungsreaktor vorlegt, auf Siedetemperatur der Komponente mit dem geringsten Siedepunkt im System aufheizt und, sobald der Umlauf in Betrieb ist, (Meth)acrylsäure und Alkohol sowie gegebenenfalls restlichen Katalysator, Polymerisationsinhibitor und Lösungsmittel gemeinsam oder getrennt zudosiert, oder
  • 2. zumindest einen Teil des Lösungsmittels, gegebenenfalls einen Teil des Katalysator(gemisches), gegebenenfalls zumindest einen Teil des Polymerisationsinhibitor(gemisches) und zumindest einen Teil des Alkohols im Veresterungsreaktor vorlegt, auf Siedetemperatur der Komponente mit dem geringsten Siedepunkt im System aufheizt und, sobald der Umlauf in Betrieb ist, (Meth)acrylsäure und gegebenenfalls den Rest des Alkohols sowie gegebenenfalls restlichen Katalysator, Polymerisationsinhibitor und Lösungsmittel gemeinsam oder getrennt zudosiert, oder
  • 3. zumindest einen Teil des Lösungsmittels, zumindest einen Teil des Katalysator(gemisches), zumindest einen Teil des Polymerisationsinhibitor(gemisches) und zumindest einen Teil der (Meth)acrylsäure im Veresterungsreaktor vorlegt, auf Siedetemperatur der Komponente mit dem geringsten Siedepunkt im System aufheizt und, sobald der Umlauf in Betrieb ist, den Alkohol und gegebenenfalls den Rest (Meth)acrylsäure sowie gegebenenfalls restlichen Katalysator, Polymerisationsinhibitor und Lösungsmittel gemeinsam oder getrennt zudosiert, oder
  • 4. zumindest einen Teil des Lösungsmittels, zumindest einen Teil des Katalysator(gemisches), zumindest einen Teil des Polymerisationsinhibitor(gemisches), zumindest einen Teil des Alkohols und einen Teil der (Meth)acrylsäure im Veresterungsreaktor vorlegt, auf Siedetemperatur der Komponente mit dem geringsten Siedepunkt im System aufheizt und, sobald der Umlauf in Betrieb ist, gegebenenfalls den Rest Alkohol und den Rest (Meth)acrylsäure sowie gegebenenfalls restlichen Katalysator, Polymerisationsinhibitor und Lösungsmittel gemeinsam oder getrennt zudosiert.

We have now found a process for the preparation of higher (meth) acrylic esters by reacting (meth) acrylic acid and the alcohol in the presence of at least one acid catalyst and at least one polymerization inhibitor and in the presence of a solvent which forms an azeotrope with water, the azeotrope is distilled off and condensed, the condensate decomposing into an aqueous phase and an organic phase, wherein

• a) esterification in a reactor with a circulation evaporator and
• b) in the presence of at least 10% by weight of solvent, based on the reaction mixture, and either
  • 1. introduces at least part of the solvent, optionally part of the catalyst (mixture) and optionally at least part of the polymerization inhibitor (mixture) in the esterification reactor, heats up to the boiling point of the component with the lowest boiling point in the system and, as soon as the circulation is in operation, (Meth) acrylic acid and alcohol and optionally any remaining catalyst, polymerization inhibitor and solvent are metered in together or separately, or
  • 2. puts at least part of the solvent, optionally part of the catalyst (mixture), optionally at least part of the polymerization inhibitor (mixture) and at least part of the alcohol in the esterification reactor, heated to the boiling point of the component with the lowest boiling point in the system and, as soon as the circulation is in operation, (meth) acrylic acid and, if appropriate, the remainder of the alcohol and, if appropriate, any remaining catalyst, polymerization inhibitor and solvent are metered in together or separately, or
  • 3. at least some of the solvent, at least some of the catalyst (mixture), at least some of the polymerization inhibitor (mixture) and at least some of the (meth) acrylic acid in the esterification reactor, heated to the boiling point of the component with the lowest boiling point in the system and , as soon as the circulation is in operation, the alcohol and optionally the rest (meth) acrylic acid and optionally the remaining catalyst, polymerization inhibitor and solvent are metered in together or separately, or
  • 4. at least part of the solvent, at least part of the catalyst (mixture), at least part of the polymerization inhibitor (mixture), at least part of the alcohol and part of the (meth) acrylic acid in the esterification reactor, at the boiling point of the component with the lowest The boiling point in the system is heated and, as soon as the circulation is in operation, the remainder of the alcohol and the remainder of (meth) acrylic acid as well as any remaining catalyst, polymerization inhibitor and solvent are metered in together or separately.

Process variants c1), c2) and c4) are preferred, c1) and c2) are particularly preferred and are very particularly preferred c1).

An advantageous embodiment consists in the Add catalyst only before adding the remaining components for example after the circulation is in operation and before the remaining components are added.

This happens advantageously when the boiling point of the submitted reaction mixture is essentially reached, ie heating has essentially ended. This is the case if the temperature of the mixture is not more than 20 ° C below the target boiling temperature is, preferably not more than 10 ° C. and particularly preferably not more than 5 ° C.

The term (meth) acrylic acid is used here for acrylic acid and Methacrylic acid used.

• 1. Es werden nur technisch einfache Apparate benötigt
• 2. Das erfindungsgemäße Verfahren kommt ohne Hilfsstoffe aus
• 3. Es tritt keine wesentliche Polymerisatbildung bei Veresterung oder Aufarbeitung auf
• 4. Es treten keine Phasentrennprobleme bei den Waschungen auf
• 5. Das Endprodukt ist weitgehend farblos, d. h. die Farbzahl überschreitet 100 APHA nicht
• 6. Das Endprodukt ist kupferfrei
• 7. Es wird ein hoher Veresterungsgrad erreicht
• 8. Es werden hohe Ausbeuten erzielt
• 9. Die Endprodukte haben eine niedrige Viskosität

The method found has the following advantages:

• 1. Only technically simple devices are required
• 2. The method according to the invention does not require any auxiliary substances
• 3. There is no significant polymer formation during esterification or workup
• 4. There are no phase separation problems with the washes
• 5. The end product is largely colorless, ie the color number does not exceed 100 APHA
• 6. The end product is copper free
• 7. A high degree of esterification is achieved
• 8. High yields are achieved
• 9. The end products have a low viscosity

The water formed during the esterification, which with the Solvent forming an azeotrope is sent to the reactor attached column discharged and condensed.

The condensate (azeotrope) breaks down into an aqueous one Phase, which is discharged and worked up advantageously (Back extraction of the acid contained) and a solvent phase, that as reflux in the column and possibly partially in the reactor and / or evaporator is returned, as in DE-A 199 41 136 and the German application with the file number 100 63 175.4 is described.

The (meth) acrylic acid contained is extracted back preferably with the solvent used as Extraction agent, for example with cyclohexane, at one temperature between 10 and 40 ° C and a ratio of aqueous phase to Extracting agent from 1: 5-30, preferably 1: 10-20. The in Acid contained in the extractant can preferably be added directly to the Esterification.

After the esterification has ended, the hot reaction mixture cooled quickly, diluted with solvent if necessary, prewashed, neutralized and washed if necessary.

Then the solvent is distilled from the target ester separated, wherein in a first step the main amount of Solvent is separated by distillation and the rest of the Solvent then by stripping with one of the Reaction conditions inert gas, preferably one oxygen-containing gas, particularly preferably air or Air-nitrogen mixtures.

The stripping gas is advantageously heated.

In addition to high-boiling monohydric alcohols come as higher alcohols Alcohols with 10 C atoms and more, preferably with 10 to 30 C atoms, particularly preferably with 10 to 20 carbon atoms, including diols and polyols with 2 to 10, preferably 2 to 6 hydroxyl groups in question.

Examples of high-boiling monohydric alcohols are tert. Butylcyclohexanol, lauryl alcohol (1-dodecanol), myristyl alcohol (1-tetradecanol), cetyl alcohol (1-hexadecanol), stearyl alcohol (1-octadecanol), 9-cis-octadecen-1-ol (oleyl alcohol), 9-trans-octadecen-1-ol (erucyl alcohol), 9-cis-octadecen-1,12-diol (Ricinol alcohol), all-cis-9,12-octadecadien-1-ol (linoleyl alcohol), all- cis-9,12,15-octadecatrien-1-ol (linolenyl alcohol), 1-eicosanol (Arachidyl alcohol), 9-cis-eicosen-1-ol (gadoleyl alcohol), 1-docosanol (behenyl alcohol), 1-3-cis-docosen-1-ol (Erucyl alcohol) and 1-3-trans-docosen-1-ol (brassidyl alcohol).

Examples of diols and polyols are 1,4-butanediol, Neopentyl glycol, 1,6-hexanediol, glycerin, trimethylol propane, Ditrimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, 1,2-, 1,2-, 1,3- or 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, bisphenol F or 2,2-bis (4-hydroxycyclohexyl) propane. under these are preferred 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, glycerol, trimethylolpropane, ditrimethylolpropane, Trimethylolethane, pentaerythritol and dipentaerythritol.

Polyetherols and polyesterols with a or more hydroxyl groups, preferably with a medium OH Functionality from 1 to 10, preferably 1 to 5 and particularly preferably 1 to 3, e.g. B. ethoxylated and / or propoxylated one and polyhydric alcohols, phenols or fatty amines.

Such polyetherols and polyesterols with a Molar mass below 2000 g / mol, preferably 100 to 2000, particularly preferably 100 to 1000 and very particularly preferably 100 to 400.

Examples of this are
Poly-THF with a molecular weight between 162 and 2000,
Poly-1,3-propanediol with a molecular weight between 134 and 1178,
Polypropylene glycol with a molecular weight between 134 and 1178, preferably di- and tripropylene glycol,
Polyethylene glycol with a molecular weight between 106 and 898,
Polyethylene glycol methyl ether with a molecular weight between 120 and 912, preferably diethylene glycol monomethyl ether and triethylene glycol monomethyl ether,
Polyethylene glycol ethyl ether with a molecular weight between 134 and 926, preferably diethylene glycol monoethyl ether and triethylene glycol monoethyl ether,
Lutensol®, Pluriol®, Pluriol E® or Pluriol P® brands from BASF AG.

Furthermore, it can be ethoxylated and / or propoxylated alcohols and mixed-ethoxylated / propoxylated alcohols such as
R ¹ - (O-CH ₂ -CH ₂ ) _x -OH or
R ¹ - (O-CH (CH ₃ ) -CH ₂ ) _x OH or R ¹ - (O-CH ₂ -CH (CH ₃ )) _x -OH,
wherein
R ¹ for C ₁ to C ₂₂ alkyl and
x for an integer between 1 and 20
stands,
act.

Examples of R ¹ are methyl, ethyl, iso-propyl, n-propyl, allyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-hexyl, n-heptyl, n-octyl, n-decyl , n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl or n-eicosyl.

Those alcohols are preferably used, which per Hydroxy group ethoxylated one to fifteen times and / or propoxylated are, particularly preferably one to ten times and very particularly preferably two to five times.

Examples of after ethoxylation and / or propoxylation usable alcohols are methanol, ethanol, iso-propanol, n-propanol, Allyl alcohol, n-butanol, iso-butanol, sec-butanol, tert-butanol, 2,2-dimethyl-1,2-ethanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,4-butynediol, 1,4-butenediol, n-hexanol, n-heptanol, n-octanol, n-decanol, n-dodecanol (lauryl alcohol), 2-ethylhexanol, 3-methylpentane-1,5-diol, 2-ethylhexane-1,3-diol, 2,4-diethyloctane-1,3-diol, 1,6-hexanediol, cyclopentanol, cyclohexanol, Cyclooctanol, cyclododecanol, but-2-in-1,4-diol, Trimethylolpropane, trimethylolethane, neopentylglycol, pentaerythritol, 2-methyl-1,3-propanediol, glycerin, ditrimethylolpropane, Dipentaerythritol, sugar alcohols, bisphenol A, bisphenol F, bisphenol B, Bisphenol S, 2,2-bis (4-hydroxycyclohexyl) propane, 1,1-, 1,2-, 1,3- and 1,4-cyclohexanedimethanol, 1,2-, 1,3- or 1,4-cyclohexanediol, Lauryl alcohol (1-dodecanol), myristyl alcohol (1-tetradecanol), Cetyl alcohol (1-hexadecanol), stearyl alcohol (1-octadecanol), 9-cis-octadecen-1-ol (oleyl alcohol), 9-trans-octadecen-1-ol (Erucyl alcohol), 9-cis-octadecen-1,12-diol (ricinol alcohol), all cis-9,12-octadecadien-1-ol (linoleyl alcohol), all-cis-9,12,15- Octadecatrien-1-ol (linolenyl alcohol), 1-eicosanol (Arachidyl alcohol), 9-cis-eicosen-1-ol (gadoleyl alcohol), 1-docosanol (Behenyl alcohol), 1-3-cis-docosen-1-ol (erucyl alcohol) 1-3-trans- Docosen-1-ol (brassidyl alcohol).

Ethoxylated and / or propoxylated are particularly preferred Methanol, trimethylolpropane, pentaerythritol, dipentaerythritol, Glycerin, ethylene glycol, 1,6-hexanediol, 1,4-butanediol, 1,4-butynediol, propylene glycol and neopentyl glycol.

Furthermore, ethoxylated and / or propoxylated alkylphenols, such as B. nonylphenol, can be used.

The process according to the invention essentially consists of following levels:

1. Esterification

The esterification apparatus consists of a reactor Circulation evaporator and a distillation column attached Condenser and phase separator.

The reactor can be, for example, a reactor with Act double wall heating and / or internal heating coils. A reactor with an external heat exchanger is preferred and natural or forced circulation (using a pump), particularly preferred natural circulation, in which the circulating stream without mechanical aids is used.

Suitable circulation evaporators are known to the person skilled in the art and described for example in R. Billet, evaporator technology, HTB- Verlag, Bibliographisches Institut Mannheim, 1965, 53rd examples for circulation evaporators are shell and tube heat exchangers, Plate heat exchanger, etc.

Of course, several heat exchangers can also circulate to be available.

The distillation column is of a type known per se and has the usual internals. Coming as column internals in principle all common installations, for example Soils, packs and / or fillings. From the floors are Bubble-cap trays, sieve trays, valve trays, Thormann trays and / or Dual-flow floors preferred, of the fillings are those with Rings, spirals, saddle bodies or braids preferred.

As a rule, 5 to 20 theoretical floors are sufficient.

The condenser and the separation vessel are of conventional construction.

(Meth) acrylic acid and the alcohols are usually in equivalent amounts based on the hydroxyl groups of the alcohol used, but it can also be a deficit or excess (Meth) acrylic acid can be used.

An excess of (meth) acrylic acid per is preferably added esterifying hydroxyl group (equivalents) of 5-100 mol% adjusted, preferably 5 to 50 mol% and particularly preferably 5 to 25 mol% and especially 5 to 10 mol%.

The usual mineral acids come as esterification catalysts and sulfonic acids in question, preferably sulfuric acid, Phosphoric acid, alkylsulfonic acids (e.g. methanesulfonic acid, Trifluoromethanesulfonic acid) and arylsulfonic acids (e.g. benzene, p-toluene or Dodecylbenzenesulfonic acid) or mixtures thereof, but also acid Ion exchangers are conceivable.

Sulfuric acid, methanesulfonic acid and p- Toluenesulfonic acid or mixtures thereof.

They are usually obtained in an amount of 0.1-5% by weight on the esterification mixture, preferably 0.5-5, particularly preferably 1-4 and very particularly preferably 2-4% by weight.

If necessary, the esterification catalyst from the Reaction mixture can be removed using an ion exchanger. The ion exchanger can go directly into the reaction mixture given and then filtered off or the reaction mixture can be passed over an ion exchange bed.

The esterification catalyst in the reaction mixture is preferred left and removed by washing (see below).

Suitable for use in esterification Polymerization inhibitors are phenothiazine, mono- and polyhydric phenols that optionally have one or more alkyl groups, such as. B. Alkylphenols, for example o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethyl-phenol, 2,6-di-tert-butyl-4-methylphenol, 2-methylhydroquinone, 2,5-di- tert-butyl hydroquinone, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 4-tert.- Butyl-2,6-dimethylphenol, 2,5-di-tert-butylhydroquinone, Toluhydroquinone, or 2,2'-methylene-bis- (6-tert-butyl-4-methylphenol), Hydroxyphenols, for example hydroquinone, pyrocatechol (1,2-dihydroxybenzene) or benzoquinone, aminophenols, such as. B. para-aminophenol, nitrosophenols such as e.g. B. para-nitrosophenol, Alkoxyphenols, for example 2-methoxyphenol (guaiacol, Catechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di- tert-butyl-4-methoxyphenol, tocopherols, such as. B. α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran), phosphorus compounds, e.g. B. Tri phenylphosphite, hypophosphorous acid or alkyl ester of Phosphorous acid, copper or manganese, cerium, nickel, chromium or Copper salts, for example chlorides, sulfates, salicylates, tosylates, acrylates or acetates, 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N- oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4,4 ', 4 "tris (2,2,6,6-tetramethyl-piperidine-N-oxyl) phosphite or 3-oxo-2,2,5,5-tetramethyl-pyrrolidine-N-oxyl, N, N-diphenylamine, N-nitrosodiphenylamine, N, N'- Dialkyl-para-phenylenediamines, phenothiazine and mixtures thereof.

At least one is preferred as the polymerization inhibitor (mixture) a compound from the hydroquinone group, Hydroquinone monomethyl ether, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-di- methyl-phenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 4-tert-butyl-2,6-dimethylphenol, Hypophosphorous acid, copper acetate, copper chloride and Copper salicylate used.

The polymerization inhibitor (mixture) is preferred as aqueous solution used.

To further support stabilization, a oxygen-containing gas, preferably air or a mixture of air and Nitrogen (lean air) must be present.

This oxygen-containing gas is preferably in the Bottom region of a column and / or in a circulation evaporator metered.

The polymerization inhibitor (mixture) is in a total amount of 0.01-1% by weight, based on the esterification mixture, used, preferably 0.02-0.8, particularly preferably 0.05-0.5% by weight.

As a solvent for azeotropic removal of the water of reaction are particularly suitable aliphatic, cycloaliphatic and aromatic hydrocarbons or mixtures thereof.

N-pentane, n-hexane, n-heptane, cyclohexane, Methylcyclohexane, benzene, toluene or xylene are used. Cyclohexane, methylcyclohexane and toluene are particularly preferred.

The amount used is 10-200% by weight, preferably 20-100 wt .-%, particularly preferably 30 to 100 wt .-% based on the Sum of alcohol and (meth) acrylic acid.

The reaction temperature is generally 60-140 ° C, preferably 70-110 ° C, very particularly preferably at 75-100 ° C. The The initial temperature is generally below 100 ° C., preferably below 90 ° C and particularly preferably below 80 ° C. As a rule, that is Final temperature of the esterification is 5-30 ° C higher than that Initial temperature. The temperature of the esterification can be varied the solvent concentration in the reaction mixture and be regulated, as in DE-A 199 41 136 and the German Registration with the file number 100 63 175.4 described.

The esterification can be depressurized but also under overpressure or Vacuum should be carried out, preferably at normal pressure worked.

The response time is usually 3-20 hours, preferably 5-15 and particularly preferably 7 to 12 hours.

A typical procedure for process variant c1) is that the mixture of at least part of the Solvent, optionally part of the Catalyst (mixture) and optionally at least part of the Inhibitor (mixture) presented in the reactor and heated to boiling temperature become. The boiling temperature means the temperature of the component the lowest boiling point in the system.

50 to 100% of the solvent are preferably introduced, particularly preferably 75-100% and in particular 100%.

0 to 100% of the Polymerization inhibitor (mixture) presented, particularly preferably 0-75% and in particular 0-50%.

0 to 50% catalyst (mixture) is preferred, especially preferably 0 to 25% and in particular 0% submitted. Corresponding the catalyst becomes 50-100%, 75-100% respectively 100% only added after heating up essentially has ended and before other substances, especially alcohol and / or acid can be added.

In the case of an esterification reactor with natural circulation special care was taken to ensure that the mixture circulates is. This is determined, for example, by sight glasses or known measuring and control devices such. B. for Flow measurement in circulation.

As soon as the circulation is in operation, the (meth) acrylic acid and the alcohol, and possibly the rest Catalyst (mixture), polymerization inhibitor (mixture) and solvent metered in together or separately.

A typical procedure for process variant c2) is that the mixture of at least part of the Alcohol, at least part of the solvent, if appropriate part of the catalyst (mixture) and optionally submitted at least a part of the inhibitor (mixture) in the reactor and be heated to boiling temperature.

25 to 100% of the alcohol are preferably initially charged, particularly preferably 50-100%, very particularly preferably 75-100% and especially 100%.

50 to 100% of the solvent are preferably introduced, particularly preferably 75-100% and in particular 100%.

0 to 100% of the Polymerization inhibitor (mixture) presented, particularly preferably 0-75% and in particular 0-50%.

0 to 50% catalyst (mixture) is preferred, especially preferably 0 to 25% and in particular 0% submitted. Corresponding the catalyst becomes 50-100%, 75-100% respectively 100% only added after heating up essentially has ended and before other substances, especially alcohol and / or acid are added.

In the case of an esterification reactor with natural circulation special care was taken to ensure that the mixture circulates is (see process variant c1)).

As soon as the circulation is in operation, the (meth) acrylic acid, and optionally residual alcohol, remaining Catalyst (mixture), polymerization inhibitor (mixture) and solvent metered in together or separately.

A typical procedure for process variant c3) consists in that the mixture of at least part of the (Meth) acrylic acid, at least part of the solvent, optionally part of the catalyst (mixture) and at least part of the inhibitor (mixture) presented in the reactor and on Boiling temperature to be heated.

25 to 100% of the (meth) acrylic acid are preferably initially charged, particularly preferably 50-100%, very particularly preferably 75-100% and especially 100%.

50 to 100% of the solvent are preferably introduced, particularly preferably 75-100% and in particular 100%.

50 to 100% of the Polymerization inhibitor (mixture) presented, particularly preferably 75-100% and in particular 100%.

0 to 50% catalyst (mixture) is preferred, especially preferably 0 to 25% and in particular 0% submitted. Corresponding the catalyst becomes 50-100%, 75-100% respectively 100% only added after heating up essentially has ended and before other substances, especially alcohol and / or acid are added.

In the case of an esterification reactor with natural circulation special care was taken to ensure that the mixture circulates is (see process variant c1)).

Once the circulation is up and running, the alcohol can, as well optionally the remaining (meth) acrylic acid, remaining Catalyst (mixture), polymerization inhibitor (mixture) and solvent metered in together or separately.

A typical procedure for process variant c4) consists in the fact that the mixture consists of part of the (meth) acrylic acid, at least part of the alcohol, at least part of the Solvent, optionally part of the Catalyst (mixture) and at least part of the inhibitor (mixture) in the Submitted reactor and heated to boiling temperature.

5 to 90% of the (meth) acrylic acid are preferably initially charged, particularly preferably 10-80% and very particularly preferred 20-75%.

10 to 100% of the alcohol are preferably initially charged, particularly preferably 25-100% and very particularly preferably 50-90%.

50 to 100% of the solvent are preferably introduced, particularly preferably 75-100% and in particular 100%.

50 to 100% of the Polymerization inhibitor (mixture) presented, particularly preferably 75-100% and in particular 100%.

0 to 50% catalyst (mixture) is preferred, especially preferably 0 to 25% and in particular 0% submitted. Corresponding the catalyst becomes 50-100%, 75-100% respectively 100% only added after heating up essentially has ended and before other substances, especially alcohol and / or acid can be added.

In the case of an esterification reactor with natural circulation special care was taken to ensure that the mixture circulates is (see process variant c1)).

As soon as the circulation is in operation, if necessary remaining alcohol, as well as the remaining (meth) acrylic acid, remaining Catalyst (mixture), polymerization inhibitor (mixture) and Solvents can be added together or separately.

Common or separate here means common or separate Lines, the metering can generally be ratio-controlled respectively.

The dosage is usually within 0.5-5 Hours continuously or in portions.

The (meth) acrylic acid which can be used is not restricted and in the case of crude (meth) acrylic acid can have, for example, the following components:
(Meth) acrylic acid 90-99.9% by weight acetic acid 0.05-3.0% by weight propionic 0.01-1.0% by weight diacrylate 0.01-5.0% by weight water 0.05-5.0% by weight aldehydes 0.01-0.3% by weight inhibitors 0.01-0.1% by weight Maleic acid (anhydride) 0.001-0.5% by weight

The crude (meth) acrylic acid used is generally stabilized with 200-600 ppm phenothiazine or other stabilizers in amounts that enable comparable stabilization.

Of course, pure (meth) acrylic acid can also be used, for example with the following purity:
(Meth) acrylic acid 99.7-99.99% by weight acetic acid 50-1000 ppm by weight propionic 10-500 ppm by weight diacrylate 10-500 ppm by weight water 50-1000 ppm by weight aldehydes 1-500 ppm by weight inhibitors 1-300 wt ppm Maleic acid (anhydride) 1-200 wt ppm

The pure (meth) acrylic acid used is generally stabilized with 100-300 ppm hydroquinone monomethyl ether or others Storage stabilizers in quantities that are comparable Enable stabilization.

The preferred natural circulation can be by metering a solvent, preferably the solvent that the organic phase from the column attached to the reactor, such as in the German application with the file number 100 63 175.4 described, are supported in the heat exchanger.

The water formed in the reaction is an azeotrope with the Solvent continuously through the reactor Column removed from the reaction mixture and condensed, wherein the condensate breaks down into a water and an organic phase.

The aqueous phase of the condensate, which is usually 0.1-10% by weight Contains (meth) acrylic acid, is separated and discharged. The (meth) acrylic acid contained therein can advantageously be combined with a Extraction agent, for example with cyclohexane, at one Temperature between 10 and 40 ° C and a ratio of aqueous Phase to extractant of 1: 5-30, preferably 1: 10-20, extracted and returned to the esterification.

All or part of the organic phase can be refluxed into the Column and any excess that may go into the reactor to be led back. Part of this phase can be used a natural circulation to support the natural circulation in the Heat exchangers are introduced into the circulation circuit of the reactor, preferably at least 10% of the organic phase, particularly preferably at least 15% by weight and very particularly preferably at least 20% by weight.

An advantageous variant is that the organic Phase (solvent phase) is passed into a storage container and that from this container the respectively required Amount of solvent to maintain reflux, to discharge into the circulation evaporator, and as a solvent for reaction and Extraction is taken.

To further support the circulation, an inert gas, preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen (lean air) can be introduced into the circulation, for example in amounts of 0.1-1, preferably 0.2-0 , 8 and particularly preferably 0.3-0.7 m ³ / m ³ h, based on the volume of the reaction mixture.

The course of the esterification can be followed by tracking the discharged amount of water and / or the decrease in (Meth) acrylic acid concentration in the reactor can be followed.

For example, the reaction can be stopped as soon as 90% of the theoretically expected amount of water through the solvent have been carried out, preferably at least 95% and particularly preferably at least 98%.

After the esterification has ended, the reactor mixture is opened conventionally cooled rapidly to a temperature of 10 to 30 ° C, optionally by adding solvent Target ester concentration of 60-80% set and a washing machine fed.

2. Prewash

The reaction mixture from 1. is in a washing machine with water or a 5-30 wt .-%, preferably 5-20, particularly preferably 5-15% by weight sodium chloride, potassium chloride, Ammonium chloride, sodium sulfate or ammonium sulfate solution, preferred Saline, treated.

The ratio of the reaction mixture to the washing liquid is usually 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.

The laundry can, for example, in a stirred container or in other conventional equipment, e.g. B. in a column or Mixer-settler equipment.

Technically, can be used for laundry in the invention Process all known extraction and washing processes and apparatuses are used, e.g. B. those in Ullmann's Encyclopedia of Industrial Chemistry, 6th ed, 1999 Electronic Release, chapter: Liquid - Liquid Extraction - Apparatus, are described. For example, these can be single or multi-level prefers single-stage extractions, as well as those in equal or Counter-current procedure, preferably counter-current procedure.

Sieve tray or packed or Packed columns, stirred tanks or mixer-settlers, as well as columns with rotating internals.

The prewash is preferably used when metal salts, preferably copper or copper salts used as inhibitors (with) become.

3. Neutralization

The organic phase of the prewash, which still contains small amounts Catalyst and the main amount of excess (meth) acrylic acid can contain, with a 5-25, preferably 5-20, particularly preferably 5-15% by weight aqueous solution of a base, such as z. B. sodium hydroxide solution, potassium hydroxide solution, sodium hydrogen carbonate, Sodium carbonate, potassium hydrogen carbonate, calcium hydroxide, ammonia water or potassium carbonate, which may contain 5-15% by weight of common salt, Potassium chloride, ammonium chloride or ammonium sulfate may be added can, preferably with sodium hydroxide solution or Sodium hydroxide solution, neutralized.

The base is added in such a way that the temperature in the Apparatus does not rise above 35 ° C, preferably between 20 and 35 ° C and the pH is 10-14. The removal of the The heat of neutralization is preferably achieved by cooling the container with the help of internal cooling coils or via a Double wall cooling.

The ratio of the reaction mixture:  Neutralizing liquid is usually 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.

With regard to the equipment, this applies under "2." Said.

4. Post-wash (optional)

To remove traces of base or salt from the neutralized Reaction mixture, it can be advantageous to wash with Water or a 5-30, preferably 5-20 and especially preferably 5-15% by weight sodium chloride, potassium chloride, ammonium chloride or ammonium sulfate solution, preferably water or saline solution, to be carried out analogously to the pre-wash

The ratio of the reaction mixture to the washing liquid is usually 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.

With regard to the equipment, this applies under "2." Said.

5. Solvent distillation

The washed reaction mixture is with such an amount on storage stabilizer, preferably hydroquinone monomethyl ether added that after removal of the solvent 100-500, preferably 200-500 and particularly preferably 200-400 ppm thereof are contained in the target ester (residue).

Removal of the bulk of the solvent by distillation takes place, for example, in a stirred tank with double-wall heating and / or internal heating coils under reduced pressure, for example at 20-700 mbar, preferably 30 to 500 and particularly preferably 50-150 mbar and a temperature of 40-80 ° C.

Of course, the distillation can also be done in a or thin film evaporators. This will be Reaction mixture, preferably several times in a circuit, under reduced pressure, for example at 20-700 mbar, preferably 30 to 500 and particularly preferably 50-150 mbar and a temperature of 40-80 ° C. passed through the apparatus.

An inert gas, preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen (lean air) can advantageously be introduced into the distillation apparatus, for example 0.1-1, preferably 0.2-0.8 and particularly preferably 0, 3-0.7 m ³ / m ³ h, based on the volume of the reaction mixture.

The residual solvent content in the residue is after Distillation generally less than 5% by weight, preferably 0.5-5% and particularly preferably 1 to 3% by weight.

The separated solvent is condensed and preferred reused.

6. Solvent stripping

The target ester, which still contains small amounts of solvent, is heated to 50-80 ° C and the remaining amounts of solvent with a suitable gas in a suitable repair away.

Suitable apparatuses are, for example, columns per se known type, which the usual internals, for. B. floors, Fills or directional packs, preferably fills exhibit. In principle, all common internals come as column internals Installations, such as floors, packings and / or Packing. Bell bottoms, sieve trays, Valve trays, Thormann trays and / or dual flow trays preferred by the Fills are those with rings, spirals, saddle bodies, Raschig, Intos or Pall rings, Barrel or Intalox saddles, Top-Pak etc. or braids, preferred.

A falling film, thin film or is also conceivable here Wiped film evaporators, such as. B. a Luwa, Rotafilm or Sambay evaporator, the equipped with a demister as a splash guard is.

Suitable gases are gases which are inert under the stripping conditions, preferably oxygen-containing gases, particularly preferably air or Mixtures of air and nitrogen (lean air), in particular those that are preheated to 50 to 100 ° C.

The amount of stripping gas is, for example, 5-20, particularly preferably 10-20 and very particularly preferably 10 to 15 m ³ / m ³ h, based on the volume of the reaction mixture.

If necessary, the ester can be stripped after stripping Filtration is subjected to failed traces of salts remove.

The higher ones obtained by the process according to the invention (Meth) acrylic acid esters are clear and largely colorless (color number <100 APHA corresponds to Hazen) and usually no longer contain as 0.05% by weight (meth) acrylic acid, not more than 0.1% by weight Solvent, not more than 0.1 ppm copper and not more than 20 ppm sodium.

Furthermore is an essentially trimethylolpropane triacrylate Reaction mixture containing the subject of the present Invention, which is obtainable by the process variant c1).

For this, at least 10% by weight, preferably at least 20% by weight, and particularly preferably at least 30% by weight of the solvent, based on the sum of trimethylolpropane and acrylic acid, and at least a part of the polymerization inhibitor (mixture) in submitted to a reactor with circulation, preferably natural circulation, heated and trimethylolpropane and acrylic acid in a ratio of 1: 3.3 -4.5, preferably 1: 3.6-4.5, particularly preferably 1: 3.9-4.5 metered in, the acid required for the reaction Catalyst, preferably para-toluenesulfonic acid, before the addition of Trimethylolpropane and acrylic acid is added.

The reaction temperature is preferably at 70-110 ° C 75-100 ° C set. The initial temperature is generally below 100 ° C, preferably below 90 ° C and particularly preferably below 80 ° C. As a rule, the final temperature of the esterification is around 5-30 ° C higher than the initial temperature.

The reaction time is less than 20 hours, preferably less than 15 hours Hours and particularly preferably less than 10 hours.

The reaction mixture is then optionally pre-washed, neutralized and optionally washed, then the solvent by distilling and stripping on one Content below 0.5 wt .-%, preferably below 0.3 wt .-% removed.

Of course, trimethylolpropane triacrylate is also after the Variants c2), c3) or c4) are available, but is preferred Variant c1) and particularly preferably the one described Reaction.

The essentially trimethylolpropane triacrylate thus obtainable containing reaction mixture is characterized by a color number less than 100 APHA, preferably less than 80 APHA and particularly preferably less than 60 APHA and a viscosity (after DN 51562 at 25 ° C) of less than 160 mPa.s, preferably less than 140 mPa.s and particularly preferably less than 120 mPa.s and an ester number (according to DIN 53401) of 180 to 570, preferably 500 to 570 and particularly preferably 520 to 560.

Analogous to this regulation is also an essential one Containing acrylic acid esters of alkoxylated trimethylolpropane Reaction mixture available. For this purpose, such an alkoxylated Trimethylolpropane used as a starting material in the esterification, that by reacting trimethylolpropane with alkylene oxides is available. This alkoxylation is not essential to the invention and known per se to the expert. Suitable alkylene oxides are for example ethylene oxide, propylene oxide, isobutylene oxide, Vinyl oxirane and / or styrene oxide, ethylene oxide is preferred, Propylene oxide and / or isobutylene oxide are particularly preferred Ethylene oxide and / or propylene oxide.

In particular, acrylic esters of this type are essentially reaction mixtures containing alkoxylated trimethylolpropane preferred by the reaction of 0.5 to 10 mol of ethylene oxide and / or propylene oxide per mole of trimethylolpropane are available.

The viscosities and color numbers of the available Reaction mixtures differ depending on the alkoxylated used Trimethylolpropane.

The process according to the invention is not only for the production of Methacrylic acid esters also for the production of other esters α, β-ethylenically unsaturated carboxylic acids, such as crotonic acid, Itaconic acid, maleic acid, fumaric acid or citraconic acid Alcohols and especially the alcohols mentioned above can be used.

Obtain ppm and percentages used in this document unless otherwise stated, weight percentages and - ppm.

APHA color numbers were determined in accordance with DIN-ISO 6271.

Unless otherwise stated, viscosities were in accordance with DIN 51562 determined at 25 ° C.

example 1

In a 10 l reactor with an external natural circulation evaporator, Distillation column, condenser and phase separation vessel were 3 g Hydroquinone monomethyl ether as a 2% aqueous solution, 6 g 50% hypophosphorous acid, 1 g copper (II) chloride as 40% aqueous solution, and 2000 g of cyclohexane and submitted Heated to reflux. The temperature in the reactor was about 70 to 75 ° C. The natural circulation evaporator was a heated with heat transfer oil Shell and tube heat exchanger. In addition, air in the Natural circulation evaporator directed, the air volume was 2 l / h. The column had a diameter of 50 mm, a length of 700 mm and was filled with 8 mm glass rings. After the mixture in the Evaporator rotated, 300 g of 65% p-toluenesulfonic acid added and then 2144 g of trimethylolpropane and 3810 g Acrylic acid added.

The azeotrope separated off via the column was condensed and the water phase removed. The cyclohexane phase was partially (800 g / h) dosed into the natural circulation evaporator from below and partially fed as reflux to the distillation column and thus regulating the internal reactor temperature. The minimum response the distillation column was 1600 g / h. After the addition (2nd Hours) the reaction temperature became within 2 hours raised to 95-99 ° C. After an esterification period of 10 The experiment was stopped for hours and the reaction mixture rapidly cooled to 20 ° C.

The separated water phase (98% of theory) contained 4.7% Acrylic acid. The reaction mixture (6960 g) contained 4.1% Acrylic acid.

By adding cyclohexane to the reaction mixture, a Crude ester concentration of approx. 65% and at 20 ° C with an 8% saline solution (1500 g) in a stirred container washed. After the aqueous phase had been separated off, the organic phase with a 12% sodium hydroxide solution up to a pH Value of 13 added, the temperature being kept at 20-40 ° C has been. The neutralized organic phase after separation of the aqueous phase was washed with a 12% saline solution (1500 g) rewashed.

The washed organic phase was washed with 1 g Hydroquinone monomethyl ether was added and the mixture was heated to 60 ° C. in a stirred container and the cyclohexane was removed by distillation (final vacuum 100 mbar). The residual cyclohexane content was approximately 1.5%).

In a packed column (5 mm Raschig rings) at 80 ° C remaining cyclohexane with preheated air (75 ° C, 30 l / h) up to depleted <0.1% and then filtered.

The end product (4550 g) was clear and largely colorless (hazen Color number 30). The degree of esterification determined via the ester number was 90% of theory, the yield was 96% of theory Acrylic acid content 0.04%, the cyclohexane content 0.03%, the Sodium content 12 ppm, the copper content <0.1 ppm and the Viscosity 110 mPa.s.

Example 2 (comparative example)

The procedure was as in Example 1, but all starting materials presented together in the reactor from the beginning. After a Esterification time of 8 hours was cooled to 20 ° C, with the Pre-washed saline and then neutralized (pH 13). No phase separation could be achieved.

Example 3 (comparative example)

The procedure was as in Example 1, but by reduction the amount of cyclohexane to 500 g a reaction temperature of 120 ° C. set, which rose to 130 ° C towards the end of the reaction. To After a reaction time of 6 hours, the mixture was cooled and washed as usual. The phase separation time in The neutralization step was three times higher than in Example 1.

The color number was 100 APHA, the viscosity was 170 mPa.s.

Example 4 (comparative example)

According to EP 331 845 A2 Example 2 was in a stirred reactor with double wall heating and column with condenser and separation vessel a mixture of 711 g acrylic acid, 6 g Methanesulfonic acid, 40 g of toluene and 1.2 g of hydroquinone heated to 120 ° C. and a trimethylol propane (402 g) heated to 145 ° C within metered in from 2.5 hours. The circulation of the water was approx. 50 minutes after the start of adding trimethylolpropane started. After a reaction time of 5 hours, 95% of the theoretical amount of water discharged.

The strongly colored reaction mixture (APHA color number: 500) was neutralized with a 12% sodium hydroxide solution at 25-40 ° C (pH 13). No phase separation occurred even after standing for several hours on.

Example 5 (comparative example)

The esterification was carried out as in Example 4. That at 25 ° C cooled reaction mixture was powdered Treated sodium carbonate and filtered. That neutralized The reaction mixture had to be filtered twice to obtain a clear product received (color number 400). A treatment with activated carbon (50 g) only led to an insignificant improvement in the color number (300 APHA). After the toluene has been separated off in vacuo (80 ° C., 20 mbar) the viscosity was 180 mPa.s and the Na content was 60 ppm.

Example 6

In a 10 l reactor with an external natural circulation evaporator, Distillation column, condenser and phase separation vessel became 3264 5 g tripropylene glycol, 3 g methoxyphenol as 2% aqueous Solution, 6 g 50% hypophosphorous acid, 1 g Copper (11) chloride as a 20% aqueous solution, 300 g 65% p- Toluene sulfonic acid and 1800 g of cyclohexane submitted.

The natural circulation evaporator was a heated with heat transfer oil Shell and tube heat exchanger. The temperature in the reactor was 72-76 ° C. In addition, air was led into the natural circulation evaporator, the air volume was 2 l / h.

The distillation column had a diameter of 50 mm, one Length of 700 mm and was filled with 8 mm glass rings.

After the mixture was circulated in the evaporator, were over 2700 g of acrylic acid were metered in for 2 hours. That about the column separated azeotrope was condensed and the water phase discharged. The cyclohexane phase was partially (800 g / h) from dosed below in the natural circulation evaporator and partly as Returned to the distillation column and thus the Regulated reactor temperature. The minimum return of the Distillation column was 1600 g / h. After the addition of acrylic acid, the Reaction temperature to 96-99 ° C within 2 hours raised. After an esterification period of 10 hours, the Experiment ended and the reaction mixture rapidly cooled to 10 ° C. The separated water phase (98% of theory) contained 6.4% Acrylic acid. The reaction mixture (7320 g) contained 3.5% Acrylic acid.

By adding cyclohexane to the reaction mixture, a Crude ester concentration adjusted to approx. 65%, cooled to 10 ° C and with an 8% saline solution (1500 g) in one Stirred container washed. After the aqueous phase had been separated off the organic phase with a 12% sodium hydroxide solution up to one pH of 13 is added, the temperature at 20-30 ° C. was held.

The neutralized organic phase was 1 g Hydroquinone monomethyl ether added and in a stirred vessel to 60 ° C. heated and the cyclohexane separated by distillation (final vacuum 100 mbar). The residual cyclohexane content was approximately 1.5%.

In a packed column (5 mm Raschig rings) at 70 ° C remaining cyclohexane with preheated air (60 ° C, 30 l / h) up to depleted with a content of <0.1%.

The end product (5010 g) was clear and largely colorless (hazen Color number 20). The degree of esterification determined via the ester number was 99% of theory, the yield was 98% of theory Acrylic acid content 0.04% and the cyclohexane content 0.03% and one Viscosity (according to DIN 51562 at 25 ° C) of 10 mPa.s.

Example 7 (comparative example)

The procedure was as in Example 6, but no prewash the saline solution. The copper content in the end product was 15 ppm.

Example 8

In a 10 l reactor with an external natural circulation evaporator, Distillation column, condenser and phase separation vessel were 2814 g Dipropylene glycol, 3 g methoxyphenol as a 2% aqueous solution, 6 g 50% hypophosphorous acid, 1 g copper (II) chloride as 40% aqueous solution, 300 g 65% p-toluenesulfonic acid and 1700 g of cyclohexane submitted.

The natural circulation evaporator was a heated with heat transfer oil Shell and tube heat exchanger. The temperature in the reactor was 73-76 ° C. In addition, air was in the natural circulation evaporator passed, the amount of air was 2 l / h.

The distillation column had a diameter of 50 mm, one Length of 700 mm and was filled with 8 mm glass rings.

After the mixture was circulated in the evaporator, were over 3200 g of acrylic acid were metered in for 2 hours. That about the column separated azeotrope was condensed and the water phase discharged. The cyclohexane phase was partially (800 g / h) from dosed below in the natural circulation evaporator and partly as Returned to the distillation column and thus the Regulated reactor temperature. The minimum reflux from the column was 1600 g / h. The reaction temperature was within 2 hours raised to 95-98 ° C. After an esterification period of 8 The experiment was stopped for hours and the reaction mixture opened rapidly Cooled to 20 ° C. The separated water phase (94% of theory) contained 8.8% acrylic acid. The reaction mixture (9000 g) contained 6.2% acrylic acid.

By adding cyclohexane to the reaction mixture, a Crude ester concentration adjusted to approx. 70%, cooled to 10 ° C and with an 8% saline solution (1500 g) in one Stirred container washed. After the aqueous phase had been separated off the organic phase with a 12% sodium hydroxide solution up to one pH of 13 is added, the temperature at 20-30 ° C. was held.

The neutralized organic phase was 1 g Hydroquinone monomethyl ether added and in a stirred vessel to 60 ° C. heated and the cyclohexane separated by distillation (final vacuum 100 mbar). The residual cyclohexane content was approximately 1.5%).

In a packed column (5 mm Raschig rings) at 70 ° C remaining cyclohexane with preheated air (60 ° C, 30 l / h) up to depleted with a content of <0.1%.

The end product (4970 g) was clear and largely colorless (hazen Color number <50). The determined via the ester number Degree of esterification was 99% of theory, the yield was 98% of theory Acrylic acid content 0.03% and the cyclohexane content 0.06% and one Viscosity (according to DIN 51562 at 20 ° C) of 9 mPa.s.

Example 9

In a 10 l reactor with an external natural circulation evaporator, Distillation column, condenser and phase separation vessel were 2000 g cyclohexane, 3 g methoxyphenol as a 2% aqueous solution, 6 g 50% hypophosphorous acid, 1 g copper (II) chloride as 40% aqueous solution and 300 g 65% p-toluenesulfonic acid submitted.

The natural circulation evaporator was a heated with heat transfer oil Shell and tube heat exchanger. The temperature in the reactor was 72-76 ° C. The distillation column had a diameter of 50 mm, a length of 700 mm and was filled with 8 mm glass rings.

After the mixture in the evaporator circulated, 3520 g one with 1 mol / mol ethylene oxide and 3 mol / mol propylene oxide oxylated trimethylolpropane and 2800 g of acrylic acid. The Azeotrope separated off via the column was condensed and the Water phase removed. The cyclohexane phase became partial (800 g / h) dosed into the natural circulation evaporator and partially fed as reflux to the distillation column and thus regulating the internal reactor temperature. The minimum return of the Column was 1600 g / h. After the addition was complete, the Reaction temperature to 95-99 ° C within 2 hours raised. After an esterification period of 8 hours, the experiment ended and the reaction mixture rapidly cooled to 20 ° C. The separated water phase (100% of theory) contained 2.6% Acrylic acid. The reaction mixture (6935 g) contained 3.2% acrylic acid.

By adding cyclohexane to the reaction mixture, a Crude ester concentration of approx. 60% and at 20 ° C with an 8% saline solution (1500 g) in a stirred container washed. After the aqueous phase had been separated off, the organic phase with a 12% sodium hydroxide solution up to a pH Value of 13 added, the temperature being kept at 20-35 ° C has been. The neutralized organic phase was with a 26% Wash saline solution (1500 g).

The washed organic phase was washed with 1 g Hydroquinone monomethyl ether was added and the mixture was heated to 60 ° C. in a stirred container and the cyclohexane was removed by distillation (final vacuum 100 mbar). The residual cyclohexane content was approximately 1.5%).

In a packed column (5 mm Raschig rings) at 80 ° C remaining cyclohexane with preheated air (75 ° C, 30 l / h) up to depleted with a content of <0.1%.

The end product (4180 g) was clear and largely colorless (hazen Color number 30). The degree of esterification determined via the ester number was 96% of theory, the yield was 96% of theory Acrylic acid content 0.04% and the cyclohexane content 0.03% and one Viscosity (according to DIN 53229 at 23 ° C) of 100 mPa.s.

Claims (15)

1. A process for the preparation of higher (meth) acrylic acid esters by reacting (meth) acrylic acid and the alcohol in the presence of at least one acid catalyst and at least one polymerization inhibitor and in the presence of a solvent which forms an azeotrope with water, the azeotrope is distilled off and condensed , wherein the condensate breaks down into an aqueous and an organic phase, characterized in that a) esterification in a reactor with a circulation evaporator and b) in the presence of at least 10% by weight of solvent, based on the reaction mixture, and either 1. introduces at least part of the solvent, optionally part of the catalyst (mixture) and optionally at least part of the polymerization inhibitor (mixture) in the esterification reactor, heats up to the boiling point of the component with the lowest boiling point in the system and, as soon as the circulation is in operation, (Meth) acrylic acid and alcohol and optionally any remaining catalyst, polymerization inhibitor and solvent are metered in together or separately, or 2. puts at least part of the solvent, optionally part of the catalyst (mixture), optionally at least part of the polymerization inhibitor (mixture) and at least part of the alcohol in the esterification reactor, heated to the boiling point of the component with the lowest boiling point in the system and, as soon as the circulation is in operation, (meth) acrylic acid and, if appropriate, the remainder of the alcohol and, if appropriate, any remaining catalyst, polymerization inhibitor and solvent are metered in together or separately, or 3. at least some of the solvent, at least some of the catalyst (mixture), at least some of the polymerization inhibitor (mixture) and at least some of the (meth) acrylic acid in the esterification reactor, heated to the boiling point of the component with the lowest boiling point in the system and , as soon as the circulation is in operation, the alcohol and optionally the rest (meth) acrylic acid and optionally the remaining catalyst, polymerization inhibitor and solvent are metered in together or separately, or 4. at least part of the solvent, at least part of the catalyst (mixture), at least part of the polymerization inhibitor (mixture), at least part of the alcohol and part of the (meth) acrylic acid in the esterification reactor, at the boiling point of the component with the lowest The boiling point in the system is heated and, as soon as the circulation is in operation, the remainder of the alcohol and the remainder of (meth) acrylic acid as well as any remaining catalyst, polymerization inhibitor and solvent are metered in together or separately. 2. The method according to claim 1, characterized in that one in steps c1), c2) or c3) the catalyst / the Catalyst mixture before adding the other substances admits after the heating has essentially ended. 3. The method according to claim 1 or 2, characterized in that the reactor is equipped with a natural circulation evaporator. 4. The method according to claim 3, characterized in that a Part of the organic phase of the condensate in the Natural circulation evaporator is performed. 5. The method according to claim 1 to 4, characterized in that an inert gas is led into the natural circulation evaporator. 6. The method according to claim 1 to 5, characterized in that the reaction mixture is prewashed. 7. The method according to claim 1 to 6, characterized in that the reaction mixture is neutralized with aqueous base. 8. The method according to claim 7, characterized in that the Temperature in the neutralization does not exceed 35 ° C. 9. The method according to claim 1 to 8, characterized in that Solvent with an inert gas from the reaction mixture is stripped. 10. The method according to claim 1 to 9, characterized in that one as a polymerization inhibitor (mixture) at least one Compound from the group hydroquinone, Hydroquinone monomethyl ether, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethyl-phenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-tert-butylphenol, 4-tert-butyl-2,6-dimethylphenol, hypophosphorous acid, copper acetate, copper chloride and uses copper salicylate. 11. Essentially containing trimethylolpropane triacrylate Reaction mixture, obtainable by at least 10% by weight Solvent based on the sum of Trimethylolpropane and acrylic acid, and at least part of Polymerization inhibitor (mixture) in a reactor with Circulation presents, heats up and trimethylolpropane and acrylic acid metered in a ratio of 1: 3.3-4.5, whereby the to Reaction required acid catalyst before metering of trimethylolpropane and acrylic acid, thereby adding the Set the reaction temperature to 70-110 ° C and the Reaction time is less than 20 hours, the reaction mixture then optionally pre-washed, neutralized and optionally washed and then the solvent by distillation and stripping to a content of less than 0.5% by weight, based on the reaction mixture, removed. 12. The method according to claim 1, characterized in that one an essentially containing trimethylolpropane triacrylate Produces reaction mixture. 13. Essentially containing trimethylolpropane triacrylate Reaction mixture obtainable by a process according to claim 12th 14. Essentially containing trimethylolpropane triacrylate Reaction mixture obtainable by a process according to claim 12 with a color number of less than 100 APHA and one Viscosity of less than 160 mPa.s and / or an ester number of 480 to 570. 15. Essentially acrylic acid ester of alkoxylated Reaction mixture containing trimethylolpropane, thereby obtainable that at least 10 wt .-% solvent, based on the sum of alkoxylated trimethylolpropane and acrylic acid, and at least part of it Polymerization inhibitor (mixture) in a reactor with circulation, heated and alkoxylated trimethylolpropane and acrylic acid in the ratio 1: 3.3-4.5 metered in, the reaction required acid catalyst before the addition of alkoxylated trimethylolpropane and acrylic acid admits, the Set the reaction temperature to 70-110 ° C and the Reaction time is less than 20 hours, the reaction mixture then optionally pre-washed, neutralized and optionally washed and then the solvent by distillation and stripping to a content of less than 0.5% by weight, based on the reaction mixture, removed.