EP1727780A1 - Procede pour la preparation d' esters (meth)acryliques - Google Patents

Procede pour la preparation d' esters (meth)acryliques

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Publication number
EP1727780A1
EP1727780A1 EP05707413A EP05707413A EP1727780A1 EP 1727780 A1 EP1727780 A1 EP 1727780A1 EP 05707413 A EP05707413 A EP 05707413A EP 05707413 A EP05707413 A EP 05707413A EP 1727780 A1 EP1727780 A1 EP 1727780A1
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EP
European Patent Office
Prior art keywords
acid
chromanol
reaction mixture
optionally
particularly preferably
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP05707413A
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German (de)
English (en)
Inventor
Reinhold Schwalm
Bärbel MEYER
Helmut Gruner
Thomas Daniel
Ulrich Riegel
Dieter Hermeling
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BASF SE
Original Assignee
BASF SE
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Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP1727780A1 publication Critical patent/EP1727780A1/fr
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/48—Separation; Purification; Stabilisation; Use of additives
    • C07C67/62—Use of additives, e.g. for stabilisation

Definitions

  • the present invention describes a process for the preparation of (meth) acrylic acid esters, in which chromanol derivatives are used as stabilizers against polymerization, and the use of the (meth) acrylic acid esters obtainable in this way.
  • (meth) acrylic acid and (meth) acrylic acid esters can be easily polymerized, for example by heat or the action of light or radical formers.
  • the polymerization must be reduced or prevented for safety reasons and economic reasons during production, workup and / or storage, there is a constant need for new, effective polymerization inhibitors.
  • (meth) acrylic acid (esters) A large number of stabilizers for (meth) acrylic acid and (meth) acrylic acid esters are known, hereinafter referred to as (meth) acrylic acid (esters).
  • JP-A 60-72980 describes a stabilizing agent against free-radical polymerization or oxidative decomposition, containing a chroman derivative of the formula (I)
  • R 1 is hydrogen, methyl, ethyl or acetyl and R 2 to R 4 is hydrogen or methyl.
  • R 1 is hydrogen, methyl, ethyl or acetyl and R 2 to R 4 is hydrogen or methyl.
  • 2,2,5,7,8-Pentamethyl-6-chromanol, 2,2,5,7-tetramethyl-6-chromanol and 2,2,8-trimethyl-6-chromanol are preferred.
  • the stabilization of vinyl monomers is disclosed in general and exemplarily the stabilization of acrylic acid in an inert atmosphere.
  • the similarity of such chromanes with vitamin E is also pointed out.
  • the examples show the superiority of 2,2,5,7,8-pentamethyl-6-chromanol over ⁇ -tocopherol in the stabilization of acrylic acid.
  • chroman derivatives are frequently used as model systems for tocopherols or vitamin E (see, for example, J. Lars, G. Nilsson, H. Sievertsson, H. Seiander, Acta Chemica Scandinavica, 22, (1968), 3160 - 3170.
  • 5,7,8-pentamethyl-6-chromanol is widely used as a model compound for ⁇ -tocopherol.
  • WO 90/07485 describes a process for the preparation of (meth) acrylic acid esters of polyhydric alcohols by esterification of (meth) acrylic acid with the corresponding alcohols, in which tocopherols and preferably at least partially ⁇ -tocopherol are used as the sterically hindered phenol compound for stabilization.
  • the stabilization can also take place in the presence of an oxygen-containing gas. It does not matter whether the tocopherol is used racemically or enantiomerically pure.
  • the object of the present compound was to provide a process for the preparation of (meth) acrylic acid esters, by means of which a stabilizer can be used to reduce the polymerization more effectively than in the prior art, this stabilizer having to be non-toxic.
  • the object was achieved by a process for the preparation of (meth) acrylic esters from (meth) acrylic acid and at least one alcohol in the presence of at least one stabilizer, in which at least one 6-chromanol derivative of the formula (III),
  • R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 and R 14 independently of one another are each hydrogen, C 1 to C 4 alkyl, C 1 to C 4 alkyloxy or C 6 to C 12 aryl and
  • R 5 additionally C 1 to C 4 alkylcarbonyl, C T to C 4 alkyloxycarbonyl, C 6 to C 12 arylcarbonyl or C 6 to C 2 aryloxycarbonyl,
  • radicals mentioned are each optionally interrupted by one or more oxygen and / or sulfur atoms and / or one or more substituted or unsubstituted imino groups or substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and / or heterocycles could be,
  • phenyl optionally interrupted by one or more oxygen and / or sulfur atoms and / or one or more substituted or unsubstituted imino groups or C 6 to C 12 -A17I substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and / or heterocycles for example phenyl, tolyl, xylyl, ⁇ -naphthyl, ⁇ -naphthyl, 4-diphenylyl, chlorophenyl, dichlorophenyl, trichlorophenyl, difluorophenyl, methylphenyl, dimethylphenyl, trimethylphenyl, ethylphenyl, diethylphenyl, / so-propylphenyl, tert-butylphenyl , Dodecylphenyl, methoxyphenyl, dimethoxyphenyl, ethoxyphenyl
  • R s , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 and R 14 are each independently of one another hydrogen or C 1 to C alkyl and particularly preferably hydrogen or methyl.
  • R 5 is preferably hydrogen, C 1 to C alkyl or d to C alkyl carbonyl, particularly preferably hydrogen or C 1 to C 4 alkyl and very particularly preferably hydrogen, methyl or acetyl.
  • R s and R 9 to R 12 are each hydrogen
  • R 6 , R 7 and R 8 are each independently hydrogen or methyl
  • R 13 and R 14 are each methyl.
  • R 5 and R 9 to R 12 are each hydrogen
  • R 6 , R 7 and R 8 are each methyl
  • R 13 and R 14 are each methyl.
  • Preferred 6-chromanol derivatives are 2,2,5,7,8-pentamethyl-6-chromanol, 2,2,5,7-tetramethyl-6-chromanol, 2,2,5,8-tetramethyl-6-chromanol , 2,2,7,8-tetramethyl-6-chromanol, 2,2,5-trimethyl-6-chromanol, 2,2,7-trimethyl-6-chromanol and 2,2,8-trimethyl-6 -chromanol, 2,2,5,7,8-pentamethyl-6-chromanol, 2,2,5,7- are particularly preferred Tetramethyl-6-chromanol, 2,2,5,8-tetramethyl-6-chromanol and 2,2,7,8-tetramethyl-6-chromanol and very particularly preferred is 2,2,5,7,8-pentamethyl- 6-chromanol.
  • 6-chromanols are used according to the invention in processes for the preparation of an ester F of a polyalcohol A with at least one ethylenically unsaturated carboxylic acid B, comprising the steps
  • the molar ratio of B to A is Qe of the hydroxyl group to be esterified in the polyalcohol A) as a rule at least 1: 1, preferably at least 1.05: 1, particularly preferably at least 1.1: 1, very particularly preferably at least 1.25 : 1 and in particular at least 1.5: 1.
  • Usable polyalcohols A are compounds which have at least two hydroxy functions (-OH), preferably at least three, particularly preferably three to ten, very particularly preferably three to six and in particular three to four.
  • the polyalcohols can be aliphatic, cycloaliphatic or aromatic, preferably aliphatic or cycloaliphatic and very particularly preferably aliphatic, straight-chain or branched and optionally substituted with functional groups.
  • the polyalcohols have two to 50 carbon atoms and preferably three to 40.
  • the molecular weight of the polyalcohols which can be used is generally below 5000 g / mol, preferably below 2500 g / mol, particularly preferably below 1500 g / mol, very particularly preferably below 1000 g / mol and in particular below 800 g / mol.
  • Preferred polyalcohols A are polyols, functionalized polyols, alkoxylated polyols, sugar alcohols, partially alkoxylated sugar alcohols, polyetherols, polyesterols, at least partially alkoxylated polyesterols and at least partially saponified, alkoxylated polyesterols.
  • polyols examples include trimethylolbutane, trimethylolpropane, trimethylolethane, neopentylglycol, hydroxypivalic acid neopentylglycol ester, pentaerythritol, glycerol, 1,2-ethylene glycol, 1,2-propylene glycol, 2-ethyl-1,3-propanediol, 2-methyl-1, 3-propanediol, hydroquinone, bisphenol A, bisphenol F, bisphenol B, 2,2-bis (4-hydroxycyclohexyl) propane, 1,1-, 1,2-, 1,3- and 1, 4- Cyclohexanedimethanol, 1,2-, 1,3- or 1,4-cyclohexanediol, but-2-en-1,4-diol and but-2-yn-1,4-diol.
  • the polyols can also carry additional functionalities such as ether functions (-O-), carboxyl functions (-COOH) or CC alkyloxycarbonyl functions (ester groups), C 1 -C 4 -alkyl in this document being methyl, ethyl, / so-propyl , n-propyl, n-butyl, / so-butyl, se / c-butyl or terf-butyl.
  • ether functions -O-
  • carboxyl functions -COOH
  • CC alkyloxycarbonyl functions esteer groups
  • Such functionalized polyols are ditrimethylolpropane, dipentaerythritol, dimethylolpropionic acid, dimethylolbutyric acid, trimethylolacetic acid, hydroxypivalic acid and the 2-hydroxyethyl or CrC 4 alkyl esters of these acids.
  • Preferred polyols are those of the formula (IV):
  • R 15 , R 16 independently of one another are hydrogen, d - C 10 -alkyl, preferably d - C 4 -alkyl, C, - C 10 -hydroxyalkyl, preferably hydroxy-Ci-C 4 -alkyl, carboxyl or Ci - C 4 -Alkyloxycarbonyl, preferably hydrogen, hydroxymethyl and d - C 4 alkyl and particularly preferably hydroxymethyl and Ci - C alkyl.
  • the alkyl radicals can each be straight-chain or branched.
  • R 15 and R 16 are hydrogen, methyl, ethyl, / so-propyl, n-propyl, n-butyl, / so-butyl, se / c-butyl, ferf-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, hydroxymethyl, carboxyl, methoxycarbonyl, ethoxycarbonyl or n-butoxycarbonyl, preferably hydrogen, hydroxymethyl, methyl and ethyl, particularly preferably hydroxymethyl, methyl and ethyl.
  • polyhydric alcohols of the formula (IV) are trimethylol butane, trimethylol propane, trimethylol ethane, neopentyl glycol, pentaerythritol, 2-ethyl-1, 3-propanediol, 2-methyl-1, 3-propanediol, 1, 3-propanediol, dimethylolpropionic acid, dimethyl olpropionTalkremethylester, Dimethylolpropionklaethylester, dimethylolbutyric acid, or Dimethylolbutterklaremethylester Dimethylolbutterklasted acid, preferred are neopentyl glycol, trimethylolpropane, pentaerythritol and dimethylol propionic acid, most preferably neopentyl glycol, trimethylolpropane and pentaerythritol, and in particular trimethylolpropane and pentaerythr
  • sugar alcohols examples include sorbitol, mannitol, maltitol, isomalt, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol and dulcitol (galactitol).
  • polyetherols are poly-THF with a molecular weight between 162 and 2000, preferably between 162 and 1458, particularly preferably between 162 and 1098, very particularly preferably between 162 and 738 and in particular between 162 and 378, poly-1, 3-propanediol and Poly-1,2-propanediol with a molar mass between 134 and 1178, preferably between 134 and 888, particularly preferably between 134 and 598 and very particularly preferably between 134 and 308, polyethylene glycol with a molar mass between 106 and 898, preferably between 106 and 458 , particularly preferably from 106 to 400, very particularly preferably between 106 and 235 and in particular diethylene glycol, triethylene glycol and tetraethylene glycol.
  • Suitable polyesterols are, for example, those which can be prepared by esterifying polycarboxylic acids, preferably dicarboxylic acids, with the abovementioned polyols.
  • the starting materials for such polyesterols are known to the person skilled in the art.
  • esterifiable Derivatives such as anhydrides or dialkyl esters, for example CC alkyl esters, preferably methyl, ethyl or n-butyl esters, of the acids mentioned are used.
  • Suitable hydroxyl-bearing carboxylic acids or lactones are 4-hydroxybenzoic acid, 6-hydroxy-2-naphthalic acid, pivalolactone or ⁇ -caprolactone.
  • Suitable polyols are the above-mentioned polyfunctional alcohols, preferably neopentyl glycol, trimethylolpropane, trimethylolethane, pentaerythritol, dimethylolpropionic acid or dimethylolbutyric acid.
  • polyesterols are those of the formula (IVa-c),
  • R 15 , R 16 have the meanings given above and
  • Y is a straight-chain or branched, optionally substituted alkylene group having 2 to 20 carbon atoms or an optionally substituted cycloalkylene or arylene group having 6 to 12 carbon atoms or a single bond.
  • Examples of Y are a single bond, methylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, cis-1 , 2-ethenylene, trans-1, 2-ethenylene, 1, 2-, 1, 3- or 1, 4-phenylene, 1, 2-cyclohex-1-enylene, 1, 2-, 1, 3- or 1 , 4-cyclohexylene, 4-carboxy-1,2-phenylene, 2-carboxy-1, 4-phenylene or 1-carboxy-2,4-phenylene.
  • Preferred groups Y are 1,2-ethylene, 1,4-butylene and 1,2-, 1,3- or 1,4-phenylene.
  • Polyester (meth) acrylates can be used in several stages or in one stage, e.g. in EP-A 279303, can be prepared from (meth) acrylic acid, polycarboxylic acid and polyol.
  • polyalcohols are alkoxylated polyols and polyesterols which can be obtained by reacting a polyol or polesterol with at least one alkylene oxide.
  • Reaction mixtures containing such compounds of the formula (V) can also be prepared.
  • R 17 is a polyvalent, straight-chain or branched C -C 10 alkyl radical
  • R 18 is independently a straight-chain or branched C 2 -C 10 alkenyl radical
  • R 19 is independently hydrogen or methyl
  • x is independently a positive integer of 2 or greater
  • the underlying alcohol has the formula (Va), R 17 - (O (CH (R 19 ) CH (R 19 ) O) yH) x (Va),
  • R 17 , R 19 , x and y are as defined above.
  • the compounds of the formula (V) are generally polyhydric alcohols (Va) having 2 to 10 carbon atoms, which are alkoxylated with between 2 and 8 alkylene oxide units per hydroxyl group and the terminal hydroxyl group of each alkylene oxide chain having 2 to 10 carbon atoms unsaturated carboxylic acid or its ester is esterified.
  • the starting alcohol is preferably a polyhydric alcohol having 3 to 6 carbon atoms and preferably carrying 2 to 4 hydroxyl groups.
  • the starting alcohol is particularly preferably trimethylolpropane, glycerol, pentaerythritol, 1,3-propanediol, propylene glycol, 1,4-butane diol or butylene glycol. Trimethylolpropane, glycerol and pentaerythritol are very particularly preferred as starting alcohol.
  • Suitable alkylene oxides are, for example, ethylene oxide, propylene oxide, / so-butylene oxide, vinyloxirane and / or styrene oxide.
  • the alkylene oxide chain can preferably be composed of ethylene oxide, propylene oxide and / or butylene oxide units. Such a chain can be composed of a species of an alkylene oxide or a mixture of alkylene oxides. If a mixture is used, the different alkylene oxide units can be present statistically or as blocks or blocks of individual species.
  • Preferred as the alkylene oxide is ethylene oxide, propylene oxide or a mixture thereof, particularly preferably it is ethylene oxide or propylene oxide and very particularly preferably ethylene oxide.
  • one radical R 19 per alkylene oxide unit is preferably hydrogen and the other is methyl or hydrogen; both radicals R 19 are particularly preferably hydrogen.
  • the preferred number of alkylene oxide units in each chain is dependent on the number of chains.
  • the compounds of formula (V) are present as a mixture of compounds described by this formula and by-products of the manufacturing process.
  • alkoxylated polyols are the alkoxylation products (Via), (VI b) or (Vlc) of polyols of the formula (IV),
  • Particularly preferred among these are those polyhydric alcohols of the formula (VIb).
  • Equally preferred is one to 20 times, preferably one to ten times, particularly preferably two to ten times, very particularly preferably two to five times, especially three to five times and especially three to four times alkoxylated, preferably ethoxylated, propoxylated or mixed-ethoxylated-propoxylated and particularly preferred ethoxylated glycerin (here, in exceptional cases, calculated in mol of alkoxy groups per mol of glycerol).
  • the degrees of alkoxylation given relate in each case to the average degree of alkoxylation.
  • the number average molecular weight M n of the alkoxylated polyols is preferably not more than 1000 g / mol, particularly preferably not more than 800 g / mol and very particularly preferably not more than 550 g / mol.
  • the information on the number-average and weight-average molecular weights M n and M w here relate to gel permeation chromatography measurements, polystyrene being used as the standard and tetrahydrofuran as the eluent. The method is described in Analytiker Taschenbuch Vol. 4, pages 433 to 442, Berlin 1984.
  • alkoxylated sugar alcohols are those compounds which are obtained from sugar alcohols, for example from the sugar alcohols listed above, by alkoxylie- tion, for example with the alkylene oxides listed above, preferably with ethylene oxide and / or propylene oxide and very particularly preferably with ethylene oxide.
  • tetrols listed which are on average 2 to 30 times, preferably 2 to 20 times, particularly preferably 3 to 10 times and in particular 3, 4, 5, 6, 7 or 8 times alkoxylated per mol of sugar alcohol
  • the listed pentols which in statistical means per mol of sugar alcohol are alkoxylated 3 to 35 times, preferably 3 to 28 times, particularly preferably 4 to 20 times and in particular 4, 5, 6, 7, 8, 9 or 10 times,
  • higher sugar alcohols which are on average 4 to 50 times, preferably 6 to 40 times, particularly preferably 7 to 30 times, very particularly preferably 8 to 20 times and in particular 10 to 15 times alkoxylated per mol of sugar alcohol.
  • Preferred alkoxylated sugar alcohols are those in which at least one hydroxyl group of the sugar alcohol is not alkoxylated.
  • alkoxylated polesterols are those of the formula (VIIa-c),
  • These are preferably unalkoxylated or one to ten times, particularly preferably two to five times ethoxylated, propoxylated or mixed ethoxylated and propoxylated neopentylglycol, trimethylolpropane, trimethylolethane or pentaerythritol enhanced with adipic acid, phthalic acid, terephthalic acid or isophthalic acid.
  • the different alkoxy groups contained therein can be in a molar ratio of, for example, 0.05-20: 1, preferably 0.1-10: 1 and particularly preferably 0.2-5: 1.
  • trihydric or higher polyalcohols are used as polyalcohols in the reaction, it may be useful for their use as radical crosslinking agents to only partially convert the polyalcohols.
  • the stoichiometric excess of carboxylic acid B to be used is calculated to the desired degree of conversion, ie it is, for example, 2 / n times the molar excesses given above.
  • the implementation can also, e.g. by cooling or dilution, if the desired degree of conversion is reached.
  • Usable ethylenically unsaturated carboxylic acids B are those compounds which have at least one carboxyl group (-COOH), preferably one, and at least one, preferably one, ethylenically unsaturated group.
  • the carboxylic acids which can be used can be aliphatic, cycloaliphatic or aromatic, preferably aliphatic or cycloaliphatic and very particularly preferably aliphatic, straight-chain or branched and optionally substituted with functional groups.
  • the carboxylic acids have three to ten carbon atoms, preferably three to five and particularly preferably three to four.
  • ethylenically unsaturated carboxylic acids B are acrylic acid, methacrylic acid, ethacrylic acid, maleic acid including its anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, vinyl acetic acid, allylacetic acid or crotonic acid.
  • Preferred carboxylic acids B are ⁇ , ⁇ -unsaturated carboxylic acids.
  • methacrylic acid and acrylic acid called (meth) acrylic acid in this document, very particularly preferred is acrylic acid.
  • the (meth) acrylic acid esters can also be prepared by transesterification instead of esterification.
  • a carboxylic acid B instead of a carboxylic acid B, a CC-alkyl ester of a carboxylic acid B is used, that is to say a methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl ester of a carboxylic acid B, preferably a methyl, ethyl or n-butyl ester, particularly preferably a methyl or ethyl ester and very particularly preferably a methyl ester.
  • Esterification catalysts C which can be used are sulfuric acid, aryl or alkylsulfonic acids or mixtures thereof.
  • arylsulfonic acids are benzenesulfonic acid, para-toluenesulfonic acid or dodecylbenzenesulfonic acid
  • alkylsulfonic acid Ren are methanesulfonic acid, ethanesulfonic acid or trifluoromethanesulfonic acid.
  • Strongly acidic ion exchangers or zeolites can also be used as esterification catalysts.
  • Sulfuric acid and sulfonic acids are preferred, particularly preferred sulfuric acid and para-toluenesulfonic acid.
  • reaction is carried out instead of an esterification as a transesterification, it is possible to use, for example, titanium alcoholates, the alkyl groups of which are d - d - alkyl radicals, for example titanium alcoholates, for the preparation of (meth) acrylic esters by transesterification.
  • titanium alcoholates the alkyl groups of which are d - d - alkyl radicals
  • titanium alcoholates for the preparation of (meth) acrylic esters by transesterification.
  • Tetramethyl, tetraethyl, tetraisopropyl, tetrapropyl, tetraisobutyl and tetrabutyl titanate see e.g. EP-B1 298 867, EP-A2 960877.
  • catalysts u. a. Titanphenolate (DE-OS 20086 18), metal chelate compounds from z. B.
  • transesterification catalysts described in the prior art can be used for the process according to the invention, preferably titanium, magnesium or aluminum alcoholates, particularly preferably titanium alcoholates and in particular titanium tetramethanolate, ethanolate, isopropanolate and n-butanolate.
  • At least one chromanol derivative of the formula (III) is present as a polymerization inhibitor D during the esterification or transesterification.
  • a chromanol derivative is present.
  • Polymerization inhibitors D which can optionally be used in addition are, for example, phenols such as
  • Alkylphenols for example o-, m- or p-cresol (methylphenol), 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethylphenol, 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, or 2,2'-methylene-bis- (6-tert-butyl-4-methylphenol), 4,4'-oxydiphenyl, 3,4-methylenedioxydiphenol (sesamol), 3,4 -Dimethylphenol, hydroquinone, pyrocatechol (1, 2-dihydroxybenzene), 2- (1 '-methylcyclohex-1' -yl) -4,6-dimethylphenol, 2- or 4- (1'-phenyl-eth- 1'-yl)
  • Aminophenols e.g. para-aminophenol, 3-diethylaminophenol
  • Nitrosophenols e.g. para-nitrosophenol, p-nitroso-o-cresol,
  • Alkoxyphenols for example 2-methoxyphenol (guaiacol, pyrocatechol monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- or di-tert-butyl-4-methoxyphenol, 3,5-di tert-butyl-4-hydroxyanisole, 3-hydroxy-4-methoxybenzyl alcohol, 2,5-dimethoxy-4-hydroxybenzyl alcohol (Syringa alcohol), 4-hydroxy-3-methoxybenzaldehyde (vanillin), 4-hydroxy-3 - ethoxybenzaldehyde (ethylvanillin), 3-hydroxy-4-methoxybenzaldehyde (isovanillin), 1- (4-hydroxy-3-methoxyphenyl) ethanone (acetovanillon), eugenol, dihydroeugenol, isoeugenol, Tocopherols, such as, for example, ⁇ -, ⁇ -
  • Oximes can be, for example, aldoximes, ketoximes or amidoximes, as described, for example, in DE 10139767, preferably diethyl ketoxime, acetone oxime, methyl ethyl ketoxime, cyclohexanone oxime or other aliphatic oximes or their reaction products with alkyl transfer reagents
  • Triphenylphosphine Triphenylphosphine, triphenylphosphite, hypophosphorous acid or triethylphosphite sulfur-containing compounds
  • Copper or metal salts for example copper, manganese, cerium, nickel, chromium chloride, dithiocarbamate, sulfate, salicylate or acetate 0
  • the phenols and quinones mentioned are preferred, hydroquinone, hydroquinone monomethyl ether are particularly preferred, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-dimethyl-phenol, 2,6-di-tert-butyl-4-methylphenol, 2,4-di-tert.- Butylphenol, triphenyl phosphite, hypophosphorous acid, CuCl 2 and guaiacol, very particularly preferred are hydroquinone and hydroquinone monomethyl ether.
  • Another object of the present invention relates to stabilizer mixtures containing at least one 6-chromanol derivative according to formula (III) and at least one stabilizer selected from the group comprising phenols, quinones and hydroquinones, N-oxyls, aromatic amines, phenylenediamines, sulfonamides, oximes , Hydroxylamines, urea derivatives, phosphorus-containing compounds, sulfur-containing compounds and metal salts.
  • Preferred stabilizer mixtures contain at least one 6-chromanol derivative according to formula (III) and at least one stabilizer selected from the group comprising phenols, hydroquinones, N-oxyls and sulfur-containing compounds.
  • Particularly preferred stabilizer mixtures contain at least one 6-chromanol derivative according to formula (III) and at least one stabilizer selected from the group comprising phenols and sulfur-containing compounds.
  • 6 Very particularly preferred are stabilizer mixtures comprising at least one 6-chromanol derivative of the formula (III) and at least one stabilizer selected from the group comprising phenothiazine, hydroquinone, hydroquinone monomethyl ether and hypophosphorous acid.
  • the stabilizer mixtures described above are used in the process according to the invention Preparation of an ester F of a polyalcohol A with at least one ethylenically unsaturated carboxylic acid B used.
  • the esterification of the ethylenically unsaturated carboxylic acid ⁇ B with a polyalcohol A is particularly preferred in the presence of, based on the esterification mixture, 0.01- ⁇ % by weight of at least one 6-chromanol derivative and up to 1000 ppm of at least one further polymerization inhibitor selected from Group consisting of phenothiazine, hydroquinone monomethyl ether, and hypophosphorous acid.
  • the reaction is carried out in the presence of an oxygen-containing gas, preferably air or a mixture of air and nitrogen (lean air).
  • an oxygen-containing gas preferably air or a mixture of air and nitrogen (lean air).
  • the reaction zone and / or the heat exchangers installed in the system, e.g.
  • Distillation units or reactors with a gas or gas mixture inert under the reaction conditions, e.g. Nitrogen, air, nitrogen-oxygen mixtures, argon, helium, carbon di- or monoxide, preferably air or air-nitrogen mixtures, in particular those with an oxygen content of 0.1 to 16% by volume, preferably from 0.1, up to 10 Vol% and very particularly preferably sol-0 before air-nitrogen mixtures with an oxygen content of 1 to ⁇ vol% continuously flushed.
  • the purge gas is preferably conducted along the existing heat exchanger surfaces, particularly preferably in an existing forced or natural circulation evaporator.
  • the purge gas is pressure or volume controlled by a suitable, known, not limited supply device in the vicinity of the existing heat exchanger surface, so that the, preferably continuous, purge gas flow in countercurrent or cocurrent to the liquid is guided along the heat exchanger surface.
  • Solvents E which can be used are particularly those which are suitable for azeotropic removal of the water of reaction, if desired, in particular 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.
  • esterification the preparation and / or processing methods of polyhydric alcohols known to the person skilled in the art can be used, for example those described in DE-A 19941 136, DE-A 3843843, DE-A 3843 8 ⁇ 4, DE-A 199 37911, DE-A 199292 ⁇ 8 , EP-A 331 84 ⁇ , EP ⁇ 46 ⁇ 1 or US 4 187 383.
  • esterification can be carried out as follows:
  • the esterification apparatus consists of a stirred reactor, preferably a reactor with a circulation evaporator and an attached distillation unit with a condenser and a phase separation vessel.
  • the reactor can be, for example, a reactor with double-wall heating and / or internal heating coils.
  • a reactor with an external heat exchanger and natural or forced circulation i.e. using a pump, particularly preferably natural circulation, in which the circulating flow is accomplished without mechanical aids.
  • reaction can also be carried out in several reaction zones, for example a reactor cascade of two to four, preferably two to three, reactors.
  • Suitable circulation evaporators are known to the person skilled in the art and are described, for example, in R. Billet, Verdampfertechnik, HTB-Verlag, bibliographisches Institut Mannheim, 1965, 63.
  • Examples of circulation evaporators are shell-and-tube heat exchangers, plate heat exchangers, etc.
  • the distillation unit is of a type known per se. This can be a simple distillation, which may be equipped with a splash guard, or a rectification column.
  • column internals for example trays, packings and / or fillings.
  • trays bubble trays, sieve trays, valve trays, Thormann trays and / or dual-flow trays are preferred; of the fillings, those with rings, coils, saddle bodies or braids are preferred.
  • the condenser and the separation vessel are of conventional design.
  • 5 Carboxylic acid B and polyalcohol A are generally used in the esterification a) in a molar excess, as indicated above, based on the hydroxyl groups of the alcohol.
  • esterification catalysts C the above can be used. They are generally used in an amount of 0.1- ⁇ % by weight, based on the esterification mixture, preferably 0, ⁇ - ⁇ , particularly preferably 1-4 and very particularly preferably 2-4% by weight.
  • the esterification catalyst can be removed from the reaction mixture using an ion exchanger.
  • the ion exchanger can be added directly to the reaction mixture and then filtered off, or the reaction mixture can be passed over an ion exchange bed.
  • the esterification catalyst is preferably left in the reaction mixture. However, if the catalyst is an ion exchanger, it is preferably removed, for example by filtration.
  • an oxygen-containing gas can be present before air or a mixture of air and nitrogen (lean air).
  • This oxygen-containing gas is preferably metered into the bottom region of a column and / or into a circulation evaporator and / or passed through the reaction mixture and / or over it.
  • the polymerization inhibitor D according to the invention or a mixture containing it (as mentioned above) is generally used in a total amount of 0.01 - ⁇ % by weight, based on the esterification mixture, preferably 0.02 - 3, particularly preferably 0.0 ⁇ - 2% by weight, very particularly preferably 0.1 to 1 and in particular -6 in particular 0.3 to 1% by weight.
  • the polymerization inhibitor (mixture) D can be used, for example, as an aqueous solution or as a solution in a starting material or product or another suitable solvent, for example those mentioned under E. If the reaction is carried out as a transesterification, the transesterification is generally analogous carried out for the described esterification. In the context of this document, transesterification is to be regarded as analogous to esterification, even if this is not explicitly stated. A major difference is that, in contrast to the esterification, the C r C 4 alcohol released has to be separated off in order to improve the shift in equilibrium.
  • the water of reaction formed during the reaction can be distilled off during or after the esterification a), this process being able to be supported by a solvent which forms an azeotrope with water.
  • the amount of solvent used is 10-200% by weight, preferably 20-100% by weight, particularly preferably 30-100% by weight, based on the sum of polyalcohol and carboxylic acid B.
  • the water contained in the reaction mixture is not removed using an azeotroping solvent, it is possible to remove it by stripping with an inert gas, preferably an oxygen-containing gas, particularly preferably with air or lean air, for example as in DE-A 3843 843 described.
  • an inert gas preferably an oxygen-containing gas, particularly preferably with air or lean air, for example as in DE-A 3843 843 described.
  • the reaction temperature of the esterification a) is generally 40-160 ° C., preferably 60-140 ° C. and particularly preferably 80-120 ° C.
  • the temperature can remain constant or rise in the course of the reaction, and is preferably raised in the course of the reaction. In this case the final temperature of the esterification is ⁇ - 30 ° C higher than the initial temperature.
  • the temperature of the esterification can be determined and regulated by varying the solvent concentration in the reaction mixture, as described in DE-A 19941 136 and DE-A 10063 176. If a solvent is used, this can be removed from the reaction mixture via the distillation unit attached to the reactor be distilled off.
  • the distillate can either be removed or, after condensation, fed into a phase separator.
  • the aqueous phase obtained in this way is generally discharged, the organic phase can be fed as reflux into the distillation unit and / or can be passed directly into the reaction zone and / or into a circulation evaporator, as described in DE-A 100 63 17 ⁇ .
  • the organic phase as described in DE-A 19941 136, can be used to control the temperature in the esterification.
  • the esterification a) can be carried out without pressure, but also under overpressure or underpressure, preferably under normal pressure.
  • the reaction time is generally 2 to 20 hours, preferably 4 to 15 and particularly preferably 7 to 12 hours.
  • reaction components are added is not essential according to the invention. All components can be mixed and then heated, or one or more components can not be or only partially and only added after heating.
  • composition of the carboxylic acid B 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 of acetic acid 0.0 ⁇ -3% by weight Propionic acid 0.01 - 1% by weight diacrylic acid 0.01 - ⁇ % by weight water 0.0 ⁇ - ⁇ % by weight carbonyl-containing 0.01 - 0.3% by weight inhibitors 0.01 - 0.1 % By weight maleic acid (anhydride) 0.001-0, ⁇ % by weight
  • the crude (meth) acrylic acid used is generally stabilized with 200-600 ppm phenothiazine or other stabilizers in amounts which enable comparable stabilization.
  • carbonyl-containing includes 0 acetone and lower aldehydes, e.g. Formaldehyde, acetaldehyde, crotonaldehyde, acrolein, 2- and 3-furfural and benzaldehyde, understood.
  • Crude (meth) acrylic acid is understood here to mean the (meth) acrylic acid-containing mixture which, after absorption of the reaction gases of the propane / propene / acrolein or isobutane / isobutene / methacrolein oxidation, is obtained in an absorbent and subsequent removal of the absorbent which is obtained by fractional condensation of the reaction gases.
  • pure (meth) acrylic acid can also be used, for example with the following purity:
  • the pure (meth) acrylic acid used is generally stabilized with 100-300 ppm hydroquinone monomethyl ether or other storage stabilizers in amounts that enable comparable stabilization.
  • Pure or pre-cleaned (meth) acrylic acid is generally understood to mean (meth) acrylic acid, the purity of which is at least 99 . ⁇ % by weight and which is essentially free of the aldehydic, other carbonyl-containing and high-boiling components.
  • carboxylic acid contained therein, for example (meth) acrylic acid with an extractant, preferably the solvent optionally used in the esterification, for example with cyclohexane can advantageously be at a temperature between 10 and 40 ° C. and a ratio of aqueous phase to extractant of 1: ⁇ - 30, preferably 1:10 - 20, extracted and returned to the esterification.
  • an inert gas preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen ⁇ (lean air) can be passed into the circulation, through or over the reaction mixture, 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 a) can be followed by monitoring the amount of water discharged and / or the decrease in the carboxylic acid concentration in the reactor.
  • the reaction can be ended, for example, as soon as 90% of the theoretically expected amount of water has been discharged through the solvent, before adds at least 95% and particularly preferably at least 98%. Of course, it is also possible to terminate the reaction at lower partial sales.
  • the reaction is ended when the acid number in accordance with. DIN EN 3682 of the reaction mixture falls below 80 mg KOH / g reaction mixture, preferably below 60, particularly preferably ⁇ O and very particularly preferably below 40 mg KOH / g.
  • the end of the reaction can be determined, for example, by essentially no further water of reaction being removed via the entrainer. If carboxylic acid B is discharged together with the water of reaction, its proportion can be determined, for example, by back-titrating an aliquot of the aqueous phase.
  • Removal of the reaction water can be dispensed with, for example, if the carboxylic acid B is used in a high stoichiometric excess, for example of at least 1.5: 1, preferably at least 2.5: 1 and very particularly preferably at least 5: 1. In this case, a substantial part of the amount of water generated remains in the reaction mixture.
  • the proportion of water which is determined by the volatility at the temperature applied is removed from the reaction mixture and, in addition, no measures are taken to separate off the water of reaction formed. For example, at least 10% by weight of the water of reaction formed can remain in the reaction mixture, preferably at least 20% by weight, particularly preferably at least 30% by weight, very particularly preferably at least 40 and in particular at least 50% by weight.
  • the reactor mixture can be cooled in a customary manner to a temperature of from 10 to 30 ° C. and, if appropriate, by adding solvent, which can be the same as or different from the solvent which may be used for azeotropic removal of water any target ester concentration can be set.
  • the reaction can be stopped with a suitable diluent G and to a concentration of, for example, 10-90% by weight, preferably 20-80%, particularly preferably 20 to 60%, very particularly preferably 30 to 60% and in particular diluted approx. 40%, for example to reduce the viscosity.
  • the diluent G is selected from the group consisting of water, a mixture of water with one or more water-soluble organic solvents or a mixture of water with one or more simple or multifunctional alcohols, e.g. Methanol and glycerin.
  • the alcohols preferably carry 1, 2 or 3 hydroxyl groups and preferably have between 1 and 10, in particular up to 4, carbon atoms. Primary and secondary alcohols are preferred.
  • Preferred alcohols are methanol, ethanol, isopropanol, ethylene glycol, 1,2-propanediol or 1,3-propanediol.
  • the reaction mixture can be decolorized, for example by treatment with activated carbon or metal oxides, e.g. Aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, boron oxide or mixtures thereof, in amounts of, for example, 0.1 to 60% by weight, preferably 0.6 to 2 ⁇ % by weight, particularly preferably 1-10% by weight % at temperatures of, for example, 10 to 100 ° C., preferably 20 to 80 ° C. and particularly preferably 30 to 60 ° C.
  • activated carbon or metal oxides e.g. Aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, boron oxide or mixtures thereof, in amounts of, for example, 0.1 to 60% by weight, preferably 0.6 to 2 ⁇ % by weight, particularly preferably 1-10% by weight % at temperatures of, for example, 10 to 100 ° C., preferably 20 to 80 ° C. and particularly preferably 30 to 60 ° C.
  • the reaction mixture can be decolorized at any point in the workup process, for example at the stage of the crude reaction mixture or after prewashing, neutralization, washing or solvent removal, if appropriate.
  • the reaction mixture can further be subjected to a pre-wash e) and / or a neutralization f) and / or a post-wash g), preferably only a neutralization f). If necessary, neutralization f) and prewash e) can also be interchanged in the order.
  • Carboxylic acid B for example (meth) acrylic acid and / or catalyst C, can be at least partially removed from the aqueous phase of the washes e) and g) and / or neutralization f) by acidification and extraction with a solvent Acidification and extraction with a solvent are at least partially recovered and used again.
  • the reaction mixture is washed in a washing apparatus with a washing liquid, for example water or a ⁇ - 30% by weight, preferably ⁇ - 20, particularly preferably ⁇ - 16% by weight -igen saline, potassium chloride, ammonium chloride, sodium sulfate or ammonium sulfate solution, preferably water or saline, treated.
  • a washing liquid for example water or a ⁇ - 30% by weight, preferably ⁇ - 20, particularly preferably ⁇ - 16% by weight -igen saline, potassium chloride, ammonium chloride, sodium sulfate or ammonium sulfate solution, preferably water or saline, treated.
  • the quantitative ratio of reaction mixture: washing liquid is generally 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.
  • the washing or neutralization can be carried out, for example, in a stirred tank or in other conventional equipment, e.g. in a column or mixer-settler apparatus.
  • Prewash e) is preferably used when metal salts, particularly preferably copper or copper salts, are also used as inhibitors.
  • Rinsing g) can be advantageous for removing base or salt traces from the reaction mixture neutralized in f).
  • the optionally prewashed reaction mixture which can still contain small amounts of catalyst and the main amount of excess carboxylic acid, for example (meth) acrylic acid, can have a ⁇ - 26, preferably 5 - 20, particularly preferably ⁇ - 16 wt.
  • % aqueous solution of a base such as alkali or alkaline earth metal oxides, hydroxides, carbonates or hydrogen carbonates, preferably sodium hydroxide solution, potassium hydroxide solution, sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, calcium hydroxide, lime milk, ammonia, ammonia water or potassium carbonate, which, if appropriate ⁇ - 15 wt .-% sodium chloride, potassium chloride, ammonium chloride or ammonium sulfate can be added, especially preferably be neutralized with sodium hydroxide solution or sodium hydroxide solution.
  • a base such as alkali or alkaline earth metal oxides, hydroxides, carbonates or hydrogen carbonates, preferably sodium hydroxide solution, potassium hydroxide solution, sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, calcium hydroxide, lime milk, ammonia, ammonia water or potassium carbonate, which, if appropriate ⁇ - 15 wt .-% sodium chloride, potassium chloride, ammonium
  • the degree of neutralization is preferably 5 to 60 mol%, preferably 10 to 40 mol%, particularly preferably 20 to 30 mol%, based on the monomers containing acid groups. This neutralization can take place before and / or during the polymerization ⁇ , preferably before the polymerization.
  • the base is added in such a way that the temperature in the apparatus does not rise above 60 ° C., preferably between 20 and 35 ° C., and the pH is 4-13.
  • the heat of neutralization is preferably dissipated by cooling the container with the aid of internal cooling coils or via double-wall cooling.
  • the quantitative ratio of reaction mixture: neutralizing liquid is generally 1: 0.1-1, preferably 1: 0.2-0.8, particularly preferably 1: 0.3-0.7.5.
  • the statements made above apply to the apparatus. h) If a solvent is present in the reaction mixture, it can be essentially removed by distillation. Preferably, solvent which is present is removed from the reaction mixture after washing and / or neutralization, but if desired, this can also be done before washing or neutralization.
  • the reaction mixture is mixed with such an amount of storage stabilizer, preferably ⁇ ⁇ hydroquinone monomethyl ether, that 100-600, preferably 200-600 and particularly preferably 200-400 ppm thereof are present in the target ester (residue) after removal of the solvent.
  • storage stabilizer preferably ⁇ ⁇ hydroquinone monomethyl ether
  • the main amount of solvent is removed by distillation, 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 ⁇ OO and particularly preferably 50-160 mbar and a temperature of 40-80 ° C ,
  • the distillation can also be carried out in a falling film or thin film evaporator.
  • the reaction mixture is passed through the apparatus, preferably several times in a circuit, under reduced pressure, for example at 20-700 mbar, preferably 30-600 and particularly preferably 60-160 mbar and at a temperature of 40-80 ° C.
  • An inert gas preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen (lean air) can advantageously be used in 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 after the distillation is generally less than 5% by weight, preferably 0.6- ⁇ % and particularly preferably 1 to 3% by weight.
  • the separated solvent is condensed and preferably reused.
  • solvent stripping i) can be carried out in addition to or instead of distillation h).
  • the target ester which still contains small amounts of solvent, is heated to 60-90 ° C., preferably 80-90 ° C., and the remaining amounts of solvent are removed with a suitable gas in a suitable device.
  • a vacuum can also be applied to assist.
  • Suitable apparatuses are, for example, columns of a type known per se, which have the usual internals, e.g. Bottoms, fillings or directional packs, preferably fillings.
  • all common internals come into consideration as column internals, for example trays, packings and / or packing elements.
  • bell bottoms, sieve bottoms, valve bottoms, Thormann bottoms and / or dual-flow bottoms are preferred, of the fillings 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 wiping film evaporator such as e.g. a Luwa, Rotafilm or Sambay evaporator, which can be equipped, for example, with a demister as a splash guard.
  • gases which are inert under the stripping conditions, preferably oxygen-containing gases, particularly preferably air or mixtures of air and nitrogen (lean air) or water vapor, in particular those which are heated to 60 to 100.degree.
  • the amount of stripping gas is, for example, ⁇ - 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.
  • the ester can be subjected to filtration j) at any stage of the work-up process, preferably after washing / neutralization and, if appropriate, solvent removal, in order to remove traces of salts and any decolorizing agent present.
  • the esterification a) of the polyalcohol A with the carboxylic acid B is carried out in a molar excess of at least 2.5: 1 as mentioned above in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D without a water-forming azeotrope. carried out.
  • the carboxylic acid B used in excess is essentially not removed in a preferred embodiment, i.e. only the proportion of carboxylic acid B is removed from the reaction mixture, which is determined by the volatility at the temperature applied, and furthermore no measures are taken to separate the carboxylic acid, such as, for example, distillative, rectificative, extractive, e.g. Washes, absorptive, e.g. Transfer over activated carbon or over ion exchanger, and / or chemical steps, e.g. Trapping the carboxylic acid with epoxides.
  • the carboxylic acid B contained in the reaction mixture is not more than 75% by weight, preferably not more than 50% by weight, particularly preferably not more than 25% by weight, very particularly preferably not more than 10% by weight and in particular not more than 5% by weight separated from the reaction mixture, based on the carboxylic acid B present in the reaction mixture after the end of the reaction.
  • step b) can be dispensed with, so that only the proportion of water of reaction and carboxylic acid B which is determined by the volatility at the temperature applied is removed from the reaction mixture. This can preferably be prevented by essentially complete condensation.
  • esterification catalyst C used essentially remains in the reaction mixture.
  • the reaction mixture thus obtained then preferably has an acid number in accordance with. DIN EN 3682 of at least 25 mg KOH / g reaction mixture, particularly preferably from 25 to 80 and very particularly preferably from 25 to 50 mg KOH / g.
  • Prewashing or afterwashing e) or g) is preferably dispensed with in this case; only one filtration step j) can be useful.
  • the reaction mixture can then be diluted in step c), in which case it is preferably converted to the hydrogel within 6 hours, particularly preferably within 3 hours. It can preferably be neutralized in step f).
  • the sequence of steps c), j) and f) is arbitrary.
  • reaction mixtures from the preparation of a (meth) acrylic acid ester of a polyalcohol and in particular the purified (meth) acrylic acid esters which contain at least one 6-chromanol derivative of the formula (III) can be used, for example
  • a coating raw material for example in radiation curing and particularly preferably as a radical crosslinker of water-absorbing hydrogels.
  • 6-chromanol derivatives of the formula (III) are non-toxic and are therefore particularly suitable for use in water-absorbing hydrogels.
  • esterification products thus obtainable can be used as radical crosslinkers in hydrogels essentially without further purification, in particular without substantial removal of the excess of carboxylic acid B and the content of esterification catalyst C.
  • crosslinking means radical crosslinking (gel crosslinking, internal crosslinking, crosslinking of linear or weakly crosslinked polymer). This crosslinking can take place via free-radical or cationic polymerization mechanisms or other, for example Michael addition, esterification or transesterification mechanisms, preferably by free-radical polymerization.
  • Aqueous liquid-absorbing hydrogel-forming polymers are preferably those with an absorption of distilled water of at least their own weight, preferably 10 times their own weight; this absorption is preferably also achieved under a pressure of 0.7 psi.
  • Reaction mixtures which have a water solubility (at 25 ° C. in distilled water) of at least 5% by weight, preferably at least, are particularly suitable for use as radical crosslinkers of water-absorbing hydrogels 10% by weight, particularly preferably at least 20% by weight, very particularly preferably at least 30% by weight and in particular at least 50% by weight.
  • the present invention further provides a method for producing a crosslinked hydrogel, comprising the steps
  • reaction mixture from the esterification including its work-up steps, as far as they are carried out, for example the reaction mixture from f), or, if f) is dispensed with, from b), or, if b) is dispensed with, the reaction mixture from a ), can optionally be mixed with additional monoethylenically unsaturated compounds N which are not acidic carry groups, but are copolymerizable with the hydrophilic monomers M, can then be polymerized in the presence of at least one radical initiator K and optionally at least one graft base L to prepare water-absorbing hydrogels.
  • Hydrophilic monomers M suitable for producing k) these hydrophilic, highly swellable hydrogels are, for example, polymerizable acids, such as acrylic acid, methacrylic acid, ethacrylic acid, ⁇ -chloroacrylic acid, crotonic acid, maleic acid, maleic anhydride, vinylsulfonic acid, vinylphosphonic acid, maleic acid including its anhydride, fumaric acid, itaconic acid, citraconic acid, Mesaconic acid, glutaconic acid, aeonitic acid, allylsulfonic acid, sulfoethylacrylate, sulfomethaerylate, sulfopropylacrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropylsulfonic acid, 2-hydroxy-3-meth-acryloxypropylsulfonic acid, allylphosphonic acid, 2-acrylpropylsulfonic acid, 2-styrenesulfonsul
  • R 20 is hydrogen, methyl or ethyl
  • R 21 is the group -COOR 24 , a sulfonyl group or phosphonyl group, a phosphonyl group esterified with a (dd) alkyl alcohol or a group of the formula (IX)
  • R 23 is hydrogen, methyl, ethyl or a carboxyl group
  • R 24 is hydrogen, dd-alkyl or hydroxy- (C r C) -alkyl
  • R 25 represents a sulfonyl group, a phosphonyl group or a carboxyl group.
  • Examples of (CC 4 ) alkyl alcohol are methanol, ethanol, n-propanol or n-butanol.
  • Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid.
  • additional monoethylenically unsaturated compounds N which do not carry acid groups but which can be copolymerized with the monomers bearing acid groups.
  • These include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acid, e.g. B. acrylamide, methacrylamide and N-vinylformamide, N-vinyl acetamide, N-methyl-vinyl acetamide, acrylonitrile and methacrylonitrile.
  • Suitable compounds are, for example, vinyl esters of saturated d- to C -carboxylic acids such as vinyl formate, vinyl delta or vinyl propionate, alkyl vinyl ethers having at least 2 carbon atoms in the alkyl group, such as, for example, B. ethyl vinyl ether or butyl vinyl ether, esters of monoethylenically unsaturated C 3 - to C 6 -carboxylic acids, for. B. esters of monohydric d to C 18 alcohols and acrylic acid, methacrylic acid or maleic acid, half esters of maleic acid, for. B.
  • vinyl esters of saturated d- to C -carboxylic acids such as vinyl formate, vinyl delta or vinyl propionate
  • alkyl vinyl ethers having at least 2 carbon atoms in the alkyl group such as, for example, B. ethyl vinyl ether or butyl vinyl ether, esters of monoethylenically unsaturated C 3 - to C
  • N-vinyl lactams such as N-vinyl pyrrolidone or N-Vi-0 nylcaprolactam
  • acrylic acid and methacrylic acid esters of alkoxylated monohydric, saturated alcohols e.g. B. of alcohols with 10 to 2 ⁇ C atoms which have been reacted with 2 to 200 moles of ethylene oxide and / or propylene oxide per mole of alcohol
  • monoacrylic acid esters and monomethacrylic acid esters of polyethylene glycol or polypropylene glycol, the molar masses (M n ) the polyalkylene glycols can be, for example, up to 5,000.
  • Other suitable monomers are styrene and alkyl-substituted styrenes such as ethylstyrene or tert-butylstyrene.
  • These monomers not carrying acid groups can also be used in a mixture with other monomers, e.g. B. Mixtures of vinyl acetate and 2-hydroxy-0 ethyl acrylate in any ratio. These monomers which do not contain acid groups are added to the reaction mixture in amounts of between 0 and 50% by weight, preferably less than 20% by weight.
  • the crosslinked (co) polymers preferably consist of mo-6 noethylenically unsaturated monomers bearing acid groups, which are optionally converted into their alkali metal or ammonium salts before or after the polymerization, and from 0 to 40% by weight, based on their total weight, no monoethylenically bearing acid groups unsaturated monomers.
  • (meth) acrylic acid-containing (co) polymers, polyacrylic acids and superabsorbers has been described many times and is therefore well known, see for example "Modern Superabsorbent Polymer Technology ", FL Buchholz and AT Graham, Wiley-VCH, 1998.
  • Preferred hydrogels are those obtained by crosslinking polymerization or copolymerization of acid-bearing monoethylenically unsaturated monomers M or their salts.
  • the starting polymer is treated with a postcrosslinker and preferably postcrosslinked and dried during or after the treatment by increasing the temperature, the crosslinker preferably being contained in an inert solvent.
  • Inert solvents are understood to mean those which in the reaction do not essentially react either with the starting polymer or with the postcrosslinker.
  • Preferred solvents are those which do not react chemically with the starting polymer or postcrosslinker to more than 90%, preferably more than 9 ⁇ %, particularly preferably more than 99%, in particular more than 99.5%.
  • Preferred for post-crosslinking I) and drying m) is the temperature range between 30 and 250 ° C., in particular 50-200 ° C., and the range between 100-180 ° C. is very particularly preferred.
  • the surface postcrosslinking solution is preferably applied by spraying onto the polymer in suitable spray mixers. Following the spraying, the polymer powder is thermally dried, and the crosslinking reaction can take place both before and during the drying. It is preferred to spray on a solution of the crosslinker in reaction mixers or mixing and drying systems such as, for example, Lödige mixers, BE-PEX mixers, NAUTA mixers, SHUGGI mixers or PROCESSALL. Fluid bed dryers can also be used.
  • Drying can take place in the mixer itself, by heating the jacket or by blowing in warm air.
  • a downstream dryer such as e.g. a rack dryer, a rotary kiln, or a heated screw. But it can also e.g. an azeotropic distillation can be used as the drying process.
  • the preferred residence time at this temperature in the reaction mixer or dryer is less than 60 minutes, particularly preferably less than 30 minutes.
  • the starting polymer being a polymeric acrylic acid or a polyacrylate, in particular a polymeric acrylic acid or a polyacrylate, which were obtained via free-radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinking agent was used.
  • Preferred methods are those in which the radical crosslinker is used in a dosage of 0.01-5.0% by weight, preferably 0.02-3.0% by weight, very particularly preferably 0.03-2.5% by weight. %, in particular 0.05-1.0 and especially 0.1 to 0.75% by weight, based on the starting polymer.
  • the invention also relates to polymers produced by one of the abovementioned processes and their use in hygiene articles, packaging materials and in nonwovens, and to the use of an abovementioned mixture of substances for the production of crosslinked or heat-crosslinkable polymers, in particular in paints and varnishes.
  • hydrophilic, highly swellable hydrogels (starting polymers) to be used are, in particular, polymers of (co) polymerized hydrophilic monomers M, graft (co) polymers of one or more hydrophilic monomers M on a suitable graft base L, crosslinked cellulose or starch ethers or in aqueous Liquid-swellable natural products, such as guar derivatives.
  • hydrogels are known to the person skilled in the art and are described, for example, in US-4286082, DE-C-27 06 135, US-4340706, DE-C-37 13601, DE-C-2840 010, DE-A-4344548, DE-A40 20780 , DE-A-40 15085, DE-A-39 17 846, DE-A-38 07289, DE-A-3533337, DE-A-3503458, DE-A-4244548, DE-A-42 19607, DE- A-4021 847, DE-A-3831 261, DE-A-36 11 086, DE-A-31 18 172, DE-A-3028043, DE-A-44 18 881, EP-A-0 801 483, EP-A-045 ⁇ 985, EP-A-0467 073, EP-A-0312952, EP-A-0205874, EP-A-0499774, DE-A 26 12 846, DE-A-4020780 EP-A-0205674, US-5 145906
  • Suitable graft bases L for hydrophilic hydrogels which can be obtained by graft copolymerization of olefinically unsaturated acids, can be of natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and other polysaccharides and oligosaccharides, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, and hydrophilic polyesters.
  • the water-absorbing polymer can be obtained via radical graft polymerization of acrylic acid or acrylate onto a water-soluble polymer matrix.
  • Suitable water-soluble polymer matrices are, for example, but not exclusively lent, alginates, polyvinyl alcohol, and polysaccharides such as starch. In this sense, a polyfunctional ethylenically unsaturated radical crosslinker is used in the graft copolymerization.
  • the water-absorbing polymer can be an organic-inorganic hybrid polymer composed of a polymeric acrylic acid or a polyacrylate on the one hand and a silicate, aluminate or aluminosilicate on the other hand.
  • polymeric acrylic acid or polyacrylate can be used, which were obtained via radical polymerization, and in which a multifunctional ethylenically unsaturated radical crosslinking agent was used and in the production process of which a water-soluble silicate or soluble aluminate or mixtures of the two was used.
  • Preferred hydrogels are in particular polyacrylates, poly methacrylates and the graft polymers described in US Pat. No. 4,931,497, US Pat. No. 011,892 and US Pat. No. 5,041,496.
  • Very particularly preferred hydrogels are the kneading polymers described in WO 01/38402 and the hybrid organic-inorganic hydrogels based on polyacrylates described in DE 198 64576.
  • radical crosslinkers in hydrogels can be used alone or in combination with other crosslinkers, for example internal or surface crosslinkers, for example the following:
  • Suitable crosslinkers are, in particular, methylenebisacryl or methacrylamide, esters of unsaturated mono- or polycarboxylic acids of polyols, such as diacrylate or triacry-delta, e.g. As butanediol or ethylene glycol acrylate or methacrylate and trimethylolpropane triacrylate and allyl compounds such as allyl (meth) acrylate, triallyl cyanurate, maleic klarediallylester, polyallyl esters, tetraallyloxyethane, triallylamine, Tetraallylethylendia- min, allyl esters of phosphoric acid and also vinylphosphonic acid derivatives as described for example in EP -A-0 343427.
  • hydrogels which are prepared using polyallyl ethers as crosslinking agents and by acidic homopolymerization of acrylic acid are particularly preferred in the process according to the invention.
  • Suitable crosslinkers are pentaerythritol tri- and tetraallyl ether, polyethylene glycol diallyl ether, monoethylene glycol diallyl ether, glycerol di and triallyl ether, polyallyl ether based on sorbitol, and ethoxylated variants thereof.
  • crosslinkers are the polyethylene glycol diacrylates, ethoxylated derivatives of trimethylolpropane triacrylate, for example Sartomer SR 9036, and ethoxylated derivatives of glycerol diacrylate and glycerol triacrylate. Mixtures of the above crosslinking agents can of course also be used. Hydrogels which are prepared with an ester F prepared according to the invention as a radical crosslinker are very particularly preferred.
  • the water-absorbing polymer is preferably a polymeric acrylic acid or a polyacrylate. This water-absorbing polymer can be prepared by a process known from the literature.
  • Polymers which contain crosslinking comonomers are preferred (0.001-10 mol%), but very particularly preferred ⁇ are polymers which have been obtained by radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinker has been used.
  • the hydrophilic, highly swellable hydrogels can be prepared by known polymerisation processes. Polymerization in aqueous solution by the so-called gel polymerization method is preferred. As mentioned above, dilute, preferably aqueous, particularly preferably 16 to 50% by weight aqueous solutions of one or more hydrophilic monomers and, if appropriate, a suitable graft base L in the presence of a radical initiator are preferably 5 without mechanical mixing using the Trommsdorff-Norrish effect ( Makromol. Chem. 1, 169 (1947)), polymerized. The polymerization reaction can be carried out in the temperature range between 0 ° C. and 150 ° C., preferably between 10 ° C.
  • the polymerization can also be carried out in a protective gas atmosphere, preferably under nitrogen.
  • a protective gas atmosphere preferably under nitrogen.
  • K can be used, e.g. B. organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, azo compounds such as azodiisobutyronitrile and inorganic peroxy- ⁇ compounds such as (NH 4 ) 2 S 2 O 8 , K 2 S 2 O 8 or H 2 O 2 ,
  • the quality properties of the polymers can be improved further by heating the polymer gels for several hours in the temperature range from 50 ° to 130 ° C., preferably from 70 ° to 100 ° C.
  • the gels obtained are 0-100 mol%, preferably 25-100 mol -%, and particularly preferably to 50-85 mol%, based on the monomer used, it being possible to use the customary neutralizing agents, preferably alkali metal hydroxides, alkali metal oxides or the corresponding alkali metal carbonates, but particularly preferably sodium hydroxide, sodium carbonate and sodium hydrogen carbonate ,
  • the neutralization is usually achieved by mixing in the neutralizing agent as an aqueous solution or preferably also as a solid.
  • the gel is mechanically comminuted, for example using a meat grinder, and the neutralizing agent is sprayed on, sprinkled on or poured on, and then mixed thoroughly.
  • the gel mass obtained can be minced several times for homogenization.
  • the neutralized gel mass is then until the residual moisture content of below 10 wt .-%, is a belt or drum dryer dried preferably under particular ⁇ wt .-%.
  • the polymerization itself can also be carried out by any of the other methods described in the literature.
  • the neutralization of the acrylic acid can also be carried out before the polymerization, as described in step f) above.
  • the polymerization can then be carried out continuously or batchwise in a belt reactor known to the person skilled in the art or in a kneading reactor.
  • initiation by means of electromagnetic radiation preferably by means of UV radiation, or alternatively initiation using a redox initiator system is particularly preferred.
  • the combination of both initiation methods is also very particularly preferred: electromagnetic radiation and chemical redox initiator system simultaneously.
  • the dried hydrogel can then be ground and sieved, roller mills, pin mills or vibrating mills usually being used for grinding.
  • the preferred particle size of the sieved hydrogel is preferably in the range 45-1000 ⁇ m, preferably 45-850 ⁇ m, particularly preferably 200-850 ⁇ m, and very particularly preferably 300-850 ⁇ m. These areas preferably contain 80% by weight of the particles, in particular 90% by weight of the particles.
  • the size distribution can be determined using established laser methods.
  • chromanols can be used for stabilization in processes for the production of (meth) acrylic esters of monoalcohols in an esterification.
  • Preferred monoalcohols are monoalcohols with 1 to 8 carbon atoms, preferably those with 1 to 4 and particularly preferably those with 1 to 2 carbon atoms.
  • Particularly preferred monoalcohols are methanol, ethanol, n-propanol, / so-propanol, n-butanol, / s ⁇ -butanol and 2-ethylhexanol, very particularly preferably methanol, ethanol and n-butanol, the correspondingly low (meth) acrylic acid esters to lead. Examples of high-boiling monoalcohols are included.
  • R 26 is d to C 22 alkyl and 0x is an integer between 1 and 20, 5 act.
  • R 26 are methyl, ethyl, / ' so-propyl, n-propyl, allyl, n-butyl, / so-butyl, sefc-butyl, ferf-butyl, n-hexyl, n-heptyl, n-octyl, n-Decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl or n-eicosyl.
  • Such (meth) acrylic acid esters of monoalcohols are often produced continuously.
  • ppm and percentages used in this document relate to percentages by weight and ppm.
  • the following examples are intended to illustrate the invention but not to restrict it to these examples.
  • the polymer deposits on the vessel were determined and the color number was measured in accordance with HAZEN (DIN ISO 6271).

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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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Abstract

L'invention concerne un procédé de production d'esters de l'acide (méth)acrylique, dans lequel on utilise des dérivés de chromanol comme stabilisants contre la polymérisation. L'invention concerne en outre l'utilisation des esters d'acide (méth)acrylique ainsi obtenus.
EP05707413A 2004-02-20 2005-02-16 Procede pour la preparation d' esters (meth)acryliques Withdrawn EP1727780A1 (fr)

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PCT/EP2005/001533 WO2005082828A1 (fr) 2004-02-20 2005-02-16 Procede de production d'esters de l'acide (meth)acrylique

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US8268131B2 (en) * 2009-03-24 2012-09-18 Amt International, Inc. Apparatus and method for recovery of acetic acid from an aqueous solution thereof
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SG11201900007VA (en) 2016-08-05 2019-02-27 Basf Se Macromonomers containing polyisobutene groups, and homopolymers or copolymers thereof

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JPS6072980A (ja) * 1983-09-29 1985-04-25 Sumitomo Chem Co Ltd クロマン誘導体よりなる有機物質の安定化剤
DE3423443A1 (de) * 1984-06-26 1986-01-02 Röhm GmbH, 6100 Darmstadt Verfahren zur herstellung von estern der acryl- und methacrylsaeure durch umesterung
DE3843930A1 (de) * 1988-12-24 1990-06-28 Henkel Kgaa Verfahren zur verbesserten herstellung von (meth)acrylsaeureestern mehrwertiger alkohole (iii)
DE10225943A1 (de) * 2002-06-11 2004-01-08 Basf Ag Verfahren zur Herstellung von Estern von Polyalkoholen

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