DE2731085B2 - Process for the production of acrylic and / or methacrylic acid esters - Google Patents

Description

The invention relates to a process for the preparation of acrylic and / or methacrylic acid esters, in which Acrylic acid and / or methacrylic acid with a hydroxy compound that has at least one primary hydroxyl group having, in the presence of an acidic esterification catalyst of a polymerization inhibitor and a water-immiscible organic solvent, optionally with the introduction of a Oxygen-containing gas is reacted in the reaction mixture.

Procedures of the type indicated above have been around since known for a long time. However, the problem arises that the acidic esterification catalyst not only Esterification reaction but also the formation of ethers from the starting alcohol or an ester the same accelerated with acrylic acid and / or methacrylic acid, this ester still having at least one Contains hydroxyl group. The etherification reaction wins especially towards the end of the esterification reaction in importance, d. H. if the remaining amount of acrylic acid and / or methacrylic acid, the is often added in excess, is removed.

The acrylic acid and / or methacrylic acid (hereinafter referred to as (meth) acrylic acid) is removed usually by distillation at a temperature generally in the range of 70 to 160 °, preferably from 85 to 140 ° C, usually the distillation is under reduced pressure performed, e.g. B. with the help of a thin film evaporator. Those under the above conditions taking place etherification reaction brings with it that by-products are formed, which difficult from End product are to be isolated, moreover the composition of the product is not constant.

Attempts have been made to solve the above-mentioned problem by adding (Ca (OH) 2) and a small amount of an ionizing liquid, e.g. water, to the methacrylic acid esters, and removing the insoluble calcium salt formed by nitration (See US-PS 37 17 672). In this process, however, often greasy and difficult to filter precipitates form.
The object of the invention is now to provide a method for

ι »to make available that no longer has the disadvantages mentioned above and that leads to a low-viscosity product that has a low acid number! and has a light color. The invention is further based on the object of making possible a process in which generally no filtration stage is required, so that the process operates with a higher yield and is more environmentally friendly and technically easier to carry out.
The object is achieved by a method with the features according to claim 1

Further developments result from claims 2 and 3.
The esterification reaction is carried out using methacrylic acid and / or acrylic acid. Acrylic acid is preferably used.

j Suitable hydroxy compounds are z. B. polyether, Alkyd resins and saturated or unsaturated polyesters and preferably alcohols having 1 to 24 carbon atoms. Examples of suitable alcohols are aliphatic, araliphatic or cycloaliphatic

in mono- or polyalcohols such as methanol, ethanol, Propanol, n-butanol, isobutanol, hexanol, 2-ethylhexanol, Decanol, stearyl alcohol, allyl alcohol, 2-bromoallyl alcohol, Benzyl alcohol, cyclohexanol, ethylene glycol, neopentyl glycol, 1,4-dimethylolcyclohexane, hexanediol,

i-> 2-ethyl-2-n-butyl-propane-l, 3-diol, glycerine, trimethylolethane, Trimethylolpropane, pentaerythritol and compounds such as diethylene glycol, trimethylene glycol, triethylene glycol, Polyethylene glycol and Ι, Ι'-isopropylidene-bis (p-phenyleneoxy) -di-2-ethanol. Mixtures of the compounds listed above can also be used.

The reaction components can be used in equimolar proportions, but can also other ratios can be chosen. if

4ί (meth) acrylic acid and an excess of a polyvalent one Hydroxy compound is used, a hydroxy ester is formed. Generally an excess effects a hydroxy compound or an acid, of course, that the esterification equilibrium to the ester side

"is moved in.

If desired, the hydroxy compound and / or the carboxylic acid can also be used as an aqueous solution Use. In general, however, there is no advantage to this. The required amounts of carbon

Vi acid and hydroxy compound can be in the reaction vessel presented or added all at once or in partial amounts during the reaction mentioned. The esterification reaction is carried out in the presence of a water-immiscible organic solvent

Wi means carried out, which usually has a boiling point between -10 and +200 ⁰ C, preferably between + 50 and + 150 ° C. Suitable solvents are aliphatic or cycloaliphatic hydrocarbons, e.g. B. pentane, hexane, heptane and mineral spirits, one

hi hydrocarbon mixture, aromatic hydrocarbons, z. B. benzene, chlorobenzene, toluene or xylene. Also mixtures of the abovementioned compounds can be used, preferably heptane,

White spirit (boiling point 80-10O ⁰ C) or toluene is used. The organic solvent is usually used in amounts of 1 to 50% by weight, preferably 2-25% by weight, based on the weight of the reaction components to be esterified Quantities used, however, generally offer no particular advantage

Any suitable or customary acidic esterification catalyst can be used as acidic esterification catalysts be used. Examples of suitable catalysts include: mentioned: inorganic acids like z. B. hydrochloric acid, sulfuric acid and phosphoric acid; Sulphonic acids such as methanesulphonic acid, paratoluenesulphonic acid and benzenesulfonic acid. Can if desired a sulfonic acid cation exchanger can also be used. The catalyst is generally used in Amounts from 0.001 to 0.1 equivalents for each equivalent of the hydroxyl groups to be esterified used

Moreover, it is usually taken to ensure that the esterification mixture containing a compound which are the polymerization of the (methacrylic acid or a (meth) acrylsäurehydroxyesters counteracts. This compound is hereinafter referred to as inhibitor referred Suitable inhibitors generally r \ quinones, hydroquinones or their alkyl ethers , for example o-benzoquinone, p-benzoquinone, naphthoquinone, hydroquinone, 2,5-di-tert-butylhydroquinone, p-tert-butylcatechol, toluene hydroquinone and the monomethyl ether of hydroquinone or compounds «1 such as phenothiazine and copper, mixtures or Complexes of the abovementioned compounds can also be used, and a compound of the general formula is preferably used as the inhibitor

K | C> OR ₂

where Ri and R2 can be identical or different and denote a hydrogen atom or an alkyl group having 1 to 4 carbon atoms and the groups -ORi and -OR2 are in the ortho or para position to one another and X and Y, identical or different, are 4 ^r > and hydrogen , Mean chlorine, bromine or an alkyl group having 1 to 4 carbon atoms. In particular, hydroquinone The inhibitor is generally employed in amounts of from 10 ppm to 3%, preferably ppm in amounts from 200 to 5000, ^r> o calculated to be esterified reaction components. If appropriate, an oxygen-containing gas can also be introduced into the reaction mixture in the process according to the invention. Examples of suitable gases are air, which is preferably used, oxygen, air / carbon dioxide or air / nitrogen mixtures. In general, oxygen (expressed as pure oxygen) is introduced into the reaction mixture in an amount of from 0.5 to 100 standard l per hour, preferably from 5 to 25 standard l per hour per 100 l of reaction mixture. Oxygen quantities in excess of 100 liters per hour per 100 liters of reaction mixture can also be introduced, but are not always desirable.

The esterification reaction is usually carried out at temperatures between 0 and 200 ⁰ C, preferably between 50 and 150 μ ⁰ C. The reaction time is usually between 1 and 25 hours, preferably 4 to 15 hours. The pressure during the

Reaction is not critical. In general, under atmospheric or sub-atmospheric pressure, but higher pressures can also be used can be set. The reaction can be carried out continuously, be carried out semi-continuously or, if desired, in a batchwise manner. That The reaction mixture can optionally contain suitable additives such as. B. Contains aids for filtration.

The process according to the invention is carried out in such a way that, at the end of the esterification reaction, a lithium compound is added to the esterification mixture in order to inactivate the acidic esterification catalyst. Although 80 to 300% of the stoichiometric amount of lithium compound is generally added, 110-200%, especially 115 to 125% of the stoichiometric amount is preferably used. If less than 80% of the stoichiometric amount is used, the advantages of the invention will generally be used not achieved to the desired extent. The use of amounts greater than that specified above generally does not bring any additional advantages.

Examples of suitable lithium compounds are: lithium oxide and / or lithium hydroxide; Lithium halides such as lithium chloride, lithium bromide and lithium iodide; Lithium salts of acids which have a pK value higher than that of the esterification catalyst, e.g. B. lithium metasilicate, lithium metaborate, lithium tetraborate, lithium pentaborate, lithium orthosilicate, lithium sulphide, lithium hydrogen sulphide, lithium nitrite, lithium carbonate, lithium bicarbonate, lithium formate, lithium acetate, lithium benzoate, lithium lactate, lithium citrate, lithium laurate, lithium tartrate, lithium acetate and lithium acetate contain. Mixtures of the lithium compounds can also be used. Lithium hydroxide, lithium chloride, lithium carbonate and / or lithium acetate are preferably used. At the same time as or after the addition of the lithium compound or lithium compounds, the remaining excess of (meth) acrylic acid is removed by distillation, which is preferably carried out under reduced pressure. The vacuum distillation is generally carried out at a temperature from 70 to 160 ⁰ C and under an absolute pressure of 0.1 to 100 mm Hg. The (meth) acrylic acid which is obtained in this manner can completely be recycled to the esterification reaction. The removal of the (meth) acrylic acid is generally continued until the acid number of the (meth) acrylic acid ester produced is between 3 and 25, preferably between 6 and 10. It goes without saying that the removal of the excess of (meth) acrylic acid requires separation the more volatile constituents of the esterification mixture such. B. precedes the water-immiscible organic solvent.

Optionally, residues of (meth) acrylic acid can still be found on any after the distillation remove other way, e.g. B. by washing with an aqueous alkaline solution z. B. by adding of solid calcium oxide. In the latter case a precipitate forms, which can be very easily obtained by filtration of the (meth) acrylic acid ester can be removed. Any remaining insoluble lithium salt becomes also separated. The unsaturated esters obtained, those with other olefinically unsaturated compounds Can be mixed, can be for everyone

possible areas of application, e.g. B. for Binder for printing inks produced by irradiation hardened, for coating compounds. Glues and Rubber and in the paper and textile industry. The esters can e.g. B. by using usual radicals initiators are networked such as B. peroxides or under the influence of heat or ionizing radiation such as B. UV rays and accelerated electrons.

The invention is explained in more detail by the following examples:

Examples 1-38

In a reaction vessel equipped with a stirrer, one Distillation column and a gas inlet tube are provided according to the information in the table 10 mol of the carboxylic acid, the hydroxy compound in the specified amount, 0.04 mol of paratoluene sulfonic acid,

150 ml of mineral spirits (boiling point 80 to 100 * C) and 0.2% by weight of hydroquinone (based on the added amounts of carboxylic acid and hydroxy compound) are mixed together. The reaction mixture is then heated to its boiling point, where it is held for about 5 to 15 hours. The water formed during the reaction is removed azeotropically. 50 Nl of air per hour per 100 liters of reaction mixture are continuously introduced into the mixture during the reaction. After the desired degree of conversion has been achieved, a corresponding lithium compound of the type and in the amount mentioned in the table is added to the esterification mixture. The (meth) acrylic acid is then ^{distilled off at a temperature of 130 °} C. and an absolute pressure of 100 mm Hg. The end product that remains after the distillation has an acid number in the range from 5 to 10.

Tabel

example Hydroxy compound lot
(Mole) Carboxylic acid mainly
ester formed Lithium compound Lot
IgI link 4.6 Acrylic acid Diacrylate link 0.72 1 Hexanediol (1.6) 4.2 dito Diacrylate Lithium oxide 1.78 2 Trimethylol propane 2.8 dito Triacrylal Lithium carbonate 3.17 3 dito 3.0 Methacrylic acid Trimethacrylate Lithium acetate 1.15 4th dito 2.8 Acrylic acid Triacrylate Lithium hydroxide 2.02 5 Pentaerythritol 2.1 dito Tetraacrylate Lithium chloride 4.18 6th dito 3.0 Methacrylic acid Trimethacrylate Lithium bromide 6.43 7th dito 4.6 Acrylic acid Diacrylate Lithium iodide 6.14 8th Monoethylene glycol 4.3 dito Diacrylate Lithium benzoate 4.61 9 Diethylene glycol 4.3 dito Diacrylate Lithium acetate 4.51 10 Ι, Γ-isopropylidene
bis- (p-phenyleneoxy) -
di-2-ethanol 4.5 Methacrylic acid Dimethacrylate Lithium citrate 1.78 11th dito 4.1 Acrylic acid Diacrylate Lithium carbonate 1.15 12th Glycerin 9.1 dito Monoacrylate Lithium hydroxide 6.14 13th Cyclohexanol 4.6 dito Diacrylate Lithium benzoate 3.17 14th 2-ethyl-2-n-butyl-
prop? .ndiol- (l, 3) 4.3 Methacrylic acid Dimethacrylate Lithium acetate 4.51 15th Meopentyl glycol 5.0 dito dito Lithium citrate 3.26 16 Polyethylene glycol (200) 4.8 Acrylic acid Diacrylate Lithium-
bicarbonate 2.50 17th dito 5.3 dito Monoacrylate Lithium formate 9.00 18th Alkyd I. 5.5 Methacrylic acid Mono metha-
crylate lithium
metaborate 8 H; O 2.16 19th Alkyd I. 5.5 Methacrylic acid Mono-methacrylate Lithium meta
silicate 2.88 20th Alkyd II 5.3 Acrylic acid Monoacrylate Lithium chloride
monohydrate 3.74 21 Alkyd III 5.3 dito dito Lithium acrylate 9.89 22nd Alkyd IV 5.3 dito dito Lithium laurate 4.32 23 Alkyd V 2.8 Acrylic acid Triacrylate Lilhium tartrate 2.40 24 Pentaerythritol 2.1 dito Tetraacrylate Lithium meta
bo rat 12.53 25th dito Lithium penta-

continuation

Example llydroxy compound link

Amount (mole) of carboxylic acid

mainly
ester formed

Lilhium compound
Compound crowd

Hexanediol- (1.6) 4.6

Trimethylol propane 4.2

Monoethylene glycol 4.6

Diethylene glycol 4.3

Ι, Γ-isopropylidene-4,3

bis- (p-phenyleneoxy) -

di-2-ethanol)

ditto 4.5

Glycerin 4.1

Cyclohexanol 9.1

Neopantyl glycol 4.3

Polyethylene glycol (200) 5.0

ditto 4.8

Alkyd I.
Alkyd I.

5.3

5.5

dito Diacrylate Lithium tetra 4.06 borate dito dito Lithium ortho- 1.44 silicate dito dito Lithium sulfide 1.10 dito dito Lithium hydro 1.92 gensulfide dito dito Lithium nitrite 3.41 1 H ₂ O Methacrylic acid Dimethacrylate Lithium bromide 5.86 2H ₂ O Acrylic acid Diacrylate Lithium iodide 9.02 3 H ₂ O dito Monoacrylate Lithium formate 3.36 1 H ₃ O Methacrylic acid Dimethacrylate Lithium metha- 4.42 crylate dito dito Lithium salicylate 6.91 Acrylic acid Diacrylate Lithium acetyl 8.93 salicylate dito Monoacrylate Lithium potassium 10.18 d, l-tartrate Methacrylic acid Monomethacrylate Lithium hydroxide 2.02 1 H ₂ O

All alkyd resins I to V mentioned are made from 0.4O 40 diethylene glycol and 0.19 mol of palmitic acid, alkyd resin

Moles of phthalic acid are formed, and alkyd resin I is above it has also been formed from 0.37 moles of glycerol, 0.37 moles of ethylene glycol and 0.19 moles of lauric acid. Alkyd resin II from 0.48 moles of glycerol and 0.19 moles of lauric acid; Alkyd resin III from 03 mol pentaerythritol, 0.24 mol IV from 0.24 mol of pentaerythritol, 0.24 mol of polyethylene glycol (200) and 0.19 mol of palmitic acid, and alkyd resin V from 0.24 mol of pentaerythritol, 0.24 mol of neopentyl glycol and 0.19 moles of lauric acid.

45

Claims (3)

Patent claims: 1. A process for the preparation of acrylic and / or methacrylic acid esters by reacting acrylic acid and / or methacrylic acid with a hydroxy compound which has at least one primary hydroxyl group, in the presence of an acidic esterification catalyst, a polymerization inhibitor and a water-immiscible organic solvent, optionally under Introduction of an oxygen-containing gas into the reaction mixture, characterized in that towards the end of the esterification reaction, lithium oxide, lithium hydroxide, a lithium halide, a lithium salt of an acid which has a pK value higher than that of the esterification catalyst used, or mixtures of lithium compounds is added in an amount of 80 to 300% of the stoichiometric amount to the esterification mixture and then the esterification mixture is subjected to a distillation. 2. The method according to claim 1, characterized in that the lithium compound is lithium carbonate, Lithium acetate or lithium chloride is used. 3. The method according to claim 1, characterized in that the lithium compounds) in an amount of 110 to 200% of the stoichiometric amount is used.