FR2924114A1 - PROCESS FOR THE SYNTHESIS OF ALCOXYPOLYALKYLENE GLYCOLS (METH) ACRYLATES BY TRANSESTERIFICATION - Google Patents

Abstract

The invention relates to a process for the synthesis of (meth) acrylic esters of alkoxypolyalkylene glycols by transesterification reaction of a light alkyl (meth) acrylate and an alkoxypolyalkylene glycol in the presence of a catalyst selected from list consisting of zirconium, lithium or calcium acetylacetonates, dibutyltin oxide, distannoxanes, and cesium carbonate, used alone or as a mixture. This method is advantageously used to prepare methacrylates of methoxypolyethylene glycols (MAMPEG) with a molar mass ranging from about 500 to about 5000.

Description

The present invention relates to a process for synthesizing (meth) acrylic (meth) acrylic monomers of alkoxypolyalkylene glycols by transesterification reaction between a (meth) acrylic ester and an alkoxypolyalkylene glycol.

In the present invention, the term (meth) acrylic means acrylic or methacrylic. Such monomers possess hydrophilic-hydrophobic sequences which confer on them interesting properties for the preparation of polymers that can be used in various fields such as thickeners, dispersants or concrete fluidizers. Numerous patents describe the synthesis of the (meth) acrylic esters of alkoxypolyalkylene glycols by direct esterification between either (meth) acrylic acid or (meth) acrylic anhydride and an alkoxypolyalkylene glycol (US 4,384,096; FR 2,739,850) .

Another synthetic route relates to the transesterification which is described, in particular in the following documents: The international application WO 00/012576 describes the reaction between an alkyl (meth) acrylate and a polyalkylene glycol monoalkyl ether catalyzed by the paratoluene sulphonic acid (APTS).

The patent application JP 2002-338519 describes the use of Li, Na, K hydroxides, Li carbonates, Na, EtONa type alkoxides, Ti alkoxides as transesterification catalysts for the synthesis of (meth) acrylates. polyalkylene glycol. US Patent 4,916,255 claims the use of an alkaline material selected from lithium hydroxide or lithium alkoxides to catalyze the synthesis of methacrylates of ether linkage alcohols. JP 2004-234877 discloses the use of Ti (OR) 4 tetraalkyl titanate with R = methyl, ethyl, isobutyl, butyl, as a catalyst for the synthesis of alkoxypolyalkylene glycol (meth) acrylates.

US Pat. No. 6,040,473 describes for its part the synthesis of these monomers by transesterification, the use of calcium hydroxide Ca (OH) 2 taken alone or mixed with lithium chloride.

The different routes of synthesis of (meth) acrylates of alkoxypolyalkylene glycols, in particular the synthesis of methacrylates of methoxypolyethylene glycols (generally known as (MAMPEG) can be summarized as follows: - Esterification: from methacrylic acid (AMA) ) and methoxypolyethylene glycol (MPEG): AMA + MPEG MAMPEG + water from methacrylic anhydride (AMA2O): AMA2O + MPEG MAMPEG + AMA - Transesterification: from methyl methacrylate (MAM): MAM + MPEG MAMPEG + methanol The choice of the synthetic route is strongly dependent on the molar mass of methoxypolyethylene glycol methacrylate (MAMPEG) For high molecular weight MAMPEGs (such as MAMPEG 5000), the direct esterification pathway from anhydride methacrylic acid (AMA2O) has often been favored, its use requiring the simple provision of a heated stirred reactor, but if the weight of AMA2O on the cost of raw materials is relatively modest for the MAMPEG 5000, but this is not the case for MAMPEG with a lower molecular weight, particularly for MAMPEG 2000, and its lower counterparts. It therefore seems preferable to envisage a synthetic route by direct esterification from methacrylic acid or a synthesis route by transesterification.

Transesterification generally encounters problems with the reactivity of MPEG alcohols, resulting in a bad conversion rate and a significant reaction time, with the attendant risk of polymerization. Direct esterification, for its part, uses acidic catalysts of the sulfuric acid type, which are very corrosive. In the presence of these catalysts, there are also breaks in the polyethoxylated links at the ether bridges. This results in an increase in polydispersity with reduction in molecular weight. Facilities must be able to withstand the 3

corrosion, which requires the use of enamelled or vitrified reactors highly sensitive to shocks. The coloration of the products prepared by esterification is also more marked. The Applicant Company has now discovered that by preparing methacrylates of methoxypolyethylene glycols by transesterification with a specific catalyst, it is possible to overcome the various aforementioned drawbacks, particularly in terms of conversion rate and cost. The subject of the present invention is therefore a process for the synthesis of (meth) acrylic esters of alkoxypolyalkylene glycols of formula (I): R 1 O (AO) 1 R 3 O (1) in which: R 1 is a hydrogen atom or a methyl group, AO is (CH2-CH2O) or (CH2-CH (CH3) O, alone or in a mixture, the units may be distributed in block or random form, n varies between 2 and 250, R3 is a linear alkyl radical or branched, which may comprise unsaturations, comprising from 1 to 6 carbon atoms, by reaction of an alkyl (meth) acrylate of formula (II): O (II) in which RI has the abovementioned meaning and R2 is a grouping linear or branched alkyl having from 1 to 4 carbon atoms, with an alcohol of the alkoxypolyalkylene glycol type of formula (III): R 3 -O (AO) nH (III) in which R 3, AO and n have the abovementioned meanings, in the presence a transesterification catalyst characterized in that the catalyst is selected from the list consisting of acetylac tonates zirconium, lithium or calcium, dibutyltin oxide, distannoxanes, and cesium carbonate, used alone or in admixture. The catalysts used in the process according to the invention have the advantage of being very active, thus leading to little residual alcohol, while being selective. The use of zirconium acetylacetonate also makes it possible to obtain (meth) acrylates of alkoxypolyalkylene glycols, such as MAMPEG, which are not very colored. As starting compounds of formula (II), mention may be made of methyl (meth) acrylate, ethyl (meth) acrylate or butyl (meth) acrylate, more particularly methyl methacrylate. In the formula (III) of the starting alcohol, R 3 is advantageously a methyl, ethyl, propyl, butyl or allyl radical. Preferably, a methoxypolyalkylene glycol is used. Preferably, AO is a unit derived from ethylene oxide, -CH2-CH2O- Advantageously, the number n varies from 2 to 100, in particular from 2 to 50. The alkoxypolyalkylene glycols are advantageously compounds of lower molecular weight. or equal to about 10,000, more particularly with a mass ranging from about 500 to about 5000, preferably from about 500 to about 2000. Mention may be made of alkoxypolyethylene glycols, and more particularly methoxypolyethylene glycols MPEG 500, 750, 1000, 2000, 5000 marketed for example by BASF under the trademark Pluriol A, by INEOS or CLARIANT under the trademark POLYGLYKOL M 250, 350, 500, 750, 1100, 2000, 5000. In the context of the present invention, the molar masses are weight average masses, the manufacture of polyalkylene glycols leading to a distribution of compounds of different molar masses according to a Gauss distribution. The catalysts that can be used in the process according to the invention are zirconium acetylacetonate (ZrAcac), lithium acetylacetonate (LiAcac), calcium acetylacetonate (CaAcac), dibutyltin oxide (DBTO), distannoxanes of formula A2XSnOSnXA2 in which A is an alkyl radical of CI to C8 and X is Cl or OB, B being CH3 or OCOCH3, such as for example tetrabutyldichloro distannoxane, or cesium carbonate (Cs2CO3). They may be used alone or as a mixture in a proportion of from 0.01 mole to 0.1 mole per mole of starting alcohol (III), preferably from 0.05 mole to 0.1 mole per mole of alcohol (III ). The preferred catalysts are zirconium acetylacetonate or tetrabutyldichloro distannoxane. The light alkyl (meth) acrylate ester of formula (II) is used in molar excess relative to the alkoxypolyalkylene glycol (III). The molar ratio between (II) and (II) is generally between 1 and 20, and preferably between 5 and 10. The excess alkyl (meth) acrylate (II) is or is not removed by distillation at the end of reaction. The alkoxypolyalkylene glycol (III) is generally in pure form, it may be in solution in the light ester (II). It can also be dissolved in water after removing excess light ester (II). The transesterification reaction is generally carried out at a temperature ranging from 80 ° C to 130 ° C, and the pressure is generally maintained between 0.025 bar and atmospheric pressure. Preferably, the reaction temperature ranges from 90 ° C to 120 ° C, and the pressure is of the order of 0.5 bar at atmospheric pressure. The transesterification reaction generates the formation of a light alcohol R2OH. The reaction is carried out by shifting the equilibrium by distillation of the light alcohol R2OH as it is formed as a light ester (II) / R2OH azeotrope. The addition of a minimum azeotrope-forming solvent with the light alcohol R2OH is also possible. Among the solvents that may be used, mention may be made, without limitation, of hexane, heptane, methylcyclohexane and toluene. In this case, the alcohol R2OH is distilled as a solvent / R2OH azeotrope.

The synthesis of (meth) acrylates of alkoxypolyethylene glycols according to the process according to the invention is carried out in the presence of one or more polymerization inhibitors chosen from the well-known compounds of 6

those skilled in the art, in particular hydroquinone, hydroquinone monomethyl ether, phenothiazine, diterbutyl para-cresol (BHT), para-phenylene diamine, TEMPO (2,2,6,6-tetramethyl- 1-piperidinyloxy), ditertiobutylcatechol (BHT), or TEMPO derivatives, taken alone or as a mixture, at 100 to 5000 ppm relative to the initial charge, preferably between 500 and 3000 ppm relative to the mixture of reagents . A bubbling of air, preferably of depleted air (8% by volume), is advantageously carried out during the entire duration of the synthesis, at the heart of the reaction mixture.

The process according to the invention is advantageously used to prepare methacrylates of methoxypolyethylene glycols (MAMPEG) with a molar mass ranging from about 500 to about 5000, preferably ranging from about 500 to about 2000. The (meth) acrylates of Alkoxypolyalkylene glycols obtainable according to the process of the invention are advantageously used to prepare additives such as dispersants, thickeners or fluidifiers.

The following examples illustrate the present invention without limiting its scope.

EXAMPLES The percentages are expressed in percentages by weight. The following abbreviations are used: MAM: methyl methacrylate MPEG: methoxypolyethylene glycol MAMPEG: methoxypolyethylene glycol methacrylate BHT: ditertiobutyl paracresol EMHQ: hydroquinone methyl ether

EXAMPLE 1 In a stirred reactor, heated by circulating thermostatically controlled oil in a jacket, surmounted by a distillation column filled with packing

Multiknit, with head condenser, vacuum separator, recipes and traps, charge: - 403g (0.2 moles) of PLURIOL A2030E from BASF (MPEG molar mass about 2000), previously melted in an oven at 70 ° C - 400g of MAM -0.8 g of BHT - 0.8 g of EMHQ A bubbling of air is maintained in the heart of the reaction medium throughout the duration of the synthesis. The reaction mixture is dried by distilling the water as a MMA / water azeotrope. 108 g of a head fraction is thus recovered. Drying is carried out at atmospheric pressure at a reactor temperature of between 95 ° C and 100 ° C. After drying, 108 g of MMA are added to the reactor and 0.86 g of zirconium acetylacetonate (0.09 mol / mole MPEG) are introduced.

The reaction mixture is heated under atmospheric pressure to a temperature between 106-107 ° C. The temperature at the top of the column is 65-66 ° C. The methanol formed is distilled as it is formed in the form of a MMA / methanol azeotrope. After 3 hours of reaction, it is complete and there is more methanol that is formed. The crude is in the form of a clear yellow solution. After cooling to 70 ° C., 400 g of water are introduced into the reactor and then the excess of MAM is distilled off in the form of a MMA / water azeotrope. The distillation of the excess of MAM is complete when at a temperature at the top of the column which corresponds to that of pure water. The final crude (MAMPEG in solution in water, 658 g to 37.9%) is in the form of a slightly colored liquid. After filtration on cellulose filter, the product is perfectly clear. NMR analysis of the final product reveals a total conversion of MPEG alcohol. Example 2: In the apparatus described in Example 1, the following are charged:

- 400g of PLURIOL A 2030 E previously melted in an oven at 70 ° C - 300g of MAM - 0.8g of BHT - 0.8g of EMHQ Air bubbling is maintained in the middle of the reaction medium for the duration of the synthesis. After drying as described in the example, 4.9 g of cesium carbonate are introduced and the reaction is carried out at atmospheric pressure at a temperature of between 100 and 120 ° C. After 6 hours of reaction, the conversion rate of MPEG measured according to the amount of distilled methanol is about 98%. The unexhausted crude of the residual MAM is hot in the form of a brown liquid.

Example 3: Example 2 is repeated using lithium acetylacetonate as a transesterification catalyst, instead of zirconium acetylacetonate (0.08 mol / mole MPEG). After 11 hours of reaction, an MPEG conversion rate of 78% is obtained.

EXAMPLE 4 Example 2 is repeated using dibutyltin oxide (DBTO) as a catalyst (3.8 g, ie 0.08 mol / mole MPEG). After 5 hours of reaction, the conversion rate of MPEG is 87%. EXAMPLE 5 In the apparatus described in the example, the following are charged: 200 g of PLURIOL A 500E - BASF (methoxypolyethylene glycol of molar mass 500) - 400 g of MAM -0,6g BHT - 0,6g EMHQ 9

Bubbling of air is maintained in the heart of the reaction medium throughout the duration of the synthesis. After drying by removing the water present in the mixture of reagents by distillation, 1.7 g of zirconium acetylacetonate and a complement of MAM corresponding to that distilled in the drying fraction are introduced. The methanol generated in the reaction is eliminated as it is formed. Residual MAM is then distilled off. Finally, 245 g of crude oil is obtained whose mass composition determined by NMR is as follows: MAMPEG 500 92% - MPEG500 6% - residual MAM 2%.

Examples 6 to 16: A battery of electrically heated tubes at a temperature of 105-110 ° C was used to effect the reaction between MAM and MPEG 2000 (PLURIOL A2030E) in a molar ratio of 15: 1, in the presence of inhibitors BHT / EMHQ in the proportions 2000 ppm / 2000 ppm for a period of 24 hours. Different catalysts were tested at 7.5-10-2 mol per mole of alcohol. The crude samples were analyzed by NMR and the efficiency of the catalysts was determined from the residual MPEG 2000 content.

The results are summarized in the table below.

Test No. Catalyst tested NMR analysis of crude Moles MPEG / 100 moles MAMPEG + MPEG 6 (Comp) LiOH 59 7 (Comp) (EtO) 2Mg 100 8 (Comp) APTS 72 9 (Comp) Na2CO3 100 10 (Comp) Zn Acetate 77 11 (comp) VERTEC AC 560 80 Ti (EtO) 4-Ti (Oisopro) 4 12 (comp) Ti (Oisopro) 4 75 13 (compare) MeONa Reaction stop, strong exotherm 14 Tetra butyl 6 dichlorodistannoxane 15 DBTO 30 EXAMPLE 17 (Comparative): In a stirred reactor, the pair of LiCl / Ca (OH) 2 catalysts as described in US Pat. No. 6,040,473 was tested at 0.075 moles per mole of alcohol, with a ratio of molar MAM / MPEG 2000 of 15/1, at a temperature between 110 ° C and 120 ° C and in the presence of BHT / EMHQ of 1000/1000 ppm.

After a reaction time of 5 h, a final solid colored solid mauve solid was obtained which still contained a high proportion (85%) of residual MPEG.

Claims (6)

A process for the synthesis of (meth) acrylic esters of alkoxypolyalkylene glycols of formula (I): R 1 D (AD) n R 3 O (I) in which: R 1 is a hydrogen atom or a methyl group, AO is ( CH2-CH2O) or (CH2-CH (CH3) O, alone or in a mixture, the units being able to be distributed in block or random form, n varies between 2 and 250, R3 is a linear or branched alkyl radical, which can comprise unsaturations , comprising from 1 to 6 carbon atoms, by reaction of an alkyl (meth) acrylate of formula (II): R 1 OR 2 O (II) in which R 1 has the abovementioned meaning and R 2 is a linear or branched alkyl group having 1 to 4 carbon atoms, with an alkoxypolyalkylene glycol alcohol of formula (III): R 3 -O (AO) nH (III) wherein R 3, AO and n have the aforementioned meanings, in the presence of a catalyst transesterification process characterized in that the catalyst is selected from the list consisting of zirconium acetylacetonates, lithium Calcium, dibutyltin oxide, distannoxanes, and cesium carbonate, used alone or as a mixture. 2. Method according to claim 1 characterized in that the alkoxypolyalkylene glycol (III) has a molar mass less than or equal to about 10,000, preferably from about 500 to about 5000. 3. Method according to claim 1 or 2 characterized in that the alkoxypolyalkylene glycol (III) is an alkoxypolyethylene glycol, preferably a methoxypolyethylene glycol. 4. Process according to any one of the preceding claims, characterized in that the catalyst is used in a proportion of 0.01 mole to 0.1 mole per mole of alcohol (III). 5. Process according to any one of the preceding claims for preparing a methoxypolyethylene glycol methacrylate. 6. Use of the (meth) acrylic esters of alkoxypolyalkylene glycols of formula (I) obtained according to the method according to any one of the preceding claims for preparing additives such as dispersants, thickeners or fluidifiers.