Method for preparing glycerol carbonate (meth) acrylate

Abstract

The present invention relates to a process for preparing glycerol carbonate (meth)acrylate by transesterifying methyl (meth)acrylate with glycerol carbonate in the presence of a zirconium acetylacetonate catalyst, wherein the catalyst is pretreated with 2 to 25% by weight of water, based on the amount of the catalyst.

Description

Technical Field

[0001] The present invention relates to a method for preparing glycerol carbonate (meth)acrylate from glycerol carbonate and methyl (meth)acrylate using zirconium acetylacetonate as a catalyst. Background Art

[0002] In the coatings and adhesives industry, (2-oxo-1,3-dioxolan-4-yl)methyl (meth)acrylate ("glycerol carbonate (meth)acrylate") is a common resin component for curing or post-treatment of thin films.

[0003] Various processes for preparing glycerol carbonate methacrylate have been described in the prior art:

[0004] In JP 2001018729, glycerol carbonate is reacted with acryloyl chloride. The chloride waste produced is a huge environmental burden. In WO 2000 / 031195, glycidyl methacrylate is reacted with CO2. The method is carried out under high pressure. The process equipment required for this is complex and expensive. In DE 3937116, alcohols with a cyclic carbonate structure are reacted with carboxylic acids at elevated temperatures and in the presence of an acid catalyst. The desired product is obtained by distillation with a purity of 75.5%. Depending on the acid used, the yield varies between 25.5% and 83%. Since only 75.5% purity is achieved here, it is impossible to use the product in many applications.

[0005] During the preparation of glycerol carbonate (meth)acrylate from glycerol carbonate and methyl (meth)acrylate in the presence of zirconium acetylacetonate (Zr(acac)4), not only the desired target product is formed, but also unwanted crosslinkers such as glycerol di(meth)acrylate and glycerol tri(meth)acrylate, which, at concentrations of more than 2.5%, can prevent the use of the product in the production of coatings or adhesives.

[0006] WO 2005 / 058862 A2 describes a process for preparing glycerol carbonate methacrylate using zirconium acetylacetonate as a catalyst. The reaction is carried out under anhydrous conditions, wherein the reaction mixture is dehydrated before the addition of the catalyst. The process provides glycerol carbonate methacrylate with a crosslinker content of between 1.8% and 2.3%. However, for some applications that are particularly sensitive to crosslinkers, for example in the coatings sector, these crosslinker contents are still too high. Summary of the invention

[0007] Therefore, the object of the present invention is to provide an improved process for preparing glycerol carbonate (meth)acrylate, with which the crosslinker content can be further reduced while still achieving good yields and high product purity. The crosslinker content should be less than 1.5%, ideally less than 1.0%. SUMMARY OF THE INVENTION

[0009] The object is achieved by the following method: methyl (meth)acrylate is transesterified with glycerol carbonate in the presence of zirconium acetylacetonate catalyst to prepare glycerol carbonate (meth)acrylate, wherein the catalyst is pretreated with 2 to 25% by weight of water based on the amount of catalyst. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the studies that form the basis of the present invention, it was surprisingly found that when the process for preparing glycerol carbonate (meth) acrylate from glycerol carbonate and methyl (meth) acrylate in the presence of a zirconium acetylacetonate catalyst is accompanied by pretreatment of the catalyst with water (2% to 25% by weight, preferably 8% to 20% by weight, and more preferably 9% to 18% by weight, based on the amount of catalyst), a significant reduction in the crosslinking agent formed as an unwanted by-product is achieved. In addition, due to this suppression of side reactions, the purity of the product is improved. This finding is particularly surprising, because water can not only act as a catalyst poison, but can also lead to the cleavage of carbonate (ring opening, release of glycerol). At a water concentration of 15% by weight, the best selectivity in terms of no formation of crosslinking agent is achieved by Zr(acac)4. The significant reduction in the crosslinking agent content makes it possible in particular to use the product as a resin component in coating formulations.

[0012] According to the above, the present invention relates to a method for preparing glycerol carbonate (meth) acrylate by transesterifying methyl (meth) acrylate with glycerol carbonate in the presence of a zirconium acetylacetonate catalyst, wherein the catalyst is pretreated with 2 to 25 wt % of water, preferably 8 to 20 wt % of water, more preferably 9 to 18 wt % of water, based on the amount of the catalyst.

[0013] The process according to the invention provides glycerol carbonate (meth)acrylate having a crosslinker content of less than 1.5%.

[0014] The pretreatment of the catalyst with water can be carried out directly in the reaction mixture, i.e. in the presence of the reactants "methyl (meth)acrylate" or "glycerol carbonate" (and optionally in the presence of at least one stabilizer). The water required for the pretreatment can be introduced into the reaction mixture, for example, together with the glycerol carbonate. However, it is preferred that the pretreatment of the catalyst with water is carried out before the start of the transesterification and in the presence of only methyl (meth)acrylate (and optionally a stabilizer) but not glycerol carbonate.

[0015] This pretreatment step may be carried out while heating the mixture, for example at a temperature in the range of 70°C to 110°C.

[0016] The transesterification itself begins when the reactants "methyl (meth)acrylate" and "glycerol carbonate" are brought into contact. Preferably, the reaction mixture is dehydrated after the pretreatment of the catalyst but before the transesterification reaction begins.

[0017] In a particular embodiment of the invention, methyl (meth)acrylate, water and optionally one or more stabilizers are charged initially and the transesterification is initiated finally by adding glycerol carbonate. The glycerol carbonate is preferably added dropwise, ideally at a temperature between 70°C and 110°C.

[0018] The mixture is preferably dehydrated before the addition of the glycerol carbonate (ie before the transesterification begins). For example, the dehydration can be achieved by distilling off water as an azeotrope with methyl (meth)acrylate.

[0019] The catalyst is preferably used in an amount of 1.0 to 5.0% by weight, based on the total weight of the mixture.

[0020] The ratio of glycerol carbonate to methyl (meth)acrylate in the reaction mixture may preferably be set to a ratio of 1:6 or higher, preferably to a ratio between 1:6 and 1:12.

[0021] In one embodiment of the present invention, the ratio of glycerol carbonate to methyl (meth)acrylate in the reaction mixture is set to 1:10.

[0022] In an alternative embodiment, the ratio of glycerol carbonate to methyl (meth)acrylate in the reaction mixture is set to 1:6.

[0023] In order to shift the equilibrium, the released methanol can be distilled off as an azeotrope with methyl (meth)acrylate. In order to remove only the true azeotrope, the tower used to remove it is best operated with sufficient reflux, which is sufficient to make the tower top temperature of the tower have the exact boiling temperature of the azeotrope. As the reaction proceeds, the reaction rate gradually decreases, with the result that only a small amount of azeotrope is still obtained near the end of the reaction. It is best to remove the restriction on the tower top temperature at this time. The result of this is that less methanol and more methyl (meth)acrylate are distilled off.

[0024] In the studies on which the present invention is based, it was surprisingly found that if the excess of methyl (meth)acrylate relative to the glycerol carbonate is insufficient, this has a significant adverse effect on the formation of the crosslinker when the restriction on the column top temperature is removed.

[0025] The continuous addition of methyl (meth)acrylate in an amount corresponding to 0.7 to 1.3 times the azeotropic distillate or in an amount equivalent to the azeotropic distillate counteracts the effect and, in addition, can significantly increase the space-time yield. The excess methyl (meth)acrylate remaining at the end of the reaction can be removed at a lower temperature and under reduced pressure without significantly increasing the crosslinker content.

[0026] Therefore, it is preferred to keep the ratio of glycerol carbonate to methyl (meth)acrylate initially set in the reaction mixture constant throughout the reaction. In one embodiment of the invention, the ratio of glycerol carbonate to methyl (meth)acrylate is kept constant at 1:6 throughout the duration of the reaction.

[0027] In order to prevent unwanted polymerization, inhibitors / stabilizers can be used in the reaction (and during purification and storage). In the context of the present invention, the terms "inhibitor" and "stabilizer" are used synonymously. These compounds, for example hydroquinone, hydroquinone ethers, for example hydroquinone monomethyl ether, or di-tert-butylcatechol, phenothiazine, N,N'-(diphenyl)-p-phenylenediamine, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, p-phenylenediamine, methylene blue or sterically hindered phenols, are very widely used in industry. These compounds can be used alone or in the form of mixtures and are generally commercially available. The mode of action of the stabilizers is generally that they act as free radical scavengers for the free radicals that occur in the polymerization. Further details are given in the relevant technical literature, in particular -Lexikon Chemie[ Chemical Dictionary]; Editors: J. Falbe, M. Regitz; Stuttgart, New York; 10th edition (1996); keyword "Antioxidantien" [antioxidants], and references cited therein.

[0028] The stabilizer or stabilizers (alone or as a mixture) are typically present in an amount of 0.005% to 0.5% by weight, based on the weight of the total reaction mixture.

[0029] These inhibitors can be added to the reaction mixture before the reaction or at the start of the reaction. In addition, a small proportion of the inhibitor used can also be introduced during the transesterification process. Of particular interest here are processes in which a portion of the inhibitor is added to the column reflux. It is particularly advantageous to use, in particular, a mixture comprising methyl (meth)acrylate, hydroquinone monomethyl ether and 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl. This measure makes it possible to avoid undesirable polymerization inside the distillation column.

[0030] In addition, dissolved oxygen can also be used for stabilization. It can be, for example, in the form of air, wherein the amount introduced is preferably such that the content in the gas phase above the reaction mixture remains below the explosion limit. Likewise, inert gas / oxygen mixtures can be used, such as nitrogen / oxygen or argon / oxygen mixtures.

[0031] In a particular embodiment of the present invention, a combination of dissolved oxygen and hydroquinone monomethyl ether (HQME) can be used for stabilization.

[0032] The reaction can be carried out under standard pressure, reduced pressure or elevated pressure. In a particularly advantageous refinement of the invention, the transesterification can be carried out under a pressure in the range of 200 to 2000 mbar, in particular in the range of 500 to 1300 mbar, and preferably in the range of 800 to 1050 mbar.

[0033] The reaction temperature can likewise be within wide ranges, depending inter alia on the pressure. In a particular embodiment of the invention, it can be carried out at a temperature in the range from 60°C to 150°C, in particular from 70°C to 140°C, and preferably from 90°C to 135°C.

[0034] The transesterification can be carried out without using another solvent. Alternatively, an inert solvent can also be used. Such solvents include in particular benzene, toluene, n-hexane, cyclohexane and methyl isobutyl ketone (MIBK) and methyl ethyl ketone (MEK).

[0035] The liberated alcohol can subsequently be removed from the reaction mixture by distillation, optionally as an azeotrope with methyl (meth)acrylate. The alcohol can also be removed as an azeotrope with n-hexane or cyclohexane.

[0036] The reaction may preferably be carried out under stirring, in which case the speed of the stirrer must be adjusted according to the scale of the reaction. For example, the stirrer speed may be in the range of 20 to 5000 rpm, preferably in the range of 50 to 2000 rpm, and more preferably in the range of 100 to 500 rpm.

[0037] The reaction times depend inter alia on the selected parameters, such as pressure and temperature. However, they are generally in the range of 1 to 24 hours, preferably 5 to 20 hours, and more preferably 6 to 18 hours.

[0038] Upon completion of the transesterification reaction (or upon termination of the reaction), the catalyst may be removed by precipitation (eg with dilute phosphoric acid) and filtration. If desired, purification of the crude product may be carried out by conventional methods.

[0039] The process according to the invention is preferably carried out as a batch process. If this is done, excess methyl (meth)acrylate can be removed by distillation near the end of the reaction. This can be used again in the next batch without further purification.

[0040] Glycerol carbonate (meth)acrylate can be used as a functional monomer in copolymers for coatings and adhesives, with which subsequent polymer-like transformation reactions can be carried out, including crosslinking with difunctional amines in coating formulations. It can also be used in battery electrolytes, extrusion resins, and for metal extraction. DETAILED DESCRIPTION

[0041] The following examples illustrate the process according to the present invention, but the process according to the present invention is not limited to the examples.

[0042] Example 1: Molar ratio 1:10; add 15% water

[0043]

[0044] mixture:

[0045]

[0046] Operation process:

[0047] In a 2-liter four-necked round-bottom flask equipped with an air inlet, a charging funnel, a mechanical stirrer, a 50 cm silver-plated packed column (d = 29 mm, filled with 8 × 8 Raschig rings), an automatic column head, a condenser and a temperature measuring sensor (at the bottom and the top of the tower), Zr (acac) 4, hydroquinone monomethyl ether (HQME), water and methyl methacrylate (MMA) were added. The mixture was boiled under reflux, and the resulting water / MMA azeotrope was finally taken out. Then, at a bottom temperature between 95 and 105 ° C, glycerol carbonate was added dropwise over a period of about one hour. This process was accompanied by a gradual decrease in the tower top temperature, and at a tower top temperature of <70 ° C, the resulting MMA / methanol mixture was taken out at a reflux ratio (take-out / reflux) of 1:50. Once the tower top temperature is no longer below 75 ° C, and there is no further restriction on the tower top temperature, and at a steady-state reflux ratio of 1:50, the resulting distillate is taken out until the tower top temperature is a constant 99-100 ° C. The total reaction time was about 12 hours. The catalyst was then precipitated with 70 g of 10% phosphoric acid at 85° C. and the mixture was stirred for 15 minutes. After filtering off the solid, the filtrate was concentrated on a rotary evaporator at an oil bath temperature of 120° C. to 20 mbar.

[0048] This afforded 193 g (86.5% of theory) of clear yellow product.

[0049] Analysis: (GC, values ​​expressed as area %)

[0050]

[0051]

[0052] Example 2: Molar ratio 1:10; add 10% water

[0053] mixture:

[0054]

[0055] Operation process:

[0056] See Example 1.

[0057] This afforded 198 g (88.8% of theory) of a clear yellow product.

[0058] Analysis: (GC, values ​​expressed as area %)

[0059]

[0060] Example 3: Molar ratio 1:10; add 20% water

[0061] mixture:

[0062]

[0063] Operation process:

[0064] See Example 1.

[0065] This afforded 201 g (90.1% of theory) of a clear yellow product.

[0066] Analysis: (GC, values ​​expressed as area %)

[0067]

[0068] Example 4: Molar ratio 1:6, add 10% water, add distilled MMA

[0069] mixture:

[0070]

[0071] Operation process:

[0072] See Example 1. In this case, however, 200 g of MMA were added during the reaction, based on the MMA / methanol mixture removed.

[0073] This afforded 333 g (89.5% of theory) of clear yellow product.

[0074] Analysis: (GC, values ​​expressed as area %)

[0075]

[0076] Examples 1-3 demonstrate that, in the case of a molar ratio of glycerol carbonate to MMA of 1:10, products with a low content of crosslinking agents can be prepared when the catalyst is first treated with a certain amount of water. In Example 4, an increased space-time yield compared to Examples 1-3 is achieved by reducing the molar ratio to 1:6. In order for the obtained product to still comply with the invention, an appropriate additional amount of MMA must be added.

[0077] Comparative Example 1: molar ratio 1:10; no water added

[0078] mixture:

[0079]

[0080] Operation process:

[0081] See Example 1, except no water was added. The reaction time was only 6 hours.

[0082] This afforded 203 g (91.0% of theory) of a clear yellow product.

[0083] Analysis: (GC, values ​​expressed as area %)

[0084]

[0085] Comparative Example 2: Molar ratio 1:6; no water added

[0086] mixture:

[0087]

[0088] Operation process:

[0089] See Example 1 except no water is added.

[0090] This afforded 333 g (89.5% of theory) of clear yellow product.

[0091] Analysis: (GC, values ​​expressed as area %)

[0092]

[0093] Comparative Example 3: Molar ratio 1:6, water added, no MMA added

[0094] mixture:

[0095]

[0096] Operation process:

[0097] See Example 1.

[0098] This afforded 330 g (88.7% of theory) of a clear yellow product.

[0099] Analysis: (GC, values ​​expressed as area %)

[0100]

[0101] Comparative Example 4:

[0102] mixture:

[0103]

[0104]

[0105] Operation process:

[0106] See Example 1.

[0107] This afforded 181 g (81.1% of theory) of a clear yellow product.

[0108] Analysis: (GC, values ​​expressed as area %)

[0109]

[0110] Comparative Examples 1 and 2 demonstrate that if no water is added at the beginning, a product with a low crosslinker content cannot be prepared. Comparative Example 3, on the other hand, demonstrates the effect of a lower molar ratio (1:6) without the addition of distilled MMA. Although this leads to a significantly lower crosslinker content compared to Comparative Examples 1 and 2, it is still higher than required. Comparative Example 4 demonstrates that if the amount of water at the beginning of the reaction is too high, the reaction no longer proceeds to completion, with 12.8% of the starting material glycerol carbonate still present at the end of the reaction time.

Claims

1. A method for preparing glycerol carbonate (meth) acrylate, which is carried out by transesterifying methyl (meth) acrylate with glycerol carbonate in the presence of a zirconium acetylacetonate catalyst, in The catalyst is pretreated with 2 to 25 wt % of water, based on the amount of the catalyst, and The ratio of glycerol carbonate to methyl (meth)acrylate in the reaction mixture was set to a ratio between 1:6 and 1:

12.

2. The method according to claim 1, Features The catalyst is pretreated with 8% to 20% by weight of water, based on the amount of catalyst.

3. The method according to claim 2, Features The catalyst is pretreated with 9% to 18% by weight of water, based on the amount of catalyst.

4. A method according to any one of claims 1 to 3, Features The catalyst is pretreated with water in the presence of methyl (meth)acrylate and optionally in the presence of at least one stabilizer.

5. The method according to any one of claims 1 to 3, Features The catalyst was pretreated with water at a temperature ranging between 70°C and 110°C.

6. A method according to any one of claims 1 to 3, Features A dehydration step is performed before the transesterification begins.

7. The method according to any one of claims 1 to 3, Features The catalyst is used in an amount of 1.0 wt % to 5.0 wt % based on the total weight of the mixture.

8. A method according to any one of claims 1 to 3, Features The ratio of glycerol carbonate to methyl (meth)acrylate in the reaction mixture was set to 1:

10.

9. The method according to any one of claims 1 to 3, Features The ratio of glycerol carbonate to methyl (meth)acrylate in the reaction mixture was set to 1:

6.

10. The method according to any one of claims 1 to 3, Features Methanol formed during the transesterification was distilled off together with methyl (meth)acrylate as an azeotrope, and methyl (meth)acrylate was continuously added to the reaction mixture in an amount corresponding to 0.7 to 1.3 times the azeotropic distillate.

11. The method according to any one of claims 1 to 3, Features The methanol formed during the transesterification was distilled off together with methyl (meth)acrylate as an azeotrope, and methyl (meth)acrylate was continuously added to the reaction mixture in an amount equivalent to the azeotropic distillate.

12. The method according to any one of claims 1 to 3, Features The reaction mixture contains at least one stabilizer.

13. The method according to claim 12, Features The reaction mixture has a stabilizer content of 0.005% to 0.5% by weight.

14. The method according to any one of claims 1 to 3, Features At least one hydroquinone-based inhibitor is present during the transesterification process, optionally in combination with dissolved oxygen.

15. The method according to claim 14, Features The at least one hydroquinone-based inhibitor is hydroquinone monomethyl ether.

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