Process for preparing N-methyl(meth)acrylamide

Abstract

The invention relates to a process for preparing N-methyl(meth)acrylamide and to the uses thereof.

Claims

1. A process for preparing N-methyl(meth)acrylamide, comprising reacting (meth)acrylic anhydride with methylamine, wherein: a) the methylamine has a water content of <1% by weight; b) the molar ratio of (meth)acrylic anhydride:amine is 1:x wherein 1≤x<2; and wherein the reaction has a yield of greater than 90%.

2. The process of claim 1, wherein the reaction is performed in the presence of a stabilizer.

3. The process of claim 2, wherein the stabilizer is selected from the group consisting of: phenothiazine, 2,4-dimethyl-6-tert-butylphenol, N,N′-diphenyl-p-phenylenediamine, 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl, 4-methyl-2,6-di-tert-butylphenol, 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, benzene-1,4-diamine, N,N′-mixed phenyl and tolyl derivatives (DTPD), 2,6-di-tert-butyl-alpha-(dimethylamino)-p-cresol, tert-butylcatechol, bis-2,2,6,6-tetramethyl-4-piperidyl sebacate, 2,2,6,6-tetramethylpiperidine N-oxyl and mixtures thereof.

4. The process of claim 1, wherein the water content of the methylamine is less than 0.1% by weight.

5. The process of claim 1, wherein the water content of the reaction mixture after the end of addition of all reactants is less than 10% by weight.

6. The process of claim 5, wherein the water content of the reaction mixture after the end of addition of all reactants is less than 5% by weight.

7. The process of claim 5, wherein the water content of the reaction mixture after the end of addition of all reactants is less than 1% by weight.

8. The process of claim 5, wherein the water content of the reaction mixture after the end of addition of all reactants is less than 0.1% by weight.

9. The process of claim 1, wherein the reaction is conducted in a polar aprotic solvent.

10. The process of claim 1, wherein the methylamine is added in liquid or gaseous form.

11. The process of claim 1, wherein the methylamine is added as a gas.

12. The process of claim 1, wherein the molar ratio of (meth)acrylic anhydride:amine is from 1:1 to 1:1.5.

13. The process of claim 1, wherein the (meth)acrylic acid by-product is removed or separated by distillation.

14. The process of claim 1, wherein the (meth)acrylic anhydride is reacted with methylamine at temperatures between −20° C. and 100° C.

15. The process of claim 1, wherein the (meth)acrylic anhydride is reacted with methylamine at a temperature between 0° C. and 80° C.

16. The process of claim 1, wherein the (meth)acrylic anhydride is reacted with methylamine at a temperature between 20° C. and 50° C.

17. The process of claim 1, wherein the (meth)acrylic anhydride is reacted with methylamine at an absolute pressure of 0.5 bar to 10 bar.

18. The process of claim 1, wherein the (meth)acrylic anhydride is reacted with methylamine at an absolute pressure of 1 bar to 5 bar.

19. The process of claim 3, wherein the (meth)acrylic anhydride is reacted with methylamine at an absolute pressure of 0.5 bar to 10 bar.

20. The process of claim 19, wherein the molar ratio of (meth)acrylic anhydride:amine is 1:1.

Description

EXAMPLE 1: PREPARATION OF N-METHYLMETHACRYLAMIDE

(1) Reaction Equation:

(2) ##STR00001##

(3) Apparatus: 2 L autoclave with glass insert, Ni—Cr—Ni thermocouple, gas feed: metal, steel methylamine gas bottle, manometer, acetone/dry ice bath

(4) Mixture:

(5) TABLE-US-00001 6.0 mol methacrylic anhydride = 940.2 g 6.0 mol methylamine, gas = 186.4 g

(6) Theoretical Yield:

(7) (=starting weight) 1126.6 g

(8) Procedure:

(9) The methacrylic anhydride is initially charged in the glass insert of the autoclave and the autoclave is screwed shut. The steel methylamine gas bottle is on a balance and is connected to the autoclave by a coiled VA feed pipe; hence the decrease in weight on introduction of methylamine can be monitored.

(10) The introduction of methylamine is commenced with a metering rate of about 4 g/3 min at room temperature. The reaction is strongly exothermic. The temperature should not exceed 40° C. (35° C.±5° C.). The mixture is cooled with an acetone-dry ice mixture. The metering rate is increased to 6 g/3 min of methylamine; no more is possible due to the cooling as a result of the poor heat transfer owing to the glass insert. Once the stoichiometric amount of methylamine (186.4 g, 6 mol) has been introduced, the bottle is closed, the remaining gas in the conduit is left to react for 10 min and then the cooling is removed and the autoclave is vented.

(11) Yield: 1125 g

(12) GC of the product, method: (GC: DB5, 30 m, Ø 0.25 mm, film thickness 0.25 μm, 50° C., 3 min isothermal, 14° C./min.fwdarw.280° C., 8 min isothermal; det: 280° C., inj.: 250° C.)

(13) TABLE-US-00002 Methyl- Methacrylic N-Methyl- Methacrylic Name amine acid methacrylamide anhydride HB Retention: 1.08 min 3.83 min 5.97 min 7.43 min 13.15 min GC area % 0.045 41.360 52.445 0.079 4.187 HB = high boilers

EXAMPLE 2: WORKUP OF N-METHYLMETHACRYLAMIDE BY DISTILLATION

(14) Apparatus: 2 l three-neck round-bottom flask with boiling capillary, Pt100 temperature sensor, 30 cm mirrored column with 8×8 Raschig rings, automatic column head (liquid divider), reflux condenser, coiled condenser, Thiele-Anschutz attachment, receivers, oil bath, vacuum pump, manometer

(15) Mixture:

(16) TABLE-US-00003 1122 g N-methylmethacrylamide from Example 1 22.4 mg 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (rad.)  (20 ppm) 224.4 mg hydroquinone monomethyl ether  (200 ppm) 1122 mg octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (1000 ppm)

(17) Procedure:

(18) TABLE-US-00004 Bath Bottom Top Pressure ° C. ° C. ° C. mbar Comment 28 28 28 13.0 start of heating 108 88.9 50 4.0 boils, RR 1:5; 1st fraction 111 99.2 58 3.8 2nd fraction 112 100.4 62 3.8 3rd fraction 128 114.7 69 2.9 4th fraction 134 119.6 89 2.8 5th fraction 136 113 91 2.9 RR 1:10 141 118 91 2.8 RR 1:5 146 122 94 2.8 6th fraction 147 122.6 94 2.7 7th fraction 131 104 77 2.4 8th fraction 138 105.9 79 2.3 9th fraction 139 106.4 79 2.3 10th fraction 144 108.5 79 2.3 RR 1:2.5 144 108.0 80 2.3 RR 1:1 143 110.4 81 2.3 11th fraction 153 130 77 2.3 end RR = reflux ratio

(19) Yield and GC Analyses:

(20) TABLE-US-00005 Name N-Methyl- Retention: Methyl- Methacrylic methacryl- Methacrylic [min] Amount amine acid amide anhydride HB 2 HB 3 HB 1 Fraction g 1.08 min 3.83 min 5.97 min 7.43 min 8.71 10.89 13.15 1st 135.7 0.003 99.867 0.124 2nd 139.1 0.007 99.993 3rd 84.2 0.004 99.938 0.037 4th 50.4 97.275 1.758 0.008 0.77 5th 58.0 0.018 62.601 33.538 0.007 3.44 6th 28.8 38.609 56.422 0.008 4.52 7th 30.4 22.935 72.339 0.005 4.30 8th 73.3 7.300 90.296 2.12 9th 38.5 3.850 94.531 1.15 0.011 10th 230.3 0.929 98.566 0.36 0.060 0.011 11th 113.6 0.116 99.120 0.23 0.339 0.053 Cold trap 1 8.5 0.004 99.921 0.067 Cold trap 2 1.5 0.027 65.237 30.016 3.97 Residue * 75.6 1.285 14.950 3.100 20.60 * viscous, further peaks: 11.257 min: 25.653%; 11.688 min: 15.458%; 12.259 min: 5.177% + further smaller peaks

EXAMPLE 3: PREPARATION OF N-METHYLMETHACRYLAMIDE IN SOLVENT

(21) Apparatus:

(22) 1 l four-neck round-bottom flask with precision glass stirrer (Teflon sleeve), Pt100 temperature sensor, gas inlet (Teflon), gas outlet of Teflon with wash bottles as safety bottles, reflux condenser, steel methylamine gas bottle, waste air conduit directly into the fume hood, feed for compressed air as added air, acetone/dry ice cooling bath

(23) Mixture:

(24) TABLE-US-00006 1.0 mol methacrylic anhydride = 156.4 g 250 ml methyl tert-butyl ether (MTBE) 1.0 mol methylamine, gas

(25) Theoretical Yield:

(26) 99.1 g

(27) Procedure:

(28) Methacrylic anhydride and MTBE are initially charged and cooled. The methylamine gas is introduced at about 2° C.-10° C. The reaction is weakly exothermic.

(29) Since the reaction proceeds only very slowly at this temperature, gas is introduced more quickly and the bottom temperature can be increased to up to 50° C. The introduction is ended when no methacrylic anhydride is detectable any longer. The MTBE is drawn off on a rotary evaporator (RE) at a bath temperature of 60° C. and a pressure down to 200 mbar.

(30) Distillate to 200 mbar: 151.5 g

(31) Residue to 200 mbar: 181.7 g

(32) The residue (180 g) is distilled through a 15 cm Vigreux column under reduced pressure with addition of 1000 ppm of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 500 ppm of hydroquinone monomethyl ether and 20 ppm of 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (rad.).

(33) TABLE-US-00007 Bath Bottom Top Pressure [° C.] [° C.] [° C.] mbar Comment Mass 24 24 24 3.8 start of heating 83 64.7 53 2.1 1st fraction 62.9 g 85 70.5 64 1.8 2nd fraction 35.3 g 90 72.3 69.0 1.7 3rd fraction 45.0 g 92 75.2 71 1.6 4th fraction 19.7 g 103 84.3 70 1.6 Thermometer no longer immersed 111 96.9 50 1.6 end 13.5 g

(34) Analyses:

(35) (GC: DB5, 30 m, Ø 0.25 mm, film thickness 0.25 μm, 50° C., 3 min isothermal, 14° C./min.fwdarw.280° C., 8 min isothermal; det: 280° C., inj.: 250° C.)

(36) TABLE-US-00008 Name Methyl- Methacrylic N-Methylmeth- Methacrylic Ret. [min] MTBE amine acid acrylamide anhydride HB 1 Probe: 1.33 1.08 3.83 5.97 min 7.43 min 13.15 Rct: 1.5 h * 3.38 2.96 89.70 2.18 Rct: 3 h * 14.82 16.23 59.33 4.19 Rct: 5 h * 37.09 45.68 9.53 3.59 Rct: 5.5 h * 40.80 51.43 0.05 3.05 RE distillate 98.63 1.27 0.11 RE residue 0.06 39.95 53.65 0.01 3.87 Dist. 1st fr. 0.02 0.02 85.52 14.26 0.01 0.02 Dist. 2nd fr. 0.04 37.91 61.80 0.10 Dist. 3rd fr. 0.03 0.05 10.45 88.92 0.29 Dist. 4th fr. 0.05 1.67 96.71 0.93 * not included in integration

(37) Yield Via GC Analyses:

(38) 89.9 g of N-methylmethacrylamide=90.7% of theory

COMPARATIVE EXAMPLE 1: PREPARATION OF N-METHYLMETHACRYLAMIDE IN EXCESS METHYLAMINE GAS

(39) Apparatus:

(40) 1 l four-neck round-bottom flask with precision glass stirrer (Teflon sleeve), Pt100 temperature sensor, gas feed of Teflon with wash bottles as safety bottles, gas inlet (Teflon), reflux condenser, steel methylamine gas bottle, waste air conduit directly into the fume hood, feed for compressed air as added air, acetone/dry ice cooling bath

(41) Mixture:

(42) 1.0 mol methacrylic anhydride=156.4 g

(43) 250 ml methyl tert-butyl ether

(44) ˜2 mol methylamine, gas

(45) Theoretical N-methylmethacrylamide yield: 99.1 g

(46) Procedure:

(47) Methacrylic anhydride and MTBE are initially charged, and methylamine gas is introduced with vigorous stirring. The conversion is monitored by GC. If no methacrylic anhydride is detectable any longer, methylamine is nevertheless introduced further, since an exothermic reaction is still taking place. As soon as this becomes weaker, the introduction is ended. After the stirring has been stopped, 2 phases form. The MTBE is drawn off on a rotary evaporator at bath temperature 60° C. and a pressure down to 200 mbar.

(48) Distillate to 200 mbar: 177.1 g

(49) Residue to 200 mbar: 215.0 g

(50) TABLE-US-00009 N- MTBE Methyl- Methacrylic Methylmeth- Methacrylic 1.328 amine acid acrylamide anhydride min 1.08 min 3.83 min 5.97 min 7.43 min 1 h 5 min * 10.35 11.15 73.14 2 h 15 min * 20.19 23.34 49.91 3 h 15 min * 27.59 32.88 32.24 4 h 15 min * 1.70 40.17 51.52 — 5 h 15 min * 5.98 37.83 46.93 — Lower phase * 8.67 35.92 45.36 Upper phase * 10.55 11.36 68.47 Distillate to 200 mbar 98.01 1.99 Residue to 200 mbar 7.36 36.33 46.47 Distillation of 1st fraction 2.42 34.07 63.32 * not included

(51) 180 g of the rotary evaporator residue is distilled through a 15 cm Vigreux column under reduced pressure with addition of 1000 ppm of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 500 ppm of hydroquinone monomethyl ether and 20 ppm of 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (rad.).

(52) Owing to the breakdown of methylammonium methacrylate, the pressure can no longer be maintained from a bottom temperature of 40° C. From a bottom temperature of 90° C., mist forms in the receiver and the apparatus. This is a clear sign of the reaction of an amine with acid. Immediately after a distillate has been obtained, a solid forms in the bottom and the mixture polymerizes completely within 10 min.

(53) TABLE-US-00010 Bath Bottom Top Pressure Time ° C. ° C. ° C. mbar Comment 10:24 25 25 25 1.6 start of heating 10:37 81 60.5 27 7.4 10:58 117 92.2 45 13.1 10:59 121 94.7 59 13.0 mist in receiver 11:01 121 97.5 80 13 1st fraction, lumps in the liquid phase 11:03 123 95.6 71 4.1 11:10 129 89.7 68 2.5 stopped, bottoms polymeric

(54) Yield: Fraction 1: 16.2 g

COMPARATIVE EXAMPLE 2: PREPARATION OF N-METHYLMETHACRYLAMIDE FROM AQUEOUS METHYLAMINE

(55) Apparatus:

(56) 2 l four-neck round-bottom flask with precision glass sabre stirrer, 500 ml dropping funnel, Pt-100 liquid phase thermometer, reflux condenser, cooling bath

(57) Mixture:

(58) TABLE-US-00011 6.15 mol methacrylic anhydride = 961.5 g 6.15 mol methylamine, 40% in H.sub.2O = 477.4 g

(59) Theoretical Yield:

(60) 609.65 g

(61) Procedure:

(62) Methacrylic anhydride is initially charged and cooled to below 10° C. while stirring. Then the metered addition of methylamine is commenced (exothermic reaction, ice bath cooling and slight mist formation). Dropwise addition and cooling are effected such that the temperature does not rise above 10° C. After dropwise addition has ended (4 h), stirring is continued for another 2 h for further reaction; the cooling is removed.

(63) Workup:

(64) The mixture (1419 g) is concentrated on a rotary evaporator with addition of 1000 ppm of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 500 ppm of hydroquinone monomethyl ether and 20 ppm of 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (rad.).

(65) TABLE-US-00012 Residue in the flask: 229.7 g Distillate to 35 mbar, bath 80° C. 340.8 g Distillate to 5 mbar, bath 80° C. 273.4 g Distillate to 0 mbar, bath 80° C.-95° C. 531.6 g

(66) GC analysis: (DB5, 30 m, Ø 0.25 mm, film thickness 0.25 μm, 50° C., 3 min isothermal, 14° C./min.fwdarw.280° C., 8 min isothermal; det: 280° C., inj.: 250° C.)

(67) TABLE-US-00013 N-Methyl- Methacrylic methacryl acid amide Mass of [GC [GC HB1r product Water content area %] area %] [GC area %] isolated Mass [g] 4.73 min 5.986 min 13.174 min [g] Distillate to 340.8 180 92.93 6.83 11.0 35 mbar Distillate to 5 273.4 83 81.02 18.74 0.03 35.7 mbar Distillate to 1 531.6 20 27.36 71.06 0.84 363.5 mbar TOTAL 410.2

(68) Without neutralization of the aqueous phase, after simple distillation, it is possible to isolate 410.2 g (67.3% of theory) of the product as a mixture with water and methacrylic acid, leaving around 230 g of solids. The distillates to 5 mbar and to 1 mbar (805 g, with 399 g of product) are fractionally distilled in Comparative Example 3.

COMPARATIVE EXAMPLE 3: DISTILLATION OF N-METHYLMETHACRYLAMIDE FROM AQUEOUS METHACRYLIC ACID

(69) Apparatus: 1 l three-neck round-bottom flask, boiling capillary, 30 cm mirrored column with 6×6 Raschig rings, Liebig condenser, Claisen attachment, Thiele-Anschutz attachment, receiver, oil bath, vacuum pump

(70) Mixture:

(71) TABLE-US-00014 805 g distillate from Comparative Example 2 66.5 mg hydroquinone monomethyl ether (100 ppm) 665 mg octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (1000 ppm) 33.3 mg 2,4-dimethyl-6-tert-butylphenol (50 ppm)

(72) Procedure:

(73) TABLE-US-00015 Bath Bottom Top Pressure Time ° C. ° C. ° C. mbar Comment 00:00 20 12.0 20 0.52 start of heating 00:10 98 40.7 27 0.56 1st fraction 00:14 97 50.3 30 0.72 00:19 93 60.8 32 2.0 solids content in liquid phase 00:25 96 68.4 52 1.1 00:52 96 69.1 42 0.35 01:22 112 72.3 37 0.20 2nd fraction, a lot of solids in liquid phase 01:36 113 73.4 38 0.21 significant bumping in the liquid phase, stopped

(74) TABLE-US-00016 1st fraction 156.3 g 2nd fraction 48.5 g (cloudy distillate, “mini-lumps”)

(75) The liquid phase is filtered through a porcelain suction filter. Filtrate.fwdarw.292.5 g.fwdarw.GC

(76) A sample of the filtercake is dissolved in MeOH.fwdarw.307 g.fwdarw.polymer.

(77) GC analysis: (Meth. F241, DB5, 30 m, Ø 0.25 mm, film thickness 0.25 μm, 50° C., 3 min isothermal, 14° C./min.fwdarw.280° C., 8 min isothermal; det: 280° C., inj.: 250° C.)

(78) TABLE-US-00017 N-Methyl- Methacrylic acid methacrylamide HB1 Water content [GC area %] [GC area %] [GC area %] Mass [g] 4.73 min 5.986 min 13.174 min 1st fraction 156.3 103 99.887 0.083 2nd fraction 48.5 — 99.616 0.320 Liquid phase 292.5 — 64.559 35.100 0.049 filtrate

(79) While it was possible to very substantially isolate water and methacrylic acid, the product prepared with aqueous methylamine polymerizes, and so only around 25% N-methylmethacrylamide was present after distillation for 90 min.

COMPARATIVE EXAMPLE 4: PREPARATION OF N-METHYLMETHACRYLAMIDE FROM AQUEOUS METHYLAMINE, WORKUP BY EXTRACTION

(80) Apparatus: analogous to Comparative Example 2

(81) Mixture:

(82) TABLE-US-00018 2.5 mol F49 (18770-45, 96.61%; 1000 ppm S49) = 398.9 g 2.5 mol N-methylamine, 40% in H.sub.2O = 194.1 g 2.5 mol ammonia, 25% = 170 g

(83) Theoretical Yield: 247.8 g

(84) Procedure: Preparation of the Crude Product Analogous to Comparative Example 2

(85) The crude product is neutralized with NH.sub.3 solution, with partial cooling. There was no phase separation.

(86) The mixture is then extracted with MTBE (by GC only methacrylic acid present). This is followed by extraction 3× with 300 ml each time of methyl methacrylate (MMA) and then again 3× with 200 ml each time of MMA (4% product is still present in the last extract). The combined MMA phases are concentrated on a rotary evaporator under reduced pressure (bath temperature 60° C.), with entrainment of H.sub.2O still present.

(87) Yield: 115.8 g

(88) GC analysis: 20.4% methacrylic acid, 69.28% N-methylmethacrylamide

(89) The water/methacrylic acid and N-methylmethacrylamide systems are very similar to one another. Extraction can enable removal of the product only with great effort and poor yield.

COMPARATIVE EXAMPLE 5: PREPARATION OF N-METHYLMETHACRYLAMIDE BY AQUEOUS METHYLAMINE AND NEUTRALIZATION OF THE RESIDUE WITH KOH

(90) Apparatus: 2 l four-neck round-bottom flask with precision glass sabre stirrer, 500 ml dropping funnel, Pt-100 liquid phase thermometer, reflux condenser, ice bath

(91) Mixture:

(92) TABLE-US-00019 6.0 mol methacrylic anhydride = 938.1 g 6.0 mol methylamine, 40% in H.sub.2O = 465.9 g*

(93) Theoretical Yield: 594.8 g

(94) Procedure: Methacrylic anhydride is initially charged and cooled to below 10° C. Then the metered addition of methylamine is started (exothermic reaction, cooling with ice/H.sub.2O, slight mist formation). Dropwise addition and cooling are effected such that the temperature does not rise above 10° C.

(95) After dropwise addition has ended, the mixture is stirred for a further 2 h for further reaction. The cooling is removed.

(96) After storage overnight (mixture becomes pale yellow), the mixture is transferred to a 4 l flask and neutralized with 5.9 mol of KOH (50% in H.sub.2O, addition via dropping funnel, cooling with H.sub.2O bath, addition of 2 drops of phenolphthalein solution).fwdarw.pH 6.5.

(97) The precipitated solids are then filtered off with suction using a porcelain suction filter, and the filtrate is concentrated on a rotary evaporator under reduced pressure (bath up to 80° C., for pressure see below) with addition of 1000 ppm of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 500 ppm of hydroquinone monomethyl ether and 20 ppm of 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl (rad.) (based on theoretical yield of N-methylmethacrylamide).

(98) TABLE-US-00020 Residue on the suction filter 77.5 g (b) Residue in the flask 1026.2 g  (a)

(99) GC analysis: (DB5, 30 m, Ø 0.25 mm, film thickness 0.25 μm, 50° C., 3 min isothermal, 14° C./min.fwdarw.280° C., 8 min isothermal; det: 280° C., inj.: 250° C.)

(100) TABLE-US-00021 N-Methyl- methacryl Methacrylic amide HB1 acid [GC [GC Proportion Mass of LB [GC area %] area %] of product product Mass 1.09-1.20 area %] 5.986 13.174 in fraction isolated [g] min 4.73 min min min [% by wt.] [g] Dist. to 316.4 1.081 6.121 89.158 1.113 7.0 22.15 60 mbar Dist. to 1 163.8 1.110 8.088 90.161 0.090 94.5 154.05 mbar LB = low boilers

(101) To ascertain the mass of the product in the fraction, an exactly defined amount of dimethylaminopropylmethacrylamide is added and the exact mass is determined via the comparison of the integrals.

(102) On neutralization of the aqueous phase with KOH, after distillation, it is possible to isolate only 144.9 g (29.6% of theory) of the product as a dilute aqueous solution.

COMPARATIVE EXAMPLE 6: PREPARATION OF N-METHYLMETHACRYLAMIDE BY AQUEOUS METHYLAMINE AND NEUTRALIZATION OF THE RESIDUE WITH NAOH

(103) Apparatus: 2 l four-neck round-bottom flask with precision glass sabre stirrer, 500 ml dropping funnel, Pt-100 liquid phase thermometer, reflux condenser, cooling bath

(104) Mixture: 6.0 mol methacrylic anhydride=938.1 g 6.0 mol methylamine, 40% in H.sub.2O=465.9 g*

(105) Theoretical Yield: 594.8 g

(106) Procedure: Methacrylic anhydride is initially charged and cooled to below 10° C. Then the metered addition of methylamine is started (exothermic reaction, cooling with ice/H.sub.2O, slight mist formation). Dropwise addition and cooling are effected such that the temperature does not rise above 10° C. After dropwise addition has ended, stirring is continued for another 2 h for further reaction; the cooling is removed.

(107) Subsequently, the mixture is transferred to a 4 l flask and neutralized with 5.9 mol of 50% NaOH in H.sub.2O (236 g of NaOH, 236 g of H.sub.2O*) by addition via dropping funnel while cooling with an H.sub.2O bath and addition of 2 drops of phenolphthalein solution up to pH 6.5-pH 7.0.

(108) The precipitated solids are filtered off using a porcelain suction filter.fwdarw.very poor filtration since the solid is waxy.

(109) Filtrate: 1634 g

(110) For analysis, in a GC vial, 1.5 g of filtrate are admixed with an internal standard and this is used to determine the content of N-methylmethacrylamide:

(111) Calculated product content by GC analysis: 36.4%˜99.9% of theory.

(112) The filtrate is concentrated on a rotary evaporator under reduced pressure (1). The condensate condensed (frozen) on the condenser is thawed out overnight and, the next day, the residue flask is concentrated once again to dryness at bath temperature 80° C. and 1 mbar (2). In the course of this, significant amounts of solids precipitate out. The distillates obtained are analysed by means of GC.

(113) GC: (DB5, 30 m, Ø 0.25 mm, film thickness 0.25 μm, 50° C., 3 min isothermal, 14° C./min.fwdarw.280° C., 8 min isothermal; det: 280° C., inj.: 250° C.)

(114) TABLE-US-00022 Product content by GC (as described in Product Sample Mass [g] CE5) [% by wt.] mass [g] Filtrate 1634 36.4 594.8 Distillate to 60 172.2 14.0 24.1 mbar Distillate flask 7.5 79.3 6.0 thawed out from 230.6 23.1 53.3 the condenser (1) thawed out from 129.2 47.7 61.6 the condenser (2) Total distillates 539.5 144.9

(115) On neutralization of the aqueous phase with NaOH, after distillation, it is possible to isolate only 144.9 g (24.4% of theory) of the product as a dilute aqueous solution.