JP3945833B2 - Method for producing N-alkoxymethyl (meth) acrylamide - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to N-alkoxymethyl acrylamide or N-alkoxymethyl methacrylamide (hereinafter simply referred to as N-alkoxymethyl (meth) acrylamide) which is used as a crosslinkable monomer in the fields of paints, inks, resins and the like. It relates to a manufacturing method.
[0002]
[Prior art]
N-alkoxymethyl (meth) acrylamide is produced by reacting acrylamide or methacrylamide (hereinafter simply referred to as (meth) acrylamide) with formaldehyde to form a methylol derivative, and then reacting with alcohol under an acid catalyst. A method is known (Japanese Patent Publication No. 38-23607).
However, since (meth) acrylamide and its derivatives are inherently polymerizable, N-alkoxymethyl (meth) acrylamide containing a polymer at a considerable concentration may be obtained depending on the operation during the production process. When mixed with the above, it may become practically difficult due to white turbidity or aggregation. For example, when methyl methacrylate 3 is mixed with N-methoxymethylacrylamide 1 containing a polymer, white turbidity is generated and a polymer is precipitated. Therefore, such N-alkoxymethyl (meth) acrylamide is difficult to use for resin production. It is. On the other hand, as a general purification method of crude N-alkoxymethyl (meth) acrylamide, only a method such as flash distillation which is extremely disadvantageous economically and further increases the polymer content in the purification process is known. Absent.
[0003]
[Problems to be solved by the invention]
The object of the present invention is to improve the disadvantages of the prior art and to contain the polymer so as not to cause precipitation, white turbidity, or aggregation when used as a modifying component for resins, paints, etc. without performing a purification operation. An object of the present invention is to provide a method for economically producing low-concentration N-alkoxymethyl (meth) acrylamide.
As a result of diligent research to achieve the above object, the present inventors have found that N-methylol acrylamide or N-methylol methacrylamide (hereinafter simply referred to as N-methylol (meth) acrylamide) and alcohol in the presence of an acid catalyst and air. After reacting while blowing, the pH of the reaction solution was adjusted to 5 or more and less than 8, and it was found that N-alkoxymethyl (meth) acrylamide having a low content of polymer was obtained by concentrating under reduced pressure while blowing air. The present invention has been reached.
[0004]
[Means for solving problems]
That is, the present invention relates to the general formula (I)
CH ₂ = C (R ₁ ) CONHCH ₂ OR ₂ (I)
In the method for producing N-alkoxymethyl (meth) acrylamide represented by the formula (wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a lower alkyl group having 1 to 3 carbon atoms) (II)
CH ₂ ═C (R ₁ ) CONHCH ₂ OH (II)
N-methylol (meth) acrylamide represented by the formula (wherein R ₁ represents a hydrogen atom or a methyl group) or a reaction solution containing these and general formula (III)
R ₂ OH (III)
(In the formula, R ₂ represents a lower alkyl group having 1 to 3 carbon atoms) After reacting the alcohol represented by blowing air in the presence of an acid catalyst, the pH of the reaction solution is adjusted to 5 or more and less than 8. The present invention relates to a method for producing N-alkoxymethyl (meth) acrylamide, characterized by adjusting and concentrating under reduced pressure while blowing air.
[0005]
The N-methylol (meth) acrylamide represented by the general formula (II) used in the present invention may be itself, or may be a reaction solution produced by methylolation reaction with (meth) acrylamide and formaldehyde. In the latter case, the reaction conditions are not particularly limited as long as the reaction product liquid containing N-methylol (meth) acrylamide is obtained. An example of a preferred reaction condition is R.I. Dowbenko, R.A. M.M. Christenson, A.M. N. Salem, J .; Org. Chem. 28, 3458 (1963).
[0006]
In the etherification reaction, alcohol is used in a molar ratio with respect to N-methylol (meth) acrylamide of 1 or more, preferably 1.5 to 8, more preferably 2.2 to 6.5. When the molar ratio is less than 1, by-products are likely to be generated, and when it exceeds 8, a large amount of alcohol is used, which is not preferable from the viewpoint of economy. Examples of the alcohol represented by the general formula (III) used in the etherification reaction include alcohols having a lower alkyl group having 1 to 3 carbon atoms such as methyl alcohol, ethyl alcohol, normal propyl alcohol, and isopropyl alcohol.
[0007]
The acid catalyst used in the reaction may be any of inorganic acids such as sulfuric acid, phosphoric acid and hydrochloric acid, and organic acids such as oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid and paratoluenesulfonic acid. The reaction solution preferably has a pH in the range of 2-5.
[0008]
The etherification reaction is usually carried out under reflux heating. Since this reaction is an equilibrium reaction involving dehydration, when water is removed from the system as the solvent is distilled off, the remaining N-methylol (meth) acrylamide is converted to the desired N-alkoxymethyl (meth) acrylamide. Thus, the reaction yield can be further improved. Specifically, when the alcohol containing the reaction product water is distilled out of the system, the effect can be improved by replenishing the system with anhydrous alcohol or alcohol which has been fractionally distilled to be substantially anhydrous.
[0009]
After the reaction, the pH of the reaction solution is adjusted to 5 or more and less than 8, preferably 5.5 to 7, and concentrated. The temperature at the time of concentration is 50-100 degreeC, Preferably it is good to carry out in the range of 55-90 degreeC.
[0010]
In the above etherification reaction and concentration step, it is necessary to carry out while actively blowing air. Thereby, the byproduct of the polymer in the etherification reaction and the concentration step can be suppressed. The amount of air blown is in the range of 10 to 400 Nml / hr, preferably 15 to 200 Nml / hr per mole of N-methylol (meth) acrylamide in the etherification reaction, and 10 to 4000 Nml / hr in the concentration step, preferably 15 What is necessary is just to select suitably in the range of -2000Nml / hr. Further, when a conventionally known polymerization inhibitor such as hydroquinone monomethyl ether or hydroquinone is used in combination, a more stable result can be obtained, but the use of only the polymerization inhibitor alone is insufficient.
[0011]
The N-alkoxymethyl (meth) acrylamide thus obtained can be suitably used as it is for general resin production without causing cloudiness or precipitation even when methyl methacrylate or acetone is added.
[0012]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The polymer concentration in the product was evaluated by comparing the situation in which 3 times the amount of methyl methacrylate or 2 times the amount of acetone was added to cause white turbidity or precipitation. Under these conditions, N-alkoxymethyl (meth) acrylamide containing a polymer of 0.1% or more produces a precipitate depending on its content.
[0013]
Example 1
In a reaction vessel equipped with a stirrer, a thermometer, and a (reflux) condenser, 215 g (6.16 mol) of 86% paraformaldehyde, 400 g (5.63 mol) of acrylamide, 170 g (5.31 mol) of methyl alcohol, 1.74 g of hydroquinone monomethyl ether and 0.24 g of triethylamine were added, and 960 g (30 mol) of methyl alcohol was added to the reaction solution containing N-methylolacrylamide obtained by heating at 60 ° C. for 4 hours, and about 1 g of oxalic acid was added. After adjusting the pH to 3.2 by heating, the mixture was heated to reflux while blowing air at 60 to 70 ° C. at a rate of about 100 Nml / hr. After 5 hours, the reaction solution was adjusted to pH 6.3 with sodium hydroxide and concentrated under reduced pressure while blowing air at a rate of about 80 ° C. and about 7 Nl / hr to recover 930 g of distillate containing methyl alcohol as a main component. As a result, 608 g of N-methoxymethylacrylamide having a purity of 98.8% was obtained. When a part of the solution was taken and mixed with 3 times the amount of methyl methacrylate, a uniform transparent solution was obtained.
[0014]
Comparative Example 1
In Example 1, 1.3 g of hydroquinone monomethyl ether was used as a polymerization inhibitor instead of blowing air when the reaction solution containing N-methylolacrylamide and methyl alcohol were reacted with PH3.2 and concentrated under reduced pressure with PH6.3. A reaction was carried out in the same manner as in Example 1 except that 600 g of N-methoxymethylacrylamide was obtained. When a part of this was taken and mixed with 3 times the amount of methyl methacrylate, it became cloudy and the sediment concentration was 0.5%.
[0015]
Comparative Example 2
In Example 1, 1.3 g of hydroquinone was added as a polymerization inhibitor instead of blowing air when the reaction solution containing N-methylolacrylamide and methyl alcohol were reacted with PH3.2 and concentrated under reduced pressure with PH6.3. The reaction was carried out in the same manner as in Example 1 except that 606 g of N-methoxymethylacrylamide was obtained. When a part of this was taken and mixed with 3 times the amount of methyl methacrylate, it became cloudy and the sediment concentration was about 1%.
[0016]
Example 2
About 7 g of oxalic acid was added to a mixture of 1313 g (12.7 mol) of N-methylolacrylamide (manufactured by Soken Chemical Co., Ltd., purity 97.6%), 2798 g (52 mol) of 85.5% denatured ethanol and 3.9 g of hydroquinone monomethyl ether. In addition, the pH was adjusted to 2.6, and heating was performed for 3.5 hours while blowing air at a rate of about 600 Nml / hr at 85 to 87 ° C. The distillate was removed from the system, and a total of 596 g of denatured ethanol was added to the system instead. Thereafter, the reaction solution was adjusted to pH 6.3 with sodium hydroxide and concentrated under reduced pressure while blowing air at a rate of about 80 ° C. and about 20 Nl / hr to obtain 1562 g of N-ethoxymethylacrylamide having a purity of 97.6%. It was. When a part of this was taken and mixed with 3 times the amount of methyl methacrylate, a uniform transparent solution was obtained.
[0017]
Comparative Example 3
In Example 2, 1.3 g of hydroquinone monomethyl ether was used as a polymerization inhibitor instead of blowing air when the reaction solution containing N-methylolacrylamide and ethyl alcohol were reacted with PH 2.6 and concentrated under reduced pressure with PH 6.3. A reaction was carried out in the same manner as in Example 2 except that 1538 g of N-ethoxymethylacrylamide was obtained. When a part of this was taken and mixed with 3 times the amount of methyl methacrylate, it became cloudy and the precipitate content concentration was 0.8%.
[0018]
Example 3
To a reaction vessel equipped with a stirrer, a thermometer, and a (reflux) condenser, 102.3 g (3.0 mol) of 88% paraformaldehyde, 255.3 g (3.00 mol) of methacrylamide, 120 g of water and 0.9 g of hydroquinone monomethyl ether were added. A solution adjusted to pH 12.6 with sodium hydroxide was heated at 60 ° C. for 1 hour to obtain a reaction solution containing N-methylolmethacrylamide. To this was added 480 g (15.0 mol) of methyl alcohol, and the pH was adjusted to 3.2 by adding about 0.9 g of oxalic acid, followed by reflux heating while blowing air at a rate of about 50 Nml / hr at 70 ° C. After 3 hours, the heating was stopped, the reaction solution was adjusted to pH 5 with sodium hydroxide, concentrated while blowing air at 65 ° C. at a rate of about 5 Nl / hr, and 364.7 g of almost pure N-methoxymethylmethacrylamide was obtained. Obtained. When a part of the solution was mixed with 2 times the amount of acetone, no cloudiness or precipitation occurred, and a transparent homogeneous solution was obtained.
[0019]
Example 4
A reaction vessel equipped with a stirrer, a thermometer, and a condenser was charged with 303 g (3.0 mol) of N-methylolacrylamide, 450 g (7.5 mol) of normal propyl alcohol, and 0.9 g of hydroquinone monomethyl ether. What was adjusted to PH2,9 by adding an acid was heated while blowing air at 96-108 degreeC and the speed | rate of about 100 Nml / hr. The distillate was removed from the system, and new normal propanol commensurate with the amount of distillate was added to the system instead. After 8 hours, heating was stopped, the reaction solution was adjusted to pH 6.5 with sodium hydroxide, concentrated while blowing air at a rate of about 5 Nl / hr at 80 to 90 ° C., and N-normal having a purity of 97.6%. 414 g of propoxymethylacrylamide was obtained. When a part thereof was taken and mixed with 3 times the amount of methyl methacrylate, a uniform transparent solution was obtained, and even in a solution test with acetone, no cloudiness or precipitation occurred.
[0020]
Example 5
A reaction vessel equipped with a stirrer, a thermometer, and a (reflux) condenser was charged with 102 g (3.0 mol) of 88% paraformaldehyde, 213 g (3.0 mol) of acrylamide, and 180.7 g (3.0 mol) of isopropyl alcohol. ), 0.9 g of hydroquinone monomethyl ether and 1.8 g of triethylamine were added, and 270.5 g (4.5 mol) of isopropyl alcohol was added to the reaction solution containing N-methylolacrylamide obtained by heating at 58 to 61 ° C. for 4 hours. After adjusting the pH to 3.32 by adding about 3.7 g of oxalic acid, the mixture was heated to reflux while blowing air at a rate of about 80 Nml / hr at 86 to 89 ° C. After 16 hours, the reaction solution was adjusted to pH 6.3 with sodium hydroxide, concentrated under reduced pressure while blowing air at a speed of about 80 ° C. and about 5 Nl / hr, N-isopropoxymethylacrylamide having a purity of 95.2%, 389.8 g was obtained. When a part of this was taken and mixed with 3 times the amount of methyl methacrylate, a uniform transparent solution was obtained.
[0021]
Comparative Example 4
In Example 5, 1.3 g of hydroquinone monomethyl ether was used as a polymerization inhibitor instead of blowing air when the reaction solution containing N-methylolacrylamide was reacted with isopropyl alcohol at pH 3.32 and concentrated under reduced pressure at PH 6.3. Except for the addition, 382 g of N-isopropoxymethylacrylamide was obtained in the same manner as in Example 5. When a part of this was taken and mixed with 3 times the amount of methyl methacrylate, it became cloudy, and the concentration of precipitated matter was 0.5%.
[0022]
【The invention's effect】
According to the method of the present invention, polymer by-product can be effectively suppressed, and N-alkoxymethyl (meth) acrylamide useful for applications such as resin modification can be produced effectively.

Claims (1)

Formula (I)
CH ₂ = C (R ₁ ) CONHCH ₂ OR ₂ (I)
(Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a lower alkyl group having 1 to 3 carbon atoms), and a method for producing N-alkoxymethyl acrylamide or N-alkoxymethyl methacrylamide represented by In general formula (II)
CH ₂ ═C (R ₁ ) CONHCH ₂ OH (II)
N-methylolacrylamide or N-methylolmethacrylamide represented by the formula (wherein R ₁ represents a hydrogen atom or a methyl group), or a reaction solution containing any of these and the general formula (III)
R ₂ OH (III)
(In the formula, R ₂ represents a lower alkyl group having 1 to 3 carbon atoms) After reacting the alcohol represented by blowing air in the presence of an acid catalyst, the pH of the reaction solution is 5 or more and less than 8. A process for producing N-alkoxymethylacrylamide or N-alkoxymethylmethacrylamide characterized by adjusting and concentrating under reduced pressure while blowing air.