JPH08176082A - Production of high-purity n-alkoxymethyl (meth) acrylamide - Google Patents

Abstract

PURPOSE: To obtain the subject compound with low polymer content, useful for e.g. resin modification, by reaction of N-methylol (meth)acrylamide with an alcohol in the presence of an acid catalyst followed by washing the resultant reaction liquor with hot water to adjust the pH level of the reaction liquor and then concentration at reduced pressures. CONSTITUTION: (A) An N-methylol (meth)acrylamide of formula CH2 =C(R1 ) CONHCH2 OH (R1 is H or methyl) or a reaction liquor containing the same is reacted with (B) an alcohol of formula R2 OH (R2 is n-butyl, isobutyl, see-butyl or t-butyl) in the presence of an acid catalyst followed by washing the resultant reaction liquor with hot water at 40-80 deg.C and then concentration under reduced pressures under aeration at >=pH5 but <pH8, thus affording (C) the objective N-alkoxymethyl (meth)acrylamide of formula CH2 =C(R1 )CONHCH2 OR2 in high purity. Preferably, the pH level of the reaction liquor before pH adjustment is 2-5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to N-alkoxymethyl acrylamide or N-alkoxymethyl methacrylamide (hereinafter simply referred to as N-alkoxymethyl) which is used as a crosslinkable monomer in the fields of paints, inks, resins and the like. (Meth) acrylamide).

[0002]

2. Description of the Related Art N-Alkoxymethyl (meth) acrylamide is a methylol derivative prepared by reacting acrylamide or methacrylamide (hereinafter simply referred to as (meth) acrylamide) with formaldehyde, and then reacting with alcohol under an acid catalyst. A method of reacting and producing is known (Japanese Patent Publication No. 38-23607). However, since (meth) acrylamide and its derivatives are polyfunctional in nature, they may contain by-products in a considerable concentration depending on the operation in the manufacturing process, and such N-alkoxymethyl (meth) acrylamide may be contained. May cause practical difficulties when mixed with other monomers or solvents. For example, N-butoxymethylacrylamide produced by using a small excess of butyl alcohol produces a relatively large amount of methylenebisacrylamide as a by-product, and solids may precipitate during the concentration and storage of the product. This precipitated solid is insoluble in methyl methacrylate and various organic solvents, which is an obstacle to operation. On the other hand, it is not economically preferable to produce N-butoxymethylacrylamide using a large excess of butyl alcohol, which is not economically preferable. It is difficult to avoid the by-product of. As a general purification method for these crude N-alkoxymethyl (meth) acrylamides, only a method such as flash distillation, which is extremely economically disadvantageous, and which further increases the by-product content in the purification process is known. Not not.

[0003]

The object of the present invention is to remedy the drawbacks of the prior art, without the need for purification operations.
An object of the present invention is to provide a method for economically producing high-purity N-alkoxymethyl (meth) acrylamide. As a result of earnest studies 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 are reacted under an acid catalyst, and the reaction solution is washed with warm water of 40 to 80 ° C.
Further, they have found that high-purity N-alkoxymethyl (meth) acrylamide can be obtained by adjusting PH to a range of 5 or more and less than 8 and then concentrating it under reduced pressure while blowing air into the present invention.

[0004]

That is, the present invention relates to the general formula (I) CH ₂ ═C (R ₁ ) CONHCH ₂ OR ₂ (I) (wherein R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a normal butyl group, an isobutyl group, a secondary butyl group or a tert-butyl group) in the method for producing N-alkoxymethylacrylamide or N-alkoxymethylmethacrylamide, represented by the general formula (II) CH ₂ ═C (R ₁ ) CONHCH ₂ OH (II) (wherein R ₁ represents a hydrogen atom or a methyl group), or contains N-methylol acrylamide or N-methylol methacrylamide. The reaction solution and the general formula (III) R ₂ OH (III) (wherein R ₂ is a normal butyl group, an isobutyl group, a secondary butyl group or (Shows a Shari-butyl group)
After reacting the alcohol represented by the formula (1) with an acid catalyst, the reaction solution is washed with warm water of 40 to 80 ° C. and the pH is 5 or more and 8 or more.
The present invention relates to a method for producing high-purity N-alkoxymethyl acrylamide or N-alkoxymethyl methacrylamide, which comprises concentrating under reduced pressure while blowing air in a range of less than.

The present invention will be described in detail below. The N-methylol (meth) acrylamide represented by the general formula (II) used in the present invention may be itself or may be one produced by a methylolation reaction with (meth) acrylamide and formaldehyde. The methylolation reaction conditions in the latter case are not particularly limited, but an example of preferable reaction conditions is described in R.M. Dowbenko, R .; M.
Christenson, A .; N. Salem, J.M. O
rg. Chem. , 28, 3458 (1963).

In the etherification reaction, the molar ratio of alcohol to N-methylol (meth) acrylamide is 1 or more, preferably 1 to 5, more preferably 1.2 to.
It is preferable to use it in the range of 2.5. If the molar ratio is less than 1, by-products are likely to occur, and if it exceeds 5, a large amount of alcohol is used, which is not preferable from the economical point of view. In particular, it is unexpected that the method of the present invention gives good results at a molar ratio of 1.5 to 2.5, which is a condition range in which the amount of alcohol is small and is usually not preferable in the prior art. Therefore, it can be said that the manufacturing method is more effective than the conventional method. General formula (III) used in the etherification reaction
Examples of the alcohol represented by include normal butyl alcohol, isobutyl alcohol, secondary butyl alcohol, and tertiary butyl alcohol.

Examples of the acid catalyst used in the reaction include inorganic acids such as sulfuric acid, phosphoric acid and hydrochloric acid, oxalic acid, malonic acid,
Any of organic acids such as succinic acid, fumaric acid, maleic acid, and paratoluenesulfonic acid may be used. The pH of the reaction solution is preferably in the range of 2-5.

Etherification is usually carried out under reflux heating.
Since this reaction is an equilibrium reaction involving dehydration, the reflux condensate can be layer-separated, only the alcohol layer is returned into the system, and the aqueous layer can be taken out of the system to further improve the reaction yield. The reaction time is usually 2 to 8 hours.

After the reaction, the reaction solution is cooled, and if necessary, alkali is added to adjust the pH to near neutral. Next 40 ~
Wash thoroughly with warm water at 80 ° C. Washing with warm water is performed 3 times or more, preferably 5 to 8 times. As a result, not only the unreacted raw materials, by-products methylenebis (meth) acrylamide, di (meth) acrylamide methyl ether, and a part of the polymer, which could not be easily removed by the conventional method, can be effectively removed. In terms of reduction in viscosity and easy separation from the aqueous layer, there are great operational advantages, and the purity of the product can be easily improved. In washing with warm water, the amount of waste water can be reduced by using the washing separation water in the latter stage as the washing water in the former stage next time. Further, the washing operation may be carried out in a countercurrent continuous type.

After washing with water, it is confirmed or adjusted that the pH of the liquid is in the range of 5 to less than 8, preferably PH of 5.5 to 7.0. Concentration is performed at a temperature as low as possible while blowing air under reduced pressure. The amount of air blown is 10 to 4000 Nm per mol of N-methylol (meth) acrylamide
It may be appropriately selected within a range of 1 / hr, preferably 15 to 2000 Nml / hr. In order to suppress side reactions during concentration and obtain a high-purity product, it is important that the pH of the liquid being blown in the air is kept within the above range. The temperature at the time of concentration is 50 to 130 ° C., preferably 55 to 12
It is preferable to perform it in the range of 0 ° C. Further, when a polymerization inhibitor such as hydroquinone monomethyl ether or hydroquinone is used in combination, the effect can be obtained more stably, but the use of the polymerization inhibitor alone is not sufficient.

The N-alkoxy (meth) thus obtained
Acrylamide is of high purity and can be used as it is for other purposes such as general resin production.

[0012]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

Example 1 In a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser with a water separator, 220% (6.30 mol) of 86% paraformaldehyde, 450 g (6.33 mol) of acrylamide, 280 g of normal butyl alcohol ( 3.78 mol), hydroquinone monomethyl ether 1.5 g and triethylamine 3.8 g
(0.038 mol), and heated at 60 ° C for 3 hours to the reaction solution containing N-methylolacrylamide, 490 g (6.62 mol) of normal butyl alcohol was added, and about oxalic acid was added.
After adjusting the pH to 3.21 by adding 7 g, 350-400 m
The mixture was heated under reflux at 100 to 110 ° C under reduced pressure of mHg. The distillate separated the aqueous layer and returned only the butyl alcohol layer to the system. After 5 hours, the reflux was stopped and 205 g of a distillate containing normal butyl alcohol as a main component was recovered. Next, the reaction solution was adjusted to pH 6.5 with sodium hydroxide, washed 6 times with 300 ml of warm water at 50 to 60 ° C., and then 100 to 150 at pH 6.4.
It is concentrated under a reduced pressure of mmHg at about 90 ° C and at a rate of about 10 Nl / hr while blowing air to collect 210 g of a distillate containing n-butyl alcohol as a main component and a purity of 99.1%.
810 g of N-normal butoxymethyl acrylamide were obtained. This was a colorless and transparent liquid, and did not cause cloudiness even when mixed with methyl methacrylate or various organic solvents.

COMPARATIVE EXAMPLE 1 The procedure of Example 1 was repeated except that the pH of the reaction solution at the time of concentration was 3.0 instead of 6.4, and the crystallinity was about 5% during concentration. A precipitate formed, which was insoluble in methyl methacrylate, acetone or benzene.

Comparative Example 2 In the concentration step of Comparative Example 1, without blowing air,
When the operation was simply carried out under reduced pressure, the amount of crystalline precipitate increased by about 5 times.

Example 2 In a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser with a water separator, 51.2 g of 88% paraformaldehyde was added.
(1.50 mol), methacrylamide 133.2 g
(1.55 mol), normal butyl alcohol 121.
7 g (1.64 mol) and 0.9 g of hydroquinone monomethyl ether were added, and triethylamine about 1.5
115 g (1.55 mol) of normal butyl alcohol was added to a reaction solution containing N-methylolmethacrylamide which was adjusted to pH 9.9 with 3 g and heated at 60 to 61 ° C. for 3 hours, and oxalic acid of about 3. A pH of 3.
After adjusting to 2, the mixture was heated under reflux at 87 to 103 ° C. and around 310 mmHg. As for the distillate, the aqueous layer was separated and only the butyl alcohol layer was returned to the system. After 7 hours and 15 minutes, stop the reflux,
The reaction solution was adjusted to pH 6.3 with a 10% aqueous sodium hydroxide solution and washed 5 times with 300 ml of water at 60 to 70 ° C.
After that, 105 to 108 ° C., 320 to 110 mmHg,
After concentrating for 7 hours while blowing air at a rate of about 2.5 Nl / hr, 237.5 g of N-normal butoxymethylmethacrylamide having a purity of 96.1% was obtained. This was a colorless and transparent liquid, and did not cause cloudiness even when mixed with methyl methacrylate or various organic solvents.

Example 3 68.2 g of 88% paraformaldehyde was placed in a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser with a water separator.
(2.00 mol), methacrylamide 170.2 g
(2.00 mol), isobutyl alcohol 85.1 g
(1.15 mol), and 1.2 g of hydroquinone monomethyl ether were added, and N-methylol methacrylamide obtained by heating at 60 to 63 ° C. for 2 hours was prepared by adjusting pH to 10.4 with about 1.4 g of triethylamine. Isobutyl alcohol (148.2 g, 2.00 mol) was added to the reaction solution, and oxalic acid (about 2.6 g) was added to obtain PH3.
After adjusting to 2, the mixture was heated under reflux at 87 to 99 ° C. and around 310 mmHg. In the distillate, the aqueous layer was separated and only the isobutyl alcohol layer was returned to the system. After 7 hours, the reflux was stopped, the reaction solution was adjusted to pH 6.3 with a 10% aqueous sodium hydroxide solution, and washed 5 times with 300 ml of water at 60 to 70 ° C. After that, 90 ~ 80 ℃, 300 ~ 100mmHg, about 3Nl
Concentrate for 6 hours while blowing air at a speed of / hr,
297.5 g of N-isobutoxymethylmethacrylamide having a purity of 95.2% was obtained. This was a colorless and transparent liquid, and did not cause cloudiness even when mixed with methyl methacrylate or various organic solvents.

[0018]

According to the method of the present invention, high-purity N-alkoxymethyl (meth) acrylamide can be produced in high yield without using a large excess of alcohol.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeki Suzuki Inventor Joban Sekifunacho, Iwaki, Fukushima 2 Miyanoshita No. 2 Nitto RIKEN CORPORATION (72) Inventor Kazushi Otsuka 1-5-1, Marunouchi, Chiyoda-ku, Tokyo Issue Nitto Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A compound represented by the general formula (I) CH ₂ ═C (R ₁ ) CONHCH ₂ OR ₂ (I) (wherein R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a normal butyl group, an isobutyl group, In the method for producing N-alkoxymethylacrylamide or N-alkoxymethylmethacrylamide represented by a secondary butyl group or a tertiary butyl group), a compound represented by the general formula (II) CH ₂ ═C (R ₁ ) CONHCH ₂ OH ( II) N-methylol acrylamide or N-methylol methacrylamide 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 normal butyl group, an isobutyl group, a secondary butyl group or a tertiary butyl group)
After reacting the alcohol represented by the formula (1) with an acid catalyst, the reaction solution is washed with warm water of 40 to 80 ° C. and concentrated under reduced pressure while blowing air in the range of PH5 or higher and lower than 8. A method for producing high-purity N-alkoxymethyl acrylamide or N-alkoxymethyl methacrylamide.