JP5649049B2 - Process for producing hydroxyalkyl (meth) acrylamide - Google Patents

Description

The present invention is a water-based paint, UV paint, polymer modifier, adhesive, and the like, alone or copolymerized with other polymerizable monomers, and has a hydrophilic property and is soluble in water or an organic solvent. The present invention relates to an industrially advantageous process for producing hydroxyalkyl (meth) acrylamides used for dispersants, thickeners, paper strength enhancers, contact lenses, biological gels, and the like.

Since the method of producing (meth) acrylamides by reacting (meth) acrylic acid esters with amines can use inexpensive raw materials, several methods for producing N-substituted (meth) acrylamides are known. In this case, since the double bond of (meth) acrylic acid ester is extremely reactive, amine, cyclopentadiene (hereinafter abbreviated as CPD), alcohol or the like is added to the double bond as a protective group in advance, In general, after completion of the amidation, the desired product is produced by removing the protecting group by heating. Further, as a method for industrial production of hydroxyethylacrylamide, for example, protection by CPD shown in Patent Document 1, Patent Document 2 and the like is known. However, since this process is complicated, it has disadvantages such as high production cost when manufacturing with a large facility, and it is difficult to say that it is an industrially advantageous process.

For example, in Patent Document 3, an amine is used as a protecting group, and an acrylate ester is reacted with one mono- or dialkylamine to convert it to N-alkyl-β-alkylaminopropionic acid amide, which is then converted into N-alkyl-β-alkylaminopropionic acid amide. A method for producing N-alkylacrylamide by thermal decomposition in the presence of an acid is disclosed in Patent Document 4 in that N-dimethylamino-β-dimethylaminopropionic acid amide is thermally decomposed in a liquid phase to obtain dimethyl in a high yield. A method for producing acrylamide, and Patent Document 5 discloses a method for producing N-monosubstituted-acrylamides in high yield without any side reaction by combining two kinds of amines. Patent Document 6 discloses a method of increasing the reaction rate by adding an alcohol when an acrylate ester and a secondary amine are reacted to convert into a β-dialkylaminopropionate ester.

JP 2005-263714 A JP 2005-314279 A US Patent 2,451,436 Japanese Patent Laid-Open No. 4-154549 JP-A-6-199752 Japanese Patent Laid-Open No. 5-23928

In the production of N-substituted- (meth) acrylamide using (meth) acrylic acid ester as a starting material, the method using amine as a protecting group is liquid phase and at a relatively low temperature compared to the method using cyclopentadiene or alcohol. It can be said that it is an industrially superior method because it can be thermally decomposed. The method of producing N-mono-substituted- (meth) acrylamide by combining two kinds of amines is the reaction of (meth) acrylic acid ester with dialkylamine having a lower alkyl group having 1 to 3 carbon atoms to produce β-dialkylamino. (Methyl) propionic acid ester (hereinafter referred to as ester adduct), and in the presence of a strongly basic catalyst, from this primary amine to N-monosubstituted-β-dialkylamino (methyl) propionic acid amide (hereinafter referred to as amide adduct) Then, N-monosubstituted- (meth) acrylamide is produced by neutralization and thermal decomposition. However, in the production of hydroxyalkyl (meth) acrylamide, when the dialkylamine used for protecting the double bond of (meth) acrylic acid ester is a lower alkyl group, sulfuric acid is used to obtain a sufficient thermal decomposition reaction rate. It is necessary to use an acidic catalyst represented by the above. However, when pyrolysis of hydroxyalkyl (meth) acrylamide is carried out in the presence of an acidic catalyst, there is a problem that a pyrolysis reaction over a long period of time is difficult due to replication of impurities due to side reactions such as dehydration condensation.

As a result of intensive studies to solve such drawbacks, the present inventors have used dibutylamine as a dialkylamine used for protecting a double bond of (meth) acrylic acid ester in the process of producing an ester adduct. It has been found that the resulting amide adduct can be stably thermally decomposed without using an acid catalyst, and the present invention has been completed.

For more information,
Reacting methyl (meth) acrylate with a dialkylamine in order to protect the double bond, wherein R ₁ represents a hydrogen atom or a methyl group, and R ₃ represents an alkyl group. The compound is converted to a compound obtained by reacting with an alkanolamine in the presence of a strongly basic catalyst, wherein R ₁ and R ₃ are the same as described above, and R ₂ represents an alkylene group having 1 to 6 carbon atoms. In the method of producing a hydroxyalkyl (meth) acrylamide by producing a compound represented by.), Recovering neutralized and unreacted alkanolamine to obtain an amide adduct as a synthetic intermediate, and then thermally decomposing it. It was found that by using dibutylamine as the dialkylamine used for protecting the double bond of methyl (meth) acrylate, the amide adduct obtained thereafter can be stably thermally decomposed without using an acid catalyst.

That is, the present invention
(1) It is characterized by thermally decomposing a compound represented by Chemical Formula 3 (wherein R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 1 to 6 carbon atoms) without a sulfuric acid catalyst. , Chemical Formula 4 (wherein R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 1 to 6 carbon atoms), a method for producing a hydroxyalkyl (meth) acrylamide,
(2) Methyl (meth) acrylate and dibutylamine are reacted to convert to a compound represented by Formula 5 (wherein R ₁ represents a hydrogen atom or a methyl group), and this is converted to a compound having 1 to 6 carbon atoms. To produce a compound represented by the chemical formula 3 (R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 1 to 6 carbon atoms), and then the compound was converted to a sulfuric acid catalyst. Hydroxyalkyl (meth) represented by the above chemical formula 4 (wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkylene group having 1 to 6 carbon atoms). A method for producing acrylamide,
(3) In the above (2), hydroxyalk (meth) acrylamide represented by Chemical formula 6 (wherein R ₁ represents a hydrogen atom or a methyl group) is characterized in that the alkanolamine is aminoethanol. Production method
Is to provide.

According to the present invention, by using dibutylamine for protecting the double bond of methyl (meth) acrylate, the amide adduct obtained later can be thermally decomposed without an acid catalyst, and stably for a long time. Since pyrolysis reaction is possible, high-purity hydroxyalkyl (meth) acrylamide can be produced.

The present invention comprises a hydroxyalkyl represented by the following three formulas (a) to (c): wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkylene group. It provides an industrially advantageous method for producing acrylamide.

(A) represented by the formula 8 (wherein R ₁ represents a hydrogen atom or a methyl group)
A step of reacting an acrylate ester with dibutylamine represented by Chemical Formula 9 to produce an ester adduct represented by Chemical Formula 10 (wherein R ₁ represents a hydrogen atom or a methyl group).

(B) An ester adduct is reacted with an alkanolamine represented by Chemical Formula 11 (wherein R ₂ represents an alkylene group having 1 to 6 carbon atoms) to form Chemical Formula 12 (wherein R ₁ is a hydrogen atom or methyl A process for producing an amide adduct represented by the group R ₂ represents an alkylene group having 1 to 6 carbon atoms.

(C) A step of thermally decomposing an amide adduct to produce a hydroxyalkyl (meth) acrylamide represented by Chemical Formula 7, which is the target product.

Hereafter, the process of this invention is explained in full detail.
Step (a) This step is performed by reacting a (meth) acrylic acid ester represented by Chemical Formula 8 with dibutylamine represented by Chemical Formula 9 under heating. The reaction is carried out by mixing 1 to 2 moles, preferably 1.1 to 1.3 moles of dibutylamine, and 1 moles of methanol with respect to the (meth) acrylic acid ester, and then a polymerization inhibitor such as methoxyhydroquinone. In the presence, the reaction is carried out by heating to the boiling temperature. The reaction time is about 5 to 10 hours depending on the reaction conditions. If an alkali metal carbonate or the like is used as a catalyst, the reaction is faster, but the non-catalyst suppresses side reactions, and the reaction can be carried out with good yield without complicated operations such as removal of the catalyst after the reaction. . After completion of the reaction, the compound represented by Chemical formula 10 is isolated by removing unreacted dibutylamine and methanol by distillation, and can be subjected to the next step without purification.

Step (b) This step is performed by reacting an ester adduct represented by Chemical Formula 10 with an alkanolamine represented by Chemical Formula 11 in the presence of a strong base catalyst. About 2 to 4 times mol, preferably 2 times mol of alkanolamine is reacted in the presence of 0.01 to 0.02 times mol of sodium methoxide, and neutralized with an equivalent amount of sulfuric acid to sodium methoxide. Can be manufactured.

Step (c) This step is carried out by thermally decomposing the amide adduct represented by Chemical Formula 12 under reduced pressure, and can be carried out without using a sulfuric acid catalyst. Pyrolysis is performed at a temperature of 100 to 200 ° C. under reduced pressure. The operating pressure is not particularly limited as long as the target product represented by Chemical Formula 7 can be quickly taken out of the system and dibutylamine as a by-product can be efficiently recovered, and is 0.5 to 10 torr. The target product represented by Chemical Formula 7 can be purified by distillation.

  Examples of the polymerization inhibitor used in the present invention include quinone-based polymerization inhibitors such as hydroquinone, methoxyhydroquinone, and p-tert-butylcatechol, 2,6-di-tert-butylphenol, 2,4-di-tert- Alkylphenol-based polymerization inhibitors such as butylphenol, amine-based polymerization inhibitors such as alkylated diphenylamine, N, N'-diphenyl-p-phenylenediamine, phenothiazine and 2,2,6,6-tetramethylpiperidine-N-oxyl, N-oxyl polymerization inhibitors such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl, etc. Is mentioned.

Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
To 189 g (2.2 mol) of methyl acrylate, 341 g (2.64 mol) of dibutylamine and 70 g (2.2 mol) of methanol were added and reacted at 70-80 ° C. for 6 hours to complete the addition to the double bond. After completion of the reaction, unreacted dibutylamine and methanol were removed by distillation to obtain 440 g (2.05 mol) of ester adduct. (Yield 92.9%). To this, 4.4 g (0.0205 mol) of sodium methoxide 25% methanol solution (hereinafter abbreviated as SM25) and 250 g (4.09 mol) of ethanolamine were added and reacted at 70-80 ° C. for 1 hour to stop the amidation reaction. . The reaction solution was neutralized by adding 2.0 g (0.0205 mol) of sulfuric acid, and the precipitated salt was filtered off, and unreacted ethanolamine and by-product methanol were removed by distillation to obtain 497 g of an amide adduct. (Yield 98.6%). As a result of analyzing the high boiling impurities in the obtained amide adduct by gas chromatography, it was not detected (detection limit: 100 ppm or less).
4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was added to the resulting amide adduct as a polymerization inhibitor, and a non-catalyzed, no-packing simple distillation apparatus was used in the presence of N2 gas. Liquid-phase pyrolysis was performed at a temperature of 174 to 175 ° C. and a degree of vacuum of 1 torr for 6 hours to obtain crude 2-hydroxyethylacrylamide having a partial compression temperature of 60 ° C. and a purity of 95.2%. During this time, no polymer was formed in the packed tower and the condenser.
Crude 2-hydroxyethyl acrylamide is 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl added as a polymerization inhibitor, and 2-hydroxyethyl with a purity of 99% or more by distillation in the presence of N2 gas. Acrylamide was obtained. During this time, no polymer was formed in the packed tower and the condenser.

Comparative Example 1
The reaction was conducted in the same manner as in Example 1 except that diethylamine was used for protecting the double bond of methyl acrylate. As a result, 494 g of amide adduct (yield 98.0%) was obtained. As a result of analyzing the high boiling impurity in the obtained amide adduct by gas chromatography, it was 0.123 mass%.
Liquid phase pyrolysis was carried out in the same manner as in Example 1. As a result, since the difference in boiling point between the amide adduct and 2-hydroxyethyl acrylamide was small, only crude 2-hydroxyethyl acrylamide having a purity of 70.0% was obtained.

Comparative Example 2
The reaction was carried out in the same manner as in Example 1 except that morpholine was used for protecting the double bond of methyl acrylate. As a result, 495 g of amide adduct (yield 98.2%) was obtained. As a result of analyzing the high boiling impurities in the obtained amide adduct by gas chromatography, it was 0.147% by mass.
Liquid phase pyrolysis was carried out in the same manner as in Example 1. As a result, the recombination reaction between crude 2-hydroxyethylacrylamide and morpholine was fast, and thus the purity of the obtained crude 2-hydroxyethylacrylamide was 55.3%.

Comparative Example 3
As a result of carrying out in the same manner as in Example 1 except that 2.05 g (0.0205 mol) of sulfuric acid was used as the acid catalyst during the liquid phase pyrolysis, many by-products of impurities were observed during the pyrolysis, and the resulting crude 2-hydroxy The purity of ethyl acrylamide was 85.1%. After 3 hours, the packed tower and the condenser were clogged with the polymer.
The results are shown in Table 1.

As described above, according to the present invention, by using dibutylamine for the double bond protection of methyl (meth) acrylate, the amide adduct obtained later can be thermally decomposed without an acid catalyst, A highly pure hydroxyalkyl (meth) acrylamide can be produced stably.

Claims (3)

A compound represented by the formula 1 (wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkylene group having 1 to 6 carbon atoms) is thermally decomposed without a sulfuric acid catalyst, (Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkylene group having 1 to 6 carbon atoms).
Methyl (meth) acrylate is reacted with dibutylamine to convert to a compound represented by Chemical Formula 3 (wherein R ₁ represents a hydrogen atom or a methyl group), and this is an alkanolamine having 1 to 6 carbon atoms. To produce a compound represented by the formula 4 (R ₁ represents a hydrogen atom or a methyl group, R ₂ represents an alkylene group having 1 to 6 carbon atoms), and then the compound was pyrolyzed without a sulfuric acid catalyst. A process for producing a hydroxyalkyl (meth) acrylamide represented by the formula 5 wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkylene group having 1 to 6 carbon atoms.
The method for producing hydroxyethyl (meth) acrylamide represented by the formula 6 (wherein R ₁ represents a hydrogen atom or a methyl group), wherein the alkanolamine is aminoethanol in claim 2.