JPS62187710A - Polymerization inhibitor for acrylic monomer - Google Patents

Abstract

PURPOSE:To obtain the titled polymerization inhibitor which can inhibit an N-monoalkyl-(meth)acrylamide from undergoing polymerization, especially, popcorn polymerizaton, by using a compound selected from among nitroso compounds and inorganic and organic stable radicals as a component therefore. CONSTITUTION:The titled polymerization inhibitor (B) is obtained by using at least one compound selected from among (a) a nitroso compound (e.g., 1- nitroso-2-naphthol), (b) an inorganic stable radical (e.g., NO) and (c) an organic stable radical [e.g., an organic nitroxide radical having vicinal gemdimethyl substituents of formula I (wherein X and Y are arbitrary substituents)]. 1-20,000, preferably, 100-10,000ppm, based on component A, of component B is added to an N-monoalkyl-(meth)acrylamide (A) of formula II (wherein R1 is H or CH3 and R2 is a 1-3C alkyl).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to polymerization inhibitors for acrylic monomers. Sometimes represented by the general formula (1), monoalkoxy N
This invention relates to a polymerization inhibitor for substituted acrylamides or monoalkyl N-substituted methacrylamides.

General formula (1) (However, R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 1 to 3 carbon atoms.) (Prior art) Monoalkyl N1jl-substituted acrylamide or mono acrylamide represented by general formula (1) Alkyl N-substituted methacrylamides are extremely easy to polymerize and #! It is known that polymerization often occurs due to heat, light, and other factors during the manufacturing process, storage, and transportation. In particular, when the monoalkyl group is a methyl group, it has extremely high polymerizability, and under heating conditions such as distillation and concentration steps, an insoluble polymer (popcorn polymer) having a three-dimensional structure is rapidly formed. Such poly-i- is more likely to be generated in the gas phase than in the liquid phase of the system.

Once formed, it continues to grow explosively in both gas and liquid phases no matter what polymerization inhibitor is added, clogging distillation columns, piping, etc., and even spontaneously igniting due to the heat of polymerization.

Conventionally, no-hydroquinone, anthraquinone, no-hydroquinone monomethyl ether, phenothianone, para-phenylenediamine, metal copper salts, etc. have been known as general polymerization inhibitors, but these are hardly effective in preventing popcorn polymerization. In addition, because monoalkyl N1jl-substituted acrylamide and monoalkyl N-substituted methacrylamide represented by general formula (1) have not been produced on an industrial scale, there has been no technology to prevent popcorn polymerization of these monomers until now.

(Means and effects for solving the problem) In view of the above-mentioned state of the prior art, the present inventors have developed a popcorn polymerization inducing factor of an acrylic monomer represented by general formula (1) in order to overcome the problem. As a result of intensive studies on measures to prevent popcorn polymerization, the present invention has been completed.

It has been found that air is the only factor that induces popcorn polymerization during distillation of acrylic monomers, and popcorn polymerization does not occur at all even when heated to about 120° C. by simple heating. Therefore, a very small amount of air leakage in the distillation equipment (
(During vacuum distillation, a small amount of air may be introduced into the system)
is a factor that induces popcorn polymerization. This shows that it is possible to prevent popcorn polymerization by completely eliminating leakage in distillation equipment, but it is no exaggeration to say that complete prevention of leakage is impossible in industrial distillation equipment. Therefore, in order to establish a practical measure for preventing popcorn polymerization of the acrylic monomer represented by general formula (1), a special polymerization inhibitor for preventing popcorn polymerization is required.

From this point of view, the present inventors have conducted intensive studies on polymerization inhibitors for monoalkyl N-substituted acrylamides and monoalkyl N-substituted methacrylamides represented by general formula (1), particularly popcorn polymerization inhibitors, and found that nitroso We have found that inorganic stable radicals and organic stable radicals are highly suitable for this purpose.

That is, the present invention uses nitroso compound #1 as exemplified below as a cross-linking inhibitor for monoalkyl-Nti-substituted acrylamide or monoalkyl-e-substituted methacrylamide represented by the general formula (1). One or more selected from inorganic stable radicals and organic stable radicals are employed.

To explain the present invention in more detail, the nitroso compounds serving as polymerization inhibitors in the present invention include N,N-dimethyl p-nitrosoaniline, p-nitrosodiphenylamine, p-
Nitron dimethylamine, p-nitrone-N, N-diethylamine, N-nitrosogetanolamine, N-nitrosodi-n-butylamine, N-nitroso-N-n
-Butyl-4-butanolamine, N-nitrosodi-
Nitrosoamines such as isoglono9olamine, N-nitroso-N-ethyl-4-butanolamine, 5-nitroso-8-hydroxyquinoline, N-nitrosomorpholine, N-nitroso-N-phenylhypoxylamine ammonium salt, etc. Trosopenzene, 2,4.6-
nitrosobenzenes such as tri-t-butylnitronbenzene, nitrosophenones such as 5-nitroso-oxyno-4-nitrosone, 130-nitronacetophenone, α-1sO-nitrosoglopiophenone, etc.
．． To N-Nitron! Nitrosoimines such as tamethyleneimine, nitrosamides such as N-nitroso-N-methyl-p-toluenesulfonamide>A,N-nitroso-N-
) Nitrosourethanes such as urethane and N-nitroso-N-n-propylurethane S 1-nitroso-2-naphtholone, 2-nitroso-1-naphthol, 1-nitroso-2-naphthol-3,6-sosulfonic acid Nda,
Nitrosonaphthols such as 2-nitroso-1-naphthol-4-sulfone IR, nitrotunoalkylaminophenols such as 2-nitrone-5-tumethylaminophenol hydrochloride, 2-nitrone-5-tumethylaminophenol hydrochloride, etc. class, 5-1so-nitrone parbitol, 4
Examples include various nitroso compounds such as I/-1-7-methyl ether.

Next, the inorganic stable radicals referred to in the present invention are those which are stable under normal distillation conditions of the acrylic monomers represented by the general formula (1) above, and specifically, oxygen.

Complex compounds of gaseous inorganic stable oxidants and transition metal ions, such as nitrogen chloride, base dioxide, chlorine dioxide, and trivalent chlorine; for example, the reaction product of 2mj copper and a hydroquinone conductor (in this case, , eu and semiquinone intermediate 1i
The iiJ side becomes a radical6).

Furthermore, the organic stable radicals referred to in the present invention are of the general formula (
The acrylic monomers shown in 1) are stable under normal distillation conditions, such as nophenylpicrylhydrazyl, αlr-bisdiphenylene-β-phenylaryl, galpinooxyl, 1.3.5-) Riphenylbada sol, not-t-butyl-nitroxide, 2,2
．． 6.6-tetramethylbiperidin-1-oxyl,
2.2,6.6-tetramethyl-4-piperidone-1-
Oxyl, 3-carbamoyl-proxyl, 2.2
．． 6.6-Tetramethyl-4-hydroxypiperinone-
Examples include various stable radicals such as 1-oxyl.

Incidentally, as mentioned above, popcorn polymerization tends to occur mainly in the gas phase, so it is likely to occur within the distillation column.

Therefore, in order to prevent popcorn polymerization, it is necessary to have the polymerization inhibitor uniformly present in the packed column. From this point of view, when distilling at least one acrylic monomer that is a gold target among the above-mentioned nitroso compounds, inorganic stable radicals, and organic stable radicals, one or more of the above-mentioned nitroso compounds, inorganic stable radicals, and organic stable radicals are selected according to the boiling point of the acrylic monomer and added to the distillation pot or packed column. This makes it possible to distribute the polymerization inhibitor in the liquid phase or both gas and liquid phases over a wide temperature range, resulting in a sufficient effect of preventing popcorn polymerization.

On the other hand, another requirement for such polymerization inhibitors is that they must not be mixed into products.

Even if it is mixed in, it can be easily removed and does not interfere with the polymerization reaction unless it is used for one polymerization reaction.

From the above viewpoint, in the case of nitroso compounds, 2
-Nitrone-1-naphthol and 1-nitroso-2-naphthol are particularly preferred in terms of their vapor pressure, and as the inorganic stable radicals, gaseous inorganic stable 2-naphthol is preferred, taking into account safety, ease of purchase, etc. Dredged nitrogen and nitrogen dioxide are then particularly preferred. Also, as organic stable radicals.

In view of the stability of the 2-carboxylic acid, an organic nitroxide radical having adjacent dieminisomethyl substituents represented by the general formula (2) is preferred.

0. Also, from the point of vapor pressure, 2,2,6,6-tetosimethylbiperidone-1-oxyl, 2,2,6,6-tetramethyl-4-piperidone-1-1oxyl, and 3 -Carbamoylproxil is preferred.

However, depending on the distillation conditions, it may be difficult to uniformly distribute the nitrones or organic stable radicals in the packed column when only the nitrones or organic stable radicals are added to the pot or the top of the column. In such a case, it is possible to sufficiently overcome the problem and achieve the purpose by using a gaseous inorganic stable 2-nocal in combination with a nitroso or an organic stable radical. By the way, if all gaseous inorganic stable radicals are used, gas will naturally dissolve in the distillate, but dissolved gas can be easily removed by performing nitrogen bubbling treatment under reduced pressure after the distillation is complete. . Of course.

It is also possible to use the polymerization inhibitor referred to in the present invention in combination with a conventionally known polymerization inhibitor such as phenothiazone, but this does not interfere with the gist of the present invention.

In the practice of the present invention, the amount of the above-mentioned compound used as a polymerization inhibitor is not particularly limited, but is 1 to 2 to 10,000 - preferably 10
It is about 0 to 10,000.

On the other hand, specific examples of monoalkyl N-substituted acrylamides or monoalkyl N-substituted methacrylamides represented by general formula (1) include N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, and their meta-forms. .

(Effect of the invention) The monoalkyl N-substituted acrylamide or monoalkyl Nwt, 3a methacrylamide represented by the above formula (1) is highly polymerizable among acrylic monomers. Without the establishment of technology for preventing polymerization, especially popcorn polymerization, it would be completely impossible to industrially supply the hexamer. It is no exaggeration to say that by adopting the present invention, the technology for preventing popcorn polymerization during rectification was established for the first time, and that the industrial supply of the acrylic monomer became possible for the first time with the establishment of this technology.
Its industrial significance is extremely large.

(Example) Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples as long as it does not exceed the spirit thereof. In the following examples, parts and weight % are not particularly limited.

[Examples 1 to 8 and Comparative Examples 1 to 4] 10 parts of N-methylacrylamide and 0 of various polymerization inhibitors
．． After completely dissolving 05 parts in a 20atJ capacity brown ampoule, repeat the operation [freezing in a dry ice methanol bath, degassing under reduced pressure (0.5 mHg or less), and melting in a water bath] until bubbles are removed when melting. The ampoule was completely degassed at 7'C until no gas came out. After degassing, the ampoule was sealed with a gas fire under reduced pressure (0.5 kg or less) and heated in an oil bath at 100°C for 23 hours. After 23:00 rA, *For samples that were not combined, the ampoule was opened, air was introduced, and the ampoule was sealed again under atmospheric pressure and heated for an additional 20 hours in an oil bath at 120°C, and the presence or absence of polymerization was visually checked. .

As a reference example, N-
Methylacrylamide alone was sealed in the same angle under reduced pressure and atmospheric pressure, and similar tests were conducted.

The experimental conditions and results are summarized in Table 1. As is clear from the results in Table 1, popcorn polymerization of N-methylacrylamide is induced by air. In a completely deaerated system, polymerization does not occur at temperatures up to 100° C., even with conventionally known polymerization inhibitors or even without the addition of a polymerization inhibitor, but popcorn polymerization occurs in the presence of air.

This is the first step: → -1 Conventionally known inhibitors cannot exhibit any polymerization inhibiting function. On the other hand, it is clear that the nitrosos of the present invention can completely prevent popcorn polymerization not only under deaerated conditions but also under atmospheric conditions. Therefore, by carrying out the present invention, the range of distillation operation conditions will be widened, and there will be immeasurable benefits in terms of reduction of production equipment, safe operation, etc.

[Examples 9-10 and Comparative Examples 5-6] Except that N-n-propylacrylamide and N-methylmethacrylamide were used instead of N-methylacrylamide and the polymerization inhibitors shown in Table 2 were used. The same procedure as in Example 1 was carried out to compare various polymerization inhibition effects. The conditions and results are summarized in Table 2.

[Example 11 and Comparative Example 7] A Schissig ring packed column with a reflux condenser was attached to a 500 d glass flask, and a
A flask was charged with 300.9 of a solution containing 00PI'Xl and 1-nitroso-2-naphthol.

Bath temperature 103℃, tower top temperature 51-57℃, system internal pressure 0.3
Reflux operation was performed under conditions of 9 to 0.78+ mHg.

Even after 12 hours of operation under the same conditions, no popcorn polymerization occurred. In addition, a portion of the reflux liquid was sampled and checked using a gas chromatograph for the presence or absence of a polymerization inhibitor, but no polymerization inhibitor was found to be present.

On the other hand, when phenothiazine i 5000 was added instead of 1-nitrone-2-naphthol, popcorn polymers were generated in the packed column after 30 minutes, and the distillation system was completely blocked after 35 minutes.

[Example 12 and Comparative Example 8] Using the same apparatus as in Example 11, phenothiazine of 50,001 JI1 m was added to N-methylacrylamide, the solution was charged into a flask, and the top of the packed column was poured. 2.2 to be ~40011111
．． The same procedure as in Example 11 was carried out while dropping 6.6-tetramethyl-4-piperidone-1-oxyl. Even after 12 hours had passed, no popcorn polymerization occurred, and no polymerization inhibitor was observed to be mixed into the distillate.

On the other hand, from the top of the packed column, 2.2.6.6-tetramethyl-
When the same procedure was followed except that phenothiazine was added instead of 4-biyridone-1-oxyl, popcorn polymerization occurred after 60 minutes, and the distillation system was completely blocked after 70 minutes.

[Example 13] A Raschig ring packed column with a reflux condenser was attached to a 500 dff flask and the SO
o Op- 1-nitrone-2-naphthol added solution 300! i into a flask, and while blowing nitrogen monoxide gas into the flask through a glass capillary, the bath temperature was 103°C, the top temperature was 51-57°C, and the system pressure was 0.39-0.78 ■Hg. A reflux operation was performed. No popcorn polymerization occurred even after 12 hours of operation under the same conditions. In addition, after sampling a portion of the reflux liquid and bubbling nitrogen gas under reduced pressure (1 tm Hg or less), we checked with a gas chromatograph for the presence or absence of polymerization inhibitor contamination, but no contamination of polymerization inhibitor was observed. )Ta.

[Example 14] All operations were carried out in the same manner as in Example 13 except that nitrogen dioxide was used instead of nitrogen monoxide. Even after 12 hours, no popcorn polymerization occurred, and the distillate was treated in the same manner as in Example 13.

The presence of contamination with a polymerization inhibitor was checked using a gas chromatograph, but no contamination with a polymerization inhibitor was observed.

[Examples 15 to 19 and Comparative Examples 9 to 10] 10 parts of various monomers f 20 tnl were placed in a brown ampoule, and while cooling in ice water, the pressure was reduced to 10 wnHg using a vacuum pump. Various stable radicals were injected into the ampoule under reduced pressure and sealed with a gas fire. However, solid radicals were operated by adding 5oooppa to the monomer to the ampoule before reducing the pressure. This ampoule was immersed in an oil bath at 120°C and heated for 20 hours, and the presence or absence of polymerization was visually checked.

Similar tests were also conducted on ampoules in which only the monomer was sealed under reduced pressure without adding any stable radicals as Natina. For comparison, similar experiments were also conducted using conventionally known polymerization inhibitors. (Additional location is s
o o Oplm. ) The conditions and results are shown in Table 1. It is clear that the stable radical of the present invention has a remarkable ability to inhibit popcorn polymerization.

Claims (1)

[Scope of Claims] 1. A monoalkyl N-substituted acrylamide or Polymerization inhibitor for monoalkyl N-substituted methacrylamide. General formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R_1 is a hydrogen atom or a methyl group, R_2 is an alkyl group having 1 to 3 carbon atoms) 2. The nitroso compound is 1-nitroso-2-naphthol ,
The polymerization inhibitor according to claim 1, which is 2-nitroso-1-naphthol. 3. The polymerization inhibitor according to claim 1, wherein the inorganic stable radicals are nitrogen monoxide or nitrogen dioxide. 4. The polymerization inhibitor according to claim 1, wherein the organic stable radicals are organic nitroxide radicals having adjacent dieminidimethyl substituents represented by general formula (2). General formula (2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, X and Y represent arbitrary substituents.) 5. Use of inorganic stable radicals and nitrosos or organic stable radicals together A polymerization inhibitor according to claim 1, which is characterized by: