JPH0613462B2 - Storage method of dimethylaminoethyl acrylate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Industrial field of application] The present invention relates to dimethylaminoethyl acrylate (hereinafter DA).
(Hereinafter, abbreviated as "), and more specifically, while storing DA, preventing polymerization during storage or storage, and suppressing deterioration in quality such as coloring and purity,
The present invention relates to an excellent storage method that does not deteriorate the polymerization reactivity of DA or an acid neutralized salt of DA or quaternary ammonium water (cationic vinyl monomer) after storage, and the physical properties of these polymers obtained by polymerization. .

DA is used as a raw material for plastic antistatic agents, ultraviolet curing agents, fiber modifiers, toner binders, paints, lubricating oil additives, paper strength agents, adhesives, ion exchange resins, polymer flocculants, etc. in a wide range of fields. It has been used in recent years as a polymer flocculant for sewage treatment, and in particular as a raw material for a cationic polymer, which has an excellent effect on the dewaterability of sludge generated in an urban sewage treatment plant, a substitute for a methacrylic cationic monomer. It has been in the spotlight, and can be effectively used in a wide range of fields including the sewage treatment field.

[Prior Art] DA is an extremely unstable compound, and immediately starts to be colored and polymerized during storage, and its tendency becomes severe over time, which significantly reduces its value including commercial value. Not only that, but also DA after storage has a problem that, when the above-mentioned cationic polymer is obtained, the polymer has poor polymerizability or is easily gelled, and further the physical properties of the obtained polymer are deteriorated.

Therefore, a method for stably storing a large number of DAs has been proposed so far. That is, a method using a dialkylhydroxyamine such as diethylhydroxyamine as a polymerization inhibitor (JP-A-47-18820) and a method using an aromatic nitroso compound such as N-nitrosodiphenylamine as a polymerization inhibitor (JP-A-53-53). 144519
No.), a method of adding oxygen after adding a polymerization inhibitor and stabilizing it by mixing oxygen (JP-A-53-144519), 2,4-
A method using a benzophenone-based UV absorber such as dihydroxybenzophenone as a stabilizer (Japanese Patent Laid-Open No. 53-1 / 53).
No. 44520), phenothiazine alone or a method of using phenothiazine in combination with hydroquinone monomethyl ether or butylhydroxyanisole as a stabilizer (JP-A No. 53-144521).

In addition, the above-mentioned proposal and the DA storage method currently performed are
It is based on the same idea as dimethylaminoethyl acrylate, which has been used in large amounts as a raw material for cationic polymer flocculants, that is, a method in which air is used as a seal gas and a storage stabilizer is used.

[Problems to be Solved by the Present Invention] However, each of the above proposals has the following problems.

Although the addition of dialkylhydroxyamine or the like has an effect of preventing polymerization during DA storage, DA containing dialkylhydroxyamine or the like has a problem in the polymerizability.
When a quaternary ammonium salt is used for polymerization, it is difficult to obtain a high molecular weight polymer having a molecular weight of 1 million or more.
Further, when the DA storage time becomes long, water-insoluble components increase in the quaternary ammonium salt polymer, and the quality tends to deteriorate. Even if an aromatic nitroso compound or a benzophenone-based ultraviolet absorber is used, the same problem occurs and it is not satisfactory at all. Also, when using phenothiazine, coloring and polymerization during storage can be considerably suppressed,
The phenothiazine-containing DA has a considerably poor polymerizability, and the yield of the high molecular weight polymer decreases. Further, in the method of mixing DA with oxygen for stabilization, DA is colored rapidly and gels easily when polymerizing a quaternary ammonium salt of DA, and the polymer produced without gelation has a large amount of water insoluble. Will be things.

As described above, in the conventional proposals, the deterioration of quality such as coloring during the storage of DA and the polymerization are largely suppressed, and the polymerization reactivity and the physical properties of the obtained polymer are improved during the production of the polymer of DA or the quaternary ammonium salt of DA. At present, there is no DA storage method that does not decrease the storage capacity and has excellent reproducibility.

(B) Structure of the Invention [Means for Solving the Problems] The present inventors have conducted various studies on an excellent DA storage method, and in the DA storage, a similar compound to the conventional one, such as dimethylaminoethyl acrylate, was stored. However, air (oxygen) is considered to be effective as a seal gas, and it is common to use oxygen as in the above proposal.
Regarding the A storage, oxygen is not preferable, and it was found that the storage stability is remarkably improved by using an inert gas and a specific stabilizer together in the absence of oxygen, and the present invention has been completed.

That is, the present invention relates to a method for storing dimethylaminoethyl acrylate, which comprises storing dimethylaminoethyl acrylate added with hydroquinone monomethyl ether in the absence of oxygen.

The state of the present invention in the absence of oxygen means that the inside of a reservoir such as a DA container or a storage tank is replaced with an inert gas to remove oxygen in the reservoir and sealing with an inert gas is performed.

Examples of the inert gas that can be used in this case include nitrogen, helium, and argon, but nitrogen gas is preferable from the viewpoint of economy.

As the method of replacing with an inert gas, any method such as a method of bubbling an inert gas in DA, a method of replacing only the gas phase portion with an inert gas, or the like can be adopted. After replacing with the inert gas, it is sufficient to seal the reservoir as it is so that air is not mixed, but in order to completely prevent the air from being mixed, the inert gas is continuously supplied. It is preferable. The continuous supply method of the inert gas may be a general method such as bubbling an inert gas in DA or passing an inert gas through the gas phase.

The additive used in the present invention is hydroquinone monomethyl ether. Although phenothiazine and the conventionally proposed additives have good storage stability of DA itself, they adversely affect the polymerization reactivity and the physical properties of the polymer when DA is polymerized to form a quaternary ammonium salt. Therefore, it cannot be practically adopted.

The addition amount of hydroquinone monomethyl ether to DA is preferably 500 to 5000 ppm, and 1000 to 30
The range of 00 ppm is more preferable. If the amount of hydroquinone monomethyl ether added to DA is less than 500 ppm, the DA polymerization inhibitory effect is reduced and the coloring prevention effect is also reduced.

On the other hand, if it exceeds 5000 ppm, it becomes difficult to obtain a high molecular weight polymer useful as an aggregating agent when DA is polymerized into a quaternary ammonium salt.

[Function] When hydroquinone monomethyl ether is used as a storage stabilizer for DA, and the inside of the DA storage is sealed with an inert gas so that there is no oxygen, DA is stored more than when sealed with air.
The effect of preventing polymerization during storage and the deterioration of the quality of DA are suppressed, and further, the polymerization reactivity when polymerizing a quaternary ammonium salt of DA and the physical properties of the obtained polymer are not deteriorated.

The reasons for these are currently unknown, but the increase in DA coloring during DA storage and the generation and increase of trace amounts of unknown components are smaller in nitrogen replacement than in air replacement. It is considered that the generation and increase of trace amounts of unknown components affect the polymerizability of the quaternary ammonium salt of DA and the physical properties of the polymer obtained by the polymerization.

[Examples] The present invention will be described in more detail based on the following examples.
In this example,% means% by weight.

○ Synthesis of DA 3840 g of n-butyl acrylate was added to a three-necked flask equipped with a stirrer, a thermometer, a condenser and a fractionation tower and equipped with a rectification tower.
(30.0 mol), 890 g of dimethylaminoethanol (1
0 mol), 68.2 g (0.2 mol) of tetra-n-butyl titanate and 4.8 g (10 mol) of phenothiazine as a polymerization inhibitor.
00 ppm) was added, and heating was started under reduced pressure of 300 Torr while stirring. After totally refluxing for 30 minutes, the reaction liquid temperature was maintained at 110 to 120 ° C. and the top temperature of the rectification column was maintained at 96 to 98 ° C., and n-butanol produced was withdrawn at a reflux ratio of 3.0 to 5.0 for 4 hours. It was

When the reaction solution was analyzed by gas chromatography, the reaction rate of dimethylaminoethanol was 92%, DA
The yield was 90%.

Next, this reaction solution was subjected to a nitrogen atmosphere at 30 Torr and 90 to 1
The catalyst was removed at 00 ° C. to obtain 3888 g of a distillate containing DA. Furthermore, after adding 3.8 g of phenothiazine to the distillate, a rectification column (15 theoretical plates) equipped with a condenser and a fractionation column was used, under a nitrogen atmosphere at 20 Torr, 70 to 85 ° C., and a reflux ratio of 1.
After n-butanol, butyl acrylate, and dimethylaminoethanol were distilled off at 0 to 10.0, the mixture was distilled under the same nitrogen atmosphere at 20 Torr, 85 to 95 ° C., and a reflux ratio of 1.0 to 2.0 to obtain DA1222 g. The overall yield of DA was 86% and the purity was 99.9%. The viscosity was 3 cps at 25 ° C. and the color tone was 5 with APHA.

Example 1 and Comparative Example 1 200 g of DA was placed in a glass flask, 2000 ppm of hydroquinone monomethyl ether was added as a polymerization inhibitor, and the sealing gas shown in Table 1 was blown into the liquid phase at a flow rate of 200 ml / min at 130 ° C. for 96 hours. It heated and the forced deterioration test was done.

Table 1 shows the color tone and viscosity of DA after heating.

As is clear from Table 1, when nitrogen is used as the sealing gas, a remarkable polymerization inhibiting effect is recognized.

Example 2, Comparative Example 2 DA added with 2000 ppm of hydroquinone monomethyl ether as a polymerization inhibitor was placed in a flask equipped with a condenser, and the gas phase part was sealed with nitrogen or air at a flow rate of 200 ml / min, and then at 50 ° C. Heated for 30 days. On the way, sampling was performed every 10 days to evaluate the quality of the DA monomer, the polymerization reactivity, and the physical properties of the polymer. The obtained results are shown in Table-2.

Various evaluation methods were performed as follows.

○ DA monomer quality evaluation ・ The color tone was indicated by APHA.

-Purity was determined by gas chromatography by quantifying the amount excluding hydroquinone monomethyl ether.

Evaluation of Polymerization Reactivity The sampled DA was evaluated by the copolymerization reactivity of a quaternized monomer with benzyl chloride and acrylamide.

The quaternary ammonium salt of DA was prepared by charging 1059 g of benzyl chloride in a flask and heating it to 30 ° C.
1194 g and 397 g of water were added dropwise over several hours, and then the mixture was aged with stirring overnight, and the next day, 350 g of water was further added to synthesize.

Regarding the polymerization reactivity, the obtained quaternary ammonium salt of DA and acrylamide were charged into a polymerization apparatus at a polymerization ratio of 8: 2, and the polymerization initiator was 30 ppm after degassing nitrogen for 1 hour while maintaining the liquid temperature at 10 ° C. Polymerization induction time (IP: time from the addition of a polymerization initiator to the time when heat generation due to polymerization is observed) and polymerization time (PT: time from the start of heat generation due to polymerization to the arrival of the maximum temperature due to polymerization) when added evaluated.

Evaluation of Physical Properties of Polymer Polymer properties were evaluated by the viscosity of a 0.5% aqueous solution of the obtained quaternary ammonium salt of DA and the acrylamide copolymer and the amount of insoluble matter in the solution.

Here, the 0.5% aqueous solution viscosity was determined by stirring the obtained pellet-shaped dried product of the copolymer at 150 rpm for 3 hours to give an aqueous solution, and measuring this with a B-type viscometer at 25 ° C.

The insoluble amount was determined by measuring the residual amount on the mesh when 400 ml of the same solution was filtered through an 80 mesh stainless steel wire mesh in a water-containing state.

As is clear from the results shown in Table 2, it is clear that a nitrogen seal is preferable for storing DA.

Comparative Example 3 Phenothiazine 1000 as a polymerization inhibitor after DA synthesis
Immediately after the addition of ppm, the polymerization reactivity was evaluated in the same manner as in Example 2.

As a result, polymerization did not occur at all and it was not practically applicable.

(C) Effect The method for storing DA of the present invention has a large effect of preventing polymerization during storage of DA, and also suppresses quality deterioration such as coloring, deterioration of purity, generation of unknown components, and the like. It does not deteriorate the polymerizability at the time of polymerization and the physical properties of the obtained polymer, and the effect of contributing particularly to the industry of using a polymer flocculant is great.

 ─────────────────────────────────────────────────── --Continued from the front page Examiner Zenichi Wakimura

Claims (1)

[Claims] 1. A method for storing dimethylaminoethyl acrylate, which comprises storing dimethylaminoethyl acrylate added with hydroquinone monomethyl ether in the absence of oxygen.