JPS5910340B2 - Stabilization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing quaternary ammonium salts of dialkylaminoalkyl (meth)acrylates.

Polymers or copolymers of quaternary ammonium salts of dialkylaminoalkyl (meth)acrylates have a wide range of uses as polymer electrolytes.

However, such quaternary ammonium salts are often used as an aqueous solution during polymerization or produced in an aqueous medium and directly used for polymer production, but quaternary ammonium salt aqueous solutions are easily polymerized during storage or transportation. Sometimes polymerization occurs before the polymerization step, making it difficult to produce a smooth polymer and causing a decrease in the quality of the product polymer.

Therefore, in the past, polymerization inhibitors such as monomethylhydroquinone were used at a concentration of 1000 to 3000 pp per quaternary ammonium salt.
However, this polymerization inhibitor acts as a chain transfer agent during the polymerization reaction, making it difficult to obtain a high molecular weight polymer. Therefore, it is desirable that the amount of the polymerization inhibitor be 1000 pμm or less, but in this case, sufficient stabilization of the quaternary salt could not be expected. The present inventors conducted repeated studies aimed at developing a method for stabilizing quaternary ammonium salts that does not have any adverse effects during polymerization and is sufficiently stable. As a result, they achieved this goal by using a polymerization inhibitor and oxygen in combination. We found that it is possible and arrived at the method of the present invention.

That is, the gist of the present invention is to add 5% to the quaternary salt to an aqueous solution of a quaternary ammonium salt of dialkylaminoalkyl acrylate or dialkylaminoalkyl methacrylate.
By adding 0 to 1000 ppm of a polymerization inhibitor and further aerating air or oxygen, 1.8% of oxygen was added to the aqueous solution.
The present invention relates to a method for stabilizing a quaternary ammonium salt, which is characterized in that the quaternary ammonium salt is maintained at a concentration of pμm or more. To explain the method of the present invention in detail, the amino (meth)acrylate quaternary ammonium salt targeted by the present invention is represented by the following general formula.

) R1/qre=CHR2 \ 11 COO-Y-N-R3XΘ (In the formula, R1 represents a hydrogen atom or a methyl group, and R2, R
3. R4 may be the same or different and represents an alkyl group having 1 to 4 carbon atoms or an aralkyl group.

Y is an alkylene group having 2 to 4 carbon atoms, θ is a hydroxy-substituted alkylene group, and X is a halogen anion or an alkyl sulfate anion) Specifically, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, 3-dimethylamino -2-hydroxypropyl acrylate, di-n-butylaminoethyl acrylate or corresponding methacrylates, alkyl halides such as methyl chloride, methyl bromide, ethyl bromide, methyl iodide, benzyl chloride, dimethyl sulfate, diethyl sulfate, etc. Examples include quaternary ammonium salts obtained by reacting with dialkyl sulfuric acid.

The concentration of quaternary ammonium salt in aqueous solution is 30-85
% is preferably 50 to 80%.

(All percentages by weight) As the polymerization inhibitor added to the aqueous solution, known polymerization inhibitors such as monomethylhydroquinone and hydroquinone are used, and the amount thereof added is 50 ppn1 or more based on the quaternary ammonium salt. However, if a large amount of polymerization inhibitor is added, it becomes an obstacle when producing a polymer, so the amount is preferably 1000 ppm or less, preferably 500 ppm.
It is better to have pn1 or less. Oxygen is generally mixed into the quaternary ammonium salt aqueous solution by bubbling oxygen or air into the aqueous solution. It is sufficient that the amount of mixed oxygen is 1.8 ppm or more to the saturation amount of the solution, preferably 2.0 ppm or more to the saturation amount of the solution, based on the aqueous solution of the quaternized compound. If you leave a quaternary ammonium salt aqueous solution mixed with oxygen in this way, the oxygen in the solution may decrease due to changes in temperature, etc., and the sufficient stabilizing effect may be lost. Need to save below.

When homopolymerizing or copolymerizing the quaternary ammonium salt aqueous solution stabilized by the method of the present invention with other monomers, polymerization can be prevented by sufficiently degassing dissolved oxygen using an inert gas such as nitrogen beforehand. It will proceed without any problems.

According to the method of the present invention, since the amount of the polymerization inhibitor is small, sufficient stability can be obtained without causing any adverse effects during the polymerization reaction. Next, the method of the present invention will be explained in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 A quaternary ammonium salt powder obtained by reacting methyl chloride and dimethylaminoethyl methacrylate off the coast of dimethylformamide was diluted to a predetermined concentration, monomethylhydroquinone was added as a polymerization inhibitor, and oxygen or air was blown into the diluted powder.

This sample was placed in a sample pin, capped, and left in a constant temperature bath at 50° C., and the stability was examined by checking the presence or absence of polymer formation. For comparison, a similar test was also conducted in the case where the amount of dissolved oxygen was outside the specification of the present application. The results are shown in the table below. Example 2 Stability at 50° C. was tested in the same manner as in Example 1 using a quaternary ammonium salt powder obtained by reacting dimethylaminoethyl methacrylate and dimethyl sulfate in acetone.

The results are shown in Table 2. In Comparative Examples 1 and 2, the water was deoxidized with nitrogen, and in Comparative Example 3, the sample was prepared without specifically blowing oxygen into the water.

Claims (1)

[Claims] 1. A polymerization inhibitor of 50 to 1000 ppm based on the quaternary salt is added to an aqueous solution of a quaternary ammonium salt of dialkylaminoalkyl acrylate or dialkylaminoalkyl methacrylate, and 1.0% of oxygen is added to the aqueous solution by aerating air or oxygen. A method for stabilizing an aqueous solution of a quaternary ammonium salt of dialkylaminoalkyl acrylate or dialkylaminoalkyl methacrylate, the method comprising mixing 8 ppm or more of a quaternary ammonium salt.