JPH08310979A - Purification of vinyl monomer - Google Patents

Abstract

PURPOSE: To purify a vinyl monomer by easily and surely removing polymerization inhibitors in a vinyl monomer. CONSTITUTION: A vinyl monomer such as acrylic, styrene, vinyl acetate, acrylonitrile or fluorinated ethylene monomer is treated with an adsorbent such as alumina, silica gel, molecular sieve, activated carbon, ion-exchange resin, chelate resin, zeolite and acid clay. The adsorption treatment is carried out e.g. by the immersion process comprising the impregnation of the adsorbent into the vinyl monomer or the column adsorption method comprising the packing of a column with the adsorbent and the passing of the vinyl monomer through the column. The vinyl monomer may be treated with the adsorbent as it is, diluted with a solvent such as hexane or used as a carrier liquid. The treating temperature is 0-150 deg.C, usually room temperature. The amount of the polymerization inhibitor is decreased to <=50% of the original content by this adsorption treatment. The transparent polymer produced by polymerizing the refined monomer has minimized color and high light transmittance and is usable as a core material of a light-transmission tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a vinyl-based monomer by removing a polymerization inhibitor contained in a vinyl-based monomer, particularly an acrylic-based monomer.

[0002]

BACKGROUND OF THE INVENTION In order to prevent polymerization during storage in vinyl monomers, especially commercial acrylic monomers, polymerization inhibitors such as hydroquinone and alkyl-substituted phenols are usually used in an amount of about 30 to 200 ppm. It contains a large amount of. When an acrylic monomer containing such a polymerization inhibitor is polymerized to obtain a transparent polymer, it is colored by the polymerization inhibitor and absorbs visible light, so that the light transmittance of the polymer decreases. . Therefore, it is desired to remove the polymerization inhibitor from the monomer and carry out the polymerization using the purified monomer.

As a method for purifying such a monomer, there are a distillation method, an alkali extraction method and the like. Although the distillation method is effective for a low boiling point acrylic monomer, a polymerization inhibitor is used for a high boiling point monomer. Distilled together to deteriorate the purity of the purified product, or acrylic monomer does not distill,
It cannot be distilled. Further, if the distillation temperature becomes high, polymerization will start during the distillation, which is dangerous. On the other hand, the alkali extraction method has a problem that the purification effect is poor and it is difficult to obtain a high-purity monomer.

The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a method for purifying a vinyl-based monomer capable of easily and surely removing a polymerization inhibitor in the vinyl-based monomer.

[0005]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, vinyl-based monomers such as acrylic-based monomers were changed to alumina, silica gel, molecular sieves, activated carbon, ion exchange resins. , Chelating resin, zeolite, hydroquinone in vinyl monomers by treatment with an adsorbent such as acid clay
It was found that the polymerization inhibitor such as an alkyl-substituted phenol can be efficiently removed, and particularly when alumina, silica gel or the like is used as the adsorbent, the polymerization inhibitor can be removed more effectively, and the present invention is made. Came to.

Therefore, according to the present invention, a method for purifying a vinyl monomer, which comprises treating a vinyl monomer containing a polymerization inhibitor with an adsorbent to adsorb and remove the polymerization inhibitor from the vinyl monomer. I will provide a.

The present invention will be described in more detail below. In the method for purifying a vinyl monomer of the present invention, the polymerization inhibitor in the monomer is removed by treating the monomer with an adsorbent.

Here, the vinyl-based monomer to be treated usually contains 1 ppm or more of a polymerization inhibitor such as hydroquinones and alkyl-substituted phenols, and the present invention particularly uses such a polymerization inhibitor in a large amount. I.e. 10
ppm or more, especially 50 ppm or more, especially 100 pp
acrylic monomer containing m or more, or styrene,
It is effectively used for treating vinyl acetate, acrylonitrile, and fluorinated ethylene monomers. The acrylic monomer is preferably used as acrylic acid, methacrylic acid, esters of these acrylic acids or methacrylic acids with monohydric alcohols having 1 to 20 carbon atoms, and particularly acrylic acid or methacrylic acid and carbon numbers. It is particularly suitable for treating high boiling esters with 8-20 monohydric alcohols.

As the adsorbent for treating the vinyl monomer, alumina, silica gel, molecular sieve,
Activated carbon, ion exchange resin, chelate resin, zeolite and acid clay are preferable, and among them, alumina, silica gel, activated carbon, and molecular sieves have the highest effect of removing the polymerization inhibitor and are preferably used.

The average particle size of the adsorbent is appropriately selected, but is preferably 50 to 500 mesh, particularly 100 to 300 mesh. Further, those obtained by molding and processing these fine particles into a certain shape can also be used.

As an adsorption treatment method using the above adsorbent,
A dipping method in which a vinyl-based monomer is impregnated with an adsorbent, a column adsorption method in which the adsorbent is packed in a column, and the vinyl-based monomer is passed through the column can be adopted. In this case, the vinyl-based monomer may be directly treated with an adsorbent, or may be diluted with an organic solvent such as hexane, or the organic solvent may be used as a carrier liquid, if necessary. The treatment temperature may be 0 to 150 ° C. and may be appropriately selected depending on the viscosity of the monomer, but room temperature is usually sufficient.

By such a treatment, the amount of the polymerization inhibitor in the vinyl-based monomer is reduced to 50% or less of the original amount, and the purified monomer having the reduced amount of the polymerization inhibitor is transparent by using the same. When the polymer is polymerized, the coloration of the polymer is reduced as much as possible and the light transmittance is high, and thus the polymer is effective as the core material of the light transmission tube. The method of polymerizing using this purified monomer may be a known method.

[0013]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Example] A glass tube having an inner diameter of 3 cm and a constricted lower part was filled with absorbent cotton, and the adsorbent 1 shown in Table 1 was placed thereon.
0 g was filled, and absorbent cotton was used by further packing absorbent cotton on it. 100 g of an acrylic monomer SLMA (ester of methacrylic acid and an aliphatic monohydric alcohol having a carbon number of 12 and 13) containing 100 ppm of methoxyhydroquinone (MEHQ) as a polymerization inhibitor was passed through this and treated to obtain MEHQ in the effluent. Was measured by the following method.
The results are shown in Table 1. MEHQ measurement method 2 g of SLMA was dissolved in 3 g of glacial acetic acid, and 0.5 ml of saturated sodium nitrite solution was added thereto to cause coloration.
The absorption intensity at 0 nm was measured. This value is compared with the MEHQ content known data (calibration curve), and the HEHQ content (pp
m) was calculated.

Next, the effluent (purified monomer) was treated with a diameter of 6
mm, length 50 cm FEP (tetrafluoroethylene-hexafluoropropylene copolymer) tube, benzoyl peroxide as a polymerization initiator acrylic monomer 1
After using 0.5 part by weight with respect to 00 parts by weight for polymerization for 3 hours at 70 ° C., the transmittance of the obtained polymer at 420 nm was measured. The results are also shown in Table 1.

[0016]

[Table 1]

[0017]

According to the method for purifying a vinyl-based monomer of the present invention, the vinyl-based monomer can be purified by efficiently and easily and surely removing the polymerization inhibitor in the vinyl-based monomer.

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Claims (4)

[Claims] 1. A method for purifying a vinyl-based monomer, which comprises treating a vinyl-based monomer containing a polymerization inhibitor with an adsorbent to adsorb and remove the polymerization inhibitor in the vinyl-based monomer. 2. The purification method according to claim 1, wherein the vinyl-based monomer is an acrylic-based, styrene-based, vinyl acetate-based, acrylonitrile-based, or fluorinated ethylene-based monomer. 3. The purification method according to claim 2, wherein the acrylic monomer is an ester of (meth) acrylic acid and a monohydric alcohol having 1 to 20 carbon atoms. 4. The purification method according to claim 1, wherein the adsorbent is selected from alumina, silica gel, molecular sieve, activated carbon, ion exchange resin, chelate resin, zeolite and acid clay.