JPH09165355A - Stabilization of vinyl monomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a vinyl monomer, especially acrylic acid or a solution containing acrylic acid by adding an inexpensive and easily separable specific polymerization inhibitor to the monomer. SOLUTION: Activated carbon is added as a polymerization inhibitor to a solution containing a vinyl monomer. The vinyl monomer is preferably dissolved in a solvent and the amount of the activated carbon is preferably 0.0001-10 pts.wt. based on the vinyl monomer. Preferably, the atmosphere in a storage vessel, etc., is substituted with a gas such as air or O2 and a vinyl monomer or a solution containing a vinyl monomer is charged together with activated carbon into the vessel and stored in air or an O2 gas atmosphere. Since the vinyl monomer is easily separable from activated carbon, the separation can be performed immediately before reacting the vinyl monomer to enable the supply of a vinyl monomer having improved purity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for stabilizing a vinyl monomer, particularly acrylic acid or a solution containing acrylic acid.

[0002]

2. Description of the Related Art Conventionally, vinyl monomers, especially acrylic acid, are active in polymerization and can easily be polymerized by heating. Therefore, various polymerization inhibitors have been proposed. There is. Currently used polymerization inhibitors are metals such as monomethylhydroquinone, phenothiazine, di-betanaphthol, copper, iron, chromium, zinc and mercury. These polymerization inhibitors are expensive, and since they dissolve in the vinyl monomer itself, there is a problem that they need to be removed before use.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a method for stabilizing a vinyl monomer, particularly acrylic acid or a solution containing acrylic acid, which is inexpensive, easy to separate, and has an excellent stabilizing effect. The purpose is to do.

[0004]

As a result of various studies on the method for achieving the above-mentioned object, the present inventors have surprisingly found that this can be achieved by using activated carbon as a polymerization inhibitor, and completed the present invention. . Such a function of activated carbon was first discovered by the present inventor.

Japanese Patent Laid-Open No. 50-143884 discloses activated carbon as a means for removing or containing hydroquinones added as a polymerization inhibitor to water-soluble monomers such as acrylic acid and sodium acrylate. Is described, but nothing about stabilization by activated carbon, polymerization inhibiting effect, etc. is described. Further, in Japanese Patent Publication No. 4-502468, in a method for producing an acrylic acid ester of a polyhydric alcohol, activated carbon is added to a mixture before the reaction to cause an ester reaction, thereby producing a reaction product which is undesirably strongly discolored. However, there is no description about the stabilization by activated carbon, the effect of inhibiting polymerization, etc.

[0006] As described above, there is no finding that the stabilization of a vinyl monomer, particularly acrylic acid or a solution containing acrylic acid, is associated with activated carbon. The gist of the present invention is as follows. (1) A method for stabilizing a vinyl monomer, which comprises allowing a vinyl monomer and activated carbon to coexist. (2) A method for stabilizing a vinyl monomer, wherein the vinyl monomer of (1) above is dissolved in a solvent. (3) A method for stabilizing a vinyl monomer according to the above (1) or (2), wherein 0.0001 to 10 parts by weight of activated carbon is added to the vinyl monomer. (4) A method for stabilizing a vinyl monomer as described in (1) to (3) above, wherein the vinyl monomer is acrylic acid.

The stabilization in the present invention is to prevent the vinyl monomer which is easily polymerized from being polymerized, and mainly to improve the storage stability.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the target vinyl monomer, acrylic acid, sodium acrylate, potassium acrylate, ammonium acrylate, acrylonitrile,
Examples thereof include acrolein, methacrylic acid, methacrylic acid salt, acrylic acid ester, methacrylic acid ester, vinyl alcohol, styrene monomer, vinyl chloride and vinylidene chloride. Further, a solution containing the above-mentioned vinyl monomer is also targeted. In particular, it can be preferably used for acrylic acid and acrylonitrile which are active in polymerization.

The solvent of the above solution is not particularly limited as long as it can dissolve the vinyl monomer, and water, organic solvents such as alcohols, ketones, carbon tetrachloride,
Saturated hydrocarbons, aromatic hydrocarbons, ethers and the like can be used. Further, the vinyl monomer or the solution containing the vinyl monomer may contain a small amount of by-products, impurities such as metal and dust, a polymerization inhibitor, or an antioxidant.

In the present invention, the target activated carbon is not particularly limited and may be powdery or granular. Also wood,
Activated carbon from any raw material such as coconut shell, coal and petroleum pitch may be used. Among them, powdery substances used for decolorizing, deodorizing and refining chemicals are preferable. The vinyl monomer and the activated carbon may coexist so that they can contact each other, and there is no particular limitation. It may be left standing or stirred.

The optimum amount of the activated carbon added to the vinyl monomer varies depending on the contact conditions, so it may be set according to the conditions, but 0.0001 to 10 to the vinyl monomer contained in the solution or the vinyl monomer contained in the solution.
It is preferable to add parts by weight. If it is less than 0.0001 parts by weight, its effect is small, and if it exceeds 10 parts by weight, the amount of activated carbon used is large, which is uneconomical.

In order to allow the vinyl monomer and the activated carbon to coexist and be stabilized, it goes without saying that the vinyl monomer or the solution containing the vinyl monomer contained in a container, a storage tank or the like should be mixed with nitric oxide or sulfur dioxide. It is better to avoid contact with active gases such as hydrogen. If possible, it is preferable to place in an atmosphere such as air or oxygen that has the effect of inhibiting polymerization. Specifically, the container or the like is replaced with a gas such as air or oxygen in advance, and then a vinyl monomer or a solution containing a vinyl monomer and activated carbon are charged, and an air or oxygen gas atmosphere is supplied while supplying air or oxygen gas. It is preferable to maintain the state. When storing, it is preferable to put it in a sealed container and keep it under the pressure of air or oxygen gas.

In order to coexist and stabilize the vinyl monomer and the activated carbon, it is preferable to place the vinyl monomer and the activated carbon in a light-shielded state at a low temperature. Although not desirable, the coexistence of the vinyl monomer and the activated carbon prevents the vinyl monomer from polymerizing even when exposed to a heating state for a short time. By coexisting the vinyl monomer and the activated carbon as described above, polymerization of the vinyl monomer does not occur even in a slightly heated state, and since a polymerization inhibitor or the like is not added, yellowing or the like caused by them does not occur. there is no problem. Further, since the vinyl monomer and the activated carbon can be easily separated, it is possible to perform the separation immediately before reacting the vinyl monomer, and it is also possible to supply a vinyl monomer of higher purity.

[0014]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. [Example 1] Acrylic acid 10 excluding the existing polymerization inhibitor
0.1 g of powdered activated carbon was added to g, and the mixture was heated and stirred at 125 ° C. for 50 minutes in an argon gas atmosphere. After cooling, the activated carbon was filtered and the NMR of the solution was measured to confirm the product.
As a result, no peaks derived from acrylic acid oligomers or polymers were confirmed, and it was found that all of them remained acrylic acid.

Comparative Example 1 2 g of acrylic acid excluding the existing polymerization inhibitor was heated at 125 ° C. in an argon gas atmosphere. Shortly after heating, the acrylic acid turned cloudy and became hop-corn like after 6 minutes. Example 2 In order to evaluate the polymerization inhibiting ability of activated carbon, hydrogen peroxide was used as a polymerization initiator, and
The effect was investigated. To 10 g of acrylic acid excluding the existing polymerization inhibitor, 7.8 g of 30% hydrogen peroxide and 0.2 g of powdered activated carbon were added, and the mixture was stirred while heating at 90 ° C. for 2 hours in an argon gas atmosphere. After cooling, the activated carbon was filtered, and the product was confirmed by measuring the NMR of the solution. As a result, it was found that no peak derived from an acrylic acid oligomer or polymer was observed, and the acrylic acid remained.

[Comparative Example 2] Hydroquinone monomethyl ether, which is a conventional polymerization inhibitor, was added to 30 parts without adding activated carbon.
When 10% of acrylic acid containing 00 ppm and 7.8 g of 30% hydrogen peroxide were added and heated in an argon gas atmosphere, a reaction was rapidly caused when the temperature of acrylic acid reached 70 ° C., and a polymer was produced. [Example 3] 5 g of acrylic acid excluding the existing polymerization inhibitor
0.05 g of powdered activated carbon was added to and heated at 125 ° C. without stirring. As a result, it was found that no polymer was formed even after heating for 80 minutes. [Example 4] Acrylic acid 10 excluding the existing polymerization inhibitor
0.2 g of powdered activated carbon was added to g, and the mixture was heated and stirred at 125 ° C. in an argon gas atmosphere. As a result, it was found that the polymer was not formed even after 10 hours.

[0017]

EFFECT OF THE INVENTION Stabilizing a solution containing a vinyl monomer, particularly acrylic acid or acrylic acid, by a method of coexisting the vinyl monomer and activated carbon as described above, which is inexpensive, easy to separate, and has an excellent stabilizing effect. It becomes possible to do.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C07C 21/02 C07C 21/02 67/62 67/62 69/54 69/54 Z 253/32 8927 -4H 253/32 255/08 8927-4H 255/08 // C08F 2/40 MCU C08F 2/40 MCU C09K 15/02 C09K 15/02

Claims (4)

[Claims] 1. A method for stabilizing a vinyl monomer, which comprises using activated carbon as a polymerization inhibitor. 2. The method for stabilizing a vinyl monomer according to claim 1, wherein the vinyl monomer is in a state of being dissolved in a solvent. 3. Activated carbon is added to 0.0 per vinyl monomer.
The method for stabilizing a vinyl monomer according to claim 1 or 2, wherein 001 to 10 parts by weight is added. 4. The method for stabilizing a vinyl monomer according to claim 1, wherein the vinyl monomer is acrylic acid.