JPH04330030A - Method for stabilizing aqueous solution of formaldehyde - Google Patents

Abstract

PURPOSE:To provide a method for stabilizing an aqueous solution of formaldehyde so as to prevent paraformaldehyde from precipitating and depositing even in the aqueous solution of the formaldehyde at a concentration as high as >=55wt.%. CONSTITUTION:The subject method is to stabilize an aqueous solution of formaldehyde by adding one or more compounds selected from compounds of ketones soluble in the aqueous solution of the formaldehyde thereto. Thereby, the aqueous solution of the formaldehyde can stably be handled even at low temperatures.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to the stabilization of aqueous formaldehyde solutions. More specifically, the present invention relates to a method for effectively preventing precipitation of paraformaldehyde in a highly concentrated formaldehyde aqueous solution.

0002

[Prior art] Formaldehyde is generally 37 wt%
It is commercially available as an aqueous formaldehyde solution. Moreover, in recent years, 40 to 50 wt % formaldehyde aqueous solutions have come to be used industrially as highly concentrated formaldehyde aqueous solutions. From the perspective of formaldehyde utilization, the higher the concentration of formaldehyde, the better; however, highly concentrated formaldehyde aqueous solutions are extremely unstable due to precipitation of paraformaldehyde.
Its handling is extremely difficult.

[0003] Generally, formaldehyde is mostly hydrated in an aqueous solution and exists as an equilibrium mixture of methylene glycol or lower polyoxymethylene glycol as shown in Formula 2 below.

0004

[Chemical 2]

[0005] As the formaldehyde concentration increases, this equilibrium shifts toward a higher degree of polymerization, and components with a higher degree of polymerization precipitate as paraformaldehyde which is insoluble in water. In severe cases, the entire product may solidify. Further, even if the temperature of the formaldehyde aqueous solution becomes low, the solubility of polyoxymethylene glycol decreases, and paraformaldehyde precipitates. An aqueous formaldehyde solution in which paraformaldehyde has precipitated is not only difficult to handle because of its varying concentration, but also causes clogging of equipment, piping, etc., making it difficult to use as an industrial raw material.

[0006] In order to prevent precipitation of paraformaldehyde in an aqueous formaldehyde solution, methods such as increasing the temperature of the aqueous formaldehyde solution, increasing the methanol content, and adding various additives have been taken. However, when the temperature is raised, formic acid is produced by the Cannizzaro reaction, causing corrosion problems. Furthermore, if the methanol content is high, there are problems such as separation of methanol during use. Various compounds have been disclosed as agents for preventing the precipitation of paraformaldehyde in an aqueous formaldehyde solution, and polyvinyl alcohol and formalized products thereof are known from Japanese Patent Publication No. 44-18282, Japanese Patent Application Laid-open No. 63-303944, and the like. In addition, triazine compounds are disclosed in Japanese Patent Publication No. 40-90 and Japanese Patent Publication No. 5
It is known from Japanese Patent Publication No. 7-61009, etc., and polyhydric alcohol compounds are disclosed in Japanese Patent Publication No. 37-4109, Japanese Patent Publication No. 3
Amide compounds are known from Japanese Patent Publication No. 12213/1982 and Japanese Patent Publication No. 26763/1989.

[0007]

[Problems to be Solved by the Invention] However, the above-mentioned additives exhibit sufficient effects when the concentration of formaldehyde is about 55 wt% or less, as described in the examples of the above-mentioned publications; There is no description of stabilization of a formaldehyde aqueous solution with a high concentration of % or more.

An object of the present invention is to provide a stabilization method that prevents paraformaldehyde precipitation even in a highly concentrated formaldehyde aqueous solution of 55 wt % or more.

[0009]

[Means for Solving the Problems] As a result of intensive studies in order to solve the above problems, the present inventors have found that by adding one or more types of ketone compounds that can be dissolved in an aqueous formaldehyde solution, 55 wt% The present invention has been completed based on the discovery that precipitation of paraformaldehyde can be effectively prevented even in formaldehyde aqueous solutions exceeding

That is, the present invention is a method for stabilizing an aqueous formaldehyde solution by adding at least one ketone compound soluble in the aqueous formaldehyde solution. The ketone compound used as a stabilizer for the formaldehyde aqueous solution according to the present invention is a ketone compound that can be dissolved in the formaldehyde aqueous solution. Specifically, it is at least one type of ketone compound selected from ketones, cyclic ketones, diketones, triketones, and tetraketones represented by the following formula 3.

[0011]

[C3]

More specifically, for example, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl hexyl ketone, diethyl ketone, ethyl propyl ketone, ethyl isopropyl ketone, ethyl butyl. Ketone, ethyl isobutyl ketone, dipropyl ketone, diisopropyl ketone, dibutyl ketone, diisobutyl ketone, holon, mesityl oxide, acetophenone, benzophenone, dipnon,
Monoketone compounds such as desoxybenzoin, phenylpropiophenone, methyldesoxybenzoin, pinacolin, cyclic ketone compounds such as cyclohexanone, methylcyclohexanone, isophorone, diacetyl, acetylacetone, propionylacetone, acetonyl acetone, diacetylpropane, diacetyl butane, Examples include diketone compounds such as diacetylpentane and dibenzoylmethane, triketone compounds such as triacetylmethane, and tetraketone compounds such as tetraacetyl ethane. These may be used alone or in combination of two or more.

Although it is not clear what mechanism these ketone compounds act to stabilize an aqueous formaldehyde solution, these ketone compounds produce methylol compounds and the like by reaction with formaldehyde in an aqueous formaldehyde solution. It is estimated that this contributes to stabilizing the formaldehyde aqueous solution. The amount of the ketone compound added to suppress the precipitation of paraformaldehyde in the formaldehyde aqueous solution is determined by the formaldehyde concentration of the formaldehyde aqueous solution, the temperature, the methanol concentration contained, etc.
It is preferable to add 1 wt% or more, more preferably 0.01 wt% or more, still more preferably 0.1 wt% or more.

[0014] The formaldehyde aqueous solution referred to in the present invention is
It refers to an aqueous solution containing formaldehyde, such as a solution produced by absorbing formaldehyde obtained through an oxidation reaction of methylal, methanol, or dimethyl ether in water, a solution produced by dissolving paraformaldehyde in water, and solutions of these solutions. Examples include solutions obtained by operations such as distillation and stripping. Further, these formaldehyde aqueous solutions may contain compounds such as methylal, methanol, dimethyl ether, formic acid, methyl formate, trioxane, etc., depending on the origin of formaldehyde, operation, etc.

[0015]

[Examples] The present invention will be explained in detail below with reference to Examples. [Example 1 and Comparative Example 1] The ketone compounds shown in Table 1 were added to a 65 wt% formaldehyde aqueous solution (containing 5.5 wt% methanol) and maintained at 90°C for 1 hour.
The temperature was gradually lowered and maintained at 67°C, and after 3 hours, the state of precipitation (white turbidity) of paraformaldehyde was visually observed. The results are shown in Table 1. [Example 2 and Comparative Example 2] The ketone compounds shown in Table 2 were added to a 65 wt% formaldehyde aqueous solution (containing 5.5 wt% methanol) and maintained at 90°C for 1 hour.
The temperature was lowered at a rate of 10° C./Hr, and the temperature at which paraformaldehyde precipitation (white turbidity) occurred was investigated. Table 2 shows the results.
Shown below. [Example 3] The ketone compounds shown in Table 3 were added to a 50 wt% formaldehyde aqueous solution (containing 4.0 wt% methanol), the temperature of the solution was maintained at 30°C, and after 1 day paraformaldehyde precipitation (white turbidity) occurred. ) was observed. The results are shown in Table 3. [Example 4 and Comparative Example 4] 70 wt% formaldehyde aqueous solution (methanol 1.6 wt%, formic acid 3.5 wt%
The ketone compound shown in Table 4 was added to the solution (containing), the temperature of the solution was maintained at 100°C for 30 minutes, and then the temperature was increased from 100°C to about 5°C.
The temperature was lowered each time and held at each temperature for 30 minutes to examine the temperature at which paraformaldehyde precipitation (white turbidity) occurred. The results are shown in Table 4. [Example 5] A solution obtained by adding 10 wt % acetylacetone to the formaldehyde aqueous solution of Example 1 was left at 70° C. for one day, but no clouding occurred. [Example 6 and Comparative Example 5] 0.001 wt % of dibenzoylmethane was added to a 37 wt % aqueous formaldehyde solution (containing 3 wt % methanol) and left at 0° C. for 1 day, but no clouding occurred. For comparison, an aqueous formaldehyde solution to which dibenzoylmethane was not added was also tested and resulted in white turbidity.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

Effects of the Invention The present invention can effectively prevent precipitation of paraformaldehyde even in an aqueous formaldehyde solution of 55% or more, and can be stably handled even at low temperatures.

Claims (2)

[Claims] 1. A method for stabilizing an aqueous formaldehyde solution, which comprises adding one or more types of ketone compounds soluble in the aqueous formaldehyde solution. 2. The method according to claim 1, wherein the ketone compound is at least one selected from ketones, cyclic ketones, diketones, triketones, and tetraketones represented by the following formula 1. [Chemical formula 1]