JP7198723B2 - Method for bagging flaky phthalic anhydride - Google Patents

Description

The present invention relates to a method for producing flakes of phthalic anhydride, and relates to a method of bagging flakes of phthalic anhydride obtained using a drum flaker.

A conventional method for producing flaky phthalic anhydride includes the method described in Patent Document 1. First, naphthalene is oxidized to obtain crude phthalic anhydride, and the resulting crude phthalic anhydride is distilled into a tank. Next, the molten phthalic anhydride in the tank is transferred to the drum flaker by a pump or the like. In the drum flaker, molten phthalic anhydride is adhered to the surface of the drum, and cooled to below the melting point of phthalic anhydride to solidify while exchanging heat by passing cooling water through the inside of the drum. The solidified phthalic anhydride is scraped off with a blade into flakes, which are then passed through the hopper of the scale and packed in bags.

That is, in the method for producing flakes of phthalic anhydride described above, the flakes of phthalic anhydride immediately after being solidified are packaged and shipped. Conventionally, paper bags have been used as bags for packaging, but in recent years, flexible container bags (hereinafter also referred to as “flexible container bags”) have become mainstream. A flexible container bag is a bag made of a soft material such as polypropylene or polyethylene. A hanging belt is attached to the top of the bag, and it has an inlet at the top and an outlet at the bottom.
When using a paper bag, the paper bag is torn at the shipping destination to release flakes of phthalic anhydride, but when using a flexible container bag, the outlet at the bottom is opened to release flakes of phthalic anhydride. Therefore, if flakes of phthalic anhydride form large agglomerates in the bag, in the case of flexible container bags, the discharge port is blocked and the problem arises that the flakes of phthalic anhydride cannot be discharged smoothly.

Patent Document 1 only states that the cooling temperature of the molten phthalic anhydride in the drum flaker is "up to the melting point of phthalic anhydride or lower", but does not describe the temperature at which flakes of phthalic anhydride are packed into bags. No.
Patent Document 2 also describes a method for producing flaky phthalic anhydride. In this method, the molten phthalic anhydride in the tank is dropped onto the upper surface of the lower stage of the steel conveyor, spread into a thin film, and cooled with cooling water from the spray nozzle while being sandwiched between the upper stages to solidify. After that, it is scraped by a scraping blade and stored in a hopper. Flakes at a temperature of 70° C. are exemplified as the coagulum stored in the hopper.

Patent Document 3 also describes a method for producing flakes of phthalic anhydride, and describes cooling the flakes of phthalic anhydride to 60°C.
Patent document 4 also describes a method for producing flaky phthalic anhydride, but this method is a method for making the final product a mixture of ellipsoidal particles, amorphous particles, and acicular crystal particles. , there is no description of the temperature at which flaky phthalic anhydride is packed.

Japanese Patent Application Laid-Open No. 2002-308865 JP-A-64-34977 U.S. Pat. No. 2,064,468 JP-A-62-42980

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of preventing the bagged flakes of phthalic anhydride from being smoothly ejected from the outlet at the bottom of the bag.

In order to solve the above problems, one aspect of the present invention provides a flaky form obtained by cooling and solidifying molten phthalic anhydride using a drum flaker, and cutting the solidified phthalic anhydride. Provided is a method for packing flakes of phthalic anhydride, wherein phthalic anhydride is packed at a temperature of 50° C. or less into a bag having a discharge port at the bottom.

According to the method of one aspect of the present invention, it is possible to prevent the bagged flakes of phthalic anhydride from being smoothly discharged from the outlet at the bottom of the bag.

FIG. 2 is a diagram for explaining a bagging method for flaky phthalic anhydride, and is a schematic diagram showing equipment used in the methods of Examples and Comparative Examples.

[Knowledge]
The present inventors made an earnest effort to investigate the cause of aggregation of flake phthalic anhydride in the flexible container bag, and found that the cause was derived from the sublimation property of phthalic anhydride. Part of the surface of the phthalic anhydride flakes sublimates in the flexible container bag, and when the sublimated material solidifies again, the re-solidified material becomes a binder and the phthalic anhydride flakes tend to aggregate with each other. It was found that the sublimation speed depends on the temperature, and when the temperature is 50° C. or higher, the sublimation becomes rapid and easy. Based on this knowledge, the present inventors discovered this invention.

[Embodiment]
Embodiments of the present invention will be described below, but the present invention is not limited to the embodiments shown below. Also, in the embodiments shown below, technically preferable limitations are made for carrying out the present invention, but these limitations are not essential requirements of the present invention.
In the method of this embodiment, a drum flaker is used to cool and solidify molten phthalic anhydride, and flaky phthalic anhydride obtained by cutting the solidified phthalic anhydride is transferred to a flexible container bag ( A bagging method for flaky phthalic anhydride to be filled in a bag having a discharge port at the bottom), wherein the temperature of the flaky phthalic anhydride to be filled in the flexible container bag is controlled to 50 ° C. or less. For this temperature control, the temperature of the cooling water used in the drum flaker is adjusted to, for example, 25° C. or less so that the temperature of the phthalic anhydride flakes immediately after cutting is always 50° C. or less.

As a result, the surfaces of the flakes of phthalic anhydride are less likely to sublimate in the flexible container bag, and a binder that aggregates the flakes of phthalic anhydride is less likely to occur. As a result, large agglomerates are less likely to be formed in the flexible container bag, so when the flaky phthalic anhydride is discharged from the flexible container bag at the shipping destination, it is possible to prevent the outlet from being clogged and the phthalic anhydride to be discharged smoothly.

The freezing point of phthalic anhydride is 131 ° C., and if the temperature is 131 ° C. or less, the molten phthalic anhydride solidifies and can be made into flakes. If the temperature is 60° C. or higher, the flaky phthalic anhydride tends to form large aggregates in the flexible container bag. If the outlet is blocked by these large aggregates, phthalic anhydride flakes will not come out of the flexible container bag just by opening the outlet at the bottom at the shipping destination. In other words, flakes of phthalic anhydride cannot be discharged smoothly from the outlet of the flexible container bag. In particular, when the outside air temperature is high in summer, the temperature of the flake-like phthalic anhydride in the flexible container bag tends to reach 60° C. or higher.

On the other hand, in the method of this embodiment, as described above, by controlling the temperature of the flaky phthalic anhydride filled in the flexible container bag to 50 ° C. or less, the flaky phthalic anhydride from the flexible container bag at the shipping destination It is possible to prevent the discharge port from being clogged when the acid is discharged.

EXAMPLES Examples and comparative examples of the present invention will be described below.
The equipment shown in FIG. 1 is for obtaining flakes of phthalic anhydride from molten phthalic anhydride and packing the obtained flakes of phthalic anhydride. It comprises a tank 1, a drum flaker 2, a pipe 3 from the tank 1 to the drum flaker 2, and a weighing machine 4.

The drum flaker 2 has a container 21 , a drum 22 , a scraping blade 23 , a flake discharge path 24 and an infrared thermometer 25 . Inside the drum 22, a downstream end portion of a cooling water inlet pipe 26 and an upstream end portion of a cooling water discharge pipe 27 are arranged. A water nozzle (not shown) for cooling the drum is installed inside the drum 22 , and cooling water is supplied to the water nozzle from a cooling water introduction pipe 26 . The cooling water accumulated in the lower part inside the drum 22 is discharged to the outside through the cooling water discharge pipe 27 .
As the drum 22 rotates, the molten phthalic anhydride 51 in the container 21 adheres to the surface of the drum 22 and is cooled and solidified. The solidified phthalic anhydride 52 is scraped off from the surface of the drum 22 by the scraping blade 23 to form flakes, which are directed toward the flake discharge path 24 . The infrared thermometer 25 detects the temperature of the phthalic anhydride flakes 53 immediately after being scraped off.

A pump 31 is installed on the tank 1 side of the pipe 3 . A downstream end portion of the pipe 3 is installed above the container 21 of the drum flaker 2 . By operating the pump 31 , the molten phthalic anhydride 51 in the tank 1 is supplied from the pipe 3 into the container 21 of the drum flaker 2 .
The weighing device 4 puts the flakes of phthalic anhydride 53 dropped from the flake discharge path 24 into the hopper and weighs them. By installing the flexible container bag 6 at the bottom of the hopper of the weighing device 4 and dropping the flake phthalic anhydride 53 in the hopper after weighing, the flexible container bag 6 is filled with a predetermined amount of flake phthalic anhydride. can be done.

In the method of the example, tap water of 36° C. was cooled and the temperature was controlled to 25° C., and the facility in FIG. 1 was operated. As a result, the temperature of the flaky phthalic anhydride 53 detected by the infrared thermometer 25 was always 50° C. or less. Therefore, flake-shaped phthalic anhydride was filled in the flexible container bag 6 at a temperature of 50°C or less.
In the method of the comparative example, tap water at 36° C. was used as it was as the cooling water, and the facility in FIG. 1 was operated. As a result, the temperature of the flaky phthalic anhydride 53 detected by the infrared thermometer 25 was 65°C. Therefore, flake-shaped phthalic anhydride was filled in the flexible container bag 6 at a temperature of about 65°C.

A flexible container bag filled with flaky phthalic anhydride by the method of the example and a flexible container bag filled with flaky phthalic anhydride by the method of the comparative example were stored in the same place for one week, and after storage, each flexible container The dimensions of the flaky phthalic anhydride in the bag were examined.
As a result, in the case of the flexible container bag filled with flaky phthalic anhydride by the method of the example, the size of the flaky phthalic anhydride in the flexible container bag was 10 cm ³ or less. Then, just by opening the discharge port of the flexible container bag, phthalic anhydride flakes could be discharged smoothly from the discharge port of the flexible container bag.

On the other hand, in the case of the flexible container bag filled with flaky phthalic anhydride by the method of the comparative example, most of the flaky phthalic anhydride in the flexible container bag is aggregates, and aggregates of 10,000 cm ³ Some of them were. Since such large agglomerates blocked the discharge port of the flexible container bag, phthalic anhydride flakes could not come out simply by opening the discharge port of the flexible container bag. Therefore, it was necessary to apply an external force in order to eject the flaky phthalic anhydride from the outlet of the flexible container bag.

As can be seen from these results, according to the method of the present invention, flaky phthalic anhydride is prevented from becoming large aggregates in the flexible container bag, and the flaky phthalic anhydride packed in the flexible container bag is It is possible to prevent it from being unable to smoothly come out from the discharge port at the bottom of the.

1 Tank containing molten phthalic anhydride 2 Drum flaker 21 Container 22 Drum 23 Scraping blade 24 Flake discharge channel 25 Infrared thermometer 26 Cooling water inlet pipe 27 Cooling water outlet pipe 3 Piping 4 Scale 51 Molten state Phthalic anhydride 52 Solidified phthalic anhydride 53 Phthalic anhydride in flakes 6 Flexible container bag (bag with outlet at the bottom)

Claims (2)

Using a drum flaker, the molten phthalic anhydride is cooled and solidified, and the flaky phthalic anhydride at a temperature of 50°C or less obtained by cutting the solidified phthalic anhydride is cut into flakes at a temperature of 50°C or less. A method of bagging phthalic anhydride flakes at temperature into bags having outlets in the bottom. 2. The method for packing flakes of phthalic anhydride according to claim 1, wherein said bag is a flexible container bag.

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