JP7654400B2 - A method for cleaning the inside of pipes using high-viscosity resin solutions - Google Patents

Description

This article describes a method for cleaning high-viscosity resin solutions inside pipes.

When a resin composition such as a liquid resin or resin solution has high viscosity and low miscibility with the solvent, it is necessary to flow a large amount of solvent at a high flow rate in order to remove the resin composition adhering to the wall surface, which can lead to problems such as the generation of a large amount of waste. Once the solvent has been flowed, the resin composition and the solvent can be mixed by leaving it to stand, which reduces the viscosity and makes it easier to remove, but in this case there is the problem of low work efficiency.

In order to solve the above problem, a separate circulation line for cleaning may be installed, but this may result in a complicated device configuration or a large amount of cleaning solution being required.
In addition, if the kneading device has a drive unit such as a screw, there is a method in which resin compositions with different viscosities are prepared separately and washed in sequence, but this may cause the subsequent resin composition to become the product to be mixed with the washing resin composition remaining in the device, resulting in a deterioration in the quality of the product resin composition (Patent Document 1).

Patent Publication No. 2018-42219

In the manufacturing process of high-viscosity resin solutions, there is a large difference in viscosity between the high-viscosity resin solution and the solvent, so the resin composition adhering to the wall surface cannot be removed unless a large amount of solvent is poured at a high flow rate, which is similar to the problem described above. In particular, when a static mixer is installed during the process, cleaning is particularly difficult because the elements inside the static mixer do not move.

The present invention aims to provide a cleaning method that improves the work efficiency of cleaning pipes and static mixers that have no driving parts inside the flow path in the manufacturing process of high-viscosity resin solutions.

The inventors conducted extensive research to solve the above-mentioned problems, and as a result, have completed the present invention. That is, the present invention has the following configuration.

[1]. A pipe cleaning method for cleaning a high-viscosity resin solution that has filled a pipe, the viscosity of the high-viscosity resin solution being 1200 to 4000 poise, the inside of the pipe being replaced with a resin solution of the same type that has a lower viscosity than the high-viscosity resin solution, the inside of the pipe being replaced several times with a resin solution of the same type that has a lower viscosity than the previous resin solution, and finally cleaning with an organic solvent.

[2]. The method for cleaning inside a pipe described in [1], characterized in that the low-viscosity resin solution is prepared by diluting the high-viscosity resin solution with an organic solvent.

[3]. The pipe cleaning method described in [1] or [2], characterized in that the low-viscosity resin solution is prepared using a batch-type mixing tank.

[4]. The pipe cleaning method according to any one of [1] to [3], characterized in that the resin solution is a polyamic acid solution.

[5]. The method for cleaning inside a pipe according to any one of [1] to [4], characterized in that the pipe is a static mixer.

The present invention makes it possible to improve the work efficiency of cleaning pipes and static mixers that do not have moving parts in the manufacturing process of high-viscosity resin solutions.

FIG. 1 is a diagram showing a polyamic acid production system.

The present invention can be suitably applied when the resin composition, such as a liquid resin or a resin solution, has high viscosity and low miscibility with the solvent. As a specific example, a method for cleaning inside pipes in a polyamic acid production system will be described, but the present invention is not limited to this.

The system is a polyamic acid production system that includes a reaction section that polymerizes polyamic acid and a mixer section that stirs the polymerization solution in which polyamic acid is dissolved. When the desired polyamic acid produced in the polyamic acid production system is a high-viscosity polymerization solution, a solvent is added to the high-viscosity polymerization solution produced in the reaction section to reduce the viscosity of the polymerization solution and obtain a low-viscosity polymerization solution, and the high-viscosity polymerization solution in the piping and mixer is replaced with the low-viscosity polymerization solution.

The system described above has a reaction section for polymerizing polyamic acid and a mixer section for stirring the polymerization solution in which polyamic acid is dissolved, but even if the mixer section is a pipe without a stirring function, if the desired polyamic acid produced in the polyamic acid production system is a high-viscosity polymerization solution, a solvent can be added to the high-viscosity polymerization solution produced in the reaction section to reduce the viscosity of the polymerization solution and obtain a low-viscosity polymerization solution, and the high-viscosity polymerization solution inside the pipe can be replaced with the low-viscosity polymerization solution.

The outline of the polyamic acid production system will be described with reference to Figure 1. The polyamic acid production system is a system for producing polyamic acid using a first solution A1 in which a first polymerizable compound having polyaddition properties is dissolved, and a second polymerizable compound having polyaddition properties that undergoes polyaddition with the first polymerizable compound as raw materials.

In the following, as an example, a case where one of the first polymerizable compound and the second polymerizable compound is a tetracarboxylic dianhydride and the other is a diamine will be described. More specifically, a case where the first polymerizable compound is a tetracarboxylic dianhydride and the second polymerizable compound is a diamine will be described.

The tetracarboxylic dianhydride is not particularly limited, and the same one as that used in conventional polyimide synthesis can be used. Specific examples of tetracarboxylic dianhydrides include 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 1,3-bis(2,3-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(2,3-dicarboxyphenoxy)benzene dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 2,2',6,6'-biphenyl tetracarboxylic dianhydride, naphthalene-1,2,4, Examples of the tetracarboxylic acid dianhydride include aromatic tetracarboxylic acid dianhydrides such as 5-tetracarboxylic acid dianhydride, anthracene-2,3,6,7-tetracarboxylic acid dianhydride, phenanthrene-1,8,9,10-tetracarboxylic acid dianhydride, and 2,2-bis(4-hydroxyphenyl)propane dibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride; aliphatic tetracarboxylic acid dianhydride such as butane-1,2,3,4-tetracarboxylic acid dianhydride; alicyclic tetracarboxylic acid dianhydride such as cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride; heterocyclic tetracarboxylic acid dianhydride such as thiophene-2,3,4,5-tetracarboxylic acid dianhydride and pyridine-2,3,5,6-tetracarboxylic acid dianhydride; and the like. The tetracarboxylic acid dianhydride may be used alone or in combination of two or more kinds.

As the solvent for the first polymerizable substance, one in which tetracarboxylic dianhydride and polyamic acid are dissolved is used. Specific examples of the solvent include amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and acetanilide; cyclic ester-based solvents such as γ-butyrolactone; chain ester-based solvents such as ethyl acetate; ketone-based solvents such as 2-propanone, 3-pentanone, acetone, and methyl ethyl ketone; ether-based solvents such as tetrahydrofuran and dioxolane; alcohol-based solvents such as methanol, ethanol, and isopropanol; aromatic hydrocarbon-based solvents such as toluene and xylene; and the like. Among these, amide-based solvents, cyclic ester-based solvents, and ether-based solvents in which polyamic acid is highly soluble are preferred. The solvent may be used alone or in a mixture of two or more types. For example, it is possible to improve the solubility of polyamic acid by mixing a highly polar alcoholic solvent with a solvent in which polyamic acid has a relatively low solubility, such as acetone, ethyl acetate, methyl ethyl ketone, toluene, or xylene.

The first solution A1 may contain a small amount of a tertiary amine such as trimethylamine or triethylamine in order to increase the solubility of the tetracarboxylic dianhydride or to increase the reactivity with the diamine.
The diamine is not particularly limited, and the same diamine as that used in conventional polyimide synthesis can be used. Specific examples of the diamine include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-bis(4-aminophenoxy)biphenyl, 1,4'-bis(4-aminophenoxy)benzene, 1,3'-bis(4-aminophenoxy)benzene, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-methylene-bis(2-chloroaniline), 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'- Examples of the diamine include aromatic diamines such as diaminodiphenyl sulfide, 2,6-diaminotoluene, 2,4-diaminochlorobenzene, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, and 4,4'-diaminobibenzyl; aliphatic diamines such as 1,2-diaminoethane, 1,4-diaminobutane, tetramethylenediamine, and 1,10-diaminododecane; alicyclic diamines such as 1,4-diaminocyclohexane, 1,2-diaminocyclohexane, bis(4-aminocyclohexyl)methane, and 4,4'-diaminodicyclohexylmethane; and heterocyclic diamines such as 3,4-diaminopyridine. One type of diamine may be used alone, or two or more types may be used in combination.

The diamine may be added as a solid, or may be added in the form of a solution using a solvent. A solvent that dissolves the diamine and polyamic acid is used. Specific examples of the solvent include amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and acetanilide; cyclic ester-based solvents such as γ-butyrolactone; chain ester-based solvents such as ethyl acetate; ketone-based solvents such as 2-propanone, 3-pentanone, acetone, and methyl ethyl ketone; ether-based solvents such as tetrahydrofuran and dioxolane; alcohol-based solvents such as methanol, ethanol, and isopropanol; and aromatic hydrocarbon-based solvents such as toluene and xylene. Among these, amide-based solvents, cyclic ester-based solvents, and ether-based solvents that have high solubility for polyamic acid are preferred. The solvent may be used alone or in a mixture of two or more types. For example, it is possible to improve the solubility of polyamic acid by mixing a highly polar alcoholic solvent with a solvent in which polyamic acid has a relatively low solubility, such as acetone, ethyl acetate, methyl ethyl ketone, toluene, or xylene.

As shown in FIG. 1, the polyamic acid production system is configured to produce polyamic acid by mixing the raw materials, a first polymerizable substance and a second polymerizable substance, in a solvent in a reaction section 11 and allowing a polymerization reaction to proceed to generate a polymerization solution A.

Next, a specific configuration of the polyamic acid production system will be described.
As shown in FIG. 1, the polyamic acid production system includes a reaction section 11, lines for supplying raw materials and a solvent to the reaction section 11, a supply pump 12 (first supply section), a mixer section 20, and a liquid transfer line L.

The reaction section 11 is a section that advances the polymerization reaction between the supplied first polymerizable compound and the second polymerizable compound. In this embodiment, the reaction section 11 advances a solvent, then advances a tetracarboxylic dianhydride and mixes it with the solvent to form a first reactant solution, and then advances a diamine, which is mixed with the first polymerizable substance solution to advance the polymerization reaction between the first polymerizable compound and the second polymerizable compound, thereby obtaining a polymerization solution A.

The first supply pump 12 (first supply section) supplies the polymerization solution A obtained in the reaction section 11 to the liquid delivery line L and the mixer section 20. The first supply pump 12 supplies the polymerization solution A at a predetermined liquid delivery rate. Although the mixer section 20 is shown in the figure, the mixer section may be a pipe without a stirring function.

The mixer section 20 is composed of a double pipe extending in a predetermined direction, and has an agitation section 21 arranged on the inside in the radial direction and a temperature adjustment section 22 arranged on the outside in the radial direction. The mixer section 20 is formed so that the polymerization solution A flows for a desired residence time.

The stirring unit 21 stirs the polymerization solution A without contacting the gas. In this embodiment, the stirring unit 21 stirs the polymerization solution A without contacting the gas in order to efficiently cool the polymerization solution A using the temperature adjustment unit 22.

The mixing section 21 is configured to include, for example, a static mixer such as a static mixer, a nozzle, or an orifice, or a driven mixer such as a centrifugal pump, a volute pump, or an in-line mixer with a mixing blade, preferably a static mixer, and more preferably a static mixer.

The static mixer is not particularly limited, and examples include static mixers such as Kenics mixer type, SuLzer SMV type, SuLzer SMX type, Tray Hi-mixer type, Komax mixer type, Lightnin mixer type, Ross ISG type, and Bran & Lube mixer type. Among these, Kenics mixer type static mixers are more preferable because they have a simple structure and therefore no dead space.

As described above, the case where one of the first polymerizable compound and the second polymerizable compound is a tetracarboxylic dianhydride and the other is a diamine has been described, but the present invention is not limited to this. For example, one of the first polymerizable compound and the second polymerizable compound may be a polyamic acid (prepolymer) with an acid anhydride group terminal or an amino group terminal, and the other may be a diamine or a tetracarboxylic dianhydride. In this case, when one of the first polymerizable compound and the second polymerizable compound is a polyamic acid with an acid anhydride group terminal, the other is a diamine. Also, when one of the first polymerizable compound and the second polymerizable compound is a polyamic acid with an amino group terminal, the other is a tetracarboxylic dianhydride.

In the polyamic acid production system of FIG. 1, after the polymerized polyamic acid solution is pumped using the first supply pump 12, a high-viscosity polyamic acid solution is present in the reaction section 11, the mixer section 20, and the liquid feed line L. When removing the high-viscosity polyamic acid solution from the reaction section, the mixer section, and the liquid feed line, a polyamic acid solution with a lower viscosity is prepared in the reaction section and pumped to replace the high-viscosity polyamic acid in the reaction section, the mixer section, and the liquid feed line, thereby enabling efficient cleaning.

A solvent is supplied to the reaction section 11 and mixed with the polymerization solution A present in the reaction section 11 to reduce the viscosity of the polymerization solution to obtain a low-viscosity polymerization solution, and the high-viscosity polymerization solution is replaced with the low-viscosity polymerization solution, thereby enabling simple and efficient cleaning.
Hereinafter, the low-viscosity polyamic acid solution for replacing the high-viscosity polymerization solution will be referred to as the "low-viscosity polymerization solution." In addition, the "viscosity" referred to in this specification is a value measured using an E-type viscometer at a temperature of 23° C. and a shear rate of 0.38 s ^-1 .

After preparing the low-viscosity polymerization solution in the reaction section 11, the low-viscosity polymerization solution is supplied from the first supply section to the mixer section and the liquid feed line, and the high-viscosity polymerization solution present in the mixer section and the liquid feed line is replaced with the low-viscosity polymerization solution. A polymerization solution with a lower viscosity than the low-viscosity polymerization solution is prepared by further supplying a solvent to the reaction section. By repeating the above operation, the viscosity of the low-viscosity polymerization solution is gradually lowered in the range of 200 to 1000 poise while being fed, and the high-viscosity polymerization solution can be washed without remaining inside the mixer section and the liquid feed line. The low-viscosity polymerization solution may be prepared by continuously supplying the solvent, or the supply of the solvent and the preparation of the low-viscosity polymerization solution may be repeated in a stepwise manner.

The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

Example 1
A 2000 poise polyamic acid N,N-dimethylformamide (hereinafter abbreviated as DMF) solution was prepared in the reaction section 11 and sent to a mixer section including a Kenics mixer type static mixer with an inner diameter of 8 mm, until the mixer section was filled with the 2000 poise polyamic acid solution. (Note that the viscosity is the viscosity at 23° C. measured with an E-type viscometer.)

In the reaction section 11, the high viscosity polyamic acid was mixed with DMF to prepare low viscosity polyamic acids of 1000, 500, 250, 100, 70 and 11 poise. 25 mL of each of the high viscosity polyamic acids was fed to the mixer section, and finally 125 mL of DMF was fed.
Observation of the mixer section revealed that all of the DMF had been replaced with DMF, and no polyamic acid solution remained.

(Comparative Example 1)
In the same manner as in the example, the mixer was filled with a 2000 poise polyamic acid solution, and 250 ml of DMF was fed into the mixer for cleaning. When the inside of the mixer was observed, it was found that the polyamic acid solution remained. Under conditions where the viscosity difference between the high-viscosity polyamic acid and N,N-dimethylformamide was large, the high-viscosity polyamic acid in the static mixer could not be completely removed.

1 Polyamic acid production system 11 Reaction section 12 First supply pump (first supply section)
20 Mixer section A Polymerization solution L Liquid delivery line

Claims (1)

A pipe cleaning method for cleaning a high-viscosity resin solution filled in a pipe, comprising the steps of:
The viscosity of the high-viscosity resin solution is 1200 to 4000 poise,
A resin solution of the same type having a lower viscosity than the high-viscosity resin solution is sent to replace the inside of the pipe,
The inside of the tube is then replaced several times with a resin solution of the same type but with a lower viscosity than the resin solution,
Finally, wash with organic solvent.
The piping is a static mixer,
the high-viscosity resin solution is a polyamic acid N,N-dimethylformamide solution,
a resin solution of the same type having a lower viscosity than the high-viscosity resin solution is a low-viscosity polymerization solution obtained by diluting the polyamic acid N,N-dimethylformamide solution with N,N-dimethylformamide;
the same kind of resin solution having a lower viscosity than the resin solution is a low-viscosity polymerization solution obtained by diluting the polyamic acid N,N-dimethylformamide solution with N,N-dimethylformamide, and has a lower viscosity than the same kind of resin solution having a lower viscosity than the high-viscosity resin solution;
The method for cleaning inside a tube , wherein the organic solvent is N,N-dimethylformamide .

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