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

Abstract

To provide a cleaning method capable of improving working efficiency for cleaning a pipe having no driving part and a static mixer, in a production process of high viscosity resin solution.SOLUTION: A pipe inside cleaning method for cleaning high viscosity resin solution filling the inside of a pipe includes setting viscosity of the high viscosity resin solution at 1,200-4,000 poise, diluting the high viscosity resin solution with a solvent, feeding the same kind of resin solution having low viscosity and substituting the inside of the pipe, substituting the inside of the pipe with the same kind of resin solution having lower viscosity than that of the resin solution a plurality of times, and finally cleaning the inside of the pipe with an organic solvent.SELECTED DRAWING: None

Description

[Technical field]

[0001] This relates to a method for cleaning high-viscosity resin solutions from inside pipes. [Background technology]

[0002] When a resin composition such as a liquid resin or a resin solution has high viscosity and low miscibility with a solvent, the resin composition adhering to the wall surface cannot be removed unless a large amount of solvent is flowed at a high flow rate, which causes problems such as the generation of a large amount of waste. Once the solvent is flowed, the resin composition and the solvent are mixed by leaving it to stand, and the viscosity is reduced, making it easier to remove, but in this case there is a problem that the work efficiency is low.

[0003] 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, it is possible to prepare resin compositions with different viscosities separately and wash them one by one, but this may result in the subsequent resin composition that will become the product being mixed with the washing resin composition remaining in the device, causing a deterioration in the quality of the product resin composition (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2018-42219 Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacturing process of a high-viscosity resin solution, there is a large difference in viscosity between the high-viscosity resin solution and the solvent, so that the resin composition adhering to the wall surface cannot be removed unless a large amount of solvent is flowed at a high flow rate, which is similar to the problem in the above-mentioned technical background. In particular, when a static mixer is installed in the process, there is a problem that cleaning is particularly difficult because the elements inside the static mixer do not move.

[0006] An object of the present invention is to provide a cleaning method that improves the efficiency of cleaning pipes and static mixers that have no moving parts inside their flow paths in a manufacturing process for a high-viscosity resin solution. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0008] [1] A pipe cleaning method for cleaning a high-viscosity resin solution that has filled a pipe, the high-viscosity resin solution having a viscosity of 1200 to 4000 poise, the method including pumping a resin solution of the same type with a lower viscosity than the high-viscosity resin solution to replace the inside of the pipe, further replacing the inside of the pipe with a resin solution of the same type but with a lower viscosity than the resin solution several times, and finally cleaning with an organic solvent.

[0009] [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.

[0010] [3] The method for cleaning the inside of a pipe according to [1] or [2], characterized in that the low-viscosity resin solution is prepared using a batch-type mixing tank.

[0011] [4] The method for cleaning inside a pipe according to any one of [1] to [3], wherein the resin solution is a polyamic acid solution.

[0012] [5] The method for cleaning inside a pipe according to any one of [1] to [4], wherein the pipe is a static mixer. Effect of the Invention

[0013] INDUSTRIAL APPLICABILITY The present invention makes it possible to improve the efficiency of cleaning of piping and static mixers that have no moving parts in a manufacturing process of a high-viscosity resin solution. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing a polyamic acid production system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention can be suitably applied when a resin composition such as a liquid resin or a resin solution has high viscosity and low miscibility with a solvent. As a specific example, a method for cleaning the inside of a pipe in a polyamic acid production system will be described, but the present invention is not limited thereto.

[0016] The system is a polyamic acid production system including a reaction section for polymerizing polyamic acid and a mixer section for stirring a polymerization solution in which polyamic acid is dissolved. When a desired polyamic acid is produced in the polyamic acid production system as 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, thereby obtaining a low-viscosity polymerization solution, and the high-viscosity polymerization solution in the piping and the mixer is replaced with the low-viscosity polymerization solution, which is a feature of the inside-pipe cleaning method.

[0017] The above-mentioned system includes a reaction section for polymerizing polyamic acid and a mixer section for stirring the polymerization solution in which polyamic acid is dissolved. Even if the mixer section is a pipe without a stirring function, when 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.

[0018] An overview 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 as raw materials 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.

[0019] 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.

[0020] The tetracarboxylic dianhydride is not particularly limited, and the same one as that used in conventional polyimide synthesis can be used. Specific examples of the tetracarboxylic dianhydride 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.

[0021] 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; and aromatic hydrocarbon-based solvents such as toluene and xylene. 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. 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.

[0022] 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 one as that used in conventional polyimide synthesis can be used. Specific examples of the diamine include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, 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'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 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. The diamines may be used alone or in combination of two or more.

[0023] The diamine may be added as a solid, or may be added in the form of a solution using a solvent. The solvent used is one in which the diamine and polyamic acid are soluble. 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 in which polyamic acid is highly soluble are preferred. The solvent may be used alone or in a mixture of two or more. 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.

[0024] As shown in FIG. 1, the polyamic acid production system is configured to produce polyamic acid by mixing raw materials, a first polymerizable substance and a second polymerizable substance, in a solvent in a reaction section 11 and causing a polymerization reaction to proceed to generate a polymerization solution A.

[0025] 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.

[0026] The reaction section 11 is a section for promoting a polymerization reaction between the supplied first polymerizable compound and the second polymerizable compound. In this embodiment, the reaction section 11 supplies a solvent, then supplies a tetracarboxylic dianhydride and mixes it with the solvent to form a first reactant solution, and then supplies a diamine, which is mixed with the first polymerizable substance solution to promote a polymerization reaction between the first polymerizable compound and the second polymerizable compound, thereby obtaining a polymerization solution A.

[0027] 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.

[0028] The mixer section 20 is composed of a double pipe extending in a predetermined direction, and has an agitator section 21 disposed on the radially inner side and a temperature adjuster section 22 disposed on the radially outer side. The mixer section 20 is formed so that the polymerization solution A flows therethrough for a desired residence time.

[0029] 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 by the temperature adjustment unit 22.

[0030] The stirring 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 having a stirring blade, preferably includes a static mixer, and more preferably includes a static mixer.

[0031] The static mixer is not particularly limited, and examples thereof 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, Bran & Lube mixer type, etc. Among these, the Kenics mixer type static mixer is more preferable because it has a simple structure and therefore has no dead space.

[0032] 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 thereto. For example, one of the first polymerizable compound and the second polymerizable compound may be a polyamic acid (prepolymer) having 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 having 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 having an amino group terminal, the other is a tetracarboxylic dianhydride.

[0033] 1, after the polymerized polyamic acid solution is delivered 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 delivery line L. When removing the high-viscosity polyamic acid solution from the reaction section, the mixer section, and the delivery line, a polyamic acid solution having a lower viscosity is prepared in the reaction section and delivered to replace the high-viscosity polyamic acid in the reaction section, the mixer section, and the delivery line, thereby enabling efficient cleaning.

[0034] 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 is referred to as the low-viscosity polymerization solution. In addition, the "viscosity" in this specification is measured by an E-type viscometer at a temperature of 23°C and a shear rate of 0.38 s -1 The values ​​were measured under the following conditions.

[0035] 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 having 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, so that 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. EXAMPLES

[0036] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0037] 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, so that 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.)

[0038] 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 sent to the mixer section, and finally 125 mL of DMF was sent. Observation of the mixer section revealed that it had all been replaced with DMF, with no polyamic acid solution remaining.

[0039] 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 pumped 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. [Explanation of symbols]

[0040] 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

[Claim 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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