Method for removing organic acid

Abstract

To provide a method of efficiently removing organic acids, which are one of causes of deterioration of the quality of a solvent for removing stains, when heating the solvent for removing stains such as processing oils, paints, inks, resins, foreign substances which adhere to parts manufactured in industrial fields such as automobiles, machines, precision equipment, printing, resin processing and molding processing, and to their manufacturing equipment and ancillary equipment, buildings, packaging materials, containers, floors, etc.SOLUTION: A solvent containing at least one of alcohol and ether in an amount of 10 vol.% or more and having an ignition point of 41°C or more or having no ignition point, and a solution containing an organic acid are brought into contact with a weak basic anion-exchange resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for removing organic acids.

Background Art

[0002] Parts manufactured in various industrial fields such as automobiles, machinery, precision instruments, printing, resin processing, and molding processing, and their manufacturing equipment, auxiliary equipment, buildings, packaging materials, containers, floors, etc. are contaminated with dirt such as processing oils, paints, inks, resins, and foreign substances. To remove these contaminants, halogen-based solvents, hydrocarbon-based solvents, glycol ether-based solvents, aqueous cleaning agents, semi-aqueous cleaning agents, and solvents obtained by mixing them are used as solvents for removing dirt.

[0003] As cleaning methods, there are a method of immersing an object to be cleaned in a cleaning tank containing a solvent for removing dirt and combining ultrasonic waves, jet flow, rocking, etc. for cleaning, or a method of spraying a solvent for removing dirt by a shower or spray for cleaning. In addition, a method of removing dirt by blowing steam into the solvent for removing dirt or by blowing steam is also used. When drying of the solvent for removing dirt is required, in addition to a method of drying by blowing warm air, a method of drying in a vacuum is also used.

[0004] In these cleaning steps, the dirt adhering to the object to be cleaned dissolves or mixes as impurities in the solvent for removing dirt. If cleaning is performed in a state where a large amount of impurities are dissolved or mixed, there is a risk that these impurities will reattach to the object to be cleaned, affecting the cleanliness and performance quality. Therefore, when impurities accumulate after using the solvent for removing dirt for a while, it is necessary to reduce the impurities and return to a clean state.

[0005] To clean the solvent for removing dirt, there is a method of discharging the solvent in which impurities have accumulated and replacing it with unused solvent. However, as a method with excellent running costs, there is a method of removing only the impurities in the solvent for removing dirt and reusing it as a regenerated liquid.

[0006] One method of obtaining a regeneration liquid is distillation separation. Generally, for a solvent that removes impurities and dirt, since the solvent for removing dirt has a lower boiling point, the impurities do not evaporate, and heating is performed under temperature and pressure conditions where only the solvent for removing dirt evaporates, and then cooling is carried out to condense and recover it as a clean regeneration liquid.

[0007] However, when regeneration by heating distillation or heating washing is repeated, and the solvent for removing dirt and the dirt are repeatedly heated for a long time, decomposition and reaction gradually occur, and a trace amount of organic acid is generated. Since the generated organic acid has a lower boiling point than the original substance, it may be mixed into the regeneration liquid. When washing is performed with a regeneration liquid containing an organic acid, there are problems such as the occurrence of stains due to a decrease in washing performance and the generation of an odor peculiar to the organic acid. For example, as an example of the decrease in washing performance, when dirt containing cations such as ammonium ions or sodium ions enters a regeneration liquid containing an organic acid, it reacts with the organic acid to form a solid salt at room temperature, resulting in stains during drying after washing. Therefore, it is necessary to remove the organic acid from the regeneration liquid.

[0008] As a method for removing organic acids in a solvent for removing dirt, in the field of dry cleaning, methods such as adsorbing fatty acids, which are a type of organic acid, onto adsorbents such as alumina silica gel and activated carbon called deacidifying agents have been used (for example, see Patent Document 1 and Patent Document 2). However, since it is in an equilibrium state only by the adsorption action and it is difficult to completely remove the organic acid, a technique that can more highly remove the organic acid using chemical reactions and the like is required.

[0009] In addition, as a method for removing organic acids from alcohol, there is a method of purifying an alcohol-containing liquid such as liquor by bringing it into contact with a strongly basic anion exchange resin, a weakly basic anion exchange resin, and a strongly acidic cation exchange resin (for example, see Patent Document 3). Although organic acids are also described as removal targets therein, the main purpose is to remove unpleasant odors such as aldehyde compounds and off-flavors caused by salts such as minerals, and the use is different from that of the present invention.

[0010] Although there is a method of removing mineral acids and organic acids from a solution using an ion exchange resin (see, for example, Patent Document 4), the actual solution is water (waste water), the object of using an anion exchange resin is a fuel cell, and although there is a description of organic acids, the acids to be actually removed are hydrofluoric acid, hydrochloric acid, sulfuric acid, etc., which are mineral acids showing high reactivity to metals compared to organic acids, that is, inorganic acids are the main targets. Different from the solvent for removing dirt which is the object of the present invention, and also different in the types of acids to be removed, so the present invention has a different use.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0012] An object of the present invention is to provide an effective method for removing trace amounts of organic acids contained in the regeneration liquid of a solvent for removing dirt.

Means for Solving the Problems

[0013] As a result of various studies to solve the above problems, the present inventors have found a method that does not adversely affect the solvent for removing dirt and can effectively remove organic acids, and thus have completed the present invention.

[0014] That is, the present invention relates to a method for removing an organic acid by bringing a solution containing a solvent having a flash point of 41 ° C or higher or no flash point and containing at least one of alcohol and ether in an amount of 10% by volume or more and an organic acid into contact with a weakly basic anion exchange resin.

[0015] Hereinafter, the present invention will be described in more detail.

[0016] The alcohol and ether described in the present invention are components constituting a solvent for removing dirt. When used as a solvent for removing dirt, it will be placed in a cleaning tank or the like, so a certain amount of inventory is required. However, if alcohol or ether is included as a component, in many cases it has a flash point, so if the inventory exceeds the specified quantity, it will be regulated by the Fire Service Act. However, if it is a mixed solvent with a flash point of 21 ° C or higher, although it falls under Class 4, Group 2 Petroleum or higher under the Fire Service Act, even if the inventory is less than the specified quantity, it can hold a sufficient amount as a solvent for removing dirt. Furthermore, if the flash point is 41 ° C or higher, it does not reach the flash point even under the cleaning condition of 40 ° C, which is often adopted to improve the cleaning effect, so it is relatively safe and commonly used. Also, if it is a mixed solvent that does not have a flash point at all, a sufficient amount can be held without being regulated by the Fire Service Act.

[0017] Note that the flash point in the present invention is for a solvent containing at least one of alcohol and ether in an amount of 10% by volume or more. When both alcohol and ether are less than 10% by volume, although it is on the safe side in terms of the flash point of the solvent, it is inferior in terms of detergency against dirt.

[0018] The alcohols and ethers described in the present invention are not particularly limited as long as they are liquid at room temperature and exhibit good detergency against dirt. However, in order to facilitate the drying of the object to be washed after washing, those having a boiling point of 230°C or lower are preferred. For example, alcohols having 6 or more carbon atoms such as hexanol, heptanol, octanol, nonanol, decanol, undecanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, etc. glycol ethers; glycols such as ethylene glycol, diethylene glycol, propylene glycol, hexylene glycol, isoprene glycol; methoxybutanols such as 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol; lactate esters such as methyl lactate, ethyl lactate; cyclic ether alcohols such as tetrahydrofurfuryl alcohol, furfuryl alcohol, etc. are exemplified.

[0019] Regarding the conditions for heating and distilling the solvent, there is no particular limitation as long as the dirt does not evaporate as a liquid or a solid and the solvent evaporates under the pressure and temperature conditions. However, temperature conditions of approximately 80°C to 250°C are generally used.

[0020] As a means for heating the solvent, there is no particular limitation, but those that do not pose a risk of ignition even when in contact with the solvent are desirable, and methods such as circulating heat transfer oil or steam in a pipeline, or heating wires can be used.

[0021] The organic acid to be removed is not particularly limited as long as it is generated by decomposition or reaction upon heating of ethanol or ether. However, since the purpose is to remove organic acids having a boiling point lower than that of the solvent for removing dirt, which are mixed into the regeneration liquid by heating and distillation, organic acids having a boiling point of 230°C or lower are particularly exemplified, such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, 3-hydroxypropionic acid, isobutyric acid, pivalic acid, 2-hydroxypropionic acid, 2,2-bis(hydroxymethyl)propionic acid, pyruvic acid, methacrylic acid, t-butylacetic acid, glyceric acid, 2,2-dimethylbutyric acid, 2-methylbutyric acid, isovaleric acid, 2-ethylbutyric acid, 2-hydroxyisobutyric acid, acrylic acid, 2-methyl-3-butenoic acid, glycolic acid, pentenoic acid, 3-ethoxypropionic acid, 2-methylvaleric acid, 3-methylvaleric acid, 4-methylvaleric acid, and other carboxylic acids.

[0022] The type of anion exchange resin is not particularly limited and can be used according to the application. However, since the solvent for removing dirt is required to be neutral, it is necessary to be neutral even in the state where the anion exchange resin is added. Therefore, weakly basic anion exchange resins are particularly preferred.

[0023] The mechanism by which the anion exchange resin removes organic acids is not particularly limited. However, in order not to reduce the cleaning quality of the solvent for removing dirt and to keep the liquid property neutral, it is preferable that the hydroxide ions derived from the anion exchange resin and the anions dissociated from the organic acids undergo an ion exchange reaction, and at the same time, the hydroxide ions and the protons dissociated from the organic acids react to form water, thereby converting the organic acids into water.

[0024] The temperature when the solvent for removing dirt is brought into contact with the anion exchange resin is not particularly limited. However, since the solvent for removing dirt may contain water, a temperature equal to or higher than the non-freezing temperature is desirable. Also, since the solvent for removing dirt may have a flash point, it is preferably below the flash point. Therefore, a temperature range of 0°C to 80°C is preferred.

[0025] When the flow rate at which the solvent for removing dirt is brought into contact with the anion exchange resin is not particularly limited, since the solvent for removing dirt may be a dangerous substance having a flash point, a flow rate of 1 m / second or less is preferred.

Advantages of the Invention

[0026] According to the method for removing organic acids of the present invention, in industrial fields such as automobiles, machinery, precision equipment, printing, resin processing, and molding processing, the organic acids in the solvents used to remove dirt such as processing oils, paints, inks, resins, and foreign substances adhering to parts manufactured, their manufacturing equipment and auxiliary equipment, buildings, packaging materials, containers, floors, etc. can be efficiently removed.

Examples

[0027] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0028] Example 1, Comparative Example 1 <Influence of Ion Exchange Resin on the Solvent for Removing Dirt> To 10 ml of Sample 1 (flash point: none) described in Table 1, 1.0% by weight of a basic anion exchange resin was added and allowed to stand for 2 days. After standing, the basic anion exchange resin was removed, and the change in the liquid color when 0.3 ml of BTB indicator was dropped was observed.

[0029] The BTB indicator shows yellow at pH 6 or lower and blue at pH 7.6 or higher. When the BTB indicator is added to the solvent for removing dirt in a state where no organic acid is generated, the liquid color becomes yellow. Therefore, even when a basic anion exchange resin is added to the solvent for removing dirt in a state where organic acid is generated, it is desirable that the liquid color becomes yellow when the BTB indicator is added. If the liquid color becomes blue, it is not preferred because the basicity of the added basic anion exchange resin is too strong. Therefore, the evaluation was performed according to the following evaluation criteria. The results are shown in Table 2.

[0030] Evaluation Criteria: 〇: The liquid color when the BTB indicator is added is yellow ×: The liquid color when the BTB indicator is added is blue Examples 2 - 3, Comparative Examples 2 - 4 <Effect of Ion Exchange Resin> To 10 ml of Sample 1 listed in Table 1, an acid remover such as an ion exchange resin was added, and the mixture was allowed to stand for 7 days. After standing, the acid remover was removed, 0.3 ml of BTB indicator was added, and neutralization titration was performed with a 0.02 N sodium hydroxide / methanol solution to measure the acid concentration.

[0031] The state where no organic acid was generated before heat distillation was defined as an acid concentration of 0%, and the acid concentration (day 0) in the state where organic acid was generated after heat distillation was defined as 100%. The degree of decrease in the acid concentration after 7 days was measured and evaluated according to the following evaluation criteria. The results are shown in Table 3.

[0032] Evaluation Criteria: ◎: Acid concentration after 7 days is 0 - 10% 〇: Acid concentration after 7 days is 11 - 50% △: Acid concentration after 7 days is 51 - 75% ×: Acid concentration after 7 days is 76 - 100% The meanings of the abbreviations in Table 1 are as follows.

[0033] DPM: Dipropylene glycol monomethyl ether DGDE: Diethylene glycol diethyl ether

[0034]

Table 1

[0035]

Table 2

[0036]

Table 3

[0037] Examples 4 - 12 <Acid Removal Effect of Weak Basic Ion Exchange Resin in Various Solvents> Each sample described in Table 4 was placed in a sample bottle, 1% by weight of a weakly basic ion exchange resin was added thereto, and the sample bottle was rotated at 100 rpm for 3 hours for stirring and then allowed to stand for 20 hours. After standing, the weakly basic ion exchange resin was removed, 0.3 ml of BTB indicator was added, and neutralization titration was performed with a 0.02N sodium hydroxide / methanol solution to measure the acid concentration.

[0038] The acid concentrations before and after adding the weakly basic ion exchange resin were compared, and an evaluation was carried out on how much acid could be removed. The results are shown in Table 5.

[0039] Comparative Examples 5 to 13 <Acid Removal Effect of Alumina Silica Gel in Various Solvents> In Examples 4 to 12, the acid removal effect of alumina silica gel was evaluated in the same manner except that alumina silica gel was added instead of the weakly basic ion exchange resin. The results are shown in Table 5.

[0040] The meanings of the abbreviations in Table 4 are as follows.

[0041] MMB: 3-Methyl-3-methoxy-1-butanol DPM: Dipropylene glycol monomethyl ether PNP: Propylene glycol monopropyl ether DGDE: Diethylene glycol diethyl ether HPN: Heptanol DGIB: Diethylene glycol monoisobutyl ether IPDM: Diethylene glycol isopropyl methyl ether

[0042]

Table 4

[0043]

Table 5

Claims

**Claim 1**: A method for removing an organic acid, comprising contacting a solution containing at least one cleaning solvent selected from the group consisting of water, n-decane, n-dodecane, alcohols having 6 or more carbon atoms, glycol ethers, glycols, methoxybutanols, and cyclic ether alcohols, wherein at least one of alcohol and ether is contained at 10% by volume or more, and the solvent has a flash point of 41 °C or higher or has no flash point, and an organic acid, with a weakly basic anion exchange resin. **Claim 2** The method for removing an organic acid according to claim 1, wherein the alcohol and ether are at least one selected from diethylene glycol monoisobutyl ether, diethylene glycol isopropyl methyl ether, 3-methyl-3-methoxy-1-butanol, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, heptanol, and diethylene glycol diethyl ether. **Claim 3** The method for removing an organic acid according to claim 1, wherein the alcohol and ether are at least one selected from diethylene glycol diethyl ether and dipropylene glycol monomethyl ether. **Claim 4** The method for removing an organic acid according to claim 1, wherein the solvent is a cleaning liquid.

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