KR100196953B1 - Cleaning method of parts - Google Patents

Abstract

An object of the present invention is to provide a cleaning method for removing an object to be removed from the object to be removed, selected from the group consisting of a braze solvent and a hot melt adhesive, the cleaning method comprising a predetermined glycol ether component and a predetermined paraffinic system. It comprises a process of washing the said to-be-cleaned object using the washing | cleaning liquid which consists of a hydrocarbon component.

Description

How to Clean Parts

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method for cleaning and removing hot melt adhesive used in solder flux, abrasive grinding, and the like attached to various devices and components. Soldering fluxes (solder fluxes) are attached to various devices and components (for example, printed circuit boards) that have been soldered. This attached solder flux must be removed after soldering. In addition, when grinding or grinding a variety of parts, a method of separating the part from the jig by fixing the part to the jig with an adhesive and removing the adhesive after processing has been performed. As the adhesive used for fixing the component, a high temperature hot melt adhesive having a softening point of about 70 ° C. containing rosin ester resin or a perphenphenol resin as a main component is common.

Conventionally, as described above, chlorinated hydrocarbons such as chlorinated fluorofluorocarbons, 1,1,1-trichloroethane, trichloroethylene and dichloromethane, commonly known as freons, are used to remove flux after soldering and hot melt adhesives after polishing and grinding processing. Solvents have been mainly used.

However, it has become apparent that such chlorine-based solvents cause environmental problems such as ozone layer destruction and groundwater contamination. Therefore, in recent years, there is a tendency to reduce the use of such chlorine solvents. Therefore, the demand for a cleaning agent that can replace such a chlorine-based solvent is increasing. As such alternative cleaning solutions, many cleaning agents such as alcohols, hydrocarbons, glycol ethers, and surfactants have been developed.

However, such alternative cleaners have insufficient cleaning ability in cleaning solder fluxes and / or hot melt adhesives. It is therefore difficult to use such alternative cleaners as cleaners for braze fluxes and / or hot melt adhesives. Furthermore, unlike these chlorine solvents, these alternative cleaners have a high volatility, and thus have a problem that it is difficult to easily remove the cleaner attached to the object to be cleaned after washing. In addition, most of these alternative cleaners require treatment as industrial waste in the waste liquid treatment after the cleaning treatment. As a result, new environmental problems arise, and in addition, the cost of washing becomes larger compared with the chlorine-based solvent. Among the conventional alternative cleaners, the alcohol-based and hydrocarbon-based cleaners can perform distillation regeneration, so that generation of industrial waste can be suppressed relatively easily. However, such a cleaner has the problem that the cleaning property with respect to a lead point flux and a hot melt adhesive is inadequate.

It is known in the art to use the cleaning agent containing a glycol ether type compound and a hydrocarbon as a substitute of a chlorine solvent. For example, JP-A-3-146597 discloses a cleaning composition containing an aliphatic hydrocarbon having 8 to 12 carbon atoms and an organic compound having a polar group. Japanese Unexamined Patent Application Publication No. 4-341592 and Japanese Unexamined Patent Application Publication No. Hei 5-148499 disclose a cleaning agent containing a glycol ether compound and a hydrocarbon, but these cleaning agents have an interface as an essential component. A predetermined amount is included in the activator and water. Japanese Unexamined Patent Application Publication No. Hei 5-239495 describes a cleaning agent for paste containing a hydrocarbon having a predetermined boiling point and a predetermined glycol ether compound. Hydrocarbons having 10 to 18 carbon atoms and polyalkyleneglycols comprise a combination of C1 to C3 alkylethers and C4 and C8 alkylethers. Detergent compositions are described. Japanese Patent Laid-Open No. Hei 6-49493 discloses a cleaning composition comprising a C4-7 aliphatic glycol monolower alkyl ether, a C6-12 hydrocarbon and a hydrocarbon. However, the use of such a cleaner, in particular for hot melt adhesives, is neither disclosed nor suggested in the publication. Neither of these publications discloses or suggests that these cleaners are recovered and reused by distillation regeneration.

The first cleaning method of the present invention is a cleaning method for removing an object to be removed from the object to be removed, selected from the group consisting of a solder flux and a hot melt adhesive, substantially a glycol ether component (A) and a paraffinic hydrocarbon component (B). Washing the object to be cleaned using a cleaning liquid consisting of: wherein component (A) is selected from the group consisting of water-soluble glycol ether compounds of general formula (I) and (II) At least one glycol ether-based compound, wherein component (B) is at least one paraffinic hydrocarbon selected from the group consisting of n-paraffinic hydrocarbons and isoparaffinic hydrocarbons having 10 to 13 carbon atoms.

In the above formula,

R ¹ and R ² are each independently a methyl group or an ethyl group and R ³ and R ⁴ are methyl groups.

In a preferred embodiment, the mixing ratio of component (A) to component (B) is A: B = 50: 50 to 90:10 by weight.

In another preferred embodiment, said component (A) is at least one glycol ether type compound selected from the group consisting of diethylene glycol dimethyl ether diethylene glycol ether methyl methyl ether and diethylene glycol diethyl ether. And component (B) is at least one paraffinic hydrocarbon selected from the group consisting of n-undecane, n-dodecane and isododecane.

In another preferred embodiment said component (A) is at least one glycol ether compound selected from the group consisting of diethylene glycol dimethyl ether and dipropylene glycol dimethyl ether, said component (B) being n-decane .

In another preferred embodiment, the first method of the present invention also includes a step of removing as a water the cleaning liquid attached to the object to be cleaned.

In another preferred embodiment, the first method of the present invention also includes a method of removing, by drying, the cleaning liquid attached to the object to be cleaned.

In another preferred embodiment, the first method of the present invention further includes a step of recovering the cleaning liquid by distillation from the cleaning liquid after washing in which the object to be removed is dissolved, and a process of washing the cleaning object by reusing the recovered cleaning liquid. do.

In a preferred embodiment, the object to be removed is a hot melt adhesive.

The second cleaning method of the present invention is a cleaning method for removing an object to be removed from the object to be removed selected from the group consisting of a solder flux and a hot melt adhesive, substantially a glycol ether component (A) and a paraffinic hydrocarbon component (B). Washing the object to be cleaned using a cleaning liquid having a difference between the average boiling point of the component (A) and the average boiling point of the component (B) within 10 ° C. at 760 mmHg, and washing the dissolved object to be removed. Recovering the cleaning liquid by distillation from the subsequent cleaning liquid, wherein the component (A) is added to at least one glycol selected from the group consisting of water-soluble glycol ether compounds of the general formulas (III) and (IV). It is a tere type | system | group compound, The said component (B) is a group which consists of n-paraffinic hydrocarbon and isoparaffinic hydrocarbon of 10-13 carbon atoms. 1 is at least one paraffinic hydrocarbon selected from.

Wherein R ⁵ is an aliphatic group having 1 to 4 carbon atoms, R ⁶ is hydrogen, R ⁷ is a methyl group or an ethyl group, and R ⁸ is hydrogen.

In a preferred embodiment, the mixing ratio of component (A) and component (B) is A: B = 50: 50 to 90:10 by weight.

In another preferred embodiment, the component (A) is diethylene glycol, monoethyl ether, dietylene glycol monoisopropyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisobutyl ether and dipropylene glycol monoethyl At least one glycol ether compound selected from the group consisting of ethers, and the component (B) is at least one paraffinic hydrocarbon selected from the group consisting of n-dodecane, n-tridecane and isotridecane.

In another preferred embodiment, the second method of the present invention also includes a step of removing, as water, the cleaning liquid attached to the object to be cleaned.

In another preferred embodiment, the second method of the present invention also includes a step of washing the object to be cleaned by reusing the cleaning liquid recovered by distillation.

Therefore, the present invention can provide the following advantages.

(1) providing a cleaning method having high detergency to the solder flux and / or the hot melt adhesive, and (2) recycling to recover the cleaning liquid by distillation from the cleaning liquid after the dissolution of the solder flux and / or the hot melt adhesive. It is possible to provide this cleaning method, (3) to provide a cleaning method capable of easily removing the cleaning liquid attached to the object to be cleaned, and (4) to easily clean the cleaning liquid attached to the object to be cleaned by drying. It provides a cleaning method that can be removed.

These and other advantages of the present invention will be apparent to those skilled in the art according to the following detailed description.

The cleaning method of the present invention is a cleaning method for removing a removal object selected from the group consisting of a solder flux and a hot melt adhesive, from a to-be-cleaned object, and includes a predetermined glycol ether component (A) and a predetermined paraffinic hydrocarbon component (B). The process of washing | cleaning a to-be-cleaned object using the cleaning liquid which consists of these is included. Hereinafter, this process is called washing process. Substantially made from components (A) and (B) means that this cleaning liquid may contain, in addition to components (A) and (B), impurities of a nature and an amount that do not affect the properties of the cleaning liquid. do.

The cleaning method of the present invention can be used to remove a solder flux used for a printed board or the like. Alternatively, in the cleaning method of the present invention, in order to fix a jig and a part to be polished and ground in a polishing step of a ferrite head used in a magnetic recording device or the like or a glass block grinding step used in an ultrasonic delay element or the like, for example. It is possible to use for the removal of the hot melt adhesive used. But. The purpose of use of the cleaning method of the present invention is not limited to the above cases, but is used for any purpose requiring removal of a solder flux and / or a hot melt adhesive.

The brazing flux component removed by the washing method of the present invention generally consists of a rosin resin and an activator, and examples of the activator include organic acids such as hydrohalide and dicarboxylic acid. Examples of the molten adhesive removed by the washing method of the present invention include rosin resins, terpene resins, terpene phenol resins, polyester resins, paraffins, and the like.

The said washing process is performed by immersing the to-be-cleaned object with the removal object in a predetermined | prescribed washing | cleaning liquid, irradiating an ultrasonic wave, or oscillating as needed. Usually, this washing | cleaning process is performed at normal temperature-801 degreeC, Preferably it is 40-601 degreeC. The cleaning step may be performed once or by changing the cleaning solution several times, or the cleaning step may be performed by wiping the object to be cleaned with a cloth or the like moistened with the cleaning solution.

After the washing step, if necessary, the to-be-cleaned object to which the washing liquid is attached may be washed with water to remove the remaining washing liquid. This process is also called rinsing process. The rinsing process is performed by immersing the object to be cleaned with the cleaning solution in water. This rinsing step can also be repeated several times in the same manner as the washing step.

After the washing step, the furnace can dry remove the water or the washing liquid attached to the object to be cleaned after the rinsing step. This process is also referred to as a drying process below. The removal drying can be performed by any means such as air drying, warm air drying, and reduced pressure drying. According to the method of the present invention, depending on the cleaning product, it is also possible to perform only the drying step after the completion of the cleaning step without performing a rinsing step. .

According to this invention, the washing | cleaning liquid after the washing | cleaning process which melt | dissolves the removal object can be easily isolate | separated from the removal object by distillation, and it can recover regeneration. The liquid obtained by distillation is equivalent to the cleaning liquid before being used for the washing process, and can be used again for the washing process. Here, the equivalent of the cleaning liquid before use is that the mixing ratio of component (A) and component (B) is substantially Meaning no change (5% by weight or less, preferably 2% or less), and substantially no incorporation of the object to be removed (5% by weight or less, preferably 2% or less). do.

Moreover, according to this invention, the water after the rinsing process in which the washing liquid is dissolved can be easily separated from the washing liquid by distillation, and regeneration and recovery can be performed. The liquid obtained by distillation is water which does not melt | dissolve the washing | cleaning liquid substantially (mixing 5 weight% or less, Preferably it is 2 weight% or less), and can use it again for a rinsing process. Moreover, the residue after distillation is equivalent to a washing bag, and can be used again for a washing | cleaning process.

Hereinafter, preferred embodiments of the present invention will be described.

(1) The glycol ether component (A) used in the 1st washing | cleaning method of this invention is 1 or more types chosen from the group which consists of water-soluble glycol ether type compounds of general formula (I) and (II).

[Formula 1]

[Formula 2]

In the above formula, R ¹ and R ² are each independently a methyl group or an ethyl group, and R ³ and R ⁴ are methyl groups.

As shown in the above formula, the compound of the general formula (1) is diethylene glycol dialkyl ether having an oxyethylene addition mole number of 2, and the alkyl group represented by R ¹ and R ² is an alkyl group having 1 or 2 carbon atoms (ie, a methyl group or an ethyl group). )to be. Diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and diethylene glycol diethyl ether are mentioned as a water-soluble glycol ether type compound of General formula (1). In general formula (I), when the glycol ether type compound which is an R <^1> or R <^2> C3 or more alkyl group is used, the washing | cleaning liquid obtained is inferior to the solubility of the removal object and the rinse property by water. When the number of moles of oxyethylene addition is 1 (that is, in case of ethylene glycol dialkyl ether), the flash point is close to the washing temperature, and thus the safety is inferior. When the number of oxyethylene addition moles is 3 or more, the solubility of the object to be removed is inferior. When the number of moles of oxyethylene addition is 1 (that is, in case of ethylene glycol dialkyl ether), the flash point is close to the washing temperature, and thus the safety is inferior. When the number of oxyethylene addition moles is 3 or more, the solubility of the object to be removed is inferior. Compounds in which R ¹ or R ² is a hydrogen atom, i.e., dialkylene glycol monoalkyl ether, may also be used in the washing method of the present invention as described below, but in particular, in order to remove the hot melt adhesive, dialkyl ether is more preferable.

The compound of the general formula (II) is dipropylene glycol dimethyl ether, and the alkyl group represented by R ³ and R ⁴ in the general formula is an alkyl group having 1 carbon atom (ie, a methyl group). In general formula (II), since the glycol ether type compound in which R <^3> or R <^4> is a C2 or more alkyl group is not water-soluble, the rinse property by the water of the washing | cleaning liquid obtained falls to the extreme. When the number of moles of oxypropylene addition is 1, the flammability is close to the washing temperature, so the safety is inferior. When the number of moles of oxypropylene addition is 3 or more, the solubility of the object to be removed is inferior. Although the compound in which R <^3> or R <^4> is a hydrogen atom, ie, a dialkylene glycol monoalkyl ether, can also be used for the washing | cleaning method of this invention as mentioned later, in particular, in order to remove a hot melt adhesive agent, dialkyl ether is more preferable.

The paraffinic hydrocarbon (B) used in the first washing method of the present invention is one or more selected from the group consisting of n-paraffinic hydrocarbons or isoparaffinic hydrocarbons having 10 to 13 carbon atoms. Examples of hydrocarbons used in the present invention include n-decane, isodecane, n-undecane, isodecane, n-dodecane, isododecane, n-tridecane and isotridecane. Paraffinic hydrocarbons having less than 10 carbon atoms have a flash point lower than the washing temperature, so in consideration of safety, it is not preferable to use them in large quantities. Paraffinic hydrocarbons having 14 or more carbon atoms are insoluble in the object to be removed.

Although component (A) and component (B) can be used in arbitrary mixing ratios, when the washing | cleaning liquid which consists only of a component (A) or a component (B) is used, the washing | cleaning property of a removal object will be inferior. Component (A) and component (B) are preferably in a weight ratio of A: B = 30,70 to 90:10, more preferably in order to obtain a cleaning liquid having excellent performance in both the cleaning property of the object to be removed and the cleaning property by water. Is used as A: B = 50: 50 to 90:10, more preferably, A: B = 50:, 50 to 70:30. Generally, when there are too many component (A), the solubility of a removal object will fall, and when there are too many component (B), there exists a tendency for the washability by water to fall.

Component (A) is at least one glycol ether compound selected from the group consisting of diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and diethylene glycol colletyl ether, and component (B) is n-undecane, n Cleaning liquid which is at least one paraffinic hydrocarbon selected from the group consisting of dodecane and isododecane is particularly preferable because of high solubility of the substance to be removed. In this case, the preferable mixing ratio of component (A) and component (B) is A: B = 50: 50-90: 10.

Component (A) is at least one glycol ether compound selected from the group consisting of diethylene glycol dimethyl ether and dipropylene glycol dimethyl ether, and the cleaning liquid in which component (B) is n-decane is particularly excellent in cleaning and volatility. It is preferable because of that. In this case, the preferable mixing ratio of component (A) and component (B) is A: B = 30: 70 to 90:10. When using this washing | cleaning liquid, after a washing | cleaning process, it does not perform the rinse process with water, but directly A drying process can be performed. In addition, this cleaning liquid can also remove processing oils used in presses, cutting operations, and the like, and fingerprints attached to various devices and components, and can be used as a cleaning liquid for towels because of its high volatility. Moreover, since this washing | cleaning liquid has high washing | cleaning property, when a solder flux is removed using this washing | cleaning liquid, the amount of ions which remain in the to-be-cleaned object after washing | cleaning can be made very small. For example, in the case of a printed board, residual ions adversely affect insulation reliability, so this cleaning solution is particularly suitable for cleaning a printed board or the like.

When a dialkyl ether is selected as a component (A) in the 1st washing | cleaning method of this invention, the washing | cleaning agent which is especially excellent in the solubility to hot melt adhesive is obtained. Thus, the first cleaning method of the present invention is used to remove solder flux or hot melt adhesive, but is particularly suitable for removing hot melt adhesive.

As mentioned above, according to this invention, the washing | cleaning liquid which does not contain the removal object can be isolate | separated from the washing | cleaning liquid after use in a washing | cleaning process by distillation. In the first cleaning method of the present invention, the temperature required for separation of the cleaning liquid depends on the type of the cleaning liquid. In the case of normal pressure, it is about 1601 degreeC-2501 degreeC, and can isolate | separate at lower temperature under reduced pressure. For example, under a pressure of 20 mmHg, the distillation temperature is about 601 ° C to 110 ° C. In addition, when the used water is separated from the washing liquid by distillation in the rinsing step, the temperature required for separation of the water is about 100 ° C., which is the boiling point of water at normal pressure, and distillation is possible at a lower temperature under reduced pressure. For example, under a pressure of 20 mmHg, the temperature required for distillation is about 35 ° C.

The vacuum distillation apparatus used to separate the cleaning liquid and the object to be removed as described above, and to separate the water from the cleaning liquid, has a heating capacity of 50 ° C. or higher, preferably 100 ° C. or higher by explosion-proof use. It is preferably in the form of a batch consisting of cans, pressure reducers and cooling condenser sections, or connected to a cleaning line and a service tank.

(2) The glycol ether component (A) used in the 2nd washing | cleaning method of this invention is 1 or more types chosen from the group which consists of water-soluble glycol ether type compounds of general formula (III) and (IV).

[Formula 3]

[Formula 4]

In the above formula, R ⁵ is an aliphatic group having 1 to 4 carbon atoms, R ⁶ is hydrogen, R ⁷ is a methyl group or an ethyl group, and R ⁸ is hydrogen.

As shown in the above formula, the compound of general formula (III) is diethyleneglycol monoaliphatic ether having 2 moles of oxyethylene addition. In the general formula (III), the aliphatic group represented by R ⁵ is preferably an alkyl group having 1 to 4 carbon atoms, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl. Thus, preferably, the compound of formula (111) is diethylene glycol monoalkyl ether. In general formula (III), when R <^5> is a C5 or more aliphatic group, the wash liquid obtained is inferior to the solubility of the removal object and washability by water. When the number of moles of oxyethylene addition is 1 (that is, in case of ethylene glycol monoaliphatic ether), the flash point is close to the washing temperature, so the safety is inferior. If the number of moles of oxyethylene addition is 3 or more, the solubility of the object to be removed becomes poor.

The compound of the general formula (IV) is dipropylene glycol monomethyl ether or dipropylene glycol monoethyl ether, and the alkyl group represented by R ⁷ in the general formula is an alkyl group having 1 or 2 carbon atoms (ie, methyl group or ethyl group). In general formula (IV), when R <^7> is a C3 or more compound, since water solubility falls, the rinse property of the wash liquid obtained by water is inferior, and the solubility of a removal object is inferior. If the number of moles of oxypropylene moiety is 1, the flash point is close to the washing temperature, so the safety is poor. If the number of moles of oxypropylene moiety is 3 or more, the solubility of the object to be removed is inferior.

In the second cleaning method of the present invention, the paraffinic hydrocarbon (B) to be used is at least one selected from the group consisting of n-paraffinic hydrocarbons having 10 to 13 carbon atoms and isoparaffinic hydrocarbons. Hydrocarbons used in the present invention include n-decane, isodecane, n-undecane, isoundecan, n-dodecane, isododecane, n-tridecane and isotridecane. Paraffinic hydrocarbons having less than 10 carbon atoms have a lower flash point below the washing temperature, thus degrading safety. Paraffinic hydrocarbons having 14 or more carbon atoms are insoluble in the object to be removed.

In the second washing method of the present invention, the difference between the average boiling point and the paraffinic hydrocarbon component (B) at 760 mmHg of the glycol ether component (A) is within 101 ° C. An average boiling point is the substantial boiling point of each component, and shows the temperature at the time of showing a maximum peak, when each component is measured, heating up by the gas chromatograph method, for example. If the average boiling point difference is more than 10 ° C at 760 mmHg, the mixing ratio of component A and component B in the washing liquid recovered by distillation after the washing step may be inconsistent with the initial mixing ratio. The paraffinic hydrocarbon having 14 or more carbon atoms is inferior in solubility of the object to be removed as described above, and the average boiling point difference with the glycol ether component (A) exceeds 10 ° C.

Although component (A) and component (B) can be used in arbitrary mixing ratios, when the washing | cleaning liquid which consists only of component (A) or component (B) is used, the washing | cleaning property of a removal object will be inferior. Component (A) and component (B) are preferably A: B = 50: 50 to 90:10 in weight ratio in order to obtain a cleaning liquid excellent in both the cleaning property of the object to be removed and the performance of rinsing with water. When the mixing ratio is A: B = 50: 50 to 70:30, the solubility of the object to be removed and rinsing with water are further improved, which is more preferable. Generally, when there are too many components (A), the solubility of a removal object will fall, and when there are too many components (B), there exists a tendency for the rinse property by water to fall.

The example of the component combination of the washing | cleaning liquid obtained by the 2nd washing | cleaning method of this invention is shown below. About each component (B), the example of the component (A) whose difference of average boiling point is 10 degrees C or less was described. The average boiling point is described after each compound name.

[Example 1]

Component B: n-undecane (1921 degreeC)

Component A: diethylene glycol monomethyl ether (194 degreeC), diethylene glycol monoethyl ether (202 degreeC), dipropylene glycol monomethyl ether (188C), dipropylene glycol monoethyl ether (202 degreeC).

[Example 2]

Component B: Isododecane (197 ° C)

Component A: diethylene glycol monomethyl ether (194 ° C.),

Diethylene glycol monoethyl ether (202 degreeC) and dipropylene glycol monomethyl ether (202 degreeC).

Example 3

Component B: n-dodecane (210C)

Component A: diethylene glycol monoethyl ether (202 degreeC), diethylene glycol monoisopropyl ether (207 degreeC), diethylene glycol monopropyl ether (216 degreeC), dipropylene glycol monoisobutyl ether (220 degreeC), di Propylene glycol monoethyl ether (202 ° C.).

Example 4

Component B: n-tridecane (227 ° C)

Component A: diethylene glycol monoisobutyl ether (220 degreeC) and diethylene glycol monobutyl ether (231 degreeC).

In the second cleaning method of the present invention, the combination of the preferred component (A) and the component (B). Component (A) is one selected from the group consisting of diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisobutyl ether, and dipropylene glycol monoethyl ether. It is the above-mentioned glycol ether, and component (B) is a combination of 1 or more types of paraffinic hydrocarbon chosen from the group which consists of n-dodecane, n-tridecane, and isotridecane. Further preferred combinations are those shown in Example 3, i.e., component (A) is diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol It is a combination of one or more glycol ethers selected from the group consisting of monoethyl ether, and component (B) being n-dodecane. In such a combination, the solubility of the solder flux and the hot melt adhesive to be removed is high and the flash point is 701 ° C. or higher, so the cleaning stability is excellent.

As mentioned above, according to this invention, the washing | cleaning liquid which does not contain the removal object by distillation can be classified in the washing | cleaning liquid after a washing | cleaning process. In the second cleaning method of the present invention, the temperature required for separation of the cleaning liquid varies depending on the type of the cleaning liquid, but, for example, in the case of a mixture of diethylene glycol monoisobutyl ether and n-tridecane, at a normal pressure of 230 It can be separated about 120 degreeC under reduced pressure. Furthermore, when water after rinsing is separated from the washing liquid by distillation, the temperature required for water separation in the second washing method of the present invention is about 1001 ° C., which is the boiling point of water at normal pressure, and distillation is possible at a lower temperature under reduced pressure. For example, under the pressure of 20 mmHg, the temperature required for distillation is about 35 ° C.

As described above, the vacuum distillation apparatus used to separate the cleaning liquid and the object to be removed or to separate the water from the cleaning liquid is preferably the same as that used in the first cleaning process of the present invention described above.

In the second cleaning method of the present invention, in particular, by changing the average boiling point of the component (A) and the component (B) within a predetermined value, the compositional change of the recovered detergent and the initial detergent is minimized when distilling and using the cleaning liquid after use. It can be limited to. Therefore, the second washing method of the present invention is particularly suitable for recovering the used washing liquid by distillation.

EXAMPLE

Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following Examples, numerals indicate parts by weight unless otherwise indicated.

Examples 1 to 7 and Comparative Examples 1 and 2 below are examples and comparative examples of the first cleaning method of the present invention.

Example 1 and Comparative Example 1

The following experiments I to III were carried out using the cleaning liquid of the composition shown in Table 1 below.

In Table 1, glycol ether type compounds A-G and hydrocarbons a-e represent the following compounds, respectively.

Glycol Ether Compounds:

A: diethylene glycol dimethyl ether

B: diethylene glycol ethyl methyl ether

C: diethylene glycol diethyl ether

D: dipropylene glycol dimethyl ether

E. Diethylene glycol dibutyl ether

F: triethylene glycol diethyl ether

G: dipropylene glycol ethyl methyl ether

Paraffinic Hydrocarbons:

a: n-undecan

b: isododecane

c: n-dodecane

d: n-tridecane

e: n-tetradecane

Experiment I (Example 1 and Comparative Example 1)

Stainless steel jig (150 × 30mm, thickness) of 10 ferrite magnetic heads (20 × 5mm, thickness 1mm) used for video heads, etc., using high temperature melt adhesive (main component rosin resin, manufactured by Jong-E Industries Co., Ltd., brand name Electron Wax) 2mm) to one sheet. This was immersed in each of the cleaning liquids shown in Table 1 at 60 ° C, ultrasonic waves (47 kHz, 120 W) were irradiated, and the time when the magnetic heads were all peeled off the jig was measured. The results are shown in Table 2. Evaluation criteria for the results in the table are shown below.

Evaluation standard:

◎: peeling time less than 3 minutes

●: Peeling time 3 minutes or more and less than 5 minutes

△: peeling time 5 minutes or more and less than 10 minutes

X: Peeling time 10 minutes or more

Experiment II (Example 1 and Comparative Example 1)

Ultrasonic nature. Glass blocks (100 mm long, 20 mm wide, 30 mm high) used for devices are made of stainless steel fixtures (150 mm long, 100 mm wide) using a high-temperature melt adhesive (main component polyester resin, Ilhwa Precision Co., Ltd. product, Adopix). , 2 mm thick). After completion of the grinding process of cutting the glass to 1 mm, each cleaning solution shown in Table 1 is immersed at 60 ° C., and ultrasonic waves (47 kHz, 120 W) are irradiated. The time to peel all is measured. The results are shown in Table 2. Evaluation criteria for the results in the table are shown below.

Rating lift:

◎: peeling time less than 5 minutes

(Circle): Peeling time 5 minutes or more and less than 10 minutes

△: peeling time 10 minutes or more and less than 15 minutes

X: Peeling time 15 minutes or more

Experiment III (Example 1 and Comparative Example 1)

Ten ferrite magnetic heads and one stainless steel jig as used in Experiment I were immersed in the cleaning solution shown in Table 1 at 601 ° C. for 3 minutes, irradiated with ultrasonic waves (471 KHz, 120 W '), and ferrite magnetic heads and stainless steels. Completely peel off the steel jig. Thereafter, a ferrite magnetic head and a stainless steel jig are immersed in ion-exchanged water at room temperature for 30 seconds. Thereafter, these ferrite magnetic heads and stainless steel jig were placed in a thermostat at 100 ° C., and left for 30 minutes. After the moisture was completely removed, the liquid remaining in the ferrite magnetic head and stainless steel jig was extracted using carbon tetrachloride. This extract is analyzed by infrared spectrophotometry to determine the presence or absence of the remaining cleaning bag. The results are shown in Table 2. The evaluation criteria for the results in the table are shown below.

Evaluation standard:

(Circle): A washing | cleaning liquid does not remain and is excellent in rinsing property.

(Triangle | delta): The washing | cleaning liquid remains a little and rinsing property is inferior.

X: Many washing | cleaning liquids remain and rinse property is inferior.

As shown in Example 1 above. The cleaning liquid used in the cleaning method of the present invention is excellent in the removal property of the hot melt adhesive and the rinsing property by water.

On the other hand, the cleaning liquid of Comparative Example 1 is not suitable for the removal of the hot melt adhesive as described below.

Washing liquid (5): It does not contain hydrocarbons and consists only of water-soluble glycol ethers, and is insoluble in hot melt adhesives.

Washing liquid (6): It does not contain water-soluble glycol ether and consists only of hydrocarbons, and the removal of hot melt adhesive is poor, and the rinsing property is not excellent.

Washing liquid (7): R in general formula (I) Or R Glycol ether compounds having 3 or more carbon atoms are used, and the hot melt adhesive is not excellent in the removal and rinsing properties of the hot melt adhesive.

Washing liquid (8): In general formula (I), 3 or more glycol ether type compound of oxyethylene is used, and the removal property of a high temperature melt adhesive is inferior.

Washing liquid (9): The hydrocarbon of 14 or more carbon atoms is used, and the hot melt adhesive is inferior in removability.

Washing liquid (10): R in general formula (II) The glycol ether type compound of C2 (ethyl group) is used, and rinsing property is inferior.

Example 2

10 parts by weight of a high-temperature melt adhesive (manufactured by Nihon Electric Co., Ltd., product name Adopix) is dissolved in 90 parts by weight of a washing solution obtained by mixing 60% by weight of diethylene glycol ethylmethyl ether and 40% by weight of n-dodecane. 16 L of this solution is distilled off by heating to 110 DEG C under a reduced pressure of 30 mimHg. Distillation is carried out for 60 minutes.

As a result of analyzing the liquid obtained by distillation by infrared spectrophotometry, mixing of the hot melt adhesive was not confirmed. Moreover, when the said distillate was analyzed by the gas chromatograph method, it was confirmed that it was the wash | cleaning liquid like the initial compounding state. Using this distillate, the ferrite head and the jig peeling test were carried out in the same manner as in Experiment 1 of Example 1, and all the ferrite heads were peeled off the jig within 3 minutes. That is, the removal property of the high temperature melt adhesive equivalent to the detergent of the initial compounding state was obtained.

Example 3

10 pieces of magnetic heads (20 x 5 mm, thickness 1 mm) are made of stainless steel jig (150 x 30 mm, thickness 2 mm) using hot melt adhesive (trade name Electron Wax Co., Ltd.). To adhere to. The magnetic head is peeled off from the jig by the process shown in Table 3. The used washing | cleaning liquid is a mixture of 70 weight% of diethylene glycol dimethyl ether, and 30 weight% of isododecane.

In Table 3, the washing | cleaning process 1 and the washing | cleaning process 2 show that wash | cleaned twice by changing a washing | cleaning liquid. Rinse step 1 and rinse step 2 indicate that the rinse with tap water and ion exchange water, respectively.

By the process shown in Table 3, the ferrite head was peeled off the jig and the hot melt adhesive was also sufficiently removed. In addition, the distillate obtained as a result of distillation under reduced pressure was heated to 35 ℃ under a reduced pressure of 20mm1Hg for the solution mixed in the rinsing step 1 and the tap water was water, the mixed solution was less than 5% by weight . This distillate could be reused in rinsing step 1.

Most of the distillation residues were washing liquids, and the water content was 5% by weight or less. In addition, the ratio of diethylene glycol dimethyl ether and isododecane in the distillation residue was hardly changed in the initial state. Therefore, it was possible to reuse this distillation residue as a washing | cleaning liquid.

[Example 4 to Comparative Example 2]

Experiments I and II below were performed using the cleaning solution of the composition shown in Table 4 below.

DEGDM: Diethylene Glycol Dimethyl Ether

DPGDM: Dipropylene Glycol Dimethyl Ether

Experiment I (Example 4 and Comparative Example 2)

Printed boards soldered with capacitors and fixed resistors (5 cm surface area) ) As a test piece. The soldering process is performed using a rosin-based solder flux (solder flux: AGF-200-J3, manufactured by Asahi Chemical Co., Ltd.). This test operation is washed with each detergent shown in Table 4. Washing is performed by the process shown in Table 5 below. In Table 5, cleaning step 1 and cleaning step 2 show that the cleaning solution was changed and washed twice. Each cleaning process is carried out by placing 1000 ml of cleaning liquid in a 1000 ml beaker and dipping the test pieces in the cleaning liquid. The frequency of the ultrasonic wave used in the cleaning process 1 is 47 kHz, and the output is 120W.

After washing and drying by the process shown in Table 5, the amount of ions remaining in each test piece and the resin content such as rosin are measured to evaluate the solder flux removal ability of each cleaning liquid. An apparatus used for measuring the amount of ions is an ionic residue amount measuring device (omegameter, model 600S, manufactured by Alpha Metals, Inc.). Remaining resin powder is visually evaluated using a stereo microscope. The results are shown in Table 6. Evaluation criteria for the results in the table are shown below.

Evaluation standard :

Experiment II (Example 4 and Comparative Example 2)

Stainless steel jig (150 × 30mm, thickness 2mm) using 10 ferrite magnetic heads (20 × 5mm, thickness 1mm) used in video heads, etc. Bond to one piece. This was immersed in each cleaning liquid (1000 ml) of Table 4 put in a 1000 ml beaker at 401 ° C, irradiated with ultrasonic waves (47 KHz, 120 W), and the time taken for the magnetic head to peel off from the jig was measured. The results are shown in Table 6. The evaluation criteria for the results in the table are shown below.

Evaluation standard :

◎: less than 3 minutes of peeling time

○: Peeling time 3 minutes or more but less than 5 minutes

△: peeling time 5 minutes or more and less than 10 minutes

X: Peeling time 10 minutes or more

As mentioned above, as shown in Example 4, the washing | cleaning liquid used for the washing | cleaning method of this invention is excellent in soldering flux removal property and hot melt adhesive removal property. On the other hand, the cleaning solution of Comparative Example 2 is composed of only one of the glycol ethyl compound and the hydrocarbon, so that it is inferior in solder flux removal property and hot melt adhesive removal property.

Example 5

Printed boards soldered with capacitors and fixed resistors (5 cm surface area) ) As a test piece. Soldering treatment is performed using a rosin-based solder flux (solder flux: AGF-200-J3, manufactured by Asahi Chemical Co., Ltd.). This test piece is washed with a mixture of 50% by weight of dipropylene glycol dimethyl ether and 50% by weight of n-decane. Cleaning is performed by the process shown in Table 7 below. In Table 7, washing step 1 and washing step 2 show that the washing solution was changed and washed twice. Each cleaning process is performed by placing 1000 ml of washing liquid or water in a 1000 ml beaker and immersing test pieces therein. The frequency of the ultrasonic wave used in the washing | cleaning process 1 is 47KHz, and an output is 120W.

After completion of the cleaning process shown in Table 7, remove the test pieces from the cleaning solution, leave them in a drying container maintained at 601 ° C, and measure the time until the cleaning solution does not remain on the test pieces. It confirms by observing the presence or absence of the infrared peak of the specific wavelength from washing liquid. As a result, it was confirmed that no washing liquid remained in the drying time of 30 seconds in the drying container, and the washing liquid was sufficiently volatilized and dried.

Example 6

A cleaning solution consisting of a mixture of 30% by weight of dipropylene glycol dimethyl ether and 70% by weight of n-decane is allowed to soak into the fabric. Fingerprints were printed on stainless steel test pieces (150 x 30 mm, thickness 2 mm) and erased by the above fabrics. In addition, after the test pieces were left at room temperature after being removed, the cleaning solution was volatilized from the test pieces within 1 minute and did not remain.

Example 7

10 parts by weight of a high-temperature melt adhesive (manufactured by Ilhwa Precision Co., Ltd., trade name advance fix) is dissolved in 90 parts by weight of a cleaning liquid composed of a mixture of 60% by weight of dipropylene glycol dimethyl ether and 40% by weight of n-decane. 16 liters of this solution was warmed to 601 ° C. under reduced pressure of 20 mmHg and distilled for 60 minutes.

When the distillate was analyzed by ultraviolet spectrophotometry, the incorporation of the hot melt adhesive was not confirmed. Moreover, when the said distillate was analyzed by the gas chromatography method, it was confirmed that it is the washing | cleaning liquid like the initial compounding state. Subsequently, the ferrite head and bedding peeling experiments were carried out in the same manner as in Experiment II of Example 4 using the liquid obtained by distillation, and all ferrite heads were peeled from the bedding within 5 minutes. That is, the removal property of the high temperature melt adhesive equivalent to the detergent of the initial compounding state was obtained.

Experimental Examples 8 and 9 and 3 and 4 below are examples and comparative examples of the second cleaning method of the present invention.

Example 3 and Comparative Example 3

Experiments I to III below were carried out using the cleaning liquid of the composition shown in Table 8 below.

In Table 8, glycol ether type compounds H-O and hydrocarbons f-j show the following compounds, respectively.

Glycol Ether Compounds:

H: diethylene glycol monomethyl ether

I: diethylene glycol monoethyl ether

J: diethyl glycol monoisopropyl ether

K: diethylene glycol monoisobutyl ether

L: diethyl anglycol monobutyl ether

M: Dipropylene Glycol Monoethyl Ether

N: triethylene glycol monoethyl ether

O: dipropylene glycol monopropyl ether

Paraffinic Hydrocarbons:

f: n-decane

g: isododecane

h: n-dodecane

i: n-tridecane

j: n-tetradecane

Experiment I (Example 8 and Comparative Example 8)

Printed boards with capacitors and fixed resistors and soldered (5 cm surface area) ) As a test piece. The soldering process is performed using a rosin-based solder flux (solder flux: AGF-200-J3, manufactured by Asahi Chemical Co., Ltd.). This test piece is washed with each detergent shown in Table 8. Washing is performed by the process shown in Table 9 below. The washing process and the rinsing process are performed by immersing the test pieces in 1000 ml of cleaning liquid or water in a 1000 ml beaker. The frequency of the ultrasonic wave used in the washing | cleaning process is 47KHz, and the output is 120W.

Experiment II (Example 8 and Comparative Example 3)

After washing and drying by the process shown in Table 9, the amount of ions remaining in each test piece and the resin powder such as rosin are measured to evaluate the removability of the solder flux of each cleaning liquid. The device used for the measurement of the amount of ions is an ionic residue amount measuring device (omega meter, model 600SC, manufactured by Alpha Metals Co., Ltd.). Remaining resin powder is visually evaluated using a stereo microscope. The results are shown in Table 10. The evaluation criteria for the results in the table are shown below.

Experiment II (Example 8 and Comparative Example 3)

Stainless steel jig (150 × 30mm, thickness) using 10 ferrite magnetic heads (20 × 5mm, thickness 1mm) used for video heads using high-temperature melting adhesive (Sheden High School Co., Ltd., product name: Electron Wax) 2mm) adhere to 1 sheet. This was immersed in each cleaning liquid (1000 ml) of Table 8 put in a 1000 ml beaker at 40 ° C, irradiated with ultrasonic waves (47 KHz, 120 W), and the time taken for the magnetic head to peel off from the jig was measured. The results are shown in Table 10. The evaluation criteria for the results in the table are shown below.

Evaluation standard:

㉧: less than 7 minutes

○: ◎ It is less than ten minutes more than seven hours

△: peeling time 10 minutes or more and less than 15 minutes

X: Peeling time 15 minutes or more

Experiment III (Example 8 and Comparative Example 3)

Ten magnetic ferrite heads and one stainless steel fixture same as those used in Experiment II were immersed in each of the cleaning liquids shown in Table 8 for 1 minute at 40 ° C, followed by immersion in ion exchanged water at room temperature for 30 seconds. Then, the ferrite magnetic head and the stainless steel jig are placed in a thermostat at 100 ° C. and left for 30 minutes. After the water is completely removed, the remaining liquid in the ferrite magnetic head and the stainless steel jig is extracted using carbon tetrachloride. . The extract is analyzed by infrared spectrophotometry to evaluate the presence or absence of the remaining liquid. The results are shown in Table 10. The evaluation criteria for the results in the table are shown below.

Evaluation standard:

O: No cleaning liquid remains and the rinsing property is excellent.

(Triangle | delta): The washing | cleaning liquid remains a little and rinsing property is inferior.

X: Many washing | cleaning liquids remain and its rinse property is inferior.

As mentioned above, as shown in Example 8, the washing | cleaning liquid used by the washing | cleaning method of this invention is excellent in the removal property of a soldering flux, the removal property of a high temperature melt adhesive, and the rinsing property by water. On the other hand, the cleaning liquid of Comparative Example 3 is not suitable for the removal of the solder flux and the hot melt adhesive as described below.

Washing liquid 28: It consists only of hydrocarbon, and it is inferior to solder flux removal property and rinseability.

Washing liquid 29: It consists only of a water-soluble glycol ether type compound, and is inferior to the removal property of a high temperature melt adhesive.

Washing liquid 30: It uses the glycol ether type compound of 3 or more oxyethylene addition mole number, and is inferior to solder flux removal property, high temperature melt adhesive removal property, and rinsing property.

Washing liquid 31: Hydrocarbon 14 or more hydrocarbons are used, and solder flux removal property, high temperature melt adhesive, and rinse property are inferior.

Washing liquid (32): R in general formula (VI) Using this C3 or more aliphatic inglirol ether type compound, solder flux removal property and rinse property are inferior.

Example 9

10 parts by weight of a high-temperature melt adhesive (Niiga Seiko Co., Ltd., trade name Adopix) is dissolved in 90 parts by weight of a cleaning liquid obtained by mixing 70% by weight of diethylene glycol monoisobutyl ether and 30% by weight of n-tridecane. 6 L of this solution were warmed to 110 ° C. under reduced pressure of 30 mmHg. Distill for 60 minutes.

Analysis of the liquid obtained by distillation by infrared spectrophotometry showed no incorporation of the hot melt adhesive. Moreover, when the said distillate was analyzed by the gas chromatography method, it was confirmed that it is the washing | cleaning liquid same as an initial compounding state. Further, using this distillate, the ferrite head and the jig peeling experiment were carried out in the same manner as in Experiment II of Example 8, and all ferrite heads were peeled from the jig within 7 minutes. That is, the removal property of the hot melt adhesive equivalent to the detergent of the initial compounding state was obtained.

In addition, to 16 l of the solution (washing water: tap water = 15% by weight: 85% by weight) mixed with the washing solution generated in the rinsing step 1 of Table 9, the mixture was heated at 35 ° C under reduced pressure at 20 mmHg for 60 minutes under reduced pressure. As a result, 12 mm Hg of distillate was obtained. Most of this distillate was water, and the mixed washing liquid was 2% by weight or less. Thus, the distillate obtained can be reused in Process 1 shown in Table 9. Distillation residues are mostly washing liquids and the amount of water incorporated is 2% by weight or less. In addition, the ratio of diethylene glycol monoisobutyl ether and n-tridecane in the distillation residue was largely unchanged from the initial state. Therefore, it was possible to reuse this distillation admiration as a washing liquid.

[Comparative Example 4]

A mixture of 85% by weight of diethylene glycol monoethyl ether (average boiling point 202C at 760mmHg) and 15% by weight of n-tridecane (average boiling point at 227mmH at 760mmHg) having an average boiling point difference of about 25 ° C at 760mmHg. 16 L of the washing liquid was distilled at 1101 DEG C for 60 minutes under reduced pressure of 30 mmHg. The composition of the obtained distillate is analyzed by gas chromatography. As a result, unlike the initial blended state, diethylene glycol monoethyl ether was a composition exceeding 90% by weight. Using this distillate, the experiment which peeled a ferrite magnetic head from the jig by the method shown in the experiment 11 of Example 8 carried out the time required for peeling more than 10 minutes.

As described above, the present invention provides a cleaning method having high cleaning property against a solder flux and / or a hot melt adhesive. According to the washing | cleaning method of this invention, by using a predetermined | prescribed glycol ether compound and a paraffinic hydrocarbon in combination as a washing | cleaning liquid, high washing | cleaning property is obtained without using surfactant, and also the washing | cleaning liquid after washing which melt | dissolves the removal object at the same time. It is possible to recover and reuse the washing liquid by distillation. Therefore, according to the method of the present invention, it is possible to remarkably reduce industrial waste, and the cost required for cleaning can be greatly reduced.

Moreover, according to the washing | cleaning method of this invention, it becomes possible to remove the washing | cleaning liquid adhered to the to-be-cleaned object easily with water, and to remove the washing | cleaning liquid attached to the to-be-cleaned object easily by drying.

Various modifications and changes of the present invention can be easily made by those skilled in the art without departing from the scope and technical spirit of the present invention. Accordingly, the scope of the appended claims is not intended to be limited by the above description, but rather is to be construed broadly.

Claims (13)

A cleaning method for removing an object to be removed from a cleansing object selected from the group consisting of a solder flux and a hot melt adhesive, wherein the cleaning liquid comprises substantially a cleaning liquid consisting of a glycol ether component (A) and a paraffinic hydrocarbon component (B). And a step of washing the object to be cleaned, wherein the component (A) is a glycol ether compound selected from the group consisting of water-soluble glycol ether compounds of the general formula (I) and the general formula (II), And (B) is a paraffinic hydrocarbon selected from the group consisting of n-paraffinic hydrocarbons and isoparaffinic hydrocarbons having 10 to 13 carbon atoms. In the above formula, R ¹ and R ² are each independently a methyl group or an ethyl group, and R ³ and R ⁴ are methyl groups. The cleaning method according to claim 1, wherein the mixing ratio of component (A) and component (B) is A: B = 50: 50 to 90:10 in weight ratio. The compound (A) is a glycol ether compound selected from the group consisting of diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and diethylene glycol diethyl ether, and component (B) is n-undone. And a paraffinic hydrocarbon selected from the group consisting of can, n-dodecane and isododecane. The cleaning method according to claim 1, wherein component (A) is a glycol ether compound selected from the group consisting of diethylene glycol dimethyl ether and dipropylene glycol dimethyl ether, and component (B) is n-decane. The cleaning method according to claim 1, further comprising the step of removing the cleaning liquid adhering to the object to be cleaned with water. The cleaning method according to claim 4, further comprising a step of removing the cleaning liquid adhered to the object to be cleaned by drying. The cleaning method according to claim 1, further comprising a step of recovering the cleaning liquid by distillation from the cleaning liquid after washing in which the object to be removed is dissolved, and a step of reusing the recovered cleaning liquid to clean the object to be cleaned. . The cleaning method according to claim 1, wherein the object to be removed is a hot melt adhesive. A cleaning method for removing a removal object selected from the group consisting of a solder flux and a hot melt adhesive, substantially comprising a glycol ether component (A) and a paraffinic hydrocarbon component (B), the component at 760 mmHg. (A) the above-mentioned process is carried out by washing the object to be cleaned using a cleaning liquid having a difference between the average boiling point and the average boiling point of the component (B) within 10 ° C., and distilling from the cleaning liquid after washing to remove the object to be removed. Recovering the washing liquid, wherein the component (A) is a glycol ether compound selected from the group consisting of (III) and a water-soluble glycol ether compound of the general formula (IV), and the component (B) Paraffinic carbonization selected from the group consisting of 10-13 n-paraffinic hydrocarbons and isoparaffinic hydrocarbons The cleaning method characterized by the hydrogen. In the above formula, R ⁵ is aliphatic having 1 to 4 carbon atoms, R ⁶ is hydrogen, R ⁷ is a methyl group or an ethyl group, and R ⁸ is hydrogen. A method according to claim 9, wherein the mixing ratio of component (A) and component (B) is A: B = 50: 50 to 90:10 by weight. A group according to claim 9, wherein component (A) is composed of diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisobutyl ether, and dipropylene glycol monoethyl ether. And a glycol ether compound selected from the group consisting of paraffinic hydrocarbons selected from the group consisting of n-dodecane, n-tridecane and isotridecane. 10. The cleaning method according to claim 9, further comprising a step of removing the cleaning liquid attached to the object to be cleaned with water. The cleaning method according to claim 9, further comprising the step of reusing the cleaning liquid recovered by distillation to clean the object to be cleaned.