JP2008007690A - Washing solvent and washing method using the same and drying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a washing solvent which can wash articles with sufficient washing forces as a substitute for washing solvents containing chlorinated washing solvents as main components, is mild for environments and human bodies, has remarkably reduced ignitability, and can easily be handled, especially to provide a washing solvent which can sufficiently dissolve and wash urethanes adhered to the insides of nozzles or the like. <P>SOLUTION: This washing solvent is characterized by adding water to a solvent containing at least n-propyl bromide and a monohydric alcohol. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a cleaning solvent for cleaning articles, and particularly to a cleaning solvent that is friendly to the environment and the human body.

  Conventionally, chlorine-based cleaning solvents have been widely used for cleaning articles. For example, when a heat insulation panel such as a refrigerator is manufactured by filling a predetermined area with a urethane stock solution, a nozzle is used for injecting urethane. When the inside of the nozzle is cleaned after use, it is cleaned with methylene chloride. Was done.

  In the nozzle used for this urethane injection, the urethane stock solution remains inside after use, the remaining urethane solidifies over time, and the inside of the nozzle is blocked by the solidified urethane. In order to prevent this, as described above, for example, methylene chloride was introduced into the nozzle, and urethane was dissolved to perform cleaning (see Patent Document 1).

  However, the above-mentioned chlorine-based cleaning solvents and cleaning solvents based on them have a very high cleaning effect, but their safety, environment, and human influence are regarded as problems. Had to consider environmental regulations such as the PRTR Law.

JP-A-9-71622

  The present invention has been made in view of the above problems, and as an alternative to a cleaning solvent mainly composed of a chlorine-based cleaning solvent, it is possible to clean an article with sufficient detergency, and to the environment and the human body. An object of the present invention is to provide a cleaning solvent that is easy and easy to handle, with extremely low flammability. In particular, it is an object of the present invention to provide a cleaning solvent that can be sufficiently cleaned by dissolving urethane adhering to the inside of the nozzle or the like.

  In order to achieve the above object, the present invention provides a cleaning solvent characterized in that water is blended with a solvent containing at least n-propyl bromide and a monohydric alcohol (Claim 1). .

  Thus, if water is blended with a solvent containing at least n-propyl bromide and a monohydric alcohol, the article can be sufficiently washed with n-propyl bromide. Since it is not a cleaning solvent mainly composed of a chlorine-based cleaning solvent, it can be made friendly to the environment and the human body.

  For example, the urethane remaining inside the nozzle used when injecting the above-mentioned urethane stock solution can be dissolved and washed. In this case, since the cleaning solvent of the present invention contains a monohydric alcohol, in the waste liquid in which the urethane after cleaning is dissolved, the urethane reaction is successively prevented from solidifying due to successive urethane reactions. be able to. For this reason, it is possible to distill and purify the waste liquid after washing and to recycle the waste liquid. In this respect as well, it is economically friendly and environmentally friendly.

  In addition, since it contains alcohol, it has a flash point. However, since the present invention is such that water is added to such a solvent containing n-propyl bromide and monohydric alcohol. It is possible to eliminate the point and make the solvent non-hazardous. Alternatively, the flash point can be increased to make it difficult to burn at least until the flash point does not disappear.

At this time, the monohydric alcohol may be n-propyl alcohol.
Thus, if the monohydric alcohol contained in the solvent is n-propyl alcohol, n-propyl alcohol is relatively easy to handle without its flash point being too low, and it should be prepared at a low price. Therefore, the cost can be reduced. In addition, the high purity can be prepared, which is suitable for cleaning that requires high cleanliness.

Moreover, it is preferable that the water is blended in an amount of 0.75 wt% or more (claim 3).
Thus, if water is blended in an amount of 0.75 wt% or more, the flash point can be raised particularly effectively to make it difficult to burn, and the flash point can be eliminated.

Further, it may contain at least one stabilizer selected from nitroalkanes, ethers, epoxides and amines (Claim 4).
In this way, if it contains at least one stabilizer selected from nitroalkanes, ethers, epoxides and amines, the decomposition of the cleaning solvent is suppressed and the physical properties are stabilized. It can be a solvent.

Furthermore, it may contain at least one solvent selected from silicon-based solvents, fluorine-based solvents, chlorine-based solvents, and petroleum-based solvents (Claim 5).
In this way, if it contains at least one solvent selected from a silicon-based solvent, a fluorine-based solvent, a chlorine-based solvent, and a petroleum-based solvent, the product can be further blended by blending an appropriate amount depending on the purpose. It can be cleaned effectively.

Moreover, this invention provides the washing | cleaning method characterized by melt | dissolving and wash | cleaning urethane using the said solvent for washing | cleaning (Claim 6).
Thus, if the cleaning method is to dissolve and wash urethane using the above-mentioned cleaning solvent, the urethane adhering to the article such as a nozzle for injecting urethane is dissolved with n-propyl bromide, and the article is sufficiently It is possible to wash.

In addition, since the urethane reaction can be stopped in the waste liquid after washing due to the presence of monohydric alcohol and solidification of the waste liquid can be effectively prevented, the waste liquid can be recycled, for example, by distillation purification. Is possible.
Since the waste liquid can be reused in this way, it is environmentally friendly and does not contain a chlorinated solvent as the main component. Therefore, the impact on the environment and the human body can be significantly reduced, and it is economical. is there.

  Further, since a cleaning solvent containing water and having a flash point that is hard to burn or has no flash point is used, it is relatively easy to handle and can be cleaned easily. It can be suitably used for any urethane of soft, semi-rigid, hard, or elastomer type.

Moreover, this invention provides the drying method characterized by performing draining drying using the said solvent for washing | cleaning (Claim 7).
Thus, if it is the drying method which drains and drys using the said solvent for washing | cleaning, the goods wash | cleaned effectively can be dried. Further, for example, an explosion-proof device is not required, and safety can be improved and equipment costs can be reduced, compared to the case where draining and drying is performed using isopropyl alcohol as in the prior art.

The cleaning solvent of the present invention can remarkably reduce the adverse effects on the environment and the human body, and can clean articles with sufficient cleaning power. Further, it can reduce flammability, improve safety, and make it easy to handle.
And by using the solvent for washing | cleaning of this invention, it can melt | dissolve and wash | clean effectively and can drain and dry articles | goods more safely.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
As described above, a solvent mainly composed of a chlorine-based cleaning solvent, which has been widely used in the past, has a problem of adversely affecting the environment and the like. There is a need for a safer alternative solvent that has a good detergency and has little impact on the environment.

  In particular, for the nozzle used when injecting the urethane stock solution, in order to prevent clogging due to solidification of the urethane remaining inside the nozzle after use, it was conventionally cleaned using methylene chloride. There is a need for an effective solvent that can replace this.

  Therefore, the present inventors conducted extensive research on this alternative solvent, and as a result, it contains at least n-propyl bromide and a monohydric alcohol, and can be used in a wide range of applications as long as it is a cleaning solvent containing water. The present invention has been completed by finding that it can be used as a solvent and that it has a high detergency, particularly with regard to urethane cleaning, and can be used as a cleaning solvent with sufficient consideration for environmental problems. It was.

Hereinafter, the cleaning solvent of the present invention will be described in more detail.
As described above, the cleaning solvent of the present invention is a cleaning solvent containing at least n-propyl bromide and a monohydric alcohol, and further containing water. This n-propyl bromide, monohydric alcohol, and water will be further described.

First, since it contains n-propyl bromide that is less toxic and relatively stable in physical properties, it has a sufficient detergency for articles and can be used relatively safely. It can be used as a solvent.
As described above, by using a bromine-based solvent as a main component as a cleaning solvent, the influence on the environment can be remarkably reduced unlike a conventional solvent containing a chlorine-based solvent as a main component. Therefore, it can be set as the solvent for washing | cleaning excellent in consideration to the environment etc., and can be used suitably.

In addition, in order to stabilize the physical property of n-propyl bromide, a stabilizer can also be included, for example. By adding a stabilizer, it becomes possible to perform washing more reliably and stably. Examples of the stabilizer include nitroalkanes, ethers, epoxides, amines and the like. It is possible to contain at least one of these.
At this time, the content of the stabilizer can be appropriately adjusted according to the material of the substance to be cleaned, the cleaning conditions when performing the cleaning, and the like.

  In addition, since it contains a monohydric alcohol, it can effectively prevent the waste liquid from solidifying when the urethane reaction (urethane bond) proceeds in the waste liquid after washing, for example, when used for washing urethane. it can. The waste liquid can be recycled by performing distillation purification or the like on the waste liquid.

  This is because, for example, when a nozzle for injecting a urethane stock solution is washed, the solidified urethane remaining inside the nozzle is dissolved and washed out by n-propyl bromide in the cleaning solvent of the present invention. In the waste liquid in which an isocyanate having a plurality of isocyanate groups and a polyol having a plurality of hydroxyl groups exist, a urethane reaction in which the isocyanate and the polyol are bonded by the isocyanate groups and the hydroxyl groups occurs. Each has a plurality of isocyanate groups or hydroxyl groups, and the molecular chain becomes larger due to the urethane reaction. In this way, the urethane reaction proceeds one after another, and the waste liquid is solidified.

  However, if a monovalent alcohol is contained in the solvent as in the present invention, the isocyanate and polyol are bonded to the isocyanate group of the isocyanate by bonding the hydroxyl group of the monohydric alcohol in the waste liquid after use. Can be inhibited from binding. Since the monohydric alcohol has only one hydroxyl group, it is possible to prevent the molecular chain from increasing, unlike a polyol having a plurality of hydroxyl groups. Thus, it is possible to prevent the urethane reaction from occurring one after another, effectively prevent the waste liquid from solidifying, and improve the recovery rate of the waste liquid.

  Although such monohydric alcohol is not specifically limited, For example, it can be set as n-propyl alcohol, methanol, isopropyl alcohol, isobutyl alcohol, n-butyl alcohol, octanol, benzyl alcohol, t-butyl cellosolve, etc. In particular, n-propyl alcohol is preferable because, as shown in Table 8, the flash point is not too low, and a relatively low price and high purity can be obtained. Of course, other monohydric alcohols can also be used. It can be determined each time in consideration of the object to be cleaned, cleaning conditions, cost, and the like.

  In addition, the larger the proportion of the monohydric alcohol in the solvent, the easier it is to inhibit the urethane reaction from proceeding, and it becomes easier to recycle by distillation purification. The larger the ratio is, of course, flammability, the lower the flash point, and the more easily the solvent burns. Such flammability is inconvenient in terms of handling because, for example, the Fire Service Act is touched.

Therefore, the present inventors have found that by intentionally blending water, such flammability can be eliminated, or the flash point can be increased to make the solvent more difficult to burn.
That is, as described above, the cleaning solvent of the present invention contains alcohol, and if the proportion of alcohol increases, it becomes a solvent having a flash point as it is, but by blending a predetermined amount of water. It is possible to make a cleaning solvent that raises the flash point and is difficult to catch fire. Furthermore, it has been discovered that flammability can be eliminated by adding an appropriate amount of water. In particular, if flammability can be eliminated, non-hazardous materials can be obtained, and handling and the like are facilitated.

As a result of further studies by the present inventors, it has been found that if water is blended in an amount of, for example, 0.75 wt% or more, it can be made particularly difficult to burn.
The concentration of water that can eliminate the flash point, or that can be made difficult to burn by raising the flash point, varies greatly depending on the amount of monohydric alcohol and the amount of other components in the cleaning solvent. Therefore, it is only necessary to conduct experiments or the like in advance each time, measure the appropriate amount of water, and add water accordingly.

Thus, since the flash point can be adjusted to some extent by adding water, the amount of monohydric alcohol in the cleaning solvent of the present invention can be made relatively large. In other words, not only soft urethane with relatively low isocyanate but also hard urethane with relatively high isocyanate is dissolved and washed, the progress of urethane reaction can be sufficiently inhibited, and waste liquid can be recycled. is there.
A large amount of isocyanate is present in the waste liquid in which hard urethane is dissolved, but a sufficient amount of monohydric alcohol can be contained in the waste liquid without being insufficient with respect to the amount of isocyanate in the waste liquid. It is possible to effectively suppress the urethane reaction.

In addition, if the proportion of water is increased more than necessary, for example, the storage can for storing the cleaning solvent of the present invention may be rusted or the stability of the solvent may be affected. Therefore, it is preferable to blend in as small a proportion as possible.
Such an appropriate proportion of water blending (upper limit etc.) also varies depending on other components of the cleaning solvent, and therefore an appropriate amount of water may be determined each time by conducting an experiment in advance.

  As described above, the cleaning solvent of the present invention containing at least n-propyl bromide and a monohydric alcohol and blended with water further includes, for example, a silicon solvent, a fluorine solvent, a chlorine solvent, petroleum It is possible to contain a solvent such as a system solvent. Each of these solvents may be contained alone in the cleaning solvent of the present invention, or a plurality of these solvents may be combined and contained in the cleaning solvent.

  For example, in the case of the cleaning solvent of the present invention further containing a fluorinated solvent, when this solvent is used for dry cleaning, etc., the cleaning solvent should not contain chlorine (or make it a trace amount). In addition, since it is possible to eliminate the influence on the human body such as burns and rough skin, it is possible to provide a suitable cleaning solvent that significantly suppresses adverse effects on the environment and the human body.

And in this invention, the washing | cleaning method which melt | dissolves urethane and wash | cleans is provided using the solvent for washing | cleaning of this invention as mentioned above.
When injecting the urethane stock solution into a predetermined space, a nozzle or the like is used. However, the urethane stock solution remains in the nozzle after the injection, and the urethane solidifies over time. Then, by solidifying, the inside of the nozzle is blocked, and as it is, it becomes impossible to inject the urethane stock solution through the nozzle.

  Therefore, if the cleaning solvent of the present invention is supplied into the nozzle, the urethane solidified inside the nozzle can be dissolved and cleaned. The inside of the nozzle can be sufficiently cleaned with n-propyl bromide, which is a bromine-based cleaning solvent, instead of a conventional solvent mainly composed of a chlorine-based cleaning solvent.

  And when the washing | cleaning method of this invention is implemented, it is possible to reuse the waste liquid after this washing | cleaning. As described above, the monohydric alcohol contained in the cleaning solvent of the present invention is combined with the isocyanate in the waste liquid, so that the isocyanate and polyol in the waste liquid are successively urethane-bonded in a chain to solidify the waste liquid. Can be effectively prevented. For this reason, the waste liquid can be purified by distillation, and the waste liquid can be recycled.

  Moreover, if the washing | cleaning method of this invention is implemented, the waste liquid wash | cleaned by melt | dissolving not only soft urethane but hard urethane can be recycled. The cleaning solvent of the present invention contains water and can eliminate the flammability by containing the above monohydric alcohol, or raise its flash point to make it more difficult to burn. It can be handled easily even if the alcohol content is relatively large. Thus, if the alcohol content is high, even a hard urethane having a relatively large amount of isocyanate can provide a monohydric alcohol without being insufficient with respect to the amount of the isocyanate. The progress of solidification of the waste liquid can be prevented by suppressing the progress of the bonding one after another.

  In the above description, the urethane inside the nozzle has been described as an example. However, the article to be cleaned is not limited to such a nozzle, and may be, for example, a tank for storing a urethane stock solution. .

In addition, the cleaning solvent of the present invention can be suitably used when draining and drying without contaminating the cleaned product.
For example, when the substrate is washed with water and then drained and dried, the substrate is conventionally placed in the vapor of isopropyl alcohol, and the water adhering to the substrate is replaced with isopropyl alcohol for dehydration. In such a conventional method, since isopropyl alcohol is ignitable, it is necessary to take measures for explosion-proofing the apparatus that performs draining and drying.

However, if the drainage drying is performed using the cleaning solvent of the present invention instead of the isopropyl alcohol, that is, the drainage drying is performed with the cleaning solvent having no flash point without contaminating the substrate by blending an appropriate amount of water. Therefore, it is possible to remarkably reduce the possibility of an explosion or the like that is a concern in the conventional method, and to improve safety.
In addition, the equipment for explosion-proofing can be relaxed compared to the conventional one, and the cost can be reduced.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this.
(Examples 1-5)
The cleaning solvent of the present invention was prepared, the Cleveland open test was performed, and the flash point of each sample was measured. The prepared samples were prepared by mixing 85 wt% of solvent X (no flash point) and 15 wt% of (n-propyl alcohol + water) (see Table 1). A to E are samples with different ratios of n-propyl alcohol and water in Table 3.
The composition of the solvent X and the physical properties of each component are shown in Table 2. As shown in Table 2, the solvent X contains 95% by weight of n-propyl bromide and 5% of a stabilizer (nitroethane, 1,2-butylene oxide, 1,3-dioxolane).
Table 3 shows the ratio of n-propyl alcohol to water.
In addition, regarding the determination of the flash point when the Cleveland open-type test was performed, the temperature at the time of continuous combustion for 5 seconds or more was taken as the flash point. Moreover, it was determined that there was no flash point when the sample did not continuously burn for 5 seconds or more even at the temperature at which the sample completely boiled.

Table 4 shows the test results. As shown in Table 4, in Examples 2 to 5, there was no flash point. That is, in the case of such a combination, it can be seen that if the ratio of water in the entire cleaning solvent is 0.75 wt% or more, there is no flammability and it can be made non-hazardous.
In Example 1, since the solvent X, n-propyl alcohol, and water were each mixed and remained white even when stirred, the Cleveland open test was not performed. The white turbidity is considered to be because the ratio of water was large and the solvent X was not completely dissolved.

(Examples 6 to 9)
N-propyl bromide (including 500 ppm of butylene oxide) was used instead of solvent X, and n-propyl bromide was mixed at a ratio of 85 wt% and (n-propyl alcohol + water) at a ratio of 15 wt% (see Tables 5 and 6). The Cleveland open-type test was conducted (Examples 6 and 7).
The same test was conducted on a cleaning solvent in which n-propyl bromide was mixed at 84.5 wt%, butylene oxide at 0.5 wt%, and (n-propyl alcohol + water) was mixed at a ratio of 15 wt% (Examples) 8, 9).

The test results are shown in Table 7. As shown in Table 7, there was no flash point in Example 6 where the proportion of water in the entire cleaning solvent was 0.75 wt%, but the sample was completely boiled in Example 7 where the proportion of water was 0.375 wt%. Occasionally ignited and continued combustion (flash point: 67 ° C.).
Further, in Example 8 (water ratio: 0.75 wt%) in which 0.5 wt% of butylene oxide which is easily flammable at a flash point of -22 ° C. was mixed with the entire cleaning solvent, the sample was completely boiled. Occasionally ignited and continued combustion (flash point: 66 ° C.). Even in Example 9 (water ratio: 0.375 wt%), when the sample completely boiled, it ignited and continued to burn (flash point 63 ° C.).

Thus, as can be seen from Examples 6 and 7, the cleaning solvent composition of Examples 6 and 7 should be a cleaning solvent having no flash point if the water ratio is 0.75 wt% or more. Can do.
Further, as can be seen from Examples 6 and 8, in the case of a solvent in which a flammable material such as butylene oxide is further mixed, a flash point may be generated. However, the flash point can be made sufficiently high, and it can be seen that the present invention makes it difficult to ignite. Thus, in the cleaning solvent, even if the ratio of water is the same, the presence or absence of flammability changes depending on the composition. As can be seen from Examples 8 and 9, the greater the proportion of water, the higher the flash point and the less likely it is to burn.

(Comparative Examples 1-8)
A cleaning solvent prepared by mixing solvent X and alcohol was prepared, and a Cleveland open-type test was conducted.
Table 8 shows a summary of the mixing ratio of solvent X and alcohol, the type of alcohol, and the flash point of each sample. The brackets in the item of alcohol type are the flash points of alcohol alone.
As shown in Table 8, all the samples were flammable.

Here, for example, the cleaning solvent (flash point 46.0 ° C.) of Comparative Example 3 in Table 8 was mixed with 95 wt% of solvent X and 5 wt% of alcohol (n-propyl alcohol (flash point 24 ° C.)). However, as described above, since the solvent X is not flammable, it is considered that if the mixing ratio of the solvent X is reduced and the mixing ratio of the alcohol is increased, the cleaning solvent is naturally more flammable. That is, for example, the cleaning solvent Y in which the solvent X is mixed at a ratio of 85 wt% and alcohol (n-propyl alcohol) at 15 wt% is considered to have a flash point of 46 ° C. or lower.
And, as can be seen by comparing this cleaning solvent Y with Example 5 and Examples 7 to 9, the proportion of alcohol in the entire cleaning solvent is almost the same (15 wt%), The cleaning solvent Y not containing water has a flash point of 46 ° C. or lower, but in Example 5 containing water, the flash point is gone.
In Examples 7 to 9, although the flash point is present as described above, the flash point is 63 ° C. or higher, and the flammability is significantly lower than the flash point of the cleaning solvent Y (46 ° C. or lower). ing.
Thus, unlike the cleaning solvent that does not contain water as in each comparative example, if water is intentionally added like the cleaning solvent of the present invention in each example, the flammability is lost. It is well understood that the cleaning solvent can be made difficult to burn by raising the flash point.

(Examples 10 to 15)
Using the cleaning solvents (solvent X + n-propyl alcohol + water) H and I in the present invention, first, the mixture was mixed with urethane (50 g) in a beaker to test whether the urethane could be sufficiently washed.
Table 9 shows the mixing ratio of solvent X, n-propyl alcohol, and water for each sample.
Moreover, the amount of each sample used for washing | cleaning is H (480g: Example 10, 240g: Example 11, 100g: Example 12) and I (480g: Example 13, 240g) with respect to 50g of urethane, respectively. Example 14, 100 g: Example 15)

Each sample was able to dissolve urethane and was found to be sufficiently washed.
Subsequently, the waste liquid after washing was distilled and purified to test whether the waste liquid could be recycled.
Table 10 shows the recycling results of the waste liquid after washing in Examples 10 to 12.
As shown in Table 10, first, the waste liquids of Examples 10 and 11 could be purified by distillation, and an amount of 65 vol% or more could be recovered. Thus, if the amount of monohydric alcohol in the cleaning solvent (in the waste liquid) is relatively large relative to the urethane, the urethane reaction can be effectively prevented from proceeding, and therefore the waste liquid does not solidify and is purified by distillation. Etc., and can be recycled.

  On the other hand, in Example 12, the waste liquid was solidified, and the waste liquid could not be subjected to the distillation purification process. This is because the urethane remaining in the nozzle could be dissolved and washed sufficiently, but the content of monohydric alcohol relative to the amount of urethane was small, so the urethane reaction of isocyanate and polyol in the waste liquid progressed. It is considered that the solidification of the waste liquid has progressed.

In addition, when the waste liquid after washing | cleaning of Examples 13-15 was tested whether it can recycle, Examples 13 and 14 with comparatively much monohydric alcohol amount with respect to urethane are Examples 10 and 11 and. Similarly, recycling was possible, and the recovery rate was 65 vol% or more.
In Example 15, as in Example 12, the waste liquid was solidified, and the waste liquid could not be subjected to a distillation purification process.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

In the above, it has been introduced that the cleaning solvent of the present invention is used for dissolving and cleaning urethane, draining and drying after cleaning of the substrate, etc., but the use of the cleaning solvent of the present invention is not limited to this, and cleaning is performed. Can be used for the cleaning of various articles that need to be followed by drying. For example, cleaning and drying of textiles such as clothing, cleaning and drying of precision substrates such as semiconductor substrates and quartz substrates, and equipment used in the manufacturing process of metal parts, lenses, sensors and ICs, and various chemical products It can be used for washing and drying.

Claims (7)

  A cleaning solvent comprising water mixed with a solvent containing at least n-propyl bromide and a monohydric alcohol.   2. The cleaning solvent according to claim 1, wherein the monohydric alcohol is n-propyl alcohol.   The cleaning solvent according to claim 1 or 2, wherein the water is blended in an amount of 0.75 wt% or more.   The cleaning solvent according to any one of claims 1 to 3, further comprising at least one stabilizer selected from nitroalkanes, ethers, epoxides, and amines. A cleaning solvent, characterized by being.   5. The cleaning solvent according to claim 1, further comprising at least one solvent selected from a silicon-based solvent, a fluorine-based solvent, a chlorine-based solvent, and a petroleum-based solvent. A cleaning solvent characterized by   A cleaning method, comprising: washing with urethane using the cleaning solvent according to any one of claims 1 to 5. A drying method comprising performing draining and drying using the cleaning solvent according to any one of claims 1 to 5.