JP3344556B2 - High cleanliness polyvinyl acetal resin porous body and its storage method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl acetal resin porous material and a method for producing and storing the same, which is free from contamination by organic substances, dissolved ions and fine particles.
In addition, in the production of the polyvinyl acetal resin porous material, it is added for the purpose of disinfecting the polyvinyl acetal resin porous material and free substances of polyvinyl alcohol which is an auxiliary material and a main material added in the process, and for preventing the polyvinyl acetal resin porous material. The present invention relates to a method for producing and storing a porous body in a wet state without contamination or residue by a drug.

[0002]

2. Description of the Related Art A polyvinyl acetal resin porous material is well known as a material which is excellent in water absorption and water retention and has favorable flexibility and rebound resilience when wet. By utilizing such properties, a polyvinyl acetal resin porous body is widely used as an optimal material for a cleaning tool and a wiper. In particular, it has a hydrophilic property, is extremely excellent in cleaning ability, and yet it is hardly damaged by the object to be rubbed and is also used in many industrial fields because of its excellent strength. It plays an important role as a member for cleaning applications in clean rooms, cleaning related to semiconductors and electronic components, and water absorption.

[0003] The porous polyvinyl acetal resin referred to herein is also called a polyvinyl acetal sponge, and is hereinafter abbreviated as "PVAt sponge".

[0004] As described above, PVAt sponge is a material that is most suitable for use in cleaning in a clean room.
The t-sponge hardens when dried and loses its flexibility and elasticity. In order to exhibit the above effects, it is generally necessary to use the t-sponge in a wet state. Further, the water absorption rate of the PVAt porous body has a large difference between the dry state and the wet state, and the water absorption rate in the dry state is much lower than that in the wet state. Furthermore, it shifts the ones dry wet are those time-consuming, it is practically preferable to keep constantly wet so as not to dry.

[0005]

However, there is a problem that the PVAt-based porous body is liable to generate mold when stored in a wet state for a long period of time. The occurrence of mold is problematic in terms of hygiene, appearance, and handling, and it is necessary to impart a fungicidal property to the PVAt-based porous body.

[0006] In the method of preserving such a PVAt sponge, problems are caused by organic substances, ionic substances, fine particles,
Contamination of the PVAt sponge by microorganisms and the like, and particularly when used in semiconductor applications, these contaminants must be reduced to the limit. On the other hand, as a conventional method of preserving a PVAt sponge, a method of impregnating and adhering a product having a fungicidal and bactericidal property to a product is generally performed. For example, aqueous solutions of sodium dehydroacetate, 4-chloro-3,5-dimethylphenol, benzalkonium chloride, benzimidazole and the like have been used.

However, when the PVAt sponge treated and stored with the aqueous solution containing the chemicals is used for cleaning semiconductors in that state, the chemicals are mixed into the ultrapure water as the cleaning water, The cleaning water and the object to be cleaned are contaminated. Therefore, in order to remove these chemicals from the PVAt sponge which has been treated and stored with an aqueous solution containing a chemical, the PVAt sponge is subjected to a cleaning process called pre-cleaning for a long time before use. Moreover, when the PVAt sponge is treated with a drug and stored, there is a problem that the porous body is deteriorated or deteriorated due to the effect of the drug depending on the type of the drug used.

[0008] In particular, when the PVAt sponge is used in applications such as semiconductor-related cleaning members and electronic-related water absorbing members, for example, precision cleaning of silicon wafers and photomasks, cleaning of printed boards and lead frames, and water absorption. When used as an application, contaminants eluted from the PVAt sponge not only reduce the quality of the product, but also lead to contamination of the production system and the environment itself, resulting in great damage. As described above, it is required to extremely reduce impurities generated from the porous body when used in a clean room or in an environment with a high degree of cleanliness. Was not obtained.

[0009] In order to deal with such problems, autoclave sterilization by heating and pressurizing, sterilization using an oxidizing gas such as ethylene oxide or ozone, putting the product in a closed container, and replacing the gas inside with an inert gas. Substitution method, sterilization by ultraviolet rays, etc.
Materials other than the sponge are appropriately selected from these methods and used. However, none of them is effective for PVAt sponge. For example, in autoclave sterilization, the material itself shrinks due to heat treatment, and the flexible elasticity which is a characteristic property of PVAt sponge is lost. Further, in sterilization using an oxidizing gas, it is difficult to allow the gas to penetrate deep into the inner portion of the porous body, and the material itself is susceptible to deterioration due to oxidation. Even with the method of performing replacement with an inert gas in a closed container, it is not easy to remove water adhering to the porous body and oxygen dissolved in the material itself, and it is not possible to completely prevent the generation of mold. . Also in the method using ultraviolet rays, ultraviolet rays only act on the surface layer of the porous body, and it has been difficult to put them to practical use.

The present inventor has conducted intensive studies in view of the above circumstances. As a result, the present inventors have found that, when a PVAt sponge is stored in a wet state, the generation of mold is prevented for a long period of time, and even when used after storage, the eluate from the PVAt sponge is used. The present invention has been found to be capable of shortening or omitting pre-cleaning before use without any dust or dust generation.
An object of the present invention is to provide an At sponge and a method for producing the same, and a storage method that can maintain the cleanliness of a high-purity PVAt sponge with high accuracy and is very easy to handle.

[0011]

SUMMARY OF THE INVENTION The present invention comprises a highly clean PVAt sponge, and particles dissolved and suspended in water.
PVAt with pure water from which impurities such as ions and organic substances have been removed
A method for producing a highly clean PVAt sponge for cleaning a sponge, and a highly clean PAt sponge thus produced.
The storage method is characterized in that the whole of the VAt sponge is hermetically sealed with an oxygen-blocking film, and an oxygen absorbent is incorporated in the sealed packaging bag.

The high cleanliness PVAt sponge of the present invention has a COD value of 5 ppm or less as a cleanliness, and further has a conductivity of less than 5 μS / cm and a particle number of 50,000 / 2.5 μm or more. cc or less. If the high cleanness sponge of the present invention is used, when used in a cleaning process in a clean room, etc.
It is possible to shorten or omit the conventionally required pretreatment, for example, a treatment of sufficiently washing beforehand so that impurities do not elute. Furthermore, by setting the cleanliness higher, it can be used under severe environmental conditions such as a semiconductor manufacturing process.

[0013] In the method for producing a high-purity PVAt sponge, the PVAt sponge is washed with pure water from which impurities such as particles, ions, and organic substances dissolved or suspended in water have been removed. The conductivity of pure water used for cleaning is 0.1 μS / cm or less and the COD value is 1 ppm or less. Further, the cleaning with pure water is performed according to US Federal Standard FS209D.
It is more preferable to carry out in an environment where the cleanliness higher than the class 100 defined by the above is maintained.

According to the production method of the present invention, a PVAt sponge with high cleanliness can be produced. Further, by increasing the cleanliness of pure water used for the manufacture, a PVAt sponge having a high cleanliness that can be used even under severe environmental conditions such as a semiconductor manufacturing process can be manufactured. Further, by increasing the cleanliness of the environment to be cleaned, it is possible to produce a PVAt sponge having a high cleanliness that can be used even when more stringent quality conditions are required.

[0015] In the method of storing a high-purity PVAt sponge, the whole of the PVAt sponge manufactured with high cleanliness is hermetically sealed with an oxygen barrier film, and an oxygen absorbent is incorporated in the hermetically sealed bag. It is characterized by doing.

According to the storage method of the present invention, high cleanliness PV
The anti-fungal agent is used by storing the At sponge in an oxygen-blocking hermetically sealed package together with an oxygen absorbent, thereby keeping the hermetically sealed package in an oxygen-free state or a low oxygen concentration state close to an oxygen-free state. No need, high cleanliness PV
The cleanliness of the At sponge can be maintained with high accuracy, and the time for pretreatment can be shortened or omitted even during use.

Further, the oxygen barrier film has an oxygen permeability of 200 cc / m ² · atm · 24 hr or less. By using such a material having excellent oxygen barrier properties, it is possible to create a state having a low oxygen concentration, which is close to an anoxic state.

It is more preferable to incorporate an oxygen detector in the hermetically sealed package. According to such a packaging method, the presence of oxygen in the package can be detected if the package is partially torn or loses hermeticity. Can be prevented beforehand.

In the method of preserving a sponge with high cleanliness, as a method of further increasing cleanliness, a high cleanliness P
After the VAt sponge is hermetically packaged, it is irradiated with an electron beam or γ-ray. By doing so, it is not necessary to use a fungicide, and high cleanliness PV
The cleanness of the At sponge can be maintained with high accuracy. In addition, since the PVAt sponge is sterilized by irradiation with an electron beam or γ-ray, mold is hardly generated even in the presence of oxygen. Therefore, the packaging for preservation should just be a thing which can be closed. Further, high cleanliness PV which can be used only by performing pretreatment at the time of use very simply.
A method for storing At sponge can be provided.

Here, when the irradiation dose of the electron beam or the γ-ray irradiation is set to 10 kGy or less, the change in the physical properties of the sponge can be extremely suppressed. When the irradiation dose increases, for example, the compressive stress increases, that is, the sponge becomes hard.

Further, when performing electron beam or gamma ray irradiation, it is preferable to lower the oxygen concentration in the sealed package. This is because oxygen is activated by irradiation with an electron beam or γ-ray, and the activated oxygen may deteriorate the sponge. Therefore, the package is hermetically sealed with an oxygen barrier film, and an oxygen absorbent is incorporated in the hermetically sealed package.
It is preferable to set the cc / m ² · atm · 24 hr or less. By doing so, the oxygen concentration in the sealed package can be kept extremely low, and the change in the physical properties of the sponge can be further suppressed. .

Further, when the package is hermetically sealed, it is preferable to cover the sheet with a sheet molding in advance. In this case, the oxygen absorbent can prevent the high cleanliness PVAt sponge from being deformed even if the inside of the package is in a reduced pressure state. In addition, deformation due to external pressure can be prevented. Further, it is more preferable that the hermetically sealed package is further covered and sealed with a film material and packaged twice. In this way, if only the exterior is discarded at the time of use, contamination of the use environment can be further reduced.

[0023] In addition, the class 100 to be sealed packaging, as Kiyoshi Kiyoshido which is defined by the US Federal Standard FS209D
It is more preferable to perform in an environment where higher cleanliness is maintained. By packaging in such an environment, high cleanliness that can be used can be maintained even under severer environmental conditions.

As described above, the PVAt sponge is widely used for cleaning in a clean room, cleaning for semiconductors and electronic parts, and a member for absorbing water.
It is useful to apply the high-cleanliness PVAt sponge of the present invention and the method for producing and storing the same to these uses and one of the uses, i.e., the cleaning sponge roller.

[0025]

Pure water used in the method of the embodiment of the present invention, 25 conductivity at ℃ is 0.1 .mu.S / cm or less, CO
D is 1 ppm or less, and the number of particles of 0.3 μ or more is 100 particles /
ml or less, the number of viable bacteria Preferably to have the following becomes water 10 / ml, more has electrical conductivity at 25 ℃ 0.055μS / cm or less, COD is 1ppm or less, 0.
It is preferable to have a water quality in which the number of particles of 1 μ or more is 1 / ml or less and the number of viable bacteria is 0.01 / ml or less. By washing the PVAt sponge using such water-quality ultrapure water, impurities adhering to the porous body are removed with high precision. Ultrapure water of such quality can be applied to general filtration, microfiltration membrane, ultrafiltration membrane, reverse osmosis membrane, dialysis membrane, ion exchange, etc., and can be obtained by any combination of these. is there.

The washed using the above ultra-pure water, the cleanliness of the resulting PVAt sponge, conductivity 5 [mu] S / cm Not
Full , COD value is 5 ppm or less, sodium ion (Na
+) The number of particles having a concentration of 1 ppm or less and 2.5 μm or more is 50,000 / cc or less. This value is a value applicable to the semiconductor manufacturing process. The values of the electrical conductivity and the sodium ion (Na +) concentration are values of sponge-adhered water itself . The COD value is a value obtained by rubbing out a PVAt sponge in pure water and then measuring the pure water.
Details of each measurement value and measurement method will be described later.

As the oxygen-barrier film used in the present invention, polyvinylidene chloride, nylon, polyvinyl acetate, polyvinyl alcohol, aluminum foil, and aluminum-deposited film can be suitably used, and more preferably, the oxygen permeability is 10 cc / cm. m ² · atm · 24 hrs (20-25
C) or less is good. Further, a film obtained by laminating several kinds of films having high oxygen barrier properties or a film obtained by combining the above-described oxygen barrier film with a film of polyethylene, polyester, polypropylene or the like is more preferable in terms of strength.

As an exterior for performing double packaging, an oxygen barrier film may be used as in the interior, but an oxygen permeable film may also be used. For example, polyethylene, polypropylene, polyester General-purpose materials such as nylon and nylon can be used. The purpose of this exterior is to remove the exterior bag when transporting the PVAt sponge outside the clean room, and if the double wrapping is applied even if the surface of the wrapper is contaminated, when bringing it back into the clean room. The contamination can be removed and the clean room can be prevented from being contaminated.

As the oxygen absorbent incorporated in the above-mentioned wrapper made of a material having a high oxygen barrier property, a substance which is easily oxidized chemically can be used. For example, ascorbic acid, active metal powder, sulfite Although iron and the like can be used, an iron-based material is preferable in consideration of handleability, oxygen absorption rate, oxygen absorption capacity, and the like. Further, the oxygen absorbent is more effective when it is a fine powder because it has higher reactivity with oxygen and is effective. However, it is necessary to prevent the oxygen absorbent from coming into direct contact with the porous body to be stored. Generally, the fine powder is closed and used with a material having air holes finer than the particle system of the oxygen absorbent fine powder and having air permeability.

According to the storage method described above, the PVA in the package
The t sponge can maintain the cleanliness immediately after being washed with pure water for a long time.

As a method for easily removing the oxygen gas in the package, there is a method in which the gas inside the package is degassed and further replaced with an inert gas such as nitrogen or argon. Since it is difficult to completely remove the oxygen present in the solution, it is more preferable to use this method together.

In order to check the presence or absence of oxygen in the package, it is also effective to incorporate a reversible colorant whose color changes depending on the concentration of oxygen as an oxygen detector in the package. Thereby, since the oxygen concentration in the wrapper can be easily confirmed, more reliable product storage is achieved.

Further, by irradiating an electron beam or γ-ray to the hermetically packaged PVAt sponge, the PVAt sponge is sterilized, and the generation of mold can be prevented even if some oxygen is present. This suffices if the package can be hermetically sealed and does not need to be an oxygen barrier film. Therefore, packaging and packaging operations can be simplified.

According to the method of the present invention, first, a PVAt sponge formed by a reaction between PVA and formalin is sufficiently washed with general water to remove reaction residues, unreacted materials, additives and the like. Then, after immersing in the pure water having the above-mentioned water quality to mechanically bend and stretch, the process of sufficiently squeezing out the water contained in the sponge and absorbing the pure water again is repeated.

Next, while the PVAt sponge after the washing is kept wet with pure water, the whole is covered with an oxygen-barrier film and completely sealed. At this time, an oxygen absorbent is enclosed and incorporated together with the PVAt sponge. At this time, an oxygen detector may be incorporated at the same time,
After covering the entire PVAt sponge using a sheet molded body, the entire PVAt sponge may be covered and sealed with an oxygen barrier film.

When oxygen in the wrapper is absorbed by the oxygen absorbent, the inside of the wrapper is depressurized, and the built-in PVAt
Deformation of the sponge product may cause a problem that the deformed portion is not restored, for example, when the deformation is held for a long time, but the entire PVAt sponge is entirely formed by the relatively hard sheet molding or the like. This problem can be avoided by coating.

Further, if the PVAt sponge wrapped with the oxygen barrier film is further entirely covered and wrapped with a film, and the package is double hermetically sealed, if the outer body alone is discarded when using the PVAt sponge, contamination of the use environment is reduced. It can be further reduced.

In consideration of reverse contamination of the PVAt sponge from the oxygen absorber and the oxygen detector, etc., which are contained in the wrapper together with the PVAt sponge, these members are positioned so as not to come into direct contact with the PVAt sponge. More preferably, for example, it is also possible to provide a structure for fixing those members to a part of the sheet molded body.

Further, the method according to the present invention is applicable not only to storage of a porous material that cures in a dry state, but also to storage of a material composed of other polymers. For example,
For even materials consist of fibrous like NBR or those rubber-based materials such as SBR or nonwoven fabric, and to prevent deterioration due to oxidation thereof material itself, for the purpose of maintaining the performance thereof to be added drug compound Is also available.

As described above, according to the present invention, PVAt
By washing and storing the sponge, the porous body is kept in a wet state for a long time without contamination by fine particles, organic substances, ions, etc. Can be saved across.

Further, according to the method of the present invention, PVAt
When using a sponge, the pre-cleaning conventionally performed can be shortened or omitted. Also, since the PVAt sponge can be maintained in an oxygen-free state for a long time,
Not only the antifungal effect but also the deterioration of the porous material itself due to oxidation can be prevented. Further, the present invention is not limited to a porous material or a material in a wet state, and can be widely used for members that need to prevent deterioration and deterioration due to oxidation.

An inspection method for each measurement item representing cleanliness will be described below. (COD, unit: ppm) Measurement target: 100 cc of sponge and 400 cc of distilled water
Water that was rubbed out 100 times and adjusted to a total of 500 cc with distilled water. Measurement method: Coulometric titration method: The amount of potassium permanganate when an organic substance in a liquid is oxidized with potassium permanganate is expressed in terms of an equivalent oxygen amount. Measuring equipment: Portable and quick COD meter (HC-50
7) Central Science Co., Ltd. (conductivity, unit: μS / cm) Object to be measured: DI water (ion-exchanged water: deio)
The sponge squeezed liquid after being allowed to stand for about 3 minutes in a state in which nized) is sufficiently contained. Measurement method: AC bipolar method: An electrode is placed in the liquid, and the electric conductivity is measured. Measuring equipment: Compact conductivity meter (B-173 type)
Manufactured by HORIBA, Ltd. (the number of particles, Unit: thousand / cc) the object to be measured: the sponge 10cc in DI water 800cc, performs a work out rubbing 100 times, total with DI water 10
Water adjusted to 00cc. Measuring method: Light-blocking particle counter; Measure the size of each particle having a diameter of 2.5 μm or more in 10 cc of the liquid to be measured by the voltage drop value caused by blocking the halogen light, and count the quantity. I do. Measuring equipment: HIAC / ROYCO (MODEL410
0) (Na ion concentration, unit: ppm) Object to be measured: Sponge liquid contained sufficiently in sponge, allowed to stand for about 3 minutes, and then measured for sponge squeezed liquid: sodium ion electrode method; flat The sample liquid is dropped on the appropriate sensor section. Measuring equipment: Compact ion meter (CANDY
C-122) manufactured by Horiba, Ltd.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 A sponge roller 1 made of polyvinyl acetal (PVAt) (size: outer diameter 60 mm × inner diameter 30 mm × length 25)
4 mm) with a COD value of 1 ppm, an electrical conductivity of 0.06 μS / cm at 25 ° C., and 0 particles / ml of 2.5 μ or more.
Immersed in pure water having the same water quality as above, mechanically bends and stretches mechanically in water, squeezes out the water contained in the sponge, drains the washing water, and repeats the same operation with fresh pure water again Thus, the PVAt sponge roller was washed. Next, after this washing, the sponge roller in a wet state is housed in a package 2 (size: 450 mm × 170 mm) made of an oxygen barrier film as shown in FIG. Agent 4 is introduced and the opening is heat-sealed and completely closed. As shown in FIG. 2, the oxygen barrier film used had a four-layer structure. As the composition, from the outer layer, polyvinylidene chloride 5,
Nylon 6, polyethylene 7, and linear low-density polyethylene 8, each having a thickness of 5μ, 10μ,
They were 25μ and 60μ. Mitsubishi Gas Chemical Company (Ageless FX-400) was used as an oxygen absorbent, and Mitsubishi Gas Chemical Company (Ageless Eye KS) was also used as an oxygen detector. Also, this sponge roller 1
Is used for precision cleaning of an aluminum disk or the like, and has a large number of projections 9 on the surface as shown in FIG. Then, as shown in FIG.
With this rotation, the projections 9 clean the object 10 such as an aluminum disk while rubbing it in the presence of water or the like.

(Example 2) In the same manner as in Example 1, the PVAt sponge roller was washed. Next, after this washing, the sponge roller in a wet state is packed with a polyethylene film package (size: 4).
(50 mm x 170 mm), heat-sealed the opening, and completely sealed without the oxygen absorber and oxygen detector. Thereafter, the entire package was irradiated with an electron beam. The irradiation energy was 5 MeV and the irradiation dose was 4 kGy.

Comparative Example 1 A sponge roller made of PVAt (size: outer diameter 60)
mm × 30 mm in inner diameter × 254 mm in length) were merely wetted with the above-described pure water, but were not washed. This is a wrapper made of oxygen barrier film (size: 450mm × 170m
m), and only the oxygen detector was added without the oxygen absorber, and the opening was heated and sealed. The same oxygen barrier film as in Example 1 was used.

Comparative Example 2 Sponge roller made of PVAt (size: outer diameter 60)
mm × 30 mm in inner diameter × 254 mm in length) were merely wetted with the above-described pure water, but were not washed. This is a wrapper made of polyethylene film (size: 450 mm x 170 m
m), an oxygen absorbent and an oxygen detector were charged, and the opening was heat-sealed and completely closed. The same oxygen absorber and oxygen detector as in Example 1 were used.

Comparative Example 3 A sponge roller made of PVAt (size: outer diameter 60)
mm × 30 mm inner diameter × 254 mm length) was immersed in a mixture of 3,000 cc of a 0.3% by weight aqueous solution of sodium dehydroacetate and 3,000 cc of a 0.3% by weight aqueous solution of oxalic acid. The rates were the same. Next, this was housed in a wrapper made of a polyethylene film (same as Comparative Example 2), and only the oxygen detector was enclosed without adding an oxygen absorbent and completely sealed. The same oxygen detector as in Example 1 was used.

Comparative Example 4 A sponge roller made of PVAt (size: outer diameter 60)
mm × 30 mm in inner diameter × 254 mm in length) were merely wetted with the above-described pure water, but were not washed. This is a wrapper made of oxygen barrier film (size: 450mm × 170m
m), the air in the package was evacuated to a vacuum, nitrogen gas was introduced, an oxygen detector was added, and no oxygen absorber was added. The same oxygen barrier film as in Example 1 was used.

Comparative Example 5 A sponge roller made of PVAt (size: outer diameter 60)
mm × 30 mm in inner diameter × 254 mm in length) were washed in the same manner as in Example 1. Next, after this washing, the wet sponge roller is stored in a polyethylene film package (size: 450 mm × 170 mm), and at the same time, an oxygen absorbent and an oxygen detector are introduced, and the opening is heat-sealed. Completely seal. The same polyethylene film as in Comparative Example 2 was used.

Comparative Example 6 A sponge roller made of PVAt (size: outer diameter 60)
mm × 30 mm in inner diameter × 254 mm in length) were washed in the same manner as in Example 1. Next, after this washing, the sponge roller in a wet state is housed in a polyethylene film package (size: 450 mm × 170 mm), and only the oxygen detector is put without the oxygen absorbent, and the opening is heat-sealed. , Completely sealed. The same polyethylene film as in Comparative Example 2 was used.

[0052] was treated as described above, respectively PVAt sponge roller, observed over time changes in appearance placed in a thermostatic chamber kept constant at 23 ° C., and stored for 200 days. The appearance of the porous roller, that is, the state of mold generation, was as shown in Table 1 below.

[0053]

[Table 1] -: No mold was found. +: One or more mold colonies were found. ++: Three or more mold colonies were found. +++: Ten or more mold colonies were found.

In Example 1 of the sponge roller made of the PVAt sponge of the present invention, and its production method and storage method, as shown in Table 1, the generation of fungi could be prevented for at least 200 days.

Also in Example 2, by irradiating the wrapped sponge roller with an electron beam, it was possible to prevent mold generation for at least 200 days, as in Example 1. This is because the sponge roller is sterilized by electron beam irradiation, and even if some oxygen is present, the generation of mold can be prevented. As a result, the package only needs to be able to be sealed, and need not be an oxygen barrier film. Also, packaging and packaging operations can be simplified.

Comparative Example 3 in Table 1 is a conventional method in which a conventional fungicide is added, and no mold is generated, but the object of the present invention cannot be achieved.

On the other hand, other comparative examples are methods in which no fungicide is added, and comparative examples 1, 2 and 4 are not washed with pure water. In Comparative Example 1, since no oxygen absorbent was added, molds were generated by the oxygen remaining in the package. In Comparative Example 2, since the packaging film does not have oxygen barrier properties, if the amount of permeated oxygen exceeds the capacity of the oxygen absorbent, mold will be generated. In Comparative Example 4, since the air in the package was first replaced with nitrogen gas and packaged with an oxygen-barrier film, the generation of mold was slower than in Comparative Examples 1 and 2. Since no absorbent is added, oxygen gradually permeates into the package, and molds are generated.

Further, Comparative Examples 5 and 6 are examples in which cleaning with pure water was performed, but in both cases, an oxygen barrier film was not used, and a polyethylene film was used. Comparative Example 5
Has an oxygen absorber, which is a good result in the comparative example, but is inferior to the example. Comparative Example 6 did not include an oxygen absorbent, and thus had worse results than Comparative Example 5.

As described above, in order to store the PVAt sponge in a wet state without generating mold, the inside of the package for storage must be in an oxygen-free state or a state having a low oxygen concentration close to the oxygen-free state. For this purpose, as in the present invention, it is necessary to hermetically seal the PVAt sponge together with the oxygen absorbent in an oxygen-barrier film.

As described above, according to the embodiment, when the PVAt sponge is stored in a wet state, the PVAt sponge is washed with pure water and then stored in an oxygen-free state or a state having a low oxygen concentration close to the oxygen-free state. By doing so, the generation of mold can be suppressed for a long period of time.

Next, the roller after storage for 200 days as described above.
-Open the oxygen-barrier packaging of the
The electrical conductivity was measured according to the test method described above. Next, use a roller
Perform pre-cleaning before use according to the usual method, pre-cleaning time
The conductivity of each was measured. The results were as shown in Table 2.

As described above, in the examples, the eluted components are within the usable range with a short pre-washing time. However, in Comparative Examples 1, 2, and 4, cleaning with pure water was not performed, so that a long pre-cleaning time was required. Furthermore, in Comparative Example 3, since the fungicide elutes, the electrical conductivity has a high value.

In Comparative Examples 5 and 6, cleaning with pure water was performed, and the results were the same as in Examples 1 and 2.

[0064]

[Table 2]

Further, the result of confirming the presence / absence of oxygen in the wrapper with the oxygen detector incorporated therein was as shown in Table 3.
In Table 3, the state where the oxygen concentration reached 0.1% or less was indicated as "absent".

[0066]

[Table 3]

Thus, in Example 1, the inside of the package is kept free of oxygen for a long time. On the other hand, in the comparative example, there is an example in which the oxygen concentration can be kept low in a short time, but cannot be kept for a long time. As described above, according to Example 1, when polyvinyl acetal sponge is stored in a wet state, it is stored in an oxygen-free state or in a state with a low oxygen concentration close to the oxygen-free state, so that the generation of mold can be prevented for a long time. Can be suppressed.

Further, according to the present invention, since the porous body can be maintained in an oxygen-free state for a long time, not only the antifungal effect but also the deterioration of the porous material itself due to oxidation can be prevented. Further, the present invention can be widely used for storage of not only a porous body and a material in a wet state but also members that need to prevent deterioration and deterioration due to oxidation.

In the second embodiment, since the sponge is sterilized by the irradiation of the electron beam, even in an environment where oxygen is present, generation of mold can be prevented if the sponge is sealed. .

[0070]

EFFECTS OF THE INVENTION According to the PVAt sponge of the present invention and the method for producing and storing the same, the eluate and dust generation from the PVAt sponge are extremely reduced, and the pre-cleaning can be shortened or omitted before use. In such a method, even when the PVAt sponge is stored in a wet state, it has an antifungal effect over a long period of time, and since the porous body is kept in an oxygen-free state, there is no deterioration or deterioration due to oxidation. It is extremely useful in practice.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a storage method according to the present invention.

FIG. 2 is an explanatory view showing the structure of an oxygen-barrier film used for hermetic packaging.

FIG. 3 is an explanatory diagram of a sponge roller according to the first embodiment.

FIG. 4 is an explanatory diagram of a state of cleaning with a brush roller of FIG. 3;

[Description of Signs] 1 Sponge roller 2 Packaging 3 Oxygen absorber 4 Oxygen detector 5 Polyvinylidene chloride 6 Nylon 7 Polyethylene 8 Linear low-density polyethylene 9 Projection

Claims (16)

(57) [Claims] 1. A high-purity polyvinyl acetal resin porous body characterized by having a COD value as a cleanness of 5 ppm or less and a conductivity of less than 5 μS / cm . 2. The method according to claim 1, wherein the conductivity as cleanliness is less than 5 μS / cm, and the number of particles having a COD value of 5 ppm or less and 2.5 μm or more is 50,000 / cc or less.
The high-purity polyvinyl acetal resin porous body described in the above. 3. A method for preserving a polyvinyl acetal resin porous body having high cleanliness, wherein a porous body of polyvinyl acetal resin produced with high cleanliness is hermetically packaged with an oxygen barrier film. 4. The method for preserving a high-purity polyvinyl acetal resin porous body according to claim 3 , wherein an oxygen absorbent is incorporated in the hermetically sealed package formed of the oxygen-barrier film. 5. The oxygen barrier film having an oxygen permeability of 20.
The method for preserving a high-purity polyvinyl acetal resin porous body according to claim 3 or 4, which is 0 cc / m ² · atm · 24 hr or less. 6. A storage method of a high cleanliness polyvinyl acetal resin porous body according to any one of claims 3 to 5, characterized in that a built-in oxygen detecting agent in the sealed package. 7. A polyvinyl acetal resin porous body produced with high cleanliness is hermetically packaged, and then electron beam or γ.
A method for preserving a porous body of polyvinyl acetal resin having high cleanliness, which comprises irradiating with radiation. 8. The irradiation dose of electron beam or gamma ray irradiation is 10
The method for preserving a porous polyvinyl acetal resin having a high degree of cleanliness according to claim 7, which is not more than kGy. 9. A sealed package in an oxygen blocking film, and preservation of high cleanliness polyvinyl acetal resin porous body according to claim 7 or 8, wherein the incorporating the oxygen absorbent into the sealed packaging Method. 10. The oxygen barrier film having an oxygen permeability of 2
00cc / m ² · atm · 24hr or less claim 9
The method for preserving the high-purity polyvinyl acetal resin porous body described in the above. 11. The method of claim 1, wherein the hermetically sealed package is a US federal standard F.
The method for preserving a high-purity polyvinyl acetal resin porous body according to any one of claims 3 to 10 , wherein the method is performed in an environment in which a degree of cleanliness higher than class 100 is maintained as the degree of cleanliness specified in S209D. . 12. When sealing packaging high cleanliness were produced in polyvinyl acetal resin porous body, of claims 3 to 11, wherein the coated polyvinyl acetal resin porous body in advance the shaped sheet The method for storing a high-purity polyvinyl acetal resin porous body according to any one of the above. 13. A sealed package, coated sealed with further film material, according to claim 3, characterized in that packed double
13. The method for preserving a high-purity polyvinyl acetal resin porous body according to any one of claims 12 to 12 . 14. The method according to claim 1, wherein the polyvinyl acetal resin porous body is a cleaning sponge roller.
Or the high-purity polyvinyl acetal resin porous body according to 2. 15. The cleaning device according to claim 3, wherein the polyvinyl acetal resin porous body is a cleaning sponge roller.
14. The method for storing a high-purity polyvinyl acetal resin porous material according to any one of items 13 to 13 . 16. The high-purity polyvinyl acetal resin porous body according to claim 1, wherein a sodium ion concentration is 1 ppm or less.