KR102533590B1 - Hydrophilic ultra-high molecular weight plastic porous sheet and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide a hydrophilic porous sheet having high water absorption. Another object of the present invention is to provide a hydrophilic porous sheet having excellent adhesive strength. Moreover, an object of this invention is to provide the simple manufacturing method of the said porous sheet. The present invention has an absorption rate of 15 mm/3 min or more when one end of the sheet is immersed in pure water under an atmosphere of 25 ° C. and 60% RH, is composed of ultra-high molecular weight plastic, and is measured by infrared spectroscopy (FT-IR). In one IR spectrum, it relates to a hydrophilic ultra-high molecular weight plastic porous sheet characterized in that no characteristic absorption is observed between 3000 and 3500 cm ^-1 .

Description

Hydrophilic ultra-high molecular weight plastic porous sheet and manufacturing method thereof

The present invention relates to a porous ultra-high molecular weight plastic sheet requiring hydrophilicity, air permeability, and pure water absorption, and a method for producing the same.

BACKGROUND OF THE INVENTION Porous sheets of polyolefin resin particles are widely used as various filters and cushioning materials for adsorption and fixation because of their excellent filtration function and permeability. Among them, a particularly hydrophilic polyethylene porous sheet is useful for applications such as water absorption, retention, diffusion, and permeation because of its hydrophilicity and absorbency, and the polyolefin sintered body described in Patent Document 1 has been developed.

As porous sheets having such a water absorbing function, sheets and nonwoven fabrics of synthetic fibers treated with hydrophilicity, fabrics made of natural fibers and microporous films of thermoplastic resins treated with hydrophilicity, or sintered bodies of absorbent polymers, metals or ceramics have also been developed.

Since such a hydrophilic polyethylene porous sheet has excellent dimensional stability, high mechanical strength, and moldability that can cope with complex shapes when absorbed, it is expected to be used in many fields such as humidifying elements for air conditioners or ink absorbers for printers.

In order to impart hydrophilicity to the polyethylene porous sheet, a method in which a substance having a hydrophilic functional group is introduced into polyethylene powder as a raw material by graft polymerization or the like is common, as in the method described in Patent Document 2, but the manufacturing process is complicated and necessary There was a problem that hydrophilicity or water absorption was difficult to obtain.

Japanese Patent Publication No. 4-28021 Japanese Unexamined Patent Publication No. 2009-114238

An object of the present invention is to provide a hydrophilic porous sheet having high water absorbency without introducing a substance having a hydrophilic functional group. Another object of the present invention is to provide a hydrophilic porous sheet having excellent adhesive strength. Moreover, an object of this invention is to provide the simple manufacturing method of the said porous sheet.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has an absorption rate of 15 mm/3 minutes or more when one end of the sheet is immersed in pure water in an atmosphere of 25 ° C. In the IR spectrum measured by (FT-IR), no characteristic absorption was observed between 3000 and 3500 cm ^-1 .

The method for producing a hydrophilic ultra-high molecular weight plastic porous sheet of the present invention includes a step of subjecting the porous sheet to antistatic treatment and/or plasma treatment, wherein the porous sheet is made of ultra-high molecular weight plastic and has an average pore diameter of 20.0 µm. less, and the plasma treatment in the case where antistatic treatment is not performed is performed in an oxygen gas atmosphere.

According to the present invention, it is possible to provide a hydrophilic ultra-high molecular weight plastic porous sheet exhibiting high water absorption without the need to introduce (eg, laminate) a substance having a hydrophilic functional group. In addition, the present invention can provide a hydrophilic porous sheet having excellent adhesive strength. In addition, by using the production method of the present invention, a porous sheet with improved pure water absorbency can be obtained simply.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has an absorption rate of 15 mm or more per 3 minutes when one end of the sheet is immersed in pure water in an atmosphere of 25 ° C. and 60% RH, is composed of ultra-high molecular weight plastic, and infrared spectroscopy ( In the IR spectrum measured by FT-IR), characteristic absorption is not observed at 3000 to 3500 cm ^-1 .

The method for measuring the absorption rate is as described in Examples to be described later. The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention can be used as a water absorption sheet, and the water absorption rate when one end of the sheet is immersed in pure water under an atmosphere of 25°C and 60% RH is preferably 20 mm/3 minutes or more. 25 mm/3 min or more is more preferable, 30 mm/3 min or more is more preferable, 35 mm/3 min or more is particularly preferable, 40 mm/3 min or more is particularly more preferable, and 45 mm/3 min or more is particularly preferable. 3 minutes or more is preferable especially, and 55 mm/3 minutes or more is the most preferable.

The adhesive force of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is preferably 0.5 N/mm or more, more preferably 2.1 N/mm or more, and still more preferably 2.5 N/mm or more. A method for measuring the adhesive force is as described in Examples to be described later.

The hydrophilic ultrahigh molecular weight plastic porous sheet of the present invention preferably has a water absorption rate of 15 mm/3 min or more and an adhesive force of 2.1 N/mm or more, and a water absorption rate of 20 mm/3 min or more and an adhesive force of 2.1 N/mm or more. It is more preferable that it is mm or more, and it is more preferable that the water absorption rate is 25 mm/3 minutes or more and the adhesive force is 2.5 N/mm or more.

The ultra-high molecular weight plastic constituting the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is not particularly limited, and examples thereof include ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, ultra-high molecular weight polyvinyl chloride, and ultra-high molecular weight polyamide. Ultra high molecular weight polyethylene (hereinafter also referred to as UHMWPE) is preferred. These may be used individually by 1 type, and may mix and use 2 or more types. In addition, these can use a commercial item. Commercially available products of high molecular weight plastics include, for example, Hijax Million (Mitsui Chemical Co.), Sanfain UH, UTS (Asahi Kasei Chemicals Co.), HIFAX 1000 (Hercules Co.), Horstaren GUR (Hexx Co.), etc. ultra high molecular weight polyethylene; ultra-high molecular weight polyvinyl chlorides such as the TK2500 series (Shin-Etsu Chemical Industry Co., Ltd.); Ultra-high molecular weight polyamides, such as diamide (Daicel Chemical Industry), etc. are mentioned.

In the present invention, the weight average molecular weight (Mw) (hereinafter also simply referred to as average molecular weight) of the ultrahigh molecular weight plastic is not particularly limited, but is preferably 500,000 or more, more preferably 1,000,000 or more, and 1,500,000 or more. More preferably, 2,000,000 or more are particularly preferable. The upper limit of the weight average molecular weight (Mw) is not particularly limited, but is preferably 15 million or less, more preferably 12 million or less, still more preferably 9 million or less, and particularly preferably 8 million or less. The said weight average molecular weight is a value measured by the light scattering measurement method.

The ultra-high molecular weight plastic porous sheet used as the material can be produced by a known method, for example, according to the method described in Japanese Patent Publication No. 7-55541 and Japanese Patent Application Laid-open No. 2002-177390. can For example, the ultra-high molecular weight plastic powder can be filled in a shape retainer (mold, etc.), and the plastic formed on the mold is sintered in a steam atmosphere heated to a temperature equal to or higher than the melting point of the plastic, and then cooled. Specifically, when the ultra-high molecular weight plastic is ultra-high molecular weight polyethylene, a predetermined dispersion containing ultra-high molecular weight polyethylene powder or the like is prepared, and the dispersion is coated in a sheet shape, followed by heat treatment at about 130 to 200 ° C. After cooling to room temperature, an ultra-high molecular weight plastic porous sheet can be produced.

Further, the ultra-high molecular weight plastic porous sheet used as the material may be manufactured using additives such as a dispersing agent and a thickening agent.

As a dispersing agent, surfactant is mentioned, and a nonionic surfactant is preferable. Examples of nonionic surfactants include glycerin fatty acid esters and their alkylene glycol adducts, polyglycerin fatty acid esters and their alkylene glycol adducts, propylene glycol fatty acid esters and their alkylene glycol adducts, sorbitan fatty acid esters and their alkylene glycol adducts. Adducts, sorbitol fatty acid esters and alkylene glycol adducts thereof, polyoxyethylene glycerin fatty acid esters, polyalkylene glycol fatty acid esters, sucrose fatty acid esters, glycerin alkyl ethers, polyoxyalkylene alkyl ethers, poly(oxyethylene)alkyl phenyl ether, poly(oxyethylene)alkyl ether, polyoxyethylene hydrogenated castor oil, alkylene glycol adducts of lanolin, polyoxyethylene-polyoxypropylene block copolymers, and the like. As for carbon number of the fatty acid in the illustration of said nonionic surfactant, 12-18 are preferable. Although the HLB value of a nonionic surfactant is not specifically limited, 12.5 or more may be sufficient as it. In addition, the HLB value of the nonionic surfactant may be less than 15.0 or less than 14.5. Commercially available products can be used for these. As a commercial item, for example, Triton X-100 (Triton X-100; HLB value 13.5, a type of polyoxyethylene alkylphenyl ether, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and the like; manufactured by Roche Applied Science) and the like. The amount of the dispersant used is not particularly limited, but the ultrahigh molecular weight plastic powder:dispersant (volume ratio) = 1:0.01 to 1:0.20 is preferable, and 1:0.05 to 1:0.15 is more preferable.

Examples of the thickener include, but are not particularly limited to, natural and synthetic clay minerals (including organic modified viscosity minerals) such as bentonite, montmorillonite, soconite, nontronite, saponite, hectorite, vermiculite and synthetic hectorite; plant-based thickeners such as gum arabic, tragacanth, and carrageenan; microbial thickeners such as xanthan gum; animal-based thickeners such as gelatin and sodium chondroitin sulfate; cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, nitrocellulose, ethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; starch-based thickeners such as rice starch and wheat starch; alginate-based thickeners such as sodium alginate and propylene glycol alginate; vinyl derivatives such as polyvinyl alcohol, polyvinylpyrrolidone, and polyvinyl acetate; and acrylic derivatives such as sodium polyacrylate, polyacrylic resin alkanolamine liquid, polyethyl methacrylate, and carboxyvinyl polymer. The amount of the thickener used is not particularly limited, but the ultrahigh molecular weight plastic powder:thickener (volume ratio) = 1:0.005 to 1:0.10 is preferable, and 1:0.01 to 1:0.08 is more preferable. In addition, the amount of the thickener used is not particularly limited, but dispersant:thickener (volume ratio) = 1:0.05 to 1:0.9 is preferable, and 1:0.1 to 1:0.8 is more preferable.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention may contain other resins as long as the effect of the present invention is not hindered, as long as it is mainly composed of ultra-high molecular weight plastic. As such another resin, high density polyethylene, low density polyethylene, etc. are mentioned, for example. The blending amount of these other resins is not particularly limited as long as it does not interfere with the effects of the present invention, but is preferably 10% by mass or less, more preferably 5.0% by mass or less, based on the entire hydrophilic ultra-high molecular weight plastic porous sheet. 1.0 mass % or less is more preferable.

As described above, the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention may contain other resins as long as the effects of the present invention are not hindered, but it is preferable that the resin material (plastic) is composed only of ultra-high molecular weight plastics. .

The average pore diameter of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is less than 20.0 μm, preferably 3.0 to 18.0 μm, more preferably 5.0 to 15.0 μm, from the viewpoint that higher water absorption is obtained after plasma treatment, More preferably, it is 8.0-13.0 micrometers. In addition, the average hole diameter of the porous sheet may be 1.0 μm or more, or 2.0 μm or more.

The average pore diameter in the present invention is determined by measuring the distribution of pore diameters by the BJH method using a specific surface area/pore distribution analyzer ASAP2010 (manufactured by Shimadzu Corporation) by a nitrogen adsorption/desorption method. is the value obtained from

The porosity of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is more than 30% and preferably 80% or less from the viewpoint of obtaining higher water absorption after plasma treatment when only plasma treatment is performed without antistatic treatment, 33 to 70% is more preferred, and 35 to 60% is still more preferred. The porosity of the porous sheet exceeds 20% and is preferably 70% or less, and more preferably 25 to 65%, from the viewpoint of obtaining higher water absorption after both treatments, when antistatic treatment is performed before or after plasma treatment. It is preferred, and 25 to 50% is more preferred.

The porosity in this invention means the volume ratio of the hole part in a porous sheet, and is a value defined by the following formula.

Porosity = {Volume of Porous Part/(Volume of Porous Material Part + Volume of Porous Part)} × 100 (%)

In addition, the porosity in the present invention is based on open pores and does not include closed pores.

By using such a porous sheet as a material, the absorbency of the sheet after plasma surface treatment can be further improved.

The thickness of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is not particularly limited, but is preferably about 5 to 500 μm, more preferably about 10 to 450 μm, still more preferably about 50 to 400 μm, and about 80 to 350 μm. The order of μm is particularly preferred.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention includes a step of subjecting the porous sheet of material to an antistatic treatment and/or a plasma treatment, wherein the porous sheet is made of the above-described ultra-high molecular weight plastic, and has an average pore diameter. It is less than 20.0 μm, and the plasma treatment in the case where antistatic treatment is not performed is performed in an oxygen gas atmosphere, and in the case where the antistatic treatment is performed before or after the plasma treatment, the plasma treatment is performed in an oxygen gas or argon gas atmosphere. can be produced by

In the manufacturing method of the present invention described above, the treatment performed on the porous sheet of material is a case where only plasma treatment is performed without performing antistatic treatment; Alternatively, it is preferable to perform the plasma treatment before or after the antistatic treatment.

In the plasma treatment step in the case where antistatic treatment is not performed, by using oxygen gas, superior absorbency can be obtained compared to non-reactive gases such as argon and helium.

In the plasma treatment step in the case where plasma treatment is performed before or after the antistatic treatment, excellent absorbency can be obtained by using oxygen gas or argon gas.

The introduction amount of oxygen gas in the plasma treatment step when antistatic treatment is not performed is not particularly limited as long as the effect of the present invention is obtained, but is preferably 10 to 100 sccm from the viewpoint of obtaining higher water absorption after plasma treatment, and to 80 sccm is more preferred, and 30 to 50 sccm is still more preferred.

The introduction amount of oxygen gas or argon gas in the plasma treatment step before or after the antistatic treatment is not particularly limited as long as the effect of the present invention is obtained, but from the viewpoint of obtaining high water absorption, 101 to 600 sccm It is preferable, 110 to 550 sccm is more preferable, 150 to 500 sccm is more preferable, and 200 to 480 sccm is particularly preferable.

The gas pressure in the plasma treatment step is not particularly limited, but is 0.5 to 0.5 to 0.5 to 0.5 in that higher water absorption is obtained after performing plasma treatment in the case of not performing antistatic treatment and after performing plasma treatment before or after antistatic treatment. 10 Pa is preferable, and 2.0-7.0 Pa is more preferable.

The product (processing energy) of the treatment density and the treatment time in the plasma treatment step in the case of not performing the antistatic treatment is preferably 10 J/cm 2 or more and 300 J/cm 2 or less, from the viewpoint of obtaining higher water absorption after the plasma treatment. /cm 2 or more and 300 J/cm 2 or less are more preferable, 20 J/cm 2 or more and 250 J/cm 2 or less are still more preferable, and 25 J/cm 2 or more and 200 J/cm 2 or less are particularly preferable. The product of the processing density (processing power [W]/processing area [cm 2 ]) and the processing time ([sec]) can be adjusted using a high-frequency power supply of 5 to 15 MHz.

The product (processing energy) of the treatment density and the treatment time in the plasma treatment step in the case of performing the plasma treatment before or after the antistatic treatment is preferably 0.10 J/cm 2 or more and less than 10 J/cm 2 from the viewpoint of obtaining higher water absorption. And, more preferably 0.20 J/cm 2 or more and 8.0 J/cm 2 or less, more preferably 0.30 J/cm 2 or more and 5.0 J/cm 2 or less, and particularly preferably 0.35 J/cm 2 or more and 4.0 J/cm 2 or less.

As an antistatic treatment, a method of coating an antistatic agent with respect to a porous sheet is mentioned. The antistatic agent is not particularly limited, and examples thereof include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants, with cationic surfactants, anionic surfactants, and nonionic surfactants being preferred. Although these antistatic agents may be used individually by 1 type, or may use 2 or more types together, it is preferable not to use together cationic surfactant and anionic surfactant. It does not specifically limit as an antistatic agent of this invention, You may further contain additives, such as a ultraviolet absorber and a release agent.

The cationic surfactant used as the antistatic agent is not particularly limited, and alkylammonium acetate salts, alkyldimethylbenzylammonium salts, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylpyridinium salts, oxyalkylenealkylamines, polyoxy Alkylene alkylamines etc. are mentioned.

Examples of the anionic surfactant used as the antistatic agent include, but are not particularly limited to, fatty acid soda soaps such as sodium stearate soap, alkyl sulfates such as sodium lauryl sulfate, α-sulfofatty acid ester salts, alkyl ether sulfates, and sodium alkylbenzenesulfonates. , sodium alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphates, and alkyl diphenyl ether disulfonates.

Alkyl carboxy betaines etc. are mentioned as an amphoteric ionic surfactant used as an antistatic agent.

Examples of the nonionic surfactant used as the antistatic agent include the same ones as the dispersing agent described above.

As an antistatic agent, a commercial item can be used. Examples of commercially available products include polyoxyethylene-polyoxypropylene block copolymer type nonionic surfactants such as Adeka (registered trademark) Pluronic L P F series and Adeka (registered trademark) Pluronic TR series; Alkyl ether type nonionic surfactants, such as Adecatol LB series, Adecatol LA series, and Adecatol TN series; ester type nonionic surfactants such as adecanol NK (glyceride ethylene oxide adduct); special phenol type nonionic surfactants such as adecatol PC; sulfate-type anionic surfactants such as the Adekahop series; Phosphoric acid ester type or succinic acid ester type anionic surfactants, such as the Adecacol series; quaternary cation type cationic surfactants such as the Adecamine series (above, manufactured by ADEKA Co., Ltd.); Cationic surfactants, such as Electron series (made by Dainichi Seika Kogyo Co., Ltd.), and amphoteric surfactants (made by Kao Co., Ltd.), such as Electrostripper AC, etc. are mentioned.

The coating method is not particularly limited, and a known method can be employed. As the coating method, for example, casting method, dipping method, roll coating method, gravure coating method, screen printing method, reverse coating method, spray coating method, kiss coating method, die coating method, metalling bar coating method, chamber doctor combined use A coating method, a curtain coating method, a bar coating method, etc. are mentioned.

After coating the antistatic agent with respect to the porous sheet, you may perform a drying process. The temperature of the drying treatment is not particularly limited, and may be, for example, about 50 to 130°C or about 60 to 110°C.

In the method for producing a porous sheet of the present invention, in order to impart hydrophilicity, treatment other than the above plasma treatment such as corona discharge treatment and antistatic treatment may be performed, but is not particularly required.

In the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention, characteristic absorption in the range of 3000 to 3500 cm ^-1 is hardly observed in the IR spectrum measured by infrared spectroscopy (FT-IR). This is because hydrophilic functional groups (OH groups) are not introduced to the surface of the hydrophilic porous sheet (up to several 10 µm in the thickness direction from the surface) enough to be detected by infrared spectroscopy (FT-IR), that is, the introduced amount of the hydrophilic functional group is extremely small. means that

The present invention includes various combinations of the above configurations within the technical scope of the present invention as long as the effects of the present invention are exhibited.

Example

Next, the present invention will be described more specifically by way of examples, but the present invention is not limited at all by these examples.

[Example 1]

UHMWPE powder (weight average molecular weight: 4,500,000) was mixed with water, a dispersant (trade name: Triton X-100 (manufactured by Roche Applied Science)), and a thickener (sodium carboxymethylcellulose) to obtain a dispersion. The compounding ratio at this time was water/UHMWPE powder/dispersant/thickener = 100/60/5/2 (volume ratio). This dispersion liquid was applied onto a polyimide film (arithmetic average roughness Ra < 0.1 of JIS B 0601: 2013) using a doctor blade in an arbitrary thickness. The dispersion liquid applied on this film was put into a dryer set at 180°C and allowed to stand for 10 minutes. After drying, the polyimide film layered product was taken out and naturally cooled to room temperature, and then the polyimide film on the back side was peeled from the layered product. Thereafter, the obtained sheet was washed with distilled water in an ultrasonic cleaning tank, and the dispersant was sufficiently extracted from the sheet to obtain a UHMWPE porous sheet having an average pore diameter of 10 μm and a porosity of 40%.

Plasma treatment was performed on the obtained UHMWPE porous sheet. As the above plasma treatment, sputter etching treatment was performed using a high-frequency plasma in the presence of O ₂ gas. As conditions for the sputter etching treatment, the amount of O ₂ gas introduced into the vacuum chamber was 30 sccm, and the gas pressure in the chamber was 3.6 Pa, and the treatment was performed using a high-frequency power supply. The product of the treatment density and the treatment time at this time was treated at 30 J/cm 2 , thereby obtaining a hydrophilic UHMWPE porous sheet.

(Measurement of FT-IR)

Each sheet of the obtained Examples and Comparative Examples was measured by FT-IR manufactured by Nippon Bunko Co., Ltd. The results are shown in Table 1.

(absorbency evaluation)

For each sheet of the obtained Examples and Comparative Examples, one end of the sheet was immersed 1 cm in pure water in an atmosphere of 25 ° C. It was pulled up after being left for 3 minutes, and the distance the water traveled within the sheet was measured and evaluated. The results are shown in Table 1.

(adhesion evaluation)

Each sheet of the obtained Examples and Comparative Examples was fixed to a SUS board with a double-sided tape (model number: No. 5000NS, manufactured by Nitto Denko Co., Ltd.). Next, an acrylic adhesive tape (model number: No.31B, manufactured by Nitto Denko Co., Ltd.) was pasted on the surface (treated surface) of the sheet. Thereafter, it was left at room temperature, and after 30 minutes had elapsed, the adhesive force between the sheet and the adhesive tape was measured using a tensile tester (trade name: Tensilon Universal Tester, model number: RTC-1210A, manufactured by A&D Co., Ltd.) saved

[Example 2]

The sputter etching treatment using O ₂ gas was carried out in the same manner as in Example 1 except that the product of the treatment density and the treatment time was 10 J/cm 2 . About the obtained sheet|seat, FT-IR measurement and water absorption evaluation were performed similarly to Example 1. The results are shown in Table 1.

[Comparative Example 1]

The ultrahigh molecular weight polyethylene porous sheet obtained in Example 1 was not subjected to plasma treatment. About the obtained sheet|seat, FT-IR measurement and water absorption evaluation were performed similarly to Example 1. The results are shown in Table 1.

[Comparative Example 2]

It was carried out similarly to Example 1 except having used Ar gas for the sputter etching process. About the obtained sheet|seat, FT-IR measurement and water absorption evaluation were performed similarly to Example 1. The results are shown in Table 1.

[Example 3]

A hydrophilic UHMWPE porous sheet was obtained in the same manner as in Example 1, except that an antistatic treatment was applied to the UHMWPE porous sheet instead of plasma treatment. As an antistatic treatment, a cationic antistatic agent (cationic surfactant, trade name: ELECNON OR-W, manufactured by Dainichi Seika Kogyo Co., Ltd.) was coated on a UHMWPE porous sheet by dipping. Specifically, deionized water was added to the cationic antistatic agent to prepare a 3% aqueous solution, and the obtained aqueous solution was coated on the porous sheet by dip coating and dried at 90°C for 2 minutes. About the obtained hydrophilic UHMWPE porous sheet, FT-IR measurement and water absorption evaluation were performed similarly to Example 1. The results are shown in Table 1.

[Example 4]

As a UHMWPE porous sheet of material, Sunmap LC-T (trade name, Nitto Denko Co., Ltd.) having an average pore diameter of 17 μm and a porosity of 30% was used. Antistatic treatment was applied to Sunmap LC-T in the same manner as in Example 3. About the obtained hydrophilic UHMWPE porous sheet, FT-IR measurement and water absorption evaluation were performed similarly to Example 1. The results are shown in Table 1.

[Examples 5 to 6]

As the UHMWPE porous sheet of material, Sunmap LC-T was used in the same way as in Example 3. Plasma treatment was performed on Sunmap LC-T in the same manner as in Example 1, except that the conditions were changed as shown in Table 1. Subsequently, antistatic treatment was performed on the obtained porous sheet in the same manner as in Example 4. About each obtained hydrophilic UHMWPE porous sheet, FT-IR measurement and water absorption evaluation were performed similarly to Example 1.

[Examples 7 to 8]

As a UHMWPE porous sheet of material, antistatic treatment was performed using Sunmap LC-T in the same manner as in Example 3. Subsequently, plasma treatment was performed on the obtained porous sheet in the same manner as in Example 1, except that each condition was changed as shown in Table 1. About each obtained hydrophilic UHMWPE porous sheet, FT-IR measurement and water absorption evaluation were performed similarly to Example 1.

From the results of Table 1, although hydrophilic functional groups (OH) were not introduced to a detectable level on the surface of the porous sheet (from the surface to about several 10 μm in the thickness direction) in each sheet of the examples, the water absorption rate It was confirmed that is 15 mm/3 min or more. In addition, as for the adhesive force, Example 3 was 0.6 N/mm, and Example 4 was 0.5 N/mm. Examples 1, 2, and 5 to 8 were 2.1 N/mm or more.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has high water absorption, especially in the case of a hydrophilic ultra-high molecular weight plastic porous sheet using ultra-high molecular weight polyethylene, has high water absorption and excellent dimensional stability derived from polyethylene, and thus absorbs liquid. It is assumed that it can be used as a battery separator or a humidifying element for an air conditioner or the like or an ink absorber for a printer, which requires retention.

Claims (11)

It is composed of ultra-high molecular weight plastic with an absorption rate of 15 mm/3 minutes or more when one end of the sheet is immersed in pure water under an atmosphere of 25°C and a humidity of 60% RH, and there is no introduction of a substance having a hydrophilic functional group by graft polymerization. , In the IR spectrum measured by infrared spectroscopy (FT-IR), characteristic absorption is not observed at 3000 to 3500 cm ^-1 , a hydrophilic ultra-high molecular weight plastic porous sheet, characterized in that. The hydrophilic ultra-high molecular weight plastic porous sheet according to claim 1, characterized in that the ultra-high molecular weight plastic is at least one selected from the group consisting of ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, ultra-high molecular weight polyvinyl chloride, and ultra-high molecular weight polyamide. The hydrophilic ultra-high molecular weight plastic porous sheet according to claim 1, characterized in that the ultra-high molecular weight plastic is ultra-high molecular weight polyethylene. The hydrophilic ultra-high molecular weight plastic porous sheet according to claim 1, wherein the porous sheet has an average pore diameter of less than 20.0 µm. The hydrophilic ultra-high molecular weight plastic porous sheet according to claim 1, wherein the porous sheet has an average pore diameter of 5.0 to 15.0 μm and a porosity of more than 30% and less than 80%. The hydrophilic ultra-high molecular weight plastic porous sheet according to claim 1, characterized in that the water absorption rate is 20 mm/3 min or more. With respect to a porous sheet, it has a process of performing antistatic treatment and/or plasma treatment,
The porous sheet is made of ultra-high molecular weight plastic and has an average pore diameter of less than 20.0 μm;
Claim 1 characterized in that the plasma treatment when not performing the antistatic treatment is performed under an oxygen gas atmosphere, and when the antistatic treatment is performed before or after the plasma treatment, the plasma treatment is performed under an oxygen gas or argon gas atmosphere. A method for producing the hydrophilic ultra-high molecular weight plastic porous sheet according to any one of claims 1 to 6. The method for producing a hydrophilic ultra-high molecular weight plastic porous sheet according to claim 7, characterized in that the plasma treatment is performed at a gas pressure of 0.5 to 10 Pa. The method for producing a hydrophilic ultra-high molecular weight plastic porous sheet according to claim 7, characterized in that an antistatic treatment is performed before or after the plasma treatment. The method for producing a hydrophilic ultra-high molecular weight plastic porous sheet according to claim 7, characterized in that the product of the treatment density and the treatment time in the plasma treatment step when antistatic treatment is not performed is 10 J/cm 2 or more and 300 J/cm 2 or less. The hydrophilic ultra-high molecular weight plastic porous sheet according to claim 7, wherein the product of the treatment density and the treatment time in the plasma treatment step when the antistatic treatment is performed before and after the plasma treatment is 0.10 J/cm 2 or more and less than 10 J/cm 2 . manufacturing method.