TWI687473B - Hydrophilic ultra-high molecular weight plastic porous sheet and manufacturing method thereof - Google Patents

Abstract

The object of the present invention is to provide a hydrophilic porous sheet with high water absorption. Furthermore, an object of the present invention is to provide a hydrophilic porous sheet excellent in adhesion. In addition, an object of the present invention is to provide a simple method for manufacturing the porous sheet. The invention relates to a hydrophilic ultra-high molecular weight plastic porous sheet, which is characterized in that the absorption speed when one end of the sheet is immersed in pure water under an environment of 25°C and 60%RH is 15mm/3min or more. The film is made of ultra-high molecular weight plastic. In the IR spectrum measured by infrared spectroscopy (FT-IR), there is no characteristic absorption at 3000~3500cm ^-1 .

Description

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

The invention relates to an ultra-high molecular weight plastic porous sheet that requires hydrophilicity or air permeability and absorption of pure water and a method for manufacturing the same.

The porous sheet of polyolefin resin particles is widely used in various filters or buffer materials used for adsorption and fixation due to its excellent filtering function or permeability. Among them, in particular, the hydrophilic porous polyethylene sheet can be used for water absorption or retention, diffusion, and permeation due to its hydrophilicity or water absorption. The polyolefin sintered body described in Patent Document 1 has been developed.

As the above-mentioned porous sheet having a water-absorbing function, a sheet or non-woven fabric of synthetic fibers subjected to hydrophilization treatment, or a cloth of natural fibers, and a microporous membrane or water-absorbing polymer or metal of thermoplastic resin subjected to hydrophilization treatment have also been developed Or ceramic sintered body, etc.

The above-mentioned hydrophilic polyethylene porous sheet has excellent dimensional stability when absorbing water, high mechanical strength, and can also handle the moldability of complex shapes, so it is expected to be used in humidifying elements for air conditioning or ink absorbers of printers. It has been widely used in many fields.

In order to impart hydrophilicity to the porous polyethylene sheet, generally, a material having a hydrophilic functional group is introduced into the raw material polyethylene powder by graft polymerization as in the method described in Patent Document 2, but there are complex manufacturing steps. Or it is not easy to obtain enough hydrophilicity or Waterborne and other topics.

Prior technical literature

Patent Literature

Patent Document 1: Japanese Patent Publication No. 4-28021

Patent Document 2: Japanese Patent Laid-Open No. 2009-114238

An object of the present invention is to provide a hydrophilic porous sheet with high water absorption without introducing a substance having a hydrophilic functional group. Furthermore, an object of the present invention is to provide a hydrophilic porous sheet excellent in adhesion. In addition, an object of the present invention is to provide a simple method for manufacturing the porous sheet.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has an absorption rate of 15 mm/3 min or more when the one end of the sheet is immersed in pure water at 25°C and 60% RH. The porous sheet is made of ultra-high molecular weight plastic In the structure, in the IR spectrum measured by infrared spectroscopy (FT-IR), no characteristic absorption was observed at 3000 to 3500 cm ^-1 .

The manufacturing method of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has the steps of performing antistatic treatment and/or plasma treatment on the porous sheet. The porous sheet is composed of ultra-high molecular weight plastic, and the average pore diameter is less than 20.0 μm, when the antistatic treatment is not performed, the above plasma treatment is performed in an oxygen environment.

According to the present invention, it is possible to provide a hydrophilic ultra-high molecular weight plastic porous sheet that exhibits relatively high water absorption without introducing (eg, laminating) a substance having a hydrophilic functional group. Furthermore, the present invention can provide a hydrophilic porous sheet excellent in adhesion. In addition, by adopting the production method of the present invention, a porous sheet having improved absorption of pure water can be easily obtained.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is characterized in that the absorption speed when one end of the sheet is immersed in pure water under an environment of 25°C and 60%RH is 15 mm/3 min or more. The porous sheet is made of The ultra-high molecular weight plastic composition, in the IR spectrum measured by infrared spectroscopy (FT-IR), has no characteristic absorption at 3000~3500cm ^-1 .

The measurement method of the above absorption rate is as described in the examples described later. The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention can be used as a water-absorbing sheet. When the one end of the sheet is immersed in pure water under an environment of 25°C and humidity of 60% RH, the absorption speed is preferably 20 mm/3 min or more. It is preferably 25 mm/3 min or more, further preferably 30 mm/3 min or more, particularly preferably 35 mm/3 min or more, still more preferably 40 mm/3 min or more, still more preferably 45 mm/3 min or more, and most preferably 55 mm/3 min or more.

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 further preferably 2.5 N/mm or more. The measuring method of the above-mentioned adhesive force is as described in the examples described later.

As the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention, the absorption speed is preferably 15 mm/3 min or more, and the adhesion force is 2.1 N/mm or more, and the absorption speed is more than 20 mm/3 min or more, and the adhesion force is 2.1 N/mm or more, it is more preferable that the absorption speed is 25 mm/3 min or more, and the adhesive force is 2.5 N/mm or more.

The ultrahigh molecular weight plastic constituting the hydrophilic ultrahigh molecular weight plastic porous sheet of the present invention is not particularly limited, and examples include ultrahigh molecular weight polyethylene, ultrahigh molecular weight polypropylene, ultrahigh molecular weight polyvinyl chloride, and ultrahigh molecular weight Polyamide and the like are preferably ultra-high molecular weight polyethylene (hereinafter also referred to as UHMWPE). One of these may be used alone, or two or more may be used in combination. In addition, these can use commercially available products. Examples of commercial products of high molecular weight plastics include Hi-Zex-Million (Mitsui Chemicals), Sunfine UH, UTS (Asahi Kasei Chemicals), HIFAX1000 (Hercules), Hostalen GUR (Hoechst), etc. Molecular weight polyethylene, ultrahigh molecular weight polyvinyl chloride such as TK2500 series (Shin-Etsu Chemical Industry), ultrahigh molecular weight polyamide such as Daiamide (Daicel Chemical Industries), etc.

In the present invention, the weight average molecular weight (Mw) of the ultra-high molecular weight plastic (hereinafter also referred to simply as the average molecular weight) is not particularly limited, preferably 500,000 or more, more preferably 1 million or more, and still more preferably 1.5 million or more, Youjia is more than 2 million. In addition, 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 above-mentioned weight average molecular weight is a value measured by light scattering measurement.

The ultra-high molecular weight plastic porous sheet used as a material can be manufactured by a known method, for example, it can be manufactured according to the method described in Japanese Patent Publication No. 7-55541 and Japanese Patent Publication No. 2002-177390. For example, it can be produced by filling the conformal tool (mold, etc.) In the ultra-high molecular weight plastic powder, the plastic formed on the mold frame is sintered in a water vapor environment heated above 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 liquid containing ultra-high molecular weight polyethylene powder and the like is prepared, and the dispersion liquid is coated into a sheet form, followed by about 130 to 200°C After the heat treatment, it is then left to cool to room temperature, whereby ultra-high molecular weight plastic porous sheets can be manufactured.

In addition, ultra-high molecular weight plastic porous sheets used as materials can also be manufactured using additives such as dispersants and tackifiers.

Examples of the dispersant include surfactants, and nonionic surfactants are preferred. 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 Glycol adducts, sorbitan fatty acid esters and their alkylene glycol adducts, sorbitol fatty acid esters and their alkylene glycol adducts, polyoxyethylene glycerin fatty acid esters, polyextensives Alkyl glycol fatty acid ester, sucrose fatty acid ester, glycerin alkyl ether, polyoxyalkylene alkyl ether, poly(oxyethylene) alkyl phenyl ether, poly(oxyethylene) alkyl ether, polyoxyethylene Hydrogenated castor oil, alkylene glycol adduct of lanolin, polyoxyethylene-polyoxypropylene block copolymer, etc. The carbon number of the fatty acid in the example of the above-mentioned nonionic surfactant is preferably 12-18. The HLB value of the nonionic surfactant is not particularly limited, and may be 12.5 or more. In addition, the HLB value of the nonionic surfactant may not reach 15.0 or 14.5. These can use commercially available products. As a commercially available product, for example, Triton X-100 (HLB value 13.5, one of polyoxyethylene alkylphenyl ethers, including polyethylene glycol-p (1,1,3,3-tetramethylbutyl) -Compounds such as phenyl ether; manufactured by Roche Applied Science), etc. The amount of the dispersant used is not particularly limited, but it is preferably a powder of ultra-high molecular weight plastic: dispersant (volume ratio) = 1:0.01~1:0.20, more preferably 1:0.05~1:0.15.

The tackifier is not particularly limited, and examples thereof include natural and synthetic ones such as bentonite, montmorillonite, sauconite, nontronite, saponite, lithium bentonite, vermiculite, and synthetic lithium bentonite. Clay minerals (including organically modified viscosity minerals); plant-based tackifiers such as gum arabic, tragacanth, carrageenan; microbial tackifiers such as Sanxian gum; animal-based tackifiers such as gelatin and chondroitin sodium sulfate Agents; cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, nitrocellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; rice starch, Starch thickeners such as wheat starch; alginic acid thickeners such as sodium alginate and propylene glycol alginate; vinyl derivatives such as polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate; sodium polyacrylate Acrylic resin alkanolamine liquid, polyethyl methacrylate, carboxyvinyl polymer and other acrylic derivatives. The amount of tackifier used is not particularly limited, but it is preferably a powder of ultra-high molecular weight plastic: tackifier (volume ratio) = 1: 0.005 to 1: 0.10, more preferably 1: 0.01 to 1: 0.08. In addition, the amount of the tackifier used is not particularly limited, but it is preferably a dispersant: tackifier (volume ratio) = 1: 0.05 to 1: 0.9, more preferably 1: 0.1 to 1: 0.8.

As long as the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention is mainly composed of ultra-high molecular weight plastic, other resins may be included within a range that does not impair the effects of the present invention. Examples of such other resins include high-density polyethylene and low-density polyethylene. The blending amount of such other resins is not particularly limited as long as the effect of the present invention is not impaired, and it is preferably 10% by mass or less and more preferably 5.0% by mass relative to the entire hydrophilic ultra-high molecular weight plastic porous sheet. Below, and further preferably 1.0% by mass or less.

As described above, the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention may contain other resins within the range that does not impair the effects of the present invention, but as the resin material (plastic), it is preferably composed only of ultra-high molecular weight plastic .

Regarding the average pore diameter of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention, in terms of obtaining higher water absorption after plasma treatment, it is less than 20.0 μm, preferably 3.0 to 18.0 μm, more preferably 5.0 to 15.0 μm, and more preferably 8.0 to 13.0 μm. In addition, the average pore diameter of the porous sheet may be 1.0 μm or more or 2.0 μm or more.

The so-called average pore diameter in the present invention uses a specific surface area based on nitrogen absorption/desorption. The micropore distribution measuring device ASAP2010 (manufactured by Shimadzu Corporation) is used to measure the pore size distribution by the BJH method, and the value obtained from this.

Regarding the porosity of the hydrophilic ultra-high molecular weight plastic porous sheet of the present invention, when antistatic treatment is not performed but plasma treatment is performed, in terms of obtaining higher water absorption by plasma treatment, It is preferably more than 30% and 80% or less, more preferably 33 to 70%, and still more preferably 35 to 60%. Regarding the porosity of the above porous sheet, when antistatic treatment is performed before or after plasma treatment, in terms of obtaining higher water absorption by both treatments, it is preferably more than 20% and 70 % Or less, more preferably 25 to 65%, and further preferably 25 to 50%.

The porosity in the present invention means the volume ratio of the pore portion in the porous sheet, and is a value defined by the following formula.

Porosity = {Volume part volume/(Porous body substance part volume + Pore body part volume)}×100(%)

Furthermore, the so-called porosity in the present invention is based on open pores and does not include closed pores.

By using the porous sheet as a material, the water absorption 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, preferably about 5 to 500 μm, more preferably about 10 to 450 μm, and still more preferably 50 ~400μm, especially 80~350μm.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention can be manufactured by the following manufacturing method, which has a step of performing antistatic treatment and/or plasma treatment on the porous sheet of the material, the porous sheet is composed of The above ultra-high molecular weight plastic is composed of an average pore diameter of less than 20.0 μm. When antistatic treatment is not performed, the above plasma treatment is performed in an oxygen environment, and when antistatic treatment is performed before or after plasma treatment The plasma treatment is carried out under oxygen or argon atmosphere.

In the manufacturing method of the present invention described above, it is preferable that the treatment of the porous sheet of the material is not only antistatic treatment but only plasma treatment; or before or after antistatic treatment.

When antistatic treatment is not performed, by using oxygen in the plasma treatment step, superior water absorption can be obtained compared with non-reactive gases such as argon and helium.

In the case of plasma treatment before or after antistatic treatment, by using oxygen or argon gas in the plasma treatment step, excellent water absorption can be obtained.

When the antistatic treatment is not performed, the amount of oxygen introduced in the plasma treatment step is not particularly limited as long as the effect of the present invention can be obtained, and the higher water absorption is obtained after the plasma treatment In other words, it is preferably 10 to 100 sccm, more preferably 20 to 80 sccm, and still more preferably 30 to 50 sccm.

When plasma treatment is performed before or after antistatic treatment, the amount of oxygen or argon gas introduced in the plasma treatment step is not particularly limited as long as the effect of the present invention can be obtained, and high water absorption is obtained In terms of performance, it is preferably from 101 to 600 sccm, more preferably from 110 to 550 sccm, further preferably from 150 to 500 sccm, and particularly preferably from 200 to 480 sccm.

The gas pressure in the plasma treatment step is not particularly limited. When the antistatic treatment is not performed, the plasma pressure treatment is performed, and the plasma treatment is performed before or after the antistatic treatment to obtain higher water absorption. In this respect, it is preferably 0.5 to 10 Pa, and more preferably 2.0 to 7.0 Pa.

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

In the case of plasma treatment before or after antistatic treatment, regarding the product (treatment energy) of the treatment density and treatment time in the plasma treatment step, in terms of obtaining higher water absorption, it is preferably 0.10J/cm ² or more and less than 10J/cm ² , more preferably 0.20J/cm ² or more and 8.0J/cm ² or less, further preferably 0.30J/cm ² or more and 5.0J/cm ² or less, especially Preferably, it is 0.35 J/cm ² or more and 4.0 J/cm ² or less.

Examples of the antistatic treatment include a method of applying an antistatic agent to the porous sheet. The antistatic agent is not particularly limited, and examples thereof include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants, and preferably cationic surfactants, anionic surfactants, and nonionics Surfactant. One type of these antistatic agents may be used alone, or two or more types may be used in combination, but it is preferable not to use a cationic surfactant and an anionic surfactant together. The antistatic agent of the present invention is not particularly limited, and may further contain additives such as ultraviolet absorbers and mold release agents.

As a cationic surfactant used as an antistatic agent, it is not particularly limited, but List: alkyl ammonium acetates, alkyl dimethyl benzyl ammonium salts, alkyl trimethyl ammonium salts, dialkyl dimethyl ammonium salts, alkyl pyridinium salts, oxyalkylene Alkylamines, polyoxyalkylene alkylamines, etc.

The anionic surfactant used as an antistatic agent is not particularly limited, and examples include fatty acid sodium soaps such as sodium stearate soap, alkyl sulfates such as sodium lauryl sulfate, and α-sulfofatty acid ester salts , Alkyl ether sulfates, sodium alkylbenzene sulfonates, sodium alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphates, alkyl diphenyl ether disulfonates Class etc.

Examples of zwitterionic surfactants used as antistatic agents include alkyl carboxybetaines.

Examples of the nonionic surfactant used as the antistatic agent include the same as the above-mentioned dispersants.

As the antistatic agent, commercially available products can be used. Examples of commercially available products include ADEKA (registered trademark) Pluronic L. P. F series, ADEKA (registered trademark) Pluronic TR series and other polyoxyethylene-polyoxypropylene block copolymer type nonionic surfactants, Adekatol LB series, Adekatol LA series, Adekatol TN series and other alkyl ether type nonionic interface activities Agents, ester-type nonionic surfactants such as Adekanol NK (glyceride ethylene oxide adduct), special phenolic nonionic surfactants such as Adekatol PC, sulfate-type anionic surfactants such as Adekahope series, Adekacol series, etc. Phosphate type or succinate type anionic surfactants, Adekamine series and other four-stage cationic cationic surfactants (above manufactured by ADEKA Co., Ltd.); Elecnon series (manufactured by Dairi Seika Chemical Co., Ltd.) and other cationic interface activities Agent; ELEC AC and other amphoteric surfactants (manufactured by Kao Co., Ltd.), etc.

The coating method is not particularly limited, and a known method can be used. As a coating method, Examples include: casting method, dipping method, roll coating method, gravure coating method, screen printing method, reverse coating method, spray coating method, contact coating method, die coating method, metal bar coating The metal (baring) coating method, the chamber squeegee combination coating method, the curtain coating method, the bar coating method, etc.

After the antistatic agent is applied to the porous sheet, it may be dried. The temperature of the drying process is not particularly limited. For example, it may be about 50 to 130°C or 60 to 110°C.

In the manufacturing method of the porous sheet of the present invention, in order to further impart hydrophilicity, treatment other than the above-mentioned plasma treatment and antistatic treatment such as corona discharge treatment may be performed, but no special requirements are made.

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has almost no characteristic absorption at 3000~3500cm ^-1 in the IR spectrum measured by infrared spectroscopy (FT-IR). This means that hydrophilic functional groups (OH groups) that can be detected by infrared spectroscopy (FT-IR) are not introduced on the surface of the hydrophilic porous sheet (from the surface to about 10 μm in the thickness direction), That is, the amount of hydrophilic functional groups introduced is extremely small.

As long as the present invention exerts the effects of the present invention, the technical scope of the present invention includes a combination of the above-mentioned various configurations.

Examples

Next, the examples will be listed to further specifically explain the present invention, but the present invention is not limited by these examples.

[Example 1]

UHMWPE powder (weight average molecular weight 4.5 million) was mixed with water, a dispersant (trade name: Triton X-100 (manufactured by Roche Applied Science)), and a thickener (sodium carboxymethyl cellulose) to obtain a dispersion liquid. The blending ratio at this time is set to water/UHMWPE powder/dispersant/increasing Adhesive = 100/60/5/2 (volume ratio). This dispersion liquid was applied to a polyimide film (arithmetic mean roughness Ra<0.1 of JIS B 0601:2013) with an arbitrary thickness using a doctor blade. The dispersion liquid coated on the film was put into a dryer set at 180°C and allowed to stand for 10 minutes. After drying, the polyimide film laminate was taken out, and after naturally cooling to room temperature, the polyimide film on the back was peeled off from the laminate. Thereafter, the obtained sheet was washed with distilled water in an ultrasonic washing tank, and the dispersant was sufficiently extracted from the above sheet, thereby obtaining a UHMWPE porous sheet having an average pore diameter of 10 μm and a porosity of 40%.

The obtained UHMWPE porous sheet was subjected to plasma treatment. The above plasma treatment is performed in the presence of oxygen by sputtering etching using high-frequency plasma. Regarding the conditions of the sputtering etching process, the amount of oxygen introduced into the vacuum chamber is set to 30 sccm, the gas pressure in the chamber is set to 3.6 Pa, and treatment is performed using a high-frequency power supply. The treatment was performed in a state where the product of the treatment density and the treatment time was 30 J/cm ² , thereby obtaining a hydrophilic UHMWPE porous sheet.

(Measurement of FT-IR)

Each piece of the obtained examples and comparative examples was measured using FT-IR manufactured by Japan Spectroscopy Corporation. The results are shown in Table 1.

(Water absorption evaluation)

According to the Byreck method of JIS L 1907:2010 (Test Method for Water Absorption of Fiber Products), the pieces of the obtained examples and comparative examples were immersed in a portion of 1 cm at one end of the piece in an environment of 25°C and 60% RH In pure water, let it stand for 3 minutes and lift it up. Measure the distance the water moves in the tablet and evaluate. The results are shown in Table 1.

(Adequacy evaluation)

Each piece of the obtained examples and comparative examples was made of double-sided tape (Model: No. 5000NS, Japan Manufactured by East Electric Co., Ltd.) fixed to the SUS board. Then, an acrylic adhesive tape (model number: No. 31B, manufactured by Nitto Denko Corporation) was attached to the surface (treated surface) of the sheet. Thereafter, it was left at room temperature, and after 30 minutes, a tensile tester (trade name: Tensilon universal material tester, model: RTC-1210A, manufactured by A&D Co., Ltd.) was used to determine the adhesion between the sheet and the adhesive tape.

[Example 2]

Regarding the sputtering etching treatment using oxygen, the product of the treatment density and the treatment time was set to 10 J/cm ² , except that it was performed in the same manner as in Example 1. The obtained sheet was subjected to FT-IR measurement and water absorption evaluation in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]

The ultra-high molecular weight polyethylene porous sheet obtained in Example 1 was not subjected to plasma treatment. The obtained sheet was subjected to FT-IR measurement and water absorption evaluation in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]

Argon gas was used for the sputtering etching process, except that it was performed in the same manner as in Example 1. The obtained sheet was subjected to FT-IR measurement and water absorption evaluation in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]

The UHMWPE porous sheet was subjected to antistatic treatment instead of plasma treatment, except that a hydrophilic UHMWPE porous sheet was obtained in the same manner as in Example 1. As an antistatic treatment, a cationic antistatic agent (cationic surfactant, trade name: Elecnon OR-W, manufactured by Dairi Seiki Chemical Industry Co., Ltd.) is applied to the UHMWPE porous sheet by dipping. in particular, Deionized water was added to the cationic antistatic agent to prepare a 3% aqueous solution, and the aqueous solution obtained by dip coating the porous sheet was dried at 90°C for 2 minutes. The obtained hydrophilic UHMWPE porous sheet was subjected to FT-IR measurement and water absorption evaluation in the same manner as in Example 1. The results are shown in Table 1.

[Example 4]

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

[Examples 5-6]

UHMWPE porous sheet using Sunmap LC-T as a material in the same manner as in Example 3. The conditions were changed as described in Table 1. Except for this, the Sunmap LC-T was subjected to plasma treatment in the same manner as in Example 1. Then, the obtained porous sheet was subjected to antistatic treatment in the same manner as in Example 4. Each hydrophilic UHMWPE porous sheet obtained was subjected to FT-IR measurement and water absorption evaluation in the same manner as in Example 1.

[Examples 7 to 8]

As in Example 3, a UHMWPE porous sheet using Sunmap LC-T as a material was subjected to antistatic treatment. Next, the conditions were changed as described in Table 1, except that the obtained porous sheet was subjected to plasma treatment in the same manner as in Example 1. Each hydrophilic UHMWPE porous sheet obtained was subjected to FT-IR measurement and water absorption evaluation in the same manner as in Example 1.

It can be confirmed from the results in Table 1 that in each of the sheets of the Examples, although the surface of the porous sheet (from the surface to about 10 μm in the thickness direction) did not introduce a detectable hydrophilic functional group (OH), But the absorption speed is above 15mm/3min. In addition, regarding the adhesive force, Example 3 is 0.6 N/mm, and Example 4 is 0.5 N/mm. Examples 1, 2, and 5 to 8 are 2.1 N/mm or more.

Industrial availability

The hydrophilic ultra-high molecular weight plastic porous sheet of the present invention has higher water absorption, especially when the hydrophilic ultra-high molecular weight plastic porous sheet made of ultra-high molecular polyethylene is used. And it has excellent dimensional stability derived from polyethylene, so it is presumed that it can be used as a humidifying element for battery separators or air conditioners that require liquid water retention, or an ink absorber of a printer.

Claims (13)

A hydrophilic ultra-high molecular weight plastic porous sheet whose absorption speed is more than 15mm/3min when immersing one end of the sheet in pure water under an environment of 25°C and humidity of 60%RH. The porous sheet is made of ultra-high molecular weight Plastic composition, in the IR spectrum measured by infrared spectroscopy (FT-IR), no characteristic absorption is observed at 3000~3500cm ^-1 , and the average pore diameter of the porous sheet is less than 20.0μm. For example, the hydrophilic ultra-high molecular weight plastic porous sheet of the first patent application, wherein the ultra-high molecular weight plastic is selected from ultra-high molecular weight polyethylene, ultra-high molecular weight polypropylene, ultra-high molecular weight polyvinyl chloride and ultra-high molecular weight poly More than one species in the group consisting of amides. For example, the hydrophilic ultra-high molecular weight plastic porous sheet according to item 1 of the patent scope, wherein the ultra-high molecular weight plastic is ultra-high molecular weight polyethylene. For example, the hydrophilic ultra-high molecular weight plastic porous sheet according to item 1 of the patent application, wherein the average pore diameter of the porous sheet is 8.0 to 13.0 μm. For example, the hydrophilic ultra-high molecular weight plastic porous sheet according to any one of claims 1 to 3, wherein the average pore diameter of the porous sheet is 5.0 to 15.0 μm, and the porosity is more than 30% and less than 80%. For example, the hydrophilic ultra-high molecular weight plastic porous sheet according to any one of items 1 to 4 of the patent application range, wherein the above-mentioned absorption rate is 20 mm/3 min or more. For example, the hydrophilic ultra-high molecular weight plastic porous sheet according to item 5 of the patent scope, wherein the above absorption rate is 20 mm/3 min or more. A method for manufacturing a hydrophilic ultra-high molecular weight plastic porous sheet according to any one of patent application items 1 to 7, which has an antistatic treatment and/or plasma treatment of the porous sheet Step, the porous sheet is composed of ultra-high molecular weight plastic, and the average pore diameter is less than 20.0 μm. When antistatic treatment is not performed, the plasma treatment is performed in an oxygen environment, before or after plasma treatment In the case of antistatic treatment, plasma treatment is carried out under oxygen or argon atmosphere. For example, the method for manufacturing a hydrophilic ultra-high molecular weight plastic porous sheet according to item 8 of the patent application, wherein the plasma treatment is performed under a gas pressure of 0.5-10 Pa. For example, the method for manufacturing a hydrophilic ultra-high molecular weight plastic porous sheet according to item 8 of the patent application scope, in which antistatic treatment is performed before or after plasma treatment. For example, a method for manufacturing a hydrophilic ultra-high molecular weight plastic porous sheet according to item 9 of the patent application scope, in which antistatic treatment is performed before or after plasma treatment. For example, the manufacturing method of the hydrophilic ultra-high molecular weight plastic porous sheet according to any one of the patent application items 8 to 11, in which, in the case where antistatic treatment is not performed, the treatment density and treatment in the above plasma treatment step the time is the product of 10J / cm ² or more and 300J / cm ² or less. For example, in the method of manufacturing a hydrophilic ultra-high molecular weight plastic porous sheet according to any one of the patent application items 8 to 11, in the case of performing antistatic treatment before and after plasma treatment, The product of the processing density and the processing time is 0.10 J/cm ² or more and less than 10 J/cm ² .