JP2003096229A - Production method of porous (co)polymer film and porous (co)polymer film produced by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing porous (co)polymer film which does not require organic solvents in production processes and is clean and not hazardous to the global environments and also provide a porous (co)polymer film having a homogenous pore size and less impurities. SOLUTION: The production method of the porous (co)polymer film comprises (a) a process in which carbon dioxide is dissolved into the (co)polymer molding at 10 deg.C to 400 deg.C under 5 to 50 MPa in a pressure container in the atmosphere of carbon dioxide, (b) a process in which the porous (co)polymer molding is obtained by reducing the pressure by 2 MPa or larger while reducing the pressure in the above process (a) at a rate of 0.02 to 30 MPa/sec. and (c) a process in which the porous (co)polymer molding obtained in the above process (b) is sliced to give the porous (co)polymer film.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a porous (co) polymer film and a porous (co) polymer film obtained by the method, more specifically, various separation membranes, optical films, The present invention relates to a porous (co) polymer film used for applications such as a dielectric constant film, a heat insulating film, a vibration and soundproof film, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, the following method has been known as a method for producing a porous (co) polymer film. (1) A porous (co) polymer film is obtained by melt-blending incompatible (co) polymers or inorganic fine particles, extrusion-molding, and stretching. (JP-A-64-3472
(6) (2) A (co) polymer is cooled under a high shearing force to form a crystal structure and stretched to obtain a porous (co) polymer film. (Japanese Patent Publication No. 46-40119) (3) Extractable organic solvent (good solvent) is added to the (co) polymer to form a film, and then the good solvent is extracted using another organic solvent (poor solvent). By doing so, a porous (co) polymer film is obtained. (Japanese Patent Publication No. 58-321171, Japanese Patent Laid-Open No. 1-304933, Japanese Patent Laid-Open No. 3-80923, Japanese Patent Laid-Open No. 6-240036, Japanese Patent Laid-Open No. 7-537.
(Publication No. 60)

In the above (1), since it is relatively difficult to uniformly disperse the incompatible (co) polymer and the inorganic fine particles and to extrude the same, the size and uniformity of the pore diameter and the thickness accuracy of the film are high. There was a problem that it was difficult to control. Further, in the above (2), although uniform fine pores can be obtained, there is a problem that the range of thickness and pore diameter is limited.

Further, in the above (3), since the (co) polymer is exposed to a plurality of organic solvents which are solvents, a small amount of these low molecular weight compounds remains in the product. This residual low molecular weight compound affects various physical properties and cannot be used for applications where organic solvents are disliked, so that the range of applications is limited. Moreover, since a large amount of organic solvent is used, the load on the global environment is large. Furthermore, this manufacturing method requires a lot of time for the extraction step, and has a problem in manufacturing cost and the like.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems, and in particular, has a uniform pore size,
To provide a low-cost porous (co) polymer film with few impurities, a clean and simplified production process, and a global environment-friendly production method, and a porous (co) polymer film obtained thereby Is intended.

[0006]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have found that if a (co) polymer molded product is treated with carbon dioxide under specific conditions, it is sliced. The present invention has been completed by finding that a porous (co) polymer film having a uniform pore size, few impurities and low cost can be obtained by processing.

That is, the present invention is specified by the items described below. (1) (a) In a pressure vessel under a carbon dioxide atmosphere,
A step of dissolving carbon dioxide in the (co) polymer molded article at a pressure of 5 to 50 MPa and a temperature of 10 to 400 ° C., (b) from the pressure of the step (a), 0.02 to 3
Reduce the pressure by 2 MPa or more at a pressure reduction rate of 0 MPa / sec,
A step of obtaining a porous (co) polymer molded product, (c) slicing the porous (co) polymer molded product obtained in the above step (b) to obtain a porous (co) polymer film. A method for producing a porous (co) polymer film, which comprises the steps of:

(2) The method for producing a porous (co) polymer film as described in (1) above, wherein the porous (co) polymer molded product has a columnar shape or a cylindrical shape.

(3) The method for producing a porous (co) polymer film as described in (1) or (2) above, wherein the slicing is skiving.

(4) The method for producing a porous (co) polymer film according to any one of (1) to (3), which comprises a stretching step after the step (c).

(5) The method for producing a porous (co) polymer film according to any one of (1) to (4) above, wherein the (co) polymer is an ultrahigh molecular weight polyolefin.

(6) The organic solvent content is 80, which is produced by the production method described in any one of (1) to (5) above.
A porous (co) polymer film having a content of ppm or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure condition in step (a) of the present invention is 5 to 50 MPa, preferably 10 to 40 MP.
a, more preferably 15 to 30 MPa, and
The temperature condition is 10 to 400 ° C., preferably 30 to 350
C., more preferably 50 to 300.degree.

Pressure and temperature conditions within the above ranges, that is, carbon dioxide is brought into a high-pressure gas phase, a high-pressure liquid phase or a supercritical fluid phase to dissolve or diffuse in the (co) polymer at a relatively high rate. Therefore, carbon dioxide can be easily contained in the (co) polymer.

The pressure reduction rate in step (b) of the present invention is
0.02 to 30 MPa / sec, preferably 0.05 to
25 MPa / sec, more preferably 0.1 to 20 M
Pa / sec speed and decompression width is 2MP
a or more, preferably 3 MPa or more, more preferably 5
It is above MPa.

By setting the pressure reduction rate and width within the above range, the carbon dioxide contained in the (co) polymer becomes supersaturated, that is, thermodynamically unstable, and a large amount of carbon dioxide is contained in the (co) polymer. Nuclei (foaming nuclei in which bubbles are generated) can be generated.

The capacity of the pressure vessel used in the present invention is not particularly limited, but is usually 0.5 to 5000 L, preferably 1 to 1000 L.

If the volume of the pressure vessel is within the above range, a porous (co) polymer molded product having a size that can be commercially produced can be produced, and the pressure can be controlled within the above-mentioned reduced pressure rate range.

The shape of the (co) polymer molded product and the shape of the porous (co) polymer molded product used in the present invention are not particularly limited, but are preferably columnar or cylindrical.

The slicing method in step (c) of the present invention is not particularly limited as long as it is a known method, but if the shape of the porous (co) polymer molded product is a column or a cylinder, skiving ( It is preferable that it is a wig peeling process. Skiving is just like the radish shaving and peeling, while rotating around the central axis of a cylindrical or cylindrical (co) polymer molded product, sliced into a film with a cutting blade such as a cutter, Co) is a processing method for forming a polymer film.

By performing a skiving process using a columnar or cylindrical porous (co) polymer molded product, a porous (co) polymer film can be continuously produced, and the production cost is also increased. It will be cheaper.

The porous (co) polymer film of the present invention comprises
If necessary, after the step (c), a stretching process can be performed. The stretching method is not particularly limited as long as it is a known method such as a uniaxial stretching method or a biaxial stretching method. In the case of skiving, an in-line stretching step may be performed so that skiving and stretching may be performed continuously or separately. The stretching ratio is not particularly limited, but usually 1.5 to
It is 30 times, preferably 3 to 10 times.

Stretching can be expected to improve the strength of the film, reduce the thickness of the film, and improve the accuracy of thickness.
It is also used for the purpose of increasing the pore size depending on the application. Furthermore, when the porous (co) polymer film is a closed-pore body (closed-cell body), by performing a stretching process,
The holes can be connected to each other to form a continuous hole body (through hole body).

The porous (co) polymer film of the present invention comprises
If necessary, the film shape can be adjusted by compression with a press or the like.

The (co) polymer used in the present invention can be used without particular limitation. For example, low density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, Ethylene-ethyl acrylate copolymer, ionomer resin (for example, ethylene-methacrylic acid copolymer ionomer resin, etc.), polypropylene, polybutene, 4-methylpentene-1 resin, cyclic polyolefin resin, ethylene-
Styrene copolymer, ultra high molecular weight polyolefin (for example, ultra high molecular weight polyethylene, ultra high molecular weight polypropylene, etc.), styrene resin (polystyrene, butadiene-
Styrene copolymer (HIPS), acrylonitrile-
Styrene copolymer (AS resin), acrylonitrile-
Butadiene-styrene copolymer (ABS resin), etc.,
Polyacrylonitrile, acrylonitrile-methyl acrylate copolymer, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyacetal, polyphenylene oxide, polyvinyl acetate, polyvinyl alcohol,
Polymethyl methacrylate, cellulose acetate, polyester (for example, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc.), polyamide resin, polyimide resin, fluororesin,
Polysulfone, polyether sulfone, polyarylate, polyether ether ketone, liquid crystal polymer, thermoplastic elastomer, biodegradable polymer (for example, hydroxycarboxylic acid condensate such as polylactic acid, polyglycolic acid, etc., polybutylene succinate Such as diol and carboxylic acid condensate), polyurethane (including thermoplastic polyurethane), epoxy resin, fluororesin (eg, polytetrafluoroethylene, etc.), phenol resin, urea resin, melamine resin, diallyl phthalate resin, etc. A (co) polymer composed of one or more kinds of (co) polymers may be mentioned.

Among these, ultrahigh molecular weight polyolefin, fluororesin, polyurethane, polyimide, phenol resin, urea resin and melamine resin are preferable, and ultrahigh molecular weight polyolefin is more preferable. As the ultra-high molecular weight polyolefin, ultra-high molecular weight polyethylene is preferable, and the weight average molecular weight (Mw) is 300,000 to
10 million ultra high molecular weight polyethylenes are preferred.

Further, in the present invention, a pigment, a dye, a lubricant, an antioxidant, a filler, a stabilizer, a flame retardant, an electrifying agent, if necessary, in the (co) polymer within a range not impairing the purpose. Inhibitors, UV inhibitors, cross-linking agents, antibacterial agents, crystal nucleating agents, shrinkage-preventing agents, foam nucleating agents, foaming assistants and the like can be added.

As a method for producing the (co) polymer raw material of the present invention, a known method can be adopted and is not particularly limited. For example, a (co) polymer and optionally another (co) polymer,
Alternatively, after uniformly mixing the additives with a high-speed stirrer, etc., a uniaxial or multiaxial extruder having sufficient kneading ability, a mixing roll,
It can be manufactured by a method such as melt-kneading with a kneader or Brabender. Further, the (co) polymer and another (co) polymer, or the additive may be used in a state of being uniformly mixed.

As the method for producing the (co) polymer molded article of the present invention, a known method can be adopted and is not particularly limited. It is possible to employ compression molding such as press molding, transfer molding, extrusion molding, ram extrusion molding, paste extrusion molding, injection molding, calendar molding and the like. Of these, compression molding, transfer molding, extrusion molding, and ram extrusion molding are preferable, and compression molding is particularly preferable.

Porous (co) obtained by the production method of the present invention
The porosity of the polymer film is not particularly limited, but is preferably 1 to 80%, more preferably 3 to 70%.

Porous (co) obtained by the production method of the present invention
The form of the pores of the polymer film is not particularly limited, and may be closed pores (closed cells) or continuous holes (through holes) (open cells). In the case of independent pores, the average pore size is 0.00
1 μm to 500 μm is preferable, and further 0.01 to 1
00 μm is preferable. In the case of continuous holes, those having a network structure are preferable. The width of the holes in the mesh structure is 0.
001 to 500 μm is preferable, and further 0.0
It is preferably 1 to 100 μm.

Porous (co) obtained by the production method of the present invention
The thickness of the polymer film is not particularly limited, but is usually 1
μm to 1000 μm, and further 10 μm to 500
μm is preferred.

Porous (co) obtained by the production method of the present invention
A characteristic of polymer films is a low organic solvent content. The organic solvent content is 80 ppm or less, 50
It is preferably less than or equal to ppm, and further 20 ppm
It is preferably the following or less, and particularly preferably 10 ppm or less.

The organic solvent is not particularly limited as long as it is miscible with the polymer or can be a solvent for the polymer, and examples thereof include dicyclohexyl phthalate, triphenylene phosphate, liquid paraffin and paraffin. Wax, xylene, toluene, decalin, decane, dodecane, docosan, tricosane, tetracosane, triacontane, benzene, dichlorobenzene, trichlorobenzene, trichloromethane, trichloroethane, acetone, methyl ethyl ketone, ethyl acetate, methanol, propanol, stearyl alcohol, isopropyl Alcohol, toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, chloroform, methylene chloride, carbon tetrachloride, ethane trifluoride, phthalic acid Ester, sebacic acid esters, trimellitic acid esters, and phosphoric acid esters.

An example of an embodiment of the method for producing a porous (co) polymer film according to the present invention will be described with reference to FIG. 1. Components constituting a (co) polymer molded product are mixed to prepare a raw material composition, A cylindrical (co) polymer molded product (1) is prepared from this by compression molding (not shown).

The above (co) polymer molded product (1) is placed in a pressure vessel (2) and sealed, and the pressure vessel (2) is heated to a predetermined temperature. Then, the air in the pressure vessel (2) is evacuated by the vacuum pump (7), and the liquefied carbon dioxide cylinder (4) is discharged.
Further, carbon dioxide is introduced by using the metering pump (3) connected to the line cooled by the refrigerant circulation device (5) to raise the pressure to a predetermined pressure. The pressure in the pressure vessel (2) is controlled by the pressure holding valve (6). By appropriately introducing carbon dioxide into the pressure vessel (2), the pressure is maintained for a predetermined time, and carbon dioxide is contained in the (co) polymer molded product (1). When the carbon dioxide content of the (co) polymer molded product (1) reaches a predetermined amount, the carbon dioxide in the pressure vessel (2) is decompressed to a predetermined pressure at a predetermined decompression rate. At this time, the pressure may be reduced to atmospheric pressure at once, or may be reduced to several times (twice or more). In this way, the porous (co) polymer molded product (10) can be obtained.

Regarding each condition, that is, temperature, pressure, time, decompression rate, decompression method, etc., appropriate conditions are selected within the above range depending on the intended porous (co) polymer molded product (10). do it.

When the (co) polymer molded product contains a low molecular weight component such as a monomer, the low molecular weight component contained in the (co) polymer is exposed to carbon dioxide within the above pressure range to reduce the pressure. The effect of extraction and removal can also be expected.

Further, the purged carbon dioxide can be reused (recycled).

Next, the obtained porous (co) polymer molded product (10) is set in a skiving machine. This time,
If necessary, cut into a cylindrical shape of a predetermined size.

Cylindrical porous (co) polymer molding (1
0) is rotated about the drive shaft (11) of the skiving machine, and is continuously sliced in the circumferential direction by the cutting blade (12) to obtain a film having a predetermined thickness, which is then rolled by the winder. Roll it up. In this way, the porous (co) polymer film (13) can be obtained.

After this, the porous (co) polymer film (1
Depending on the purpose of 3), it is possible to perform processing such as stretching.

The porous (co) polymer film obtained by the above-mentioned production method is a separator film for various separation membranes used for filtration and separation for medical and industrial purposes, batteries, and electrolytic capacitors. It is preferably used for applications such as optical films for light reflection and ultraviolet reflection, low dielectric constant films, heat insulation films, vibration and soundproof films.

[0044]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples. The physical property evaluations described in Examples and Comparative Examples are
It carried out according to the following method. 1) The density (D1) of a porous (co) polymer film having a porosity of 30 mm × 30 mm and the density (D2) of a raw material (co) polymer were measured using an electronic densitometer. The porosity was calculated by the following formula. (D2-D1) / D2 x 100

2) Average Pore Size The cross-sectional photograph of the porous (co) polymer film photographed with a scanning electron microscope was image-processed to calculate the equivalent circle diameter, and the value was taken as the average pore diameter. 3) A porous (co) polymer film having an organic solvent content rate of 2 mm × 2 mm was used in a Soxhlet extractor using carbon tetrachloride at a water bath temperature of 9
Extraction was performed at 5 ° C for 10 hours, and the obtained extract was concentrated to 50 ml of solution by an evaporator. This solution was detected and identified by gas chromatography, FT-IR, and mass spectrometry.

Example 1 Ultra high molecular weight polyethylene (HIZEX Million 340M (trade name) manufactured by Mitsui Chemicals, Inc.) was used as a (co) polymer by a compression molding method.
A plate-shaped molded product having a thickness of 50 mm was molded, and the plate-shaped molded product was cut to have a diameter of 13 as a (co) polymer molded product.
A 0 mm cylindrical ultra high molecular weight polyethylene molded product was produced.

The above cylindrical ultra-high molecular weight polyethylene molded product had a volume of 1000 cc (a diameter of 140 mm and a height of 65 m).
m) was placed in a pressure vessel (manufactured by AKICO) and sealed, and the pressure vessel was heated to a temperature of 170 ° C. by a band heater. Next, the air in the pressure vessel is evacuated by a vacuum pump, and carbon dioxide is introduced and pressurized by using a siphon-type liquefied carbon dioxide cylinder and a metering pump connected to a line cooled by a refrigerant circulation device to increase the pressure in the pressure vessel to 20 MPa. And After that, the temperature and the pressure conditions (170 ° C., 20 MPa) were maintained for 6 hours, and carbon dioxide was contained in the cylindrical ultra high molecular weight polyethylene molded product.

After 6 hours, heating of the band heater was stopped, the purge valve was opened, and carbon dioxide in the pressure vessel was adjusted to 8M.
Purging was performed at a pressure reduction rate of Pa / sec, and when the pressure was reduced to 12 MPa, the purge valve was closed.

Next, water is flowed through the cooling jacket covering the pressure vessel to increase the temperature in the pressure vessel from 170 ° C to 40 ° C.
Cooled to ° C. The time during this period was about 2 hours. Then, the carbon dioxide in the pressure vessel was purged at a decompression rate of 0.4 MPa / sec, and the pressure was completely reduced to atmospheric pressure to obtain a porous ultrahigh molecular weight polyethylene molded product as a porous (co) polymer molded product. Prepared.

Next, the obtained porous ultra high molecular weight polyethylene molded product was set so that it could be set on a skiving machine.
Shape it into a cylindrical shape by cutting, set it on the drive shaft of the skiving machine, and apply a cutting blade to the surface of the cylindrical porous ultra-high molecular weight polyethylene molding in the axial direction so that it is parallel to the axial direction. It was Then, the cylindrical ultra-high molecular weight polyethylene molded product was rotated around a drive shaft, and continuously sliced into a film having a thickness of 300 μm, which was wound into a roll by a winder. Thus, a porous ultra high molecular weight polyethylene film was obtained. The obtained porous ultra-high molecular weight polyethylene film had a porosity of 10%, independent pores with an average pore diameter of 0.1 μm, and an organic solvent content of 0 p.
It was pm.

(Example 2) As a (co) polymer, ultrahigh molecular weight polyethylene (HIZEX Million 340M (trade name) manufactured by Mitsui Chemicals, Inc.) was used, and compression molding was performed.
A plate-shaped molded product having a thickness of 30 mm was molded, and the plate-shaped molded product was cut to obtain a (co) polymer molded product having a diameter of 10
A 0 mm cylindrical ultra high molecular weight polyethylene molded product was produced.

The above cylindrical ultra-high molecular weight polyethylene molded product had a volume of 1000 cc (diameter 140 mm, height 65 m).
m) was placed in a pressure vessel (manufactured by AKICO) and sealed, and the pressure vessel was heated to a temperature of 150 ° C. by a band heater. Next, the air in the pressure vessel is evacuated by a vacuum pump, and carbon dioxide is introduced and pressurized by using a siphon-type liquefied carbon dioxide cylinder and a metering pump connected to a line cooled by a refrigerant circulation device to increase the pressure in the pressure vessel to 20 MPa. And Thereafter, the temperature and the pressure conditions (150 ° C., 20 MPa) were maintained for 6 hours, and carbon dioxide was contained in the cylindrical ultrahigh molecular weight polyethylene molded product.

After 6 hours, heating of the band heater was stopped, the purge valve was opened, and carbon dioxide in the pressure vessel was reduced to 0.
Purging was performed at a reduced pressure rate of 7 MPa / sec, and the pressure was reduced to atmospheric pressure to prepare a porous ultrahigh molecular weight polyethylene molded product as a porous (co) polymer molded product.

Next, the obtained porous ultra-high molecular weight polyethylene molded product was set so that it could be set on a skiving machine.
Shape it into a cylindrical shape by cutting, set it on the drive shaft of the skiving machine, and apply a cutting blade to the surface of the cylindrical porous ultra-high molecular weight polyethylene molding in the axial direction so that it is parallel to the axial direction. It was Then, the cylindrical ultra-high molecular weight polyethylene molded product was rotated around a drive shaft and continuously sliced to form a film having a thickness of 300 μm, which was wound into a roll by a winder. Thus, a porous ultra high molecular weight polyethylene film was obtained. The obtained porous ultra high molecular weight polyethylene film has a porosity of 75%,
The average pore size is 100μm, and the organic solvent content is 0.
It was ppm.

(Comparative Example 1) Ultrahigh molecular weight polyethylene (HIZEX Million 340M (trade name) manufactured by Mitsui Chemicals, Inc.) was used as a (co) polymer by a compression molding method.
A plate-shaped molded product having a thickness of 50 mm was molded, and the plate-shaped molded product was cut to have a diameter of 13 as a (co) polymer molded product.
A 0 mm cylindrical ultra high molecular weight polyethylene molded product was produced.

The above cylindrical ultra-high molecular weight polyethylene molded product had a volume of 1000 cc (diameter 140 mm, height 65 m).
m) was placed in a pressure vessel (manufactured by AKICO) and sealed, and the pressure vessel was heated to a temperature of 150 ° C. by a band heater. Next, the air in the pressure vessel is evacuated by a vacuum pump, and carbon dioxide is introduced and pressurized by using a siphon-type liquefied carbon dioxide cylinder and a metering pump connected to a line cooled by a refrigerant circulation device to increase the pressure in the pressure vessel to 3 MPa. And Thereafter, the temperature and the pressure conditions (150 ° C., 3 MPa) were maintained for 6 hours, and carbon dioxide was contained in the cylindrical ultrahigh molecular weight polyethylene molded product.

After 6 hours, heating of the band heater was stopped, the purge valve was opened, and carbon dioxide in the pressure vessel was reduced to 0.
Purging was performed at a reduced pressure rate of 7 MPa / sec, and the pressure was reduced to atmospheric pressure to prepare an ultrahigh molecular weight polyethylene molded product.

Next, the obtained ultra-high molecular weight polyethylene molded product was shaped into a cylindrical shape by cutting so that it could be set in a skiving machine, and was set on the drive shaft of the skiving machine to form a cylindrical shape. A cutting blade was placed on the surface of the outer peripheral portion in the axial direction of the ultrahigh molecular weight polyethylene molded product so as to be parallel to the axial direction. Then, the cylindrical ultra-high molecular weight polyethylene molded product was rotated around a drive shaft and continuously sliced into a film having a thickness of 300 μm, which was wound into a roll by a winder. Thus, an ultra high molecular weight polyethylene film was obtained. The obtained ultra-high molecular weight polyethylene film was a non-porous film having a porosity of 0%, and the organic solvent content was 0 ppm.

(Comparative Example 2) The same procedure as in Example 1 was carried out except that the temperature inside the pressure vessel was set to 5 ° C by flowing the refrigerant through the cooling jacket. The obtained ultra-high molecular weight polyethylene film was a non-porous film having a porosity of 0%, and the organic solvent content was 0 ppm.

(Comparative Example 3) The pressure reduction rate of carbon dioxide was set to 0.
It carried out like Example 1 except having set it as 01 MPa / sec. The obtained ultra high molecular weight polyethylene film is a non-porous film having a porosity of 0% and an organic solvent content of 0 pp.
It was m.

(Comparative Example 4) 2 parts by weight of ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of 2.5 × 10 ⁶
A polyethylene resin composition was prepared by mixing 85 parts by weight of liquid paraffin (64 cst / 40 ° C.) and a raw material resin having Mw / Mn = 11 mixed with 13 parts by weight of polyethylene having a weight average molecular weight (Mw) of 3.7 × 10 ⁵ . Was prepared. Next, 100 parts by weight of a solution of this polyethylene composition was added with 2,6
-Oxidize 0.125 parts by weight of di-t-butyl-p-cresol and 0.25 part by weight of tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxylphenyl) -propionate] methane. Add as inhibitor and mix. This mixed solution was charged into an autoclave equipped with a stirrer and stirred at 200 ° C. for 90 minutes to obtain a uniform solution.

This solution was extruded from a T-die by an extruder having a screw having a diameter of 45 mm, and a gel-like sheet was formed while taking it out with a cooling roll. Subsequently, this gel-like sheet was subjected to 5 × 5 at a temperature of 115 ° C. and a stretching speed of 0.5 m / min.
Double simultaneous biaxial stretching was performed. The stretched film thus obtained was washed with methylene chloride, dried, and further stretched 1.5 times in the transverse direction at 90 ° C. and a stretching speed of 0.5 m / min to obtain a porous ultra high molecular weight polyethylene film. It was

The obtained porous ultra high molecular weight polyethylene film had continuous pores with a porosity of 55% and an average pore diameter of 0.1 μm, and the organic solvent content was 10% for liquid paraffin.
It was 0 ppm.

[0064]

[Table 1]

[0065]

EFFECTS OF THE INVENTION By using the method for producing a porous (co) polymer film of the present invention, a porous (co) polymer film having a uniform pore size, a small amount of impurities in the product and a low cost is provided. In addition, it is possible to provide a global environment-friendly manufacturing method in which the production process is clean and simplified.

[Brief description of drawings]

FIG. 1 is a plan view of the porous (co) polymer film of the present invention, wherein carbon dioxide is dissolved and decompressed to produce a porous (co) polymer film.
It is a schematic block diagram which shows an example of the manufacturing apparatus used for process (a) and (b) which obtains a polymer molded product.

FIG. 2 is a schematic configuration diagram showing an example of a production apparatus used in a step (c) of slicing a porous (co) polymer molded product in the production of the porous (co) polymer film of the present invention. .

[Explanation of symbols]

(1) (Co) polymer molded product (2) Pressure vessel (3) Metering pump (4) Liquefied carbon dioxide cylinder (5) Refrigerant circulator (for metering pump) (6) Pressure control valve (7) Vacuum pump (8) Cooling jacket (9) Refrigerant circulator (for pressure vessel) (10) Porous (co) polymer molded product (11) Drive shaft (12) Cutting blade (13) Porous (co) polymer film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 C08L 101: 00 C08L 101: 00 B29C 67/22 F term (reference) 4F074 AA16 AA17 AA97 BA32 CA21 CA24 CA25 CB91 CC04X CC04Y CC04Z CC10X CC32X CC32Y CC34X CC34Y CD20 4F212 AA06 AG01 AG14 AG20 UA09 UB01 UE26 UN11 UW21 UW23 4F213 AA06 AA16 AD05 WA18 WA33 WA53 WA65 WB01 WK01

Claims (6)

[Claims] (A) A (co) polymer molded article in a pressure vessel under a carbon dioxide atmosphere, having a pressure of 5 to 50 MPa,
And a step of dissolving carbon dioxide at a temperature of 10 ° C. to 400 ° C., (b) from the pressure of the step (a), 0.02 to
Depressurizing at 2 MPa or more at a depressurizing rate of 30 MPa / sec to obtain a porous (co) polymer molded product, (c) the porous (co) polymer molded product obtained in the above step (b),
A process for producing a porous (co) polymer film, comprising a step of slicing to obtain a porous (co) polymer film. 2. The method for producing a porous (co) polymer film according to claim 1, wherein the porous (co) polymer molded product has a columnar shape or a cylindrical shape. 3. The method for producing a porous (co) polymer film according to claim 1, wherein the slicing process is a skiving process. 4. The method for producing a porous (co) polymer film according to claim 1, further comprising a stretching step after the step (c). 5. The method for producing a porous (co) polymer film according to claim 1, wherein the (co) polymer is an ultrahigh molecular weight polyolefin. 6. A porous (co) polymer film produced by the production method according to claim 1 and having an organic solvent content of 80 ppm or less.