JPH0220531A - Preparation of hydrophilic porous film - Google Patents

Abstract

PURPOSE:To obtain a hydrophilic porous film having excellent air permeability, moisture permeability, bending strength etc., by mixing a linear low-densithy polyethylene resin, a filler and an olefin termpolymer, forming the mixture into a film, drawing the film and performing a high-frequency sputter etching treatment on the surface of the obtd. porous film. CONSTITUTION:A resin compsn. comprising a linear low-density polyethylene resin (e.g. ethylene/bytene-1 copolymer), a filler (e.g. calcium carbonate or alumina) and an olefin terpolymer (e.g. ethylene/propylene/dicyclopentadiene terpolymer) as the essential components is formed into a film, which is drawn to form a porous film. The surface of the porous film is treated by high-frequency sputter etching to obtain a hydrophilic porous film, which is suitably used for separative membranes, moisture-controlling sheets etc.

Description

Detailed Description of the Invention (a) Industrial Field of Application The present invention is directed to a hydrophilized porous film that has excellent gas and liquid permeability, stable quality, and is suitable for use in substance separation membranes, humidity control sheets, etc. This relates to a manufacturing method.

(b) Prior Art Conventionally, porous films used for air-permeable bags, pressure filtration membranes, filtration supports, etc. have been manufactured using the following method.

That is, (1) a polyolefin resin is mixed with a Kuroiso filler that can be eluted with acid, alkali, or water and a nonionic surfactant with an HL B of 9 to 15, formed into a film, stretched, and then filled with the Kuroiso filler described above. A porous film is produced by eluting the agent with the above-mentioned acid or the like (Japanese Unexamined Patent Publication No. 5O-74G67 TL).

■ In the above ■, a porous film is produced in the same manner as in the above ■, using an ethylene-vinyl acetate copolymer instead of using a nonionic surfactant with an HLB of 9 to 15. Publication No. 54-43982).

■ A porous film is made by stretching a film obtained by melt-molding a composition made of a high-density polyolefin resin, a filler, and a liquid rubber (Japanese Patent Application Laid-Open No. 1983-1999-
No. 47334).

(c) Problems to be solved by the invention However, in the above-mentioned methods (1) and (2), a surfactant is kneaded into a resin composition and this is molded into a film. There are problems such as separation of the surfactant, and when performing substance separation using porous films obtained by these methods, the surfactant may be extracted and the properties may vary. Furthermore, these methods have problems such as bleeding of the surfactant during storage and handling.

In addition, the porous film obtained by the method (2) above is hydrophobic and therefore difficult to permeate with water, and there is a problem that, for example, when separating solids in an aqueous solution, the desired separation effect cannot be obtained.

In the present invention, the surface of a porous film formed from a specific resin composition is subjected to high-frequency sputter etching to introduce parent wood groups such as carboxyl groups and hydroxyl groups onto the surface to make it hydrophilic, thereby making it hydrophilic. An object of the present invention is to provide a method for producing a hydrophilized porous film that can efficiently separate solids and the like.

(d) Means for Solving the Problems The present inventors have made extensive studies to solve the above problems, and as a result, have obtained the following knowledge.

That is, as described above (in the case of obtaining a porous film,
8! It has a high mechanical strength, has little stretching unevenness after stretching, has relatively uniform molecular orientation during stretching, and has a tear strength of 8! It has good mechanical strength (J) After repeated consideration of the fat component, it was found that the fringe low-density polyethylene resin has high crystallinity and high mechanical strength. It has been found that by uniaxially or biaxially stretching the formed film, a porous film with extremely less stretching unevenness can be obtained compared to using other thermoplastic resins.

Also, according to the experimental results of the present inventors, the filler and the tree 11F
In order to improve the compatibility with the 7 composition, the primary softening agent added to the IJ4 IN component is an extremely important factor, and it is clear that the selection of the softening agent is extremely important.

Therefore, the present inventors conducted further studies using various softeners, and found that a resin composition in which a linear low-density polyethylene resin was mixed with an olefin terpolymer had the best compatibility with fillers. Moreover, when the film formed using this resin composition is stretched or biaxially stretched, a porous film with very little stretching unevenness can be obtained compared to using a thermoplastic (M resin composition). Therefore, the cracks in the film at the through-holes that occur during stretching are uniform and there are no large cracks, and there is extremely little non-uniform orientation of molecules at the through-holes in the film (I (! Mechanical strength is large). It was also found that it has a high tearing force when changing bending strength and tensile strength, and that it is highly reliable and does not burst when used in a single layer even when used as a breathable bag or pressurized filtration membrane.

Therefore, when using the above-mentioned porous film and subjecting the surface to colon discharge treatment or flame treatment, there are problems such as large pores created by sparks, which may cause problems in substance separation accuracy, and thermal shrinkage. However, when the surface of this porous film is subjected to high-frequency sputter etching, parent groups such as carboxyl groups and hydroxyl groups are introduced into the porous film, making it hydrophilic, which makes it possible to efficiently separate solids in an aqueous solution. This knowledge led to the completion of the present invention.

That is, in the method for producing a hydrophilized porous film of the present invention, a resin film is produced from a resin composition containing a linear low-density polyethylene resin, a light atomizer, and an olefin terpolymer as essential components, and then 1 liter of this ( The method is characterized in that a porous film is formed by stretching a resin +91 film, and the surface of the porous film is subjected to a high-frequency spuntaenoting treatment.

The present invention will be explained in detail below.

In the present invention, first, linear low density polyethylene? 3
Step A is carried out to form a resin composition containing a 4-fat filler and an olefin terpolymer as essential components.

In this step A, linear low density polyethylene tj (fat (A), filler (I3) and olefin terpolymer
When forming a resin composition containing (C) as an essential component, the blending ratio of (A) and (B) is (A) 100mf
B) is 100 to 300 parts by weight, preferably 150 to 25 parts by weight, based on the fi part! ffi parts is desirable. If (B) is too small (less than 100g/1 part), the strength of the obtained film may decrease, and the air permeability and moisture permeability may decrease. ) exceeds 300 parts by weight, the kneading properties and moldability will be poor (and the film strength will also be reduced).

In addition, in the above resin composition, the addition of the olefin terpolymer (C) is intended to further improve crosstalk and dispersibility of the filler, to further improve moldability and processability, and to improve the above (A). Improve the familiarity of (B) and get 8! This is to obtain a porous film with extremely excellent mechanical strength.

In this case, the mixing ratio of (A) and (C) above is (A)
It is desirable that (C) be in the range of 5 to 95 parts by weight, preferably 30 to 70 parts by weight, per 100 parts by weight. The 1I film has higher mechanical strength and even better gas and liquid permeability.

In the present invention, linear low density polyethylene a(l
By using a resin composition containing ff1, a filler, and an olefin terpolymer as essential components, a porous film with extremely low stretching unevenness can be obtained, and the porous film thus obtained has high hardness, bending strength, and tensile strength. It has a high tensile strength when subjected to strong changes, so even if this thin porous film is used, for example, as a breathable bag or a pressurized filtration membrane, it will not burst during use and will be highly reliable. The production and processability of the porous film is excellent and the production cost is low.Moreover, the strength of the obtained porous film is high, and the single layer can be used as a source for breathable bags or pressurization. It can be used as a jJ film.

In addition, mixing linear low-density polyethylene resin, filler, olefin terpolymer, etc. does not require any special equipment or technology; a publicly known mixer is used; In order to improve the film formation of the resin composition, it is desirable to use a mixer such as a mixing roll, a Banbury mixer-two-screw hot kneading machine, or a Henschel mixer.

The linear low-density polyethylene resin used in the present invention is a copolymer of ethylene and a-olefin, and examples of the a-olefin include butene, hexene, octene, and the like.

In addition, the above fillers include calcium carbonate, talc, clay kaolin, silica, barium sulfate, kaolin sulfate,
Examples include aluminum hydroxide, zinc oxide, calcium oxide, titanium oxide, alumina, and mica.

The average particle size of the filler used is 30 μm or less, preferably in the range of 0.1 to 10 μm.

If the particle size is too large, the pores 1j will become large, whereas if the particle size is too small, agglomeration will occur and dispersibility will be poor, which is not preferable.

As the olefin terpolymer, if it is a rubber-like material with a number average molecular weight of 30,000 to aoo, ooo,
There are no particular limitations, and specific representative examples include ethylene, a-olefin, and a cyclic or acyclic copolymer having a nonconjugated double bond (hereinafter referred to as EPDM).
) is used.

The above EPDM is a terpolymer consisting of ethylene, propylene or 7'ten-1 and the polyene monomers listed below, and the polyene monomers include dicyclopentanoene, 1,5-cyclooctanoene, 1.
1-cyclooctadiene, 1.6-cyclooctadiene, 1.7-cyclooctanoene, 1.5.9-cyclododecatriene, 1.4-cycloheptadiene, 1,4-
These include cyclohexanoene, 1,6-hebutadiene, norbornatsuene, methylenenorbornene, 2-methylpentanoene-1,4,1,5-hexanoene, methyl-tetrahydroindene, and 1,4-hexadiene. The copolymerization ratio of each monomer is preferably 30 to 80 mol% of ethylene, 01 to 20 mol% of polyene, and the remainder is a terpolymer that forms α-shaped fins with Mooney viscosity ML and (100°C ) 1 to 60 is good.

In the present invention, other softeners (
D) may be added to 100 parts by weight of the olefin terpolymer (C) in an amount of up to 25 parts by weight, and the (D)
If the amount added exceeds 25 parts by weight, the strength of the porous film deteriorates, which is not preferable.

The softener has a number average molecular weight of 1000 to 300.
There is no particular limitation as long as the softener is 0.00, and typical examples include petroleum process oil, liquid paraffin, aliphatic oil, and low molecular weight plasticizers as low viscosity softeners. As a high viscosity softener, polybutene,
Softeners such as low molecular weight polyisobutylene and liquid rubber are preferably used.

Furthermore, the above resin composition may contain commonly used antioxidants, ultraviolet stabilizers, antistatic agents, pigments, lubricants, fluorescent agents, and the like.

In the present invention, next, Step B is carried out, in which a fat film is produced using the fat composition obtained in Step A above.

For manufacturing this If 1ift 91 film, a normal film manufacturing apparatus and manufacturing method may be used, and an inflation molding machine, a T-shaped molding machine, etc. are suitably used.

In the present invention, next, the product obtained in the above step B (side 1
Step C is carried out in which a porous film is formed by stretching the resin film monoaxially or biaxially.

In this step C, the resin film is stretched mono- or bi-axially to make it porous. The X film is formed, and this stretching may be carried out in a conventional manner using a conventional stretching device, such as roll stretching, simultaneous biaxial stretching, sequential biaxial stretching, etc.

In this stretching process, in the case of -axial stretching, the stretching rate is 100 to 400%, and in the case of biaxial stretching, the stretching rate is 10.-3 (] 0%). This is preferable from the viewpoint of the strength of the through holes, the permeability of gases and liquids, etc. In particular, in the case of -axial stretching, if the stretching ratio is less than 1()0%, the stretched part and the unstretched part will be separated. Stretched parts are mixed and the stretching is uneven, and on the other hand, 400%
Exceeding this is not preferable because it may result in intermediate breakage during stretching.

In addition, in the present invention, the stretching ratio is calculated using the following formula.

In this case, when producing the porous film, do you melt the resin composition? A porous film is formed directly by stretching the film obtained by MA molding, or a porous film is obtained by stretching, and then the filler is eluted with acid, alkali, or water to form a porous film. It is also good.

In the present invention, the surface of the porous film obtained in step C is finally subjected to a high frequency sputter etching process.

Through this process, parent groups such as carboxyl groups and hydroxyl groups are introduced into the porous film obtained in the above step C, making the film hydrophilic. It is uruno.

Although the sputter etching treatment in this step can be performed by a known method, the processing conditions for this sputter etching will be specifically explained as follows.

Sputter etching treatment is usually 0.005 = at room temperature.
Atmospheric pressure of 0.5 Torr, preferably from 0.05
This is carried out in an atmosphere of 0.2 Torr. If the atmospheric pressure is less than 0,005 Torr, discharge will not continue, and if it exceeds 0.5 To+/r, the sputter etching rate will drop smoothly and the discharge will become unstable, especially if it is continuous. This is not preferable because it is not possible to obtain a homogeneous treated surface when sputter etching is performed on the substrate.

Further, the discharge processing amount, that is, the product of the discharge power (w/c 2) and the processing time (seconds) is 0.001-1 w seconds/Cm2,
Preferably, the range is 0.01-0.8 wsec/C1n2. In this case, it is obvious that the lower the processing power density, the more the processing time needs to be reduced, but it is practically desirable to increase the processing power density and shorten the processing time.

As a power source, a high frequency power source of several hundred KIIZ to several tens of M I-1z can be used, but in practice it is 13.56 M
It is convenient to use the 112 industrially allocated frequencies. The required distance between the electrodes is 1 / when the atmospheric pressure is p.
I is proportional to p, for example, p is 0,005 T.

When rr, the distance between the electrodes needs to be 3011 or more, and is usually adjusted to about 40 mm. Further, a gap is provided between the cathode electrode and the shield electrode to prevent discharge from occurring between the two electrodes, and for example, when the atmospheric pressure is 0.005 Torr, the gap is usually about 4 mm.

Practically speaking, inert gases such as argon and nitrogen, air, carbon dioxide, and water vapor are used as atmospheric gases during sputter etching.

(e) Effect The method for producing a hydrophilized porous film of the present invention comprises forming a resin composition having the above-mentioned structure and containing a fringe-shaped low density polyethylene resin, a filler, and an olefin terpolymer as essential components, and It is not clear why the use of the composition I (II) gives a porous film with high tearing strength and excellent bending strength and tensile strength, but this linear low-density polyethylene resin has a high degree of crystallinity. In addition to having high mechanical strength, when a film formed using this resin composition is mono- or biaxially stretched, a porous film with extremely less stretching unevenness can be obtained compared to using other thermoplastic resin compositions. Moreover, during this stretching, the olefin terpolymer improves the compatibility between the linear low-density polyethylene 0 (oil) and the optical material, and therefore the a! The non-uniform orientation of molecules at the through-holes in the film is extremely small compared to when other thermoplastic resins are used, and therefore the tearing force increases when bending strength and tensile strength change, resulting in rupture upon first use. For this reason, the porous 'I!' film has extremely excellent air permeability and moisture permeability, and has the ability to be used as a single-layer air-permeable bag or pressurized filtration membrane.

In addition, in the method of the present invention, the surface of a porous film formed from a hydrophobic glue (fat composition) is subjected to high-frequency sputter etching to introduce parent wood groups such as carboxyl groups and hydroxyl groups into the surface to make it hydrophilic. It is possible to efficiently separate solids in an aqueous solution, and since no surfactant is used, it has the effect of increasing reliability.

(') EXAMPLES The present invention will be explained in detail based on Examples below, but the present invention is not limited thereto.

Example 1 100 parts by weight of linear low-density polyethylene resin (MI 2.0, density 0.93), 200 parts by weight of rhusium carbonate (average particle size 2 μm, fatty acid treatment) as filler, EPDM as olefin terpolymer (Product name, EPT9
720, manufactured by Mitsui Petrochemical) in a twin-screw kneader (T
A resin composition obtained by sufficiently kneading with EM-50 (manufactured by Toshiba Machine Co., Ltd.) is granulated by a conventional method (Step A).

This resin composition was melted and formed into a film using a 65φ inflation extrusion mill to produce a resin film having a thickness of μIII (Step B).

The Resin 91 film thus obtained was stretched by a roll stretching machine (stretching rate: 200%) to obtain a porous film (Step C).

In this case, the stretching conditions were a stretching temperature of 60°C and a stretching speed of Cm/Min, and the stretching rate was adjusted by changing the speed ratio of the rolls.

The obtained porous film had no stretching unevenness and was a porous film.

Finally, the porous film thus obtained is
．． Discharge path J'l! in a nitrogen gas atmosphere of ITorr!
Hydrophilic pores are treated with an amount of O, 1wsec/c+112? ? Got the film.

When this hydrophilized porous 11 film was immersed in water, it was recognized that it absorbed water and had been subjected to hydrophilic treatment.

In addition, the water permeation rate was set at 0.7 kg/ell from one side of the membrane-like material.
! The result of measuring water permeability by applying water pressure of 2.0 m1/
Cl was 112·min.

Example 2-4 A material formed in the same manner as in Example 1 was used except that the sputtering conditions were changed as shown in Table 1.

The results are shown in Table 1.

Comparative Example 1 A porous + f1 film was obtained in the same manner as in Example 1, and this porous film was subjected to corona discharge treatment under the conditions of a voltage of 3 KV, a current of 1 + aωA, and a processing speed of the porous film of 5 + a/min. There are areas where the porous film shrinks due to the heat of the discharge, causing the pores to shrink and water permeation to decrease, and conversely, there are areas where the pores become larger and water permeation increases, resulting in poor reliability. The result was a lack.

Furthermore, it was observed that the treatment effect decreased with time.

The water permeability of this film was measured under the same conditions as in Example 1, and it was found to be 1 to 8 IIIl/c+a2·min, which was found to be highly variable and unreliable.

Comparative Example 2 A film with f = 75 pores obtained through steps A to C in Example 1, that is, a film that had not been subjected to sputter etching at all, was used.

The water permeability of this film was measured under the same conditions as in Example 1 and was found to be 0.2 we/c+o2·min,
It is recognized that the water permeability U is extremely low.

Comparative Example 3 Using the porous film obtained through Steps A to C in Example 1, it was processed under the conditions shown in Table 1, under the conditions that the sputtering amount was 1.5 W-see/cIll''. The formed one was used.

It was found that under this condition f'l, thermal shrinkage due to electrical discharge occurred, resulting in partially enlarged pores similar to corona discharge treatment, resulting in a lack of reliability.

(Blank below) Table t51 (B) Effects of the Invention The method for producing a hydrophilic porous film of the present invention is characterized in that the method for producing a hydrophilic porous film of the present invention is characterized in that a Q1 resin composition containing a linear low-density polyethylene resin, a photonic agent, and an olefin terpolymer as essential components is used to produce a hydrophilized porous film. A film manufactured by Jltl is manufactured, and then this resin film is stretched to form a porous film, and the surface of the porous film is subjected to high-frequency sputter etching treatment. The film is attracted to its bending strength and tensile strength change! The 2P force is high, and since the mechanical strength is high, there is no need to form any heat-treated parts, and therefore the porous film has extremely high air permeability and moisture permeability. As a result, even if this porous film is used as a single layer, for example, as a breathable bag or a pressurized filtration membrane, it will not burst during use and has the effect of increasing reliability.

In addition, in the method of the present invention, the surface of a porous film formed from a hydrophobic film (fat composition) is subjected to high-frequency spanner etching to make the porous film hydrophilic, without using special techniques or equipment. This has the effect that a highly reliable hydrophilized porous If1 film that can efficiently separate solids and the like in an aqueous solution can be easily obtained.

Claims (1)

[Claims] (1) A resin film is produced from a resin composition containing a linear low-density polyethylene resin, a filler, and an olefin terpolymer as essential components, and then this resin film is stretched to form a porous film. A method for producing a hydrophilized porous film, which comprises subjecting the surface of the porous film to high-frequency sputter etching treatment.