JPS61264031A - Hydrophilicized porous film or sheet - Google Patents

Abstract

PURPOSE:To produce a hydrophylicized porous film or sheet having excellent moisture permeability, hygroscopicity and flexibility and suitable for medical use or cell separator, etc., by forming a film or sheet from a polyolefin resin composition containing a filler, and subjecting the film, etc., to hydrophilic treatment. CONSTITUTION:(A) 100pts.(wt.) of a polyolefin resin is compounded with (B) 25-400pts. of a filler having an average particle diameter of <=30mu, e.g. calcium carbonate surface-treated preferably with a fatty acid (metal salt) and if necessary, (C) a liquid (waxy) hydrocarbon polymer, etc. The obtained resin composition is formed to a film (or sheet) by melt-extrusion molding, and the film is drawn uniaxially or biaxially. The drawn film is subjected to the hydrophilic treatment with a surfactant, deliquescent inorganic salt or their mixture to obtain a porous film (or sheet) having a void volume of >=0.1cc/cm<3>, a moisture absorption of >=0.1wt%, a moisture permeability of >=500g/m<2>.24hr and a longitudinal and transversal bending resistances satisfying the formula (bending resistance, mm: film thickness, mu).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Decomposition] The present invention relates to a hydrophilized porous film or sheet. More specifically, it is a porous film or sheet obtained by uniaxially or biaxially stretching a film or sheet made by melt-molding a polyolefin resin composition containing at least a filler, which has moisture permeability, moisture permeability, The present invention relates to a porous film or sheet that has excellent hygroscopicity and is suitable for packaging, battery separators, convulsive materials, medical applications, etc.

[Conventional technology]

The present inventors previously filed an application for a method for producing a filler-containing polyolefin porous film or sheet for use in packaging, battery separators, filter materials, medical applications, etc. -77λ!??, Tokugansho, tt!”
-10ko 3.2, special request Akio? -/4t937).

[Problem that the invention seeks to solve]

However, although the porous film or sheet exhibits excellent moisture permeability, it exhibits almost no hygroscopicity, and is not necessarily suitable for use in fields where hygroscopicity is desirable, such as for battery separators and medical applications.

[Means for solving problems]

The inventors of the present invention have completed the present invention as a result of intensive studies aimed at providing a film or sheet that has excellent moisture permeability and moisture absorption properties and is highly flexible. .

That is, the present invention melt-forms a polyolefin resin composition containing at least a filler to form an unstretched film or sheet, and uniaxially or biaxially stretches the unstretched film or sheet. A porous film or sheet having a pore volume of o,ice or more, a moisture absorption rate of 0.1% by weight or more and a moisture permeability j0θ11/
ml・,24thr or more, and the bending resistance of the film in both the vertical and horizontal directions is expressed by the formula (I)≦θ, /3×film thickness+3t (1
) Here, the unit of bending resistance is mi, and the unit of film thickness is μ.
It is.

The present invention relates to a hydrophilized film or sheet that satisfies the following.゛The polyolefin resin used in the present invention includes high-density polyethylene, medium-density polyethylene, and linear low-density polyethylene alone or as a mixture of two or more types, and furthermore, high-pressure low-density polyethylene is mixed. Good too. Crystalline polyethylene may also be used.

Inorganic and organic fillers are used as fillers.
Inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium sulfate, calcium sulfate, alionium hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, Mica, asbestos powder, glass powder, shirasu balloon, zeolite, clay silicate, etc. are used, and as the organic filler, cellulose powder such as wood flour, pulp powder, etc. are used. These may be used alone or in combination. The average particle size of the filler is 30
Those below μ are preferable, and those below /θμ are more preferable. It is most preferable to have a particle size of less than 10 μm, and if the particle size is too large, the density of the pores in the drawn product will deteriorate. Surface treatment of the filler is preferably carried out in terms of dispersibility in the resin and further stretchability, and treatment with a fatty acid or a metal salt thereof gives preferable results.

The porous film or sheet of the present invention basically consists of a polyolefin resin and a filler, but in order to give the film or sheet flexibility, for example, a liquid or waxy hydrocarbon polymer may be added. You may. As the liquid or waxy hydrocarbon polymer, liquid polybutadiene, liquid polybutene, liquid polyisoprene, and derivatives thereof are used. Among these, hydroxyl group-terminated liquid polybutadiene and derivatives thereof, such as liquid products whose terminals are modified with isocyanate, maleic anhydride, or epoxy, are used. Furthermore, polyhydroxy saturated hydrocarbon obtained by hydrogenating hydroxyl group-terminated liquid polybutadiene shows good results.

The polyhydroxy saturated hydrocarbon has a molecular weight of 1. A hydrocarbon polymer whose main chain is saturated or mostly saturated and has hydroxyl groups from 4tOθ to 4
tF00θ, preferably number average molecules in the range j 00-20.00θ! (by vapor pressure method) is used. If the number average molecular weight is too small, the weather resistance will not be sufficient, and if it is too large, the fluidity will decrease, making handling difficult. The average number of hydroxyl groups per molecule is at least Hema, preferably Hema or more, and particularly preferably 2 or more! It is. The hydroxyl group is preferably located at the end of the main chain or the end of a long chain branch.However, such a polyhydroxy saturated hydrocarbon can be prepared by a known method such as butadiene alone using hydrogen peroxide as a polymerization initiator. Alternatively, it can be obtained by hydrogenating a butadiene-based liquid polymer obtained by radical polymerization with a copolymerizable monomer. Examples of copolymerizable monomers include isoprene, polypropylene, styrene, methyl (meth)acrylate, and methyl vinyl ether.

Hydrogenation is carried out in a conventional manner using a nickel-based catalyst (eg reduced nickel, Raney nickel), cobalt-based catalyst, platinum catalyst, palladium catalyst, rhodium catalyst, ruthenium catalyst, or a mixture or alloy catalyst thereof. or,
When polyhydroxy saturated hydrocarbons are used, liquid epoxy resins or liquid organic compounds containing epoxy groups such as epoxidized vegetable oils may also be used in combination.

Incidentally, heat stabilizers, ultraviolet absorbers, antistatic agents, pigments, fluorescent agents, etc. may be added to the polyolefin resin according to conventional methods.

The blending ratio of the polyolefin resin and filler is preferably 2 to 00 parts by weight per 100 M parts of the polyolefin resin. θ~, 2o θ parts by weight. Furthermore, when a liquid or waxy hydrocarbon polymer or an epoxy group-containing organic compound is used, the liquid or waxy hydrocarbon polymer is preferably 7 to 700 parts by weight per 100 parts by weight of the polyolefin resin. is 3 to 70 parts by weight, the epoxy group-containing organic compound is 0 to 100 parts by weight, preferably 0 to 20 parts by weight, and the total amount of the liquid or waxy hydrocarbon polymer and the epoxy group-containing organic compound is 7 parts by weight.
~100 parts by weight, preferably 3 to 70 parts by weight. When the blending ratio of the filler is less than 21 parts by weight, sufficient pores are not formed in the stretched film, resulting in a low degree of porosity.

Furthermore, if the blending ratio of the filler exceeds 700 parts by weight, the wire crosstalk, dispersibility, and formability of the film or sheet will be poor.

The proportion of liquid or waxy hydrocarbon polymer is 700%
If the amount exceeds parts by weight, the properties of the polyolefin resin will be weakened, making it impossible to ensure satisfactory cross-talk properties, film or sheet formability, and stretchability.

Molding of the film or sheet may be carried out according to a conventional film or sheet molding apparatus and method, and inflation molding using a circular die, T-die molding using a T-die, etc. may be appropriately employed. The selection depends on the method of subsequent stretching.

That is, in the case of -axial stretching, roll stretching is usually preferred, but even in tubular stretching, which emphasizes the -axial direction (take-up direction), there is intrusion. Further, the stretching may be carried out in one stage or in multiple stages of two or more stages, and the stretching ratio is 8 times or more, preferably 1 times or more.

Next, the case of biaxial stretching will be described.

The biaxial stretching may be simultaneous stretching or sequential stretching, and the stretching ratio is 70.2 times or more in at least one direction.

In addition, the dimensions of the film can be stabilized by carrying out heat treatment after stretching (for both -axial stretching and biaxial stretching).

Further, known surface treatments such as corona treatment and flame treatment can also be applied.

The pore volume per unit volume 77 of the film obtained by uniaxially or biaxially stretching a film or sheet obtained by melt extrusion molding a polyolefin resin composition containing at least a filler is 0.100 or more. Some porous films or sheets are subjected to hydrophilic treatment.

As a hydrophilic treatment method, for example, treatment with a surfactant, a deliquescent inorganic salt, or a mixture of both may be used.

The surfactants used in the treatment are nonionic surfactants,
Either a cationic surfactant or anionic surfactant may be used, or two or more of these surfactants may be used in combination.

Examples of nonionic surfactants include polyol fatty acid heptanoglyceride, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylaryl x-thyl, and polyoxyethylene alkyl ether phosphate. etc.

Examples of cationic surfactants include quaternary ammonium salts, polyoxyethylene alkylamines, and alkylamine oxides; examples of anionic surfactants include alkylsulfonates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, and alkylsulfosuccinates. Acid salts, alkyl sulfonic acid ester salts, polyoxyethylene alkyl sulfonic acid ester salts, polyoxyethylene alkylaryl sulfonic acid ester salts, alkyl phosphates, polyoxyethylene alkyl phosphates, and the like are used.

In addition, as the deliquescent inorganic salt used in the treatment, halides of metals from Groups I and II of the periodic table are preferred, and specifically, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, etc. are used. . Among them, alkali metals,
Alkaline earth metal halides are preferred. Two or more of these deliquescent inorganic salts may be used in combination.

To treat a porous film or sheet with a surfactant, a deliquescent inorganic salt, or a mixture of both, a dipping method, a spraying method, etc. are used, but usually a simple method such as a surfactant, A processing agent is mixed or dissolved in a liquid that substantially uniformly mixes with a processing agent consisting of either a deliquescent inorganic salt or a mixture of both, and a porous film or sheet is immersed in the solution, and the processing agent is added to the film or sheet. A dipping method is used in which the material is impregnated with water. Examples of the liquid that mixes substantially uniformly with the surfactant include pure water and alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol. Mixtures of these can also be used. Furthermore, aliphatic hydrocarbon scale, aromatic hydrocarbons, chloroform, acetone, carbon tetrachloride, etc., or mixtures thereof may also be used.

Liquids that mix substantially uniformly with deliquescent inorganic salts include:
Alcohols such as methyl alcohol and ethyl alcohol, acetone, diethyl ether, chloroform, and the like, as well as mixtures of pure water and liquids that can be uniformly mixed with pure water among the above liquids, can also be used.

Examples of liquids that can be mixed substantially uniformly with the mixture of surfactant and deliquescent inorganic salt include pure water, alcohols such as methyl alcohol and ethyl alcohol, chloroform, and acetone. Certain b may also be used as mixtures thereof.

The concentration of the surfactant is 007% by weight or more, preferably 7% by weight or more, and the concentration of the deliquescent inorganic salt is θ,
or more than 0.1% by weight, preferably more than 0.1% by weight.

When using a mixture of a surfactant and a deliquescent inorganic salt, the concentration of the surfactant is preferably 7.0% by weight or more.
Weight% or more, the concentration of deliquescent inorganic salt is O0θ! - or more by weight, preferably 0.7% by weight or more.

If the concentration of the surfactant is less than O0/weight it* or the concentration of the deliquescent inorganic salt is less than 0.02% by weight, even if hydrophilic treatment is possible, the improvement effect will be small, which is not preferable. .

The above-mentioned hydrophilic treatment can also be carried out after surface treatment such as known corona treatment or flame treatment is applied to the porous film or film. The film of the present invention has moisture permeability, moisture absorption rate, and flexibility above a certain level, has a moisture absorption rate of 0.7% by weight or more, and has both longitudinal and transverse bending resistance (
1) Formula rule: Softness ≦0. /93×film thickness+3s (I
) Here, the unit of bending resistance is dragon, and the unit of film thickness is μ.

satisfy.

A film that satisfies these required properties can be suitably used for battery separators, medical applications, etc., and a film with appropriate moisture permeability and moisture absorption rate is selected according to the requirements within the scope of the detailed explanation of the present invention. be able to.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Reference example/(Production of polyhydroxy saturated hydrocarbon) Volume t/
Commercially available liquid polybutadiene [manufactured by Nippon Soda ■; G-2000, molecular weight, zoθo] was placed in an autoclave.
3 kg, cyclohexane 3 to 9 and carbon-supported ruthenium (%) N (manufactured by Nippon Engelhard) 30θI
After charging and purging the system with purified argon gas, high-purity hydrogen gas was supplied to the autoclave and heating was started at the same time.It took about 30 minutes to reach steady conditions (internal temperature approx./θ0℃, internal pressure approx.!). 9/cd). Approximately /!
The hydrogenation reaction was then stopped. The obtained polymer has an iodine value! l//θ09, hydroxyl value &g
It was a liquid polyhydroxy saturated hydrocarbon of KOH~/I.

Example/ Melt index is 80 g/ /θ min, density is θ,
9//1170m”T: Certain linear low-density polyurethane resin [N0VA, TEO-U, FW,
20G E Ryo Kasei Kogyo■] 3, '1kg and calcium carbonate (average particle size θ, RIμ, fatty acid treatment)! .

This blending operation was carried out 10 times, and finally a mixture of /θθ of 9 was obtained.

The melt index is ASTM D/23♂-7.
0), 790°C, load, /akg, and the density is AEITM Di! 06, and was determined at 20°C using the density gradient tube method.

The mixture thus obtained was mixed in a twin-screw kneader DE3M-4j.
[Manufactured by Japan Steel Works ■] was mixed with p and granulated. T this
An inflated V-sheet was molded using an ommB extruder to form a film with a thickness of /zoμ.

Here, the film forming conditions are as follows.

Extruder cylinder temperature: 2/7θ-/9θ-/0°C Head, die temperature: 2/7θ-/9θ°C Blow ratio; 4.
j The thus obtained film was uniaxially stretched using a roll stretching machine, and then further heat-relaxed to -1 film thickness? A porous film having a pore volume of 0.27 CQ per unit volume of film/cnt was obtained.

The stretching and thermal relaxation conditions are as follows.

Stretching temperature: 70°C Stretching ratio: 3.0 times Heat relaxation temperature: 100°C Heat relaxation rate: 73% The porous film was coated with anionic surfactants such as sodium alkylnaphthalene sulfonate [Perex NB paste, Kao soap ■] and lithium chloride. Either or a mixture of both at a predetermined ratio was immersed in a solution of a predetermined concentration dissolved in either ethyl alcohol, pure water, or a mixture of the two at a predetermined ratio for a predetermined time, squeezed with a roll, and then air-dried.

The moisture permeability, moisture absorption rate, and bending resistance of this treated film are shown below.
As shown in Figure 7, it can be seen that the moisture absorption rate is greatly improved compared to Comparative Example.

The methods for measuring these are as follows.

/) Pore volume (cc/m): Mercury porosimeter [AM
The measurement was performed using a 60,000 pe1 porosimeter manufactured by KonoO Co., Ltd.

In the cumulative pore volume distribution diagram, the pore volume is expressed as the cumulative pore volume from micropore diameter to radius/θμ in unit volume/d of the film.

2) Moisture permeability (1/rr? 9.2 & hr): Measured at a temperature of 30° C. and a relative humidity of 2θ- according to J-EJZ0.20F-/R7O.

3) Moisture absorption rate (wt%): After drying the film in a desiccator containing calcium chloride for 24 hours (in a constant temperature room at 20°C), it was dried at -0°C and relative humidity tj'% for 24 hours.
The weight gain after y hours is measured and expressed as a weight percentage.

4t) Bending resistance (mm): J Engineering S L 10/?
-/? It was measured by the 77×4tj0 cantilever method. Measurements were made at a temperature of 20℃ and relative humidity! It was done in %.

Comparative Example/Example/This is a film obtained by uniaxial stretching using a roll stretching machine, which is not subjected to hydrophilic treatment, and is a porous film having a thickness of θμ.

The measurement results are shown in Table 1. Although the moisture permeability is high and the sardine softness is low, both of which are good, the moisture absorption rate is low and shows almost no hygroscopicity or only insufficient hygroscopicity. .

Comparative Example: What is the thickness of the film obtained by uniaxial stretching using a roll stretching machine in Example/? Using a porous film of θμ,
After being immersed in a jwt% aqueous solution of lithium chloride for 70 seconds, it was air-dried in the same manner as in Example. The measurement results are shown in Table 1, and the moisture absorption rate is 0.09 wt %, which is unsatisfactory.

Comparative Example 3 In Example/, by uniaxial stretching with a roll stretching machine)
Using the obtained porous film with a film thickness of ♂θμ,
0.0 of sodium alkylnaphthalene sulfonate used in Example/! After being immersed in a wt% aqueous solution for 70 seconds, it was air-dried in the same manner as in Example. The measurement results are shown in Table 1, and the moisture absorption rate was insufficient at θ, ot wt %.

Example 3.9 kg of the same linear low density polyethylene resin used in Example 1 and melt index 01/10
High pressure method low density yj with density Q, ri, 2Q, 9/m
IJ 工'j-し：／CN0VATEO-L、F
/30. Mitsubishi Chemical Industries■] o, zkg and examples/
First, add 2 kg of the same calcium carbonate Z used in Henschel.

The mixture was stirred and mixed in a mixer, and then the polyhydroxy saturated hydrocarbon θ, tlcg obtained in Reference Example/ and epoxidized soybean oil [ADK 01zer O-/JθL1 ADEKA・
Argus Chemical ■] o and ikg were added and further stirred and mixed. Next, the mixture was kneaded and granulated in exactly the same manner as in Example 1, and then, inflation film formation was performed under the same conditions as in Example 1 to obtain a film having a film thickness of 2θμ. Next, the film was subjected to sea-axis stretching and heat relaxation treatment using a roll stretching machine. The stretching and thermal relaxation conditions are as follows.

Stretching temperature: 70°C Stretching ratio: 2.0 times Thermal relaxation temperature: 100°C Thermal relaxation rate: 73% After reading, the -axially stretched film is stretched in the transverse direction using a tenter horizontal □ stretching machine, and then heat-relaxed in the transverse direction. Did. The conditions are as follows.

Lateral stretching temperature Lamp °C Lateral stretching ratio Ko,! The film thus obtained has a film thickness of 7! μ, pore volume per 1crll film unit volume 0.34cc
It was a porous film.

The porous film was prepared by adding either the same sodium dialkylnaphthalene sulfonate or lithium chloride used in Examples/1, or a mixture of both in a predetermined ratio to ethylalyol,
It was immersed in a solution of either pure water or a mixture of the two at a predetermined ratio for a predetermined time, and air-dried in the same manner as in the example.

Table 1 shows the moisture permeability, moisture absorption rate, and bending resistance of this treated film.

Comparative Example This is a porous film having a film thickness of 7jμ obtained by transverse stretching using a tenter transverse stretching machine in Example λ.

Table 2 shows the measurement results.

Example 3 In Example/, linear low density polyethylene was prepared with melt index O6θ4tg7iθ, density θ, 96θl
/Cd high density polyethylene [N0VATKO.

Inflation molding was performed in the same manner as in Example/, except that ESjθθ, Mitsubishi Chemical Corporation
A film of μ was formed. Next, axial stretching was performed using a roll stretching machine to obtain a film thickness of 7.2μ and a unit volume of the film/cII! A porous film with a pore volume of O0.2 CC was obtained. The stretching conditions are the same as in Example.

The porous film was coated with a nonionic surfactant, polyoxyethylene sorbitan monolaurate [Rheodor TV
-L/, 20. Kao soap ■], lithium chloride (B), or a mixture of both in a predetermined ratio, is immersed in a solution of a predetermined concentration in either ethyl alcohol, pure water, or a mixture of the two in a predetermined ratio, for a predetermined time, It was air-dried in the same manner as in Example.

Table 3 shows the moisture permeability, moisture absorption rate, and bending resistance of this treated film.

Comparative example! This is a porous film with a film thickness of 22 μm obtained by roll stretching in Example 3.

A film with a thickness of 2.2μ obtained by stretching was treated with IJ chloride.
10 in a 0.03 wt% ethyl alcohol solution of lithium.
After being immersed for seconds, it was air-dried in the same manner as in Example. The measurement results are shown in Table 3, and the moisture absorption rate is θ, 07wt%, which is the comparative example! Although the effect of the hydrophilic treatment is recognized compared to that of the previous example, the moisture absorption rate is low and is still unsatisfactory.

〔Effect of the invention〕

The film or sheet of the present invention has excellent moisture permeability, moisture absorption rate, and flexibility, and is used for packaging, battery separators, etc.
It is very effective when used as an over-the-counter medicine or for medical purposes.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (7 others)

Claims (1)

[Claims] (1) Voids per unit volume/cm^3 of a film obtained by uniaxially or biaxially stretching a film or sheet obtained by melt extrusion molding a polyolefin resin composition containing at least a filler. A porous film or sheet with a volume of 0.1 cc or more, a moisture absorption rate of 0.1% by weight or more, a moisture permeability of 500 g/m^2.24 hr or more, and flexibility in the longitudinal and lateral directions of the film. (I) Bending resistance≦0.193×film thickness+35 (I) Here, the unit of bending resistance is mm, and the unit of film thickness is μ. A hydrophilized porous film or sheet that satisfies the following.