JPH0625277B2 - Hydrophilized porous film or sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Utilization Decomposition] The present invention relates to a hydrophilized porous film or sheet. More specifically, a film or sheet produced by melt molding from a polyolefin resin composition containing at least a filler is uniaxially stretched, or a porous film or sheet obtained by biaxially stretching, having a moisture permeability, The present invention relates to a porous film or sheet which has excellent hygroscopicity and is suitable for packaging, battery separators, excess materials, medical applications and the like.

[Conventional technology]

The present inventors have previously filed a method for producing a filled polyolefin porous film or sheet used for packaging, for battery separators, for excess materials, for medical purposes, etc. (Japanese Patent Application No. 57-172598, (JP-A-59-62117)),
Japanese Patent Application No. 58-10232, (Japanese Patent Application Laid-Open No. 59-136334), Japanese Patent Application No. 58-14937 ((Japanese Patent Application Laid-Open No. 59-140235)).

[Problems to be solved by the invention]

However, the porous film or sheet exhibits good hygroscopicity, but hardly exhibits hygroscopicity, and is not necessarily preferable for use in fields where it is desirable to have hygroscopicity such as for battery separators and medical applications.

[Means for solving problems]

The present inventors have conducted intensive studies for the purpose of providing a film or sheet that is excellent in both moisture permeability and hygroscopicity and is highly flexible, and as a result, the present invention has been completed. .

That is, the present invention is the unstretched film or sheet by melt-molding a polyolefin resin composition containing at least a filler, a unstretched film or sheet obtained by uniaxial stretching or biaxial stretching, unit volume 1 cm ³ per Porous film or sheet having a pore volume of 0.1 cc or more, a moisture absorption rate of 0.1% by weight or more and a moisture permeability of 500 g / m ² · 24 h
R is equal to or greater than r, and the vertical and horizontal bending resistances of the film are both (I) Formula bending resistance ≤ 0.193 × film thickness + 35 (I) where the bending resistance unit is mm and the film thickness unit is is μ.

And a hydrophilized film or sheet satisfying the above conditions.

As the polyolefin resin used in the present invention, high-density polyethylene, medium-density polyethylene, linear low-density polyethylene may be used alone or as a mixture of two or more kinds, and high-pressure low-density polyethylene may be mixed. Crystalline polypropylene is also used.

As the filler, inorganic and organic fillers are used, and as the inorganic filler, calcium carbonate, talc, clay,
Kaolin, silica, diatomaceous earth, magnesium carbonate, barium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite, Silicate clay or the like is used, and as the organic filler, cellulose powder such as wood powder or pulp powder is used. These may be used alone or in combination. The average particle size of the filler is 30μ
The following are preferred, those of 10μ or less are more preferred, and those of 5μ or less are most preferred. If the particle size is too large, the denseness of the pores of the stretched product deteriorates. The surface treatment of the filler is preferably carried out from the viewpoint of dispersibility in a 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 comprises a polyolefin resin and a filler, and in order to impart flexibility to the film or sheet, for example, a liquid or wax hydrocarbon polymer is blended. May be. As the liquid or wax hydrocarbon polymer, liquid polybutadiene, liquid polybutene, liquid polyisoprene, and derivatives thereof are used. Among them, hydroxyl group-terminated liquid polybutadiene and derivatives thereof, for example, liquid substances whose end is isocyanate-modified, maleic anhydride-modified, epoxy-modified, etc. are used. Furthermore, a polyhydroxy saturated hydrocarbon obtained by hydrogenating a hydroxyl group-terminated liquid polybutadiene shows good results.

The polyhydroxy saturated hydrocarbon is a hydrocarbon-based polymer in which the main chain having at least 1.5 hydroxyl groups per molecule is saturated or mostly saturated, and is 400 to 4800.
Those having a number average molecular weight (by vapor pressure method) in the range of 0, preferably 500 to 20000 are used. If the number average molecular weight is too small, the weather resistance will be insufficient, and if it is too large, the fluid pressure will decrease, making handling difficult. The average number of hydroxyl groups per molecule is 1.5 or more, preferably 1.8 or more, and particularly preferably 2 to 5. The hydroxyl group is preferably at the end of the main chain and the end of the long chain branch.

Thus, such a polyhydroxy saturated hydrocarbon is
Known methods, for example, hydrogen peroxide as a polymerization initiator,
It is obtained by hydrogenating a butadiene-based liquid polymer obtained by radically polymerizing butadiene alone or a copolymerizable monomer. Examples of the copolymerization monomer include isoprene, chloroprene, styrene, methyl (meth) acrylate, methyl vinyl ether and the like.

Hydrogenation is carried out by a conventional method using a nickel catalyst (for example, reducing nickel, Raney nickel), a cobalt catalyst, a platinum catalyst, a palladium catalyst, a rhodium catalyst, a ruthenium catalyst, a mixture thereof, or an alloy catalyst. When polyhydroxy saturated hydrocarbon is used, liquid epoxy resin or liquid organic compound containing epoxy group such as epoxidized vegetable oil may be used together.

In addition, a heat stabilizer, an ultraviolet absorber, an antistatic agent, a pigment, a fluorescent agent and the like may be added to the polyolefin resin according to a conventional method.

The mixing ratio of the polyolefin resin and the filler is 25 to 400 parts by weight, preferably 50 to 250 parts by weight, based on 100 parts by weight of the polyolefin resin. Further, when a liquid or wax hydrocarbon polymer and an epoxy group-containing organic compound are used, the liquid or wax hydrocarbon polymer is 1 to 100 parts by weight, preferably 3 parts by weight, based on 100 parts by weight of the polyolefin resin. To 70 parts by weight, the epoxy group-containing organic compound is 0 to 100 parts by weight, preferably 0 to 70 parts by weight, and the total amount of the liquid or wax hydrocarbon polymer and the epoxy group-containing organic compound is 1 to 1.
00 parts by weight, preferably 3 to 70 parts by weight. When the blending ratio of the filler is less than 25 parts by weight, pores are not sufficiently formed in the stretched film, resulting in a low porosity. or,
If the blending ratio of the filler exceeds 400 parts by weight, kneading property,
Poor dispersibility and film or sheet moldability.

The ratio of liquid or wax hydrocarbon polymer is 100
When it exceeds the weight part, the properties of the polyolefin resin are deteriorated, and satisfactory kneading properties, film or sheet moldability and stretchability cannot be ensured.

The film or sheet may be formed according to a normal film or sheet forming apparatus and forming method, and inflation molding with a circular die, T die forming with a T die, or the like may be appropriately adopted. The selection depends on the subsequent stretching method.

That is, in the case of uniaxial stretching, roll stretching is usually preferred, but tubular stretching may be employed in which the uniaxial direction (take-up direction) is emphasized. The stretching may be performed in one stage or in multiple stages of two or more stages, and the stretching ratio is 1.2 times or more, preferably 1.5 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 1.2 times or more in at least one direction.

Further, by carrying out heat treatment after stretching in both uniaxial stretching and biaxial stretching, the dimensions of the film can be stabilized.
Further, surface treatment such as known corona treatment and frame treatment can be applied.

A unit volume of a film obtained by uniaxially or biaxially stretching a film or sheet obtained by melt-extruding a polyolefin resin composition containing at least a filler, 1 cm ³
The porous film or sheet having a pore volume of 0.1 cc or more is subjected to a hydrophilic treatment.

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

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

Examples of nonionic surfactants include polyol fatty acid monoglyceride, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, and polyoxyethylene alkyl ether phosphoric acid.

Cationic surfactants include quaternary ammonium salts, polyoxyethylene alkyl amines, alkyl amine oxides, etc.Anionic surfactants include alkyl sulphonates, alkyl benzene sulphonates, alkyl naphthalene sulphonates, Alkyl sulfosuccinate, alkyl sulfonic acid ester acid, polyoxyethylene alkyl sulfonic acid ester salt, polyoxyethylene alkyl allyl sulfonic acid ester salt, alkyl phosphate, polyoxyethylene alkyl phosphate and the like are used.

Further, as the deliquescent inorganic salt used for the treatment, Group I and Group II metal halides of the periodic table are preferable, and specifically, lithium chloride, calcium chloride, magnesium chloride,
Zinc chloride or the like is used. Of these, halides of alkali metals and alkaline earth metals are preferable. Two or more kinds of these deliquescent inorganic salts may be used in combination.

To treat the porous film or sheet with a surfactant, a deliquescent inorganic salt, or a mixture of both, for example, a dipping method, a spraying method or the like is used, but usually a simple surfactant, deliquescent inorganic salt is used. The treating agent is mixed or dissolved in a liquid which is substantially uniformly mixed with the treating agent comprising one or both of salts and the porous film or sheet is immersed in the solution to impregnate the film or sheet with the treating agent. The dipping method is used. Examples of the liquid that is substantially uniformly mixed with the surfactant include pure water and alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol. Also, a mixture of these can be used. Further, aliphatic hydrocarbons, aromatic hydrocarbons, chloroform, acetone, carbon tetrachloride, etc., or a mixture thereof can also be used.

As the liquid that is substantially uniformly mixed with the deliquescent inorganic salt,
Alcohols such as methyl alcohol, ethyl alcohol, acetone, diethyl ether, chloroform, etc.
Further, among the above liquids, a mixture of pure water and a liquid that can be uniformly mixed with pure water can be used.

Examples of the liquid that is substantially uniformly mixed with the mixture of the surfactant and the deliquescent inorganic salt include pure water, alcohols such as methyl alcohol and ethyl alcohol, chloroform, and acetone. Alternatively or additionally, mixtures of these can also be used.

The concentration of the surfactant is 0.1% by weight or more, preferably 1% by weight or more, and the concentration of the deliquescent inorganic salt is 0.05% by weight or more, preferably 0.1% by weight or more. When a mixture of a surfactant and a deliquescent inorganic salt is used, the concentration of the surfactant is 0.1% by weight or more, preferably 1% by weight or more, and the concentration of the deliquescent inorganic salt is 0.05% by weight or more, preferably 0.1% by weight. % Or more.

When the concentration of the surfactant is less than 0.1% by weight or the concentration of the deliquescent inorganic salt is less than 0.05% by weight, even if the hydrophilic treatment can be performed, the improvement effect is small, which is not preferable.

It is also possible to subject the porous film or sheet to surface treatment such as known corona treatment and flame treatment, and then to carry out the above-mentioned hydrophilic treatment. The film of the present invention has moisture permeability, moisture absorption and flexibility of a certain level or more, and a moisture permeability of 500 g / m ² · 24 hr or more, preferably 1000 g / m ² · 24 hr.
The moisture absorption rate is 0.1% by weight or more, and the bending stiffness in the machine direction and the transverse direction of the film is (I) Formula: Bending flexibility ≤0.193 × film thickness +35 (I) Is mm and the unit of film thickness is μ.

To be satisfied.

A film satisfying these required characteristics can be suitably used for battery separators, medical applications, etc., and has a suitable water vapor transmission rate and moisture absorption rate according to the requirements within the range described in detail in the present invention. can do.

〔Example〕

Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Reference Example 1 (Production of Polyhydroxy Saturated Hydrocarbon) In an autoclave with a capacity of 10, commercially available liquid polybutadiene (manufactured by Nippon Soda Co., Ltd .; G-2000, molecular weight 2000) 3 kg,
3 kg of cyclohexane and carbon-supported ruthenium (5
%) 300 g of a catalyst (manufactured by Nippon Engelhardt) was charged, the inside of the system was replaced with purified argon gas, high-purity hydrogen gas was supplied to the autoclave, and heating was started at the same time.
It takes about 30 minutes and the steady condition (internal temperature about 100 ° C, internal pressure about 50k
g / cm ² ) was reached. Keep this condition for about 15 hours,
Then the hydrogenation reaction was stopped. The obtained polymer was a liquid polyhydroxy saturated hydrocarbon having an iodine value of 5 g / 100 g and a hydroxyl value of 44 KOH mg / g.

Example 1 Melt index 1.0 g / 10 minutes, density 0.918 g /
cm ³ and a linear low density polyethylene resin [NOVATEC-U, FW
20G Mitsubishi Kasei Co., Ltd.] 3.4 kg and calcium carbonate (average particle size 0.9 μ, treated with fatty acid) 5.8 kg are first mixed by stirring in a Henschel mixer, and then the polyhydroxy saturated carbonization obtained in Reference Example 1 is added. 0.8 kg of hydrogen was added and further mixed by stirring to obtain 10 kg of a mixture.

The blending operation was carried out 10 times to finally obtain 100 kg of a mixture.

The melt index is 1 according to ASTM D 1238-70.
The extrusion amount of resin at 90 ° C and a load of 2.16 kg is shown. The density is ASTM
According to D 1505, it was obtained by a density gradient tube method at 20 ° C.

The mixture thus obtained was kneaded by a twin-screw kneader DSM-65 [Japan Steel Works, Ltd.] and granulated. This was inflation-molded by a 50 mmφ extruder and formed into a film having a thickness of 120 μm.

Here, the film forming conditions are as follows.

Extruder Cylinder temperature: 170-190-190 ° C Head, Die temperature: 190-190 ° C Blow ratio: 2.5 The film thus obtained is uniaxially stretched by a roll stretching machine, followed by further heat relaxation treatment to obtain a film. 80μ thickness, 0.2 hole volume per 1 cm ^{3 of} film unit volume
A 7 cc porous film was obtained.

The stretching and thermal relaxation conditions are as follows.

Stretching temperature: 70 ° C. Stretching ratio: 3.0 times Thermal relaxation temperature: 100 ° C. Thermal relaxation rate: 13% The porous film was treated with anionic surfactant sodium alkylnaphthalene sulfonate [Perex NB paste, Kao Soap Co., Ltd.], chloride. Either lithium, or a mixture of both in a predetermined ratio, ethyl alcohol, pure water, or a solution of a mixture of both in a predetermined ratio at a predetermined concentration, soak for a predetermined time, roll squeeze, and air dry. did.

Shows the moisture permeability, moisture absorption, and bending resistance of this treated film.
1 shows that the moisture absorption rate is greatly improved compared with Comparative Example 1.

In addition, these measuring methods are as follows.

1) Pore volume (cc / cm ³ ): Mercury porosimeter [AMINC
O, 60,000 psi porosimeter].

Regarding the pore volume, in the cumulative pore volume distribution chart, the cumulative pore volume from a small diameter to a radius of 10 μ is shown by the amount per 1 cm ^{3 of the} film unit volume.

2) Water vapor transmission rate (g / m ² · 24 hr) Measured at a temperature of 30 ° C and a relative humidity of 90% according to JIS Z 0208-1976.

3) Moisture absorption rate (% by weight): The film was dried in a desiccator containing calcium chloride for 24 hours (20 ° C. constant temperature room), and then the weight after 24 hours at 20 ° C. and 65% relative humidity. The increase is measured and expressed as a percentage by weight.

4) Bending resistance (mm): Measured by the 45 ° cantilever method of JIS L 1018-1977. The measurement was performed at a temperature of 20 ° C. and a relative humidity of 65%.

Comparative Example 1 The film obtained in Example 1 by uniaxial stretching with a roll stretching machine, which has not been subjected to a hydrophilization treatment, is a porous film having a thickness of 80 μm.

The measurement results are shown in Table-1, but the moisture permeability is large, the bending resistance is small, and both are good, but the hygroscopicity is small and almost no hygroscopicity is shown, or only insufficient hygroscopicity is shown. Absent.

Comparative Example 2 In Example 1, a porous film having a film thickness of 80 μ obtained by uniaxial stretching with a roll stretching machine was used,
After immersing in a 5 wt% aqueous solution of lithium chloride for 10 seconds, it was air-dried in the same manner as in Example 1. The measurement results are shown in Table-1, and the moisture absorption rate is 0.009 wt%, which is unsatisfactory.

Comparative Example 3 In Example 1, a porous film having a film thickness of 80 μ obtained by uniaxial stretching with a roll stretching machine was used,
It was immersed in a 0.05 wt% aqueous solution of sodium alkylnaphthalene sulfonate used in Example 1 for 10 seconds and then air-dried in the same manner as in Example 1. The measurement results are shown in Table-1, but the moisture absorption rate was insufficient at 0.05 wt%.

Example 2 The same linear low density polyethylene resin as used in Example 1 (3.9 kg), melt index 2.0 g / 10 min, density 0.924 g / cm ³ high pressure low density polyethylene [NOVATE
CL, F150, Mitsubishi Kasei Co., Ltd.] 0.2 kg and 5.2 kg of the same calcium carbonate as used in Example 1 are first mixed by stirring in a Henschel mixer, and then the polyhydroxy obtained in Reference Example 1 is added. Saturated hydrocarbon 0.6kg and epoxidized soybean oil [ADK Cizer 0-130L, Adeka Argus Chemical Co., Ltd.]
1 kg was added, and further mixed by stirring. Next, kneading and granulation were carried out in the same manner as in Example 1, and thereafter inflation film formation was carried out under the same conditions as in Example 1 to obtain a film thickness of 12
A 0 μ film was obtained. Then, the film was uniaxially stretched and heat-relaxed by 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: 13% Subsequently, the uniaxially stretched film was stretched in the transverse direction by a tenter transverse stretching machine and further subjected to a heat relaxation treatment in the transverse direction. The conditions are as follows.

Lateral stretching temperature 95 ° C Lateral stretching ratio 2.5 times Lateral heat relaxation temperature 105 ° C Lateral heat relaxation rate 15% The film thus obtained has a film thickness of 75μ and a pore volume of 0.36cc per unit film volume of 1 cm ³ . It was a porous film.

The porous film was prepared by adding one of the same sodium alkylnaphthalene sulfonate as used in Example 1, lithium chloride, or a mixture of both at a predetermined ratio to ethyl alcohol,
It was immersed in a solution prepared by dissolving either pure water or a mixture of both of them in a predetermined ratio for a predetermined time, and air-dried in the same manner as in the examples.

Table 2 shows the moisture vapor transmission rate, moisture absorption rate, and bending resistance of this treated film.

Comparative Example 4 A porous film having a film thickness of 75 μ obtained by transverse stretching with a tenter transverse stretching machine in Example 2.

The measurement results are shown in Table-2.

Example 3 In Example 1, the linear low-density polyethylene was replaced by a high-density polyethylene having a melt index of 0.04 g / 10 min and a density of 0.960 g / cm ³ [NOVATEC, ES300, Mitsubishi Kasei Co., Ltd.
Co., Ltd.], and inflation molding was performed in the same manner as in Example 1 to form a film having a thickness of 120 μm. Then, by uniaxial stretching using a roll stretching machine, a porous film having a film thickness of 72 μ and a pore volume of 0.26 cc per unit volume of the film of 1 cm ³ was obtained. The stretching conditions are the same as in Example 1.

The porous film was prepared by using polyoxyethylene sorbitan monolaurate (Rheodol T, a nonionic surfactant).
W-L120, Kao Soap Co., Ltd.], lithium chloride, or a mixture of both at a predetermined ratio with ethyl alcohol,
It was immersed in a solution of either pure water or a mixture of both in a predetermined ratio at a predetermined concentration for a predetermined time, and air-dried in the same manner as in Example 1.

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

Comparative Example 5 A porous film having a thickness of 72 μm obtained by roll stretching in Example 3.

The measurement results are shown in Table-3.

Comparative Example 6 In Comparative Example 3, a film having a thickness of 72 μ obtained by uniaxial stretching with a roll stretching machine was mixed with 0.03% of lithium chloride.
After dipping in a wt% ethyl alcohol solution for 10 seconds, it was air-dried in the same manner as in Example 1. The measurement results are shown in Table 3. The moisture absorption rate is 0.07% by weight, and although the effect of the hydrophilic treatment is recognized as compared with Comparative Example 5, the moisture absorption rate is small and still unsatisfactory.

[Effects of the Invention] The film or sheet of the present invention has excellent moisture permeability, moisture absorption, and flexibility, and is used for packaging, for an electrostatic relaxation separator,
It is very effective when used as a drug and as a medicine.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Suzuki, 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryoh Chemical Industry Co., Ltd. (72) Inventor Hiroshi Kamata 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa (56) References JP-A-60-215034 (JP, A) JP-A-61-95043 (JP, A)

Claims (1)

[Claims] 1. Voids per unit volume of 1 cm ^{3 of} a film obtained by uniaxially or biaxially stretching a film or sheet obtained by melt-extruding a polyolefin resin composition containing at least a filler. A porous film or sheet having a volume of 0.1 cc or more, a moisture absorption rate of 0.1% by weight or more, a moisture vapor transmission rate of 500 g / m ² · 24 hr or more, and both the longitudinal and lateral bending resistance of the film ( Formula I) Bending degree ≦ 0.193 × film thickness + 35 (I) Here, the unit of bending degree is mm and the unit of film thickness is μ. A hydrophilized porous film or sheet, characterized in that: