JP3325091B2 - Method for producing porous film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous film having gas permeability, and more particularly, to a method for producing a porous film in which a polyolefin resin, a polycarbonate resin and a thermoplastic elastomer are mixed and formed into a film.

[0002]

2. Description of the Related Art A porous film using a polyolefin resin as a matrix resin has gas permeability and water resistance, and is frequently used in various fields where such performance is required. Conventionally, such a porous film is produced by a method of mechanically or electrically piercing the film, a method of adding a soluble filler to a film, forming a film on the film, and then eluting the filler to make the film porous, and adding a filler. A method of forming a film in which the resin and incompatible resin particles are dispersed in a matrix resin by melt-kneading two types of resins having low compatibility, by stretching the film at least uniaxially to form a porous film, Next, a method of stretching the film at least uniaxially to make the film porous is known, and from the viewpoint of productivity and the like, a method of mainly stretching a filler-added film is performed.

[0003] However, in the method of stretching the filler-added film, dropping of the filler becomes a problem depending on the use. Also, when using an inorganic filler,
In addition to this problem, problems such as easy dielectric breakdown and a large amount of ash after burning the film occur, and the use of the obtained porous film is limited.

[0004]

On the other hand, the method in which two kinds of resins having low compatibility are kneaded, formed into a film and stretched does not cause various problems caused by the addition of the filler, and the production of the film does not occur. Because of good properties, it is expected as a useful method for producing a porous film. However, in such a method, in the melt-kneading of the resin, the dispersibility of the resin dispersed in the matrix resin (hereinafter referred to as “dispersed resin”) is insufficient, or the dispersed resin aggregates and the particles having an excessively large particle diameter are formed. Is easy to form. In addition, the film may not be stretched uniformly due to poor releasability at the interface between the matrix resin and the dispersed resin particles. Therefore, according to the method, the pores formed in the obtained film are not sufficiently reduced, and as a result, the film tends to have properties that are not satisfactory in gas permeability and water resistance. For this reason, a method of increasing the dispersibility of the polyester resin by adding a polyester elastomer when kneading the polyolefin resin and the polyester resin has been proposed (Japanese Patent Application Laid-Open No. 64-26655). However, the dispersibility of the dispersing resin in the matrix resin is still insufficient, and the resulting porous film cannot be satisfied with water resistance such as water pressure.

[0005] From such a background, the development of a method capable of producing a porous film having excellent gas permeability and water resistance, having excellent dispersibility of the dispersing resin in the matrix resin, excellent film stretchability, and the like. Was desired.

[0006]

Means for Solving the Problems The present inventors diligently studied a method for solving the above-mentioned disadvantages. As a result, the dispersibility of the polycarbonate resin and the stretchability of the film are significantly improved by further blending a thermoplastic elastomer with the combination of the polyolefin resin and the polycarbonate resin,
The inventors have found that the resulting porous film has good gas permeability and water resistance, and have completed the present invention.

That is, according to the present invention, a resin composition comprising (a) 100 parts by weight of a polyolefin resin, (b) 20 to 100 parts by weight of a polycarbonate resin, and (c) 5 to 50 parts by weight of a thermoplastic elastomer is formed into a film, It is a porous film obtained by stretching at least in a uniaxial direction.

As the polyolefin resin used in the present invention, known resins can be used without any limitation.
For example, polyethylene, polypropylene, polybutylene, ethylene-α olefin copolymer, propylene-α
Olefin copolymers and the like can be mentioned. Here, as the α-olefin as the copolymer component, for example, ethylene,
Examples include propylene, hexene, and octene. Among them, it is most preferable to use polyethylene or an ethylene-α-olefin copolymer. Where polyethylene is
Any material such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene may be used.

Known polycarbonate resins are used without any limitation. It is preferred to use aromatic polycarbonates. Specific examples include polybisphenol A carbonate and polytetrachlorobisphenol A carbonate starting from bisphenol A and its derivatives, and copolymers thereof, such as copolymers with dioxydiarylalkane.

The viscosity at 260 ° C. of the melt-kneaded polycarbonate resin is preferably 1 to 100 times, preferably 3 to 30 times the viscosity of the polyolefin resin. At this viscosity, the polycarbonate resin is easily dispersed as fine spherical particles in the polyolefin resin, and as a result, the interfacial releasability between the dispersed particles and the polyolefin resin when the film is stretched becomes the best, and The generated pores tend to be fine. The viscosity of such a polycarbonate resin at 260 ° C.
Generally, 1 × 10 ⁴ to 1 × 10 ⁶ Pa · S, preferably 3 ×
Adopted from 10 ^{4 to} 3 × 10 ⁵ Pa · S.

The addition amount of the polycarbonate resin is 20 to 100 parts by weight, preferably 30 to 60 parts by weight, based on 100 parts by weight of the polyolefin resin. When the addition amount of the polycarbonate resin is less than 20 parts by weight, the number of micropores generated is too small to be a communication hole, and gas or liquid permeability cannot be obtained. On the other hand, by increasing the blending amount of the polycarbonate resin, the number of pores to be generated increases and the gas permeability increases, but if the amount is excessively increased, the peeling interface increases, and the uniformity of stretching decreases. . For these reasons, when the addition amount of the polycarbonate resin exceeds 100 parts by weight, not only is it difficult to form a film having a thickness of 50 μm or less, but also the film frequently breaks in the stretching step, which is not practical. In addition, the water resistance of the obtained film is not sufficient, which is not preferable.

As the thermoplastic elastomer used in the present invention, known elastomers can be used without any limitation.
Such an elastomer has an initial flexural modulus of 10 to 20.
It is preferable to use an elastic body having a property of 0 MPa, preferably 10 to 100 MPa. Further, it is preferable to use one having excellent thermal stability at a temperature higher than the melting point of the polycarbonate resin. In the present invention, by combining this thermoplastic elastomer with the combination of the polyolefin resin of the matrix resin and the polycarbonate resin of the dispersion resin, the thermoplastic elastomer has a synergistic effect on the dispersibility of the polycarbonate resin and the stretchability of the film. To significantly improve such physical properties. Therefore,
According to the present invention, it is possible to obtain a porous film having extremely good gas permeability and water resistance.

In the present invention, if the above-mentioned thermoplastic elastomer is specifically described, an ethylene-propylene copolymer or an ethylene-propylene-diene copolymer is used as a blend component, a block copolymer component or a graft copolymer component to have elasticity. Polyolefin-based thermoplastic elastomer provided; polyester-based thermoplastic elastomer whose soft segment is composed of polyalkylene oxide, polylactone, etc .; polyurethane-based thermoplastic elastomer whose soft segment is composed of polyalkylene oxide, polylactone, linear polyester, etc .; polystyrene-based Thermoplastic elastomer; Polyamide thermoplastic elastomer; Polybutadiene thermoplastic elastomer; Polyfluorocarbon thermoplastic elastomer and the like. Among them, it is most preferable to use a polyolefin-based thermoplastic elastomer or a polyester-based thermoplastic elastomer.

The addition amount of these thermoplastic elastomers is as follows:
It is appropriate to add 5 to 50 parts by weight based on 100 parts by weight of the polyolefin. When the addition amount of the thermoplastic elastomer is 5 parts by weight or less, the effect is hardly expected. On the contrary, when the addition amount exceeds 50 parts by weight, the interface between the polyolefin resin and the polycarbonate resin is stretched without peeling, and sufficient gas is obtained. No permeability is obtained.

In the present invention, it is preferable to further mix a liquid surfactant in addition to the components of the polyolefin resin, the polycarbonate resin, and the thermoplastic elastomer in order to further improve the effects of the present invention. In the present invention, the liquid surfactant is a liquid organic compound having a nonpolar portion and a hydrophilic portion together, for example, a polyetherester or polyetherether having a repeating unit of an ether portion of about 5 to 20, Examples thereof include a polysiloxane bonded to an alkyl group having a hydroxyl group or an amino group at a terminal, a liquid polyolefin having a hydroxyl group, an amino group, or the like at a terminal, and a low molecular weight liquid polyester.

The amount of the liquid surfactant to be added is preferably 1 to 10 parts by weight based on 100 parts by weight of the polyolefin resin. When the addition amount is 1 part by weight or less, the effect can hardly be expected. On the contrary, when the addition amount exceeds 10 parts by weight, the resin is not sufficiently sheared at the time of kneading, so that the effect of improving the dispersibility of the polycarbonate resin is sufficient. Or the liquid surfactant may bleed out to the surface of the obtained film.

In the present invention, in order to impart various properties to the film produced as required, additives suitable for the properties can be added. For example, antioxidants,
Examples include a weathering agent such as an ultraviolet absorber and carbon black, an antiblocking agent, a flame retardant, a pigment, a colorant, a matting agent, an antistatic agent, an enzyme, a deodorant, a fragrance, a pesticide, and the like.
In addition, other components may be added as needed as long as the characteristics of the present invention are not impaired.

In the present invention, the method for forming the resin composition comprising the above components into a film is not particularly limited, and it can be performed by a known film forming method. Generally, it is preferable to adopt extrusion molding using an inflation die, a T die, or the like. In addition, the resin composition used in the present invention, particularly a composition having a high viscosity of a polycarbonate resin as a dispersing resin component, is liable to die swell when kneading each component. Therefore, in the present invention, when kneading each component of the resin composition, the first half of the extruder is set to a temperature not lower than the melting point of all components, while the extruder tip is not higher than the glass transition temperature of the polycarbonate resin and polyolefin. It is preferable to knead the mixture with a negative temperature gradient such that the temperature is equal to or higher than the melting point of the resin. Kneading with such a negative temperature gradient is also effective from the viewpoint of preventing reaggregation of the polycarbonate resin.

Next, the obtained kneaded material is extruded into a film at a temperature not lower than the melting point of the polyolefin resin and not higher than the glass transition temperature of the polycarbonate resin by an extruder having a die at the tip. In the present invention, the film formation step does not necessarily need to be performed through the extruder in two steps, ie, the kneading step, and the kneading extruder may be directly formed by attaching a die to the tip of the extruder.

In the present invention, the thus-obtained unstretched film is stretched at least uniaxially in a usual stretching temperature range, preferably 10 to 200 ° C., depending on the type of the polyolefin resin. In the stretching, it is preferable to perform the preliminary stretching at a low magnification, and it is usually sufficient to perform the preliminary stretching about 1.2 times in the MD direction.

The stretching ratio is not particularly limited, but is preferably in the range of 1.5 to 10 times in terms of area ratio in consideration of the tear strength and water resistance of the obtained film. It is preferable to select an appropriate magnification according to the blending amount of the polycarbonate resin and the required gas permeability. In the present invention, when the area magnification is 2 to 5 times, the uniformity of stretching becomes the best. Therefore, in the present invention, if the film is stretched at such a draw ratio and the gas permeability is controlled by the blending amount of the polycarbonate, a film having the best balance between gas permeability, mechanical properties and water resistance and a small heat shrinkage can be obtained. Can be obtained and is preferred.

[0022]

The film thus obtained is excellent in the dispersibility of the polycarbonate resin and the stretchability of the film, and is excellent in the appearance of the film, gas permeability such as water vapor and water resistance.

Since the film obtained by the present invention has the above-mentioned excellent properties, it is suitably used for applications requiring gas permeability and water resistance. For example, patch medicine equipment such as ship medicine and paste medicine, sanitary materials such as disposable diapers,
Examples include various packaging materials such as packaging for seafood and desiccants, simple clothing such as gloves and clothing, clothing fields such as sheets and surgical gowns, other construction materials, and civil engineering materials. In particular, it is optimal for applications such as patches and sanitary materials, since there is almost no deviation in pH of the film derived from the inorganic filler and almost no ash after burning.

[0024]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention.

The physical properties of the films shown in Examples and Comparative Examples were measured by the following methods.

Moisture permeability: according to JIS-Z-208.
(40 ° C., 90 RH%) Maximum pore diameter (Dmax): conforms to ASTM-F-316.

Water resistance: according to JIS-L-1092.

The resins used in the following examples are as follows.

(A) Polyolefin resin: Linear low density polyethylene (LLDPE) having a viscosity of 1 × 10 ⁴ Pa · S at 260 ° C .: Ultzex 15
20L (manufactured by Mitsui Petrochemical)-Ethylene-butene copolymer (ULDPE) having a viscosity of 7 × 10 ³ Pa · S at 260 ° C .: Toughmer A409
0 (manufactured by Mitsui Petrochemical) (b) Polycarbonate resin: Polybisphenol A carbonate resin (PC) having a viscosity of 7 × 10 ⁴ Pa · S at 260 ° C .: Panlite K1300 (manufactured by Teijin Chemicals) (c) Thermoplastic elastomer -Polyolefin-based thermoplastic elastomer (TPO) having an initial flexural modulus of 90 MPa: Mirastomer 8030
(Mitsui Petrochemical)-Polyester thermoplastic elastomer (TPEE) with initial flexural modulus of 35 MPa: Hytrel 3548 (Mitsui DuPont Polychemical) (d) Liquid surfactant-Polyethylene glycol monooleate liquid surfactant : MYO-10 (manufactured by Nikko Chemicals) ・ Terminal hydroxylated polybutadiene-based liquid surfactant: GI-
1000 (manufactured by Nippon Soda) (e) Polyester resin (PEst) C700N (manufactured by Teijin Chemicals) Examples 1 to 7 and Comparative Examples 1 to 4
After mixing for 1 minute, the mixture was extruded into a strand using a twin-screw extruder set at 160 to 260 ° C. with a negative temperature gradient toward the tip, and cut into pellets.

[0030] The obtained pellets were screwed with a screw diameter of 30 mm.
1 mm lip gap attached to an extruder with φ, L / D = 24
Extruded at 150-170 ° C from the die of
A cooling roll having a diameter of 100 mm and circulating cooling water at a temperature of 100 ° C. was brought into contact with the cooling roll and taken out at a rate of 1 m / min to obtain a film having a thickness of about 30 μm.

The obtained film was stretched in the MD direction using a roll stretching machine, and then further stretched in a direction perpendicular to the above stretching direction, if necessary. Table 2 shows the values of the moisture permeability, the maximum pore diameter, and the water pressure resistance of the obtained porous film.

[0032]

[Table 1]

[0033]

[Table 2]

Claims (1)

(57) [Claims] 1. A resin composition comprising (a) 100 parts by weight of a polyolefin resin, (b) 20 to 100 parts by weight of a polycarbonate resin, and (c) 5 to 50 parts by weight of a thermoplastic elastomer, is formed into a film, and is formed in at least a uniaxial direction. A method for producing a porous film, comprising: