JPH06298977A - Porous film - Google Patents

Abstract

PURPOSE:To obtain an odorless porous film, excellent in moisture permeability, leakage preventing properties, heat sealability and surface strength and useful as a sanitary material, etc., by melt molding a composition composed of a polyolefinic resin, etc., in a specific proportion and then subjecting the resultant film to drawing treatment. CONSTITUTION:The porous film is obtained by melt molding a composition comprising (A) 100 pts.wt. polyolefinic resin such as PE, (B) 10-130 pts.wt. polyester resin, (C) a thermoplastic elastomer or an olefinic copolymer blended in an amount of 0.05-30 pts.wt. [based on 100 pts.wt. sum total of the components (A) and (B)] and (D) an oily component such as liquid paraffin blended in an amount of 1-30 pts.wt. [based on 100 pts.wt. sum total of the components (A) and (B)] and subjecting the resultant film to the drawing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous film, and more specifically, it has a supple texture, good moisture permeability and leakproofness and strength useful for sanitary materials, medical materials, clothing materials and the like. And a porous film having the same.

[0002]

2. Description of the Related Art Conventionally, a composition in which a polyolefin resin such as polyethylene or polypropylene is added and mixed as an inorganic filler with a large amount of 40% by weight or more of inorganic particles such as calcium carbonate at the time of film formation is formed into a film. After that, a porous film obtained by uniaxially or biaxially stretching is widely used as a moisture-permeable or air-permeable film.

The above-mentioned porous film can be produced relatively inexpensively, but has the following problems. In the case of biaxial stretching, there arises a problem in stretchability and surface strength for uniformly performing the whitening phenomenon, that is, the phenomenon of interfacial peeling between the filler and the resin matrix. Since the adhesiveness between the filler and the matrix resin is low, opening by stretching is easy, but on the other hand, the inorganic filler is likely to fall off, which may impair the production environment conditions. Usually, calcium carbonate is generally used as the inorganic filler, but the hydrophilicity of calcium carbonate causes the waterproof property to decrease with time. Since the inorganic filler is contained in a large amount, there is a possibility that the fusion between the films or the film and another article may be melted and bonded together, that is, fusion due to so-called heat sealing or ultrasonic embossing may be hindered. When an adhesive or a pressure-sensitive adhesive is used for the film, the inorganic filler on the surface of the film may fall off to cause a decrease in the adhesive strength. In particular, when used as a constituent material that shares a fastening function with a fastening tape, such as a moisture-permeable leak-proof film of a disposable diaper, peeling of the fastening tape during use due to dropping of the filler. Problems such as the above occur, and the field of use is extremely limited.

In order to solve such a problem, two kinds of resins having a small compatibility with each other are melt-kneaded into a film, and then uniaxially or biaxially stretched to obtain a porosity using a phase separation behavior between resins. A variety of functional films have been proposed.

For example, JP-A-58-198536 discloses a mixture of a thermoplastic resin A and a thermoplastic resin B having a low compatibility with the thermoplastic resin A and a melting point higher than 20 ° C. Melt-kneading at a temperature equal to or higher than the melting point of the thermoplastic resin B, then formed into a sheet at a temperature higher than the melting point of the thermoplastic resin A and lower than the melting point of the thermoplastic resin B, and further the melting point of the thermoplastic resin A. A porous film obtained by stretching at the following temperature is described.

Further, in JP-A-62-218428 and JP-A-62-297130, melt kneading,
Liquid or wax polybutadiene, liquid polyisoprene, ethylene-propylene random copolymer is used as a viscosity modifier for the matrix resin in order to control the stretchability and porosity after film formation by the particle size of the dispersed phase. Porous films to which elastomers such as are added are described.

Further, in JP-A-64-26655 and JP-A-4-142341, a polyolefin resin, a polyester / polyether type thermoplastic elastomer, and a thermoplastic polyester having an intrinsic viscosity of 0.5 or less are essential. As a component, the porous film described in JP-A No. 64-26655 has a polyester / polyether type thermoplastic elastomer added to adjust the dispersed particle size, and is further disclosed in JP-A-4-142341. Describes a porous film in which a polyester / polyether type thermoplastic elastomer is added to adjust the dispersed particle size and an ethylene copolymer is added as a gas permeability improver.

[0008]

However, all of the above-mentioned porous films are provided with breathability and moisture permeability by being stretched, but they have flexibility, water pressure resistance, odor, and thermal adhesion. They have not yet satisfied all of their demands such as sex.

That is, the porous film described in JP-A-58-198536 mentioned above is composed of a thermoplastic resin A which is a continuous phase and a thermoplastic resin B which has a small compatibility with the thermoplastic resin A. Since it is only a component, it is difficult to control the stretchability of the continuous phase resin and the partial peeling at the (continuous phase-dispersed phase) interface. There is a problem in that pores cannot be obtained, or conversely, the pores become too large and the leakproofness decreases.

In the porous films described in JP-A-62-218428 and JP-A-62-297130, the particle size can be controlled to some extent by adding an elastomer which is a viscosity modifier. However, there is a problem in that it is not always appropriate for controlling the stretching process and openness of the film. For example, in the case of stretching at a low magnification, uniform stretchability is lowered, the appearance becomes poor, and further, sufficient openings cannot be obtained, and in stretching at a high magnification, regardless of the dispersed particle size (continuous The phase-dispersed phase) is rapidly separated at the interface, resulting in the formation of more pores than necessary, which causes a drop in water pressure resistance. Furthermore, many of the above-mentioned elastomers emit an odor, and it is difficult to use them as a hygienic material.

Further, in the porous films described in JP-A-64-26655 and JP-A-4-142341, the particle diameter can be controlled to some extent by adding an elastomer for adjusting the dispersed particle diameter. However, there is a problem in that it is not always appropriate for controlling the stretching process and openness of the film.

Therefore, an object of the present invention is to provide a porous film which has good stretchability, moisture permeability, leakproofness, heat sealability and surface strength, and which can be used as a sanitary material and is close to odorless. It is to be.

[0013]

The present invention shows a polyolefin resin (A), a polyester resin (B), a thermoplastic elastomer or an olefin copolymer (C), and an oil component (D) below and in the following. The above object is achieved by providing a porous film which is obtained by subjecting a film obtained by melt-molding a composition containing the compounding ratio to a stretched film. 10 to 130 parts by weight of the polyester resin (B) with respect to 100 parts by weight of the polyolefin resin (A), and 100 parts by weight of a mixture of the polyolefin resin (A) and the polyester resin (B). , 0.05 to 30 parts by weight of the thermoplastic elastomer or the olefin copolymer (C), and 1 to 3 of the oil component (D).
0 parts by weight.

The porous film of the present invention will be described in detail below. The porous film of the present invention is characterized in that the film obtained by melt-molding a specific composition is stretched.

The above specific composition used in the present invention contains the polyolefin resin (A) as an essential component for forming a continuous phase (matrix phase). Examples of the polyolefin resin (A) (hereinafter referred to as “resin (A)”) include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, polybutene, and modified products or derivatives thereof. It is also possible to use a commercially available product.

The above-mentioned specific composition used in the present invention contains the polyester resin (B) as an essential component for forming the dispersed phase. Examples of the polyester resin (B) (hereinafter, referred to as “resin (B)”) include polyethylene terephthalate, polybutylene terephthalate, and modified products thereof. As the above-mentioned modified product, for example, as dicarboxylic acid in the molecular chain, other aromatic dicarboxylic acid such as isophthalic acid, aliphatic dicarboxylic acid such as adipic acid, sebacic acid, or the like is used, and as ethylene glycol as a diol component, , 1,4-butanediol, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, etc.,
Examples thereof include polyesters polymerized by various combinations of these. Further, as the resin (B), a commercially available product can be used.

The mixing ratio of the resin (A) to the resin (B) is 100 parts by weight of the resin (A) with respect to the resin (B).
Is 10 to 130 parts by weight, preferably 40 to 110 parts by weight. When the amount of the resin (B) is less than 10 parts by weight,
The amount of dispersed phase is small and no through-holes are formed in the film,
Good moisture permeability cannot be obtained. On the other hand, when the amount exceeds 100 parts by weight, the resin (A) that should be the matrix phase and the resin (B) that should be the dispersed phase are likely to undergo phase inversion, and it is difficult to form the porous film intended by the present invention. Therefore, it must be within the above range.

The above-mentioned specific composition used in the present invention contains the above-mentioned thermoplastic elastomer or olefin copolymer (C) as an essential third component. The thermoplastic elastomer (C) and the olefin copolymer (C) used as the indispensable third component are the dispersed state of the resin (B) which is the dispersed phase, and the dispersed phase of the resin (B) and the resin. It is a component for controlling the degree of peeling that occurs at the interface with the continuous phase due to (A), and is required to have high compatibility with the resin (B) that is the dispersed phase.

Preferred examples of the thermoplastic elastomer (C) include polystyrene as a hard segment and styrene-based thermoplastic elastomer which is a block copolymer having butadiene rubber, hydrogenated butadiene rubber or isoprene rubber as a soft segment. A commercially available product can also be used.

The above olefin copolymer (C) is
It is a block copolymer having a segment having a large compatibility with the resin (A) which is a continuous phase. For example, when polyethylene is used as the resin (A), the olefin copolymer (C) is ethylene. -Acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid-acrylic acid ester copolymer, ethylene-methacrylic acid- Acrylic ester copolymer, ethylene-vinyl acetate-glycidyl methacrylate copolymer, ethylene-maleic anhydride-
Preferable are ethylene copolymers composed of one kind or a mixture of two or more kinds selected from acrylate copolymers, and commercially available products can be used.

Further, the above specific composition used in the present invention contains an oil component (D) as an essential fourth component. The oil component (D) is a component as a softening agent, and examples of the oil component (D) include liquid paraffin, α-olefin copolymer oil such as ethylene-α-olefin copolymer, and process oil. Preferred examples are commercial products.

In the present invention, the thermoplastic elastomer or the olefin copolymer (C) used as the essential third component in the specific composition, and the essential fourth component.
The blending ratio of the oil component (D) used as a component is
0.05 to 30 parts by weight of the thermoplastic elastomer or olefin copolymer (C), 100 parts by weight of the mixture of the resin (A) and the resin (B), and the oil component (D)
Is 1 to 30 parts by weight. The blending ratio of the thermoplastic elastomer or the olefin copolymer (C) is 0.0
If the amount is less than 5 parts by weight, the uniform stretchability will be deteriorated and the desired sheet cannot be obtained. If the amount is more than 30 parts by weight, the cost will increase and the properties of the matrix will change. Also,
When the blending ratio of the oil component (D) is less than 1 part by weight, uniform stretchability is deteriorated, and thus the target sheet cannot be obtained. When it exceeds 30 parts by weight, the oil component bleeds out, resulting in stickiness. Occurs.

The porous film of the present invention contains the resin (A), the resin (B), the thermoplastic elastomer or the olefin copolymer (C), and the oil component (D) in the mixing ratio. A film obtained by melt-molding the composition is stretched.

When the above composition is melted and kneaded, it is mixed macroscopically, but is microscopically phase-separated into a sea-island (continuous phase-dispersed phase) structure, which is molded (film formation). When the film obtained by) is stretched at an appropriate temperature, a part of the phase-separated resin interface is peeled off, and fine continuous pores are generated from the front surface to the back surface of the film, which results in moisture-permeable porosity. A film is obtained. At this time, a component having a large volume fraction of the resin (A) and the resin (B) tends to become a sea phase (continuous phase), and a component having a high melt viscosity becomes an island phase (disperse phase). Tends to become. Therefore, since the proportion of the dispersed phase can be increased by selecting the resin (B) having a high melt viscosity as the resin (B), various resins should be used according to the required moisture permeability and water pressure resistance. You can

To obtain a film by melt-molding the composition, for example, the composition is dry-blended with a Henschel mixer or the like, and then the resin (A) and the resin (B) are mixed with a biaxial kneader or the like. ) Are melted and kneaded at a temperature equal to or higher than the melting points of both to form pellets, and then the obtained pellets are molded (film formation) by an inflation extruder or the like.
It can be obtained by doing.

As described above, the resin (A) and the resin (B) are melted and kneaded at a temperature equal to or higher than the melting points of both, and the resin (B) is dispersed in the resin (A) to form an emulsion form. . When the compatibility of the resin (A) and the resin (B) is good, the size of the island formed by the resin (B) which is the dispersed phase becomes small and the number increases.

The above-mentioned stretching treatment can be carried out by stretching the above-mentioned film obtained by melt-formation by roll longitudinal uniaxial stretching or the like. At this time, it is preferable that the stretching is performed at a stretching temperature of 30 to 140 ° C. and a stretching ratio of 1.2 to 10.

The above composition is melt-molded and then subjected to the above-mentioned stretching treatment, whereby a part thereof is separated at the interface between the continuous phase and the dispersed phase to form fine pores. At that time, the average pore diameter is It is preferable to prepare 0.1 to 100 μ, particularly 0.1 to 20 μ. If the average pore diameter is less than 0.1 μ, the moisture permeability is low, and if it exceeds 100 μ, the moisture permeability is large but the leakproofness is insufficient.

In order to prevent the dispersed particles from falling off, it is preferable to adjust the average particle diameter of the dispersed phase to 0.5 to 30 μ as the above average pore diameter. If it is less than 0.5 μm, the open pore size tends to be small, and dispersed particles may fall off when trying to obtain large pores. On the other hand, when it exceeds 30 μ, the aperture diameter may be large and the leakproof property may be deteriorated, which is not preferable.

In the present invention, the above composition contains a heat stabilizer, a slip agent, an anti-blocking agent, a coloring agent,
An antistatic agent or the like may be added to form a porous film.

[0031]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these.

[Example 1] Linear low-density polyethylene (L
LDPE / Mitsui Petrochemical Industry Co., Ltd., "Ultox", MI = 2) 50 parts by weight, 1,4-cyclohexanedimethanol-modified polyethylene terephthalate (PET)
G / Eastman Kodak Co., Ltd.) 45 parts by weight, ethylene-maleic anhydride-acrylic acid ester copolymer (E-EA-MAH / Sumitomo Chemical Co., Ltd.) as the third component
2.5 parts by weight of "Bondaine", and liquid paraffin as a fourth component (Chuo Kasei, "350S") 9.5.
After dry blending a composition comprising 1 part by weight with a Henschel mixer, a twin-screw kneading extruder (manufactured by Ikegai Tekko KK,
"PCM-45", L / D = 26) was melt-kneaded at 200 ° C. to give pellets. The pellets were film-formed by an inflation extruder having a screw diameter of 50 mm and L / D = 28 to obtain a film. Then, the obtained film was stretched by roll longitudinal uniaxial stretching to obtain a porous film.

Example 2 The third component used in Example 1 was used as a styrene-isoprene-styrene block copolymer (S
A porous film was obtained by forming and stretching in the same manner as in Example 1 except that IS / Shell Chemical Co., Ltd. was used.

Example 3 A film was formed in the same manner as in Example 1 except that the fourth component used in Example 1 was ethylene-α-olefin copolymer oil (manufactured by Mitsui Petrochemical Industry Co., Ltd.).
The film was stretched to obtain a porous film.

[Example 4] A film was formed and stretched in the same manner as in Example 1 except that the fourth component used in Example 1 was process oil (manufactured by Shell Chemical Co., Ltd., "Shelf Rex"). A film made was obtained.

Example 5 The same as Example 1 except that the third component used in Example 1 was an ethylene-acrylic acid ester copolymer (EEA / Nippon Petrochemical Co., Ltd., “LEXRON”). The film was formed and stretched to obtain a porous film.

Comparative Example 1 Linear low density polyethylene (L
LDPE / Mitsui Petrochemical Industry Co., Ltd., "Ultox", MI = 2) 50 parts by weight, 1,4-cyclohexanedimethanol-modified polyethylene terephthalate (PET)
G / Eastman Kodak Co., Ltd. 45 parts by weight, and liquid hydrogenated polyisoprene (Kuraray Co., Ltd., "Klaprene LIR-290") 2.5 parts by weight as a third component After dry blending with a mixer, twin-screw kneading extruder (made by Ikegai Tekko Co., Ltd., "PC
M-45 ", L / D = 26) was melt-kneaded at 200 ° C. to give pellets. Screw the pellet with a screw diameter of 50
A film was obtained by forming a film with an inflation extruder of mm, L / D = 28. The obtained film was stretched by roll longitudinal uniaxial stretching to obtain a porous film.

Comparative Example 2 Linear low density polyethylene (L
LDPE / Mitsui Petrochemical Industry Co., Ltd., “Ultox”, MI = 2, 37 parts by weight, calcium carbonate (Shiraishi Industry Co., Ltd., “Ryton”) 58 parts by weight, and liquid paraffin (Chuo Kasei, "350S") 10 parts by weight of a composition was dry blended with a Henschel mixer, and then a twin-screw kneading extruder (manufactured by Ikegai Tekko KK, "PCM-4").
5 ", L / D = 26) and melt-kneaded at 200 ° C. to give pellets. Screw the pellet with a screw diameter of 50 mm, L
A film was obtained by forming a film with an inflation extruder of / D = 28. The obtained film was stretched by roll longitudinal uniaxial stretching to obtain a porous film.

The following tests were conducted on the porous films obtained in the above Examples and Comparative Examples, and evaluated. The results are shown in [Table 1] and [Table 2]. The test method for each performance item is as follows. -Water vapor transmission rate: JIS Z-0208-Water pressure resistance: JIS L-1092-Tensile strength: JIS K-7113-Heat sealability: Using a 3 mm wide heating plate at 118 ° C for 0.2 seconds, 5 kg / cm ² pressure The heat-sealed sample was subjected to T and peeled, and the strength was evaluated.
The sample was prepared by cutting it so as to have a width of 30 mm and perpendicular to the heat-sealing line. In this test, the adhesive strength between the same films was measured. Dispersion of dispersed phase: The transfer of dispersed phase particles existing on the surface of the porous film to the adhesive tape was measured by adhering the adhesive tape to the surface of the porous film and peeling it off. At the time of measurement, the surface of the adhesive tape was analyzed by the ATR method using FT-IR and determined. The evaluation is as follows. ◯: Absorption peak peculiar to dispersed phase particles is not detected. X: An absorption peak specific to the dispersed phase particles is detected. -Appearance / Smell The sensory test by 10 people's monitor evaluated by the following criteria. ○: 8 or more people do not care about the appearance and smell. Δ: 5 or more and less than 8 people do not care about the appearance and smell. ×: 4 people or less who do not care about appearance and smell.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

EFFECT OF THE INVENTION The porous film of the present invention has good stretchability, moisture permeability, leakproofness, heat sealability and surface strength, and is almost odorless and can be used as a sanitary material. It is useful as a backsheet for sanitary materials such as diapers and sanitary napkins, and specifically, has the following effects (1) to (3). Since no inorganic filler is contained, the inorganic filler does not fall off and environmental conditions are impaired, and the hydrophilicity of the inorganic filler to be used does not deteriorate the waterproof property over time. In the secondary processing, the films of the present invention or the film of the present invention and other articles are melted and joined, so that fusion such as so-called heat sealing or ultrasonic embossing is possible, and thus an adhesive such as hot melt In addition, there is an advantage that an adhesive coating device is not required and the cost is reduced, and at the same time, the trouble of the processing equipment is reduced and the maintenance is simplified. When an adhesive or pressure-sensitive adhesive is used for the porous film of the present invention, dispersed particles on the surface of the film do not easily fall off, so that it is possible to suppress a decrease in the adhesive force of the pressure-sensitive adhesive or the like. The component used as the third component in the porous film of the present invention is odorless, and stable stretchability and openability can be controlled, so that the field of use is not limited.

Claims (1)

[Claims] 1. A composition containing a polyolefin resin (A), a polyester resin (B), a thermoplastic elastomer or an olefin copolymer (C), and an oil component (D) in the following mixing ratios. A porous film obtained by subjecting a film obtained by melt molding to a stretching treatment. 10 to 130 parts by weight of the polyester resin (B) with respect to 100 parts by weight of the polyolefin resin (A), and 100 parts by weight of a mixture of the polyolefin resin (A) and the polyester resin (B). , 0.05 to 30 parts by weight of the thermoplastic elastomer or the olefin copolymer (C), and 1 to 3 of the oil component (D).
0 parts by weight.