JPH0662796B2 - Porous film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a porous film, and its object is to provide a supple air among sanitary materials, medical materials, clothing materials and the like. In other words, it is to provide a porous film which is required to have both good moisture permeability and leakproofness / strength. Among them, it is an object of the present invention to provide a porous film that is a constituent material that shares a fastening function with a fastening tape by a fastening tape, such as a moisture-permeable leak-proof film of a diaper that is used, and also has the above physical properties. It is a thing.

[Conventional technology and problems]

By kneading a polyolefin resin with a filler and uniaxially or biaxially stretching a film obtained by melt molding,
Many attempts have been made to obtain a porous film.

These porous films have a problem that uniaxial stretching has extremely weak strength anisotropy, that is, tear strength in the stretching direction and tensile stress in the transverse direction. As a method of improving the anisotropy of strength, there is a method of stretching at a draw ratio as low as possible, but a stretched film at a low draw ratio cannot provide a uniform stretched film.

In biaxial stretching, although the problem of strength anisotropy is solved, the problem of markedly deteriorated drawability occurs.

On the other hand, in the compounding system of only polyolefin resin and filler,
Even if stretched, a porous film having a supple texture cannot be obtained. As a means to solve these problems in recent years,
A combination system of several additives including a liquid hydrocarbon as a third component has been proposed in the system of the polyolefin resin and the filler. For example, as a third component for improving the above problems, JP-A-58-15538 discloses liquid polybutadiene, liquid polybutene, and liquid hydroxy terminated polybutadiene, and JP-A-58-149925 discloses liquid polyisoprene. Rubber is disclosed.

However, even these improved techniques are not sufficiently satisfactory in terms of the balance between moisture permeability and tear strength in the stretching direction (vertical tear strength). Especially when it is used as a constituent material that shares a fastening function with a fastening tape, such as a moisture-permeable leak-proof film of a diaper, it is difficult to attach the fastening tape if the vertical tear strength is weak. At the time of peeling and during use, the stress is locally concentrated on the portion around the fastening tape of the moisture-permeable leakproof film, so that tearing occurs at the portion around the fastening tape, and the field of use is extremely limited.

[Means for solving problems]

As a result of intensive studies aimed at providing a porous film that solves the above-mentioned problems, the present inventors have found that by blending a specific ester mixture as the third component, the supple texture of the porous film is improved. Thus, the inventors have found that the vertical tear strength and the appearance can be improved while maintaining good moisture-permeable leakproofness, and have completed the present invention.

That is, the present invention relates to a polyolefin resin, a filler, and a third
A composition containing the components is melt-formed into a film,
A porous film obtained by subjecting the film to a stretching treatment, wherein the third component is a mixture of a monoester A composed of a monobasic acid and a monohydric alcohol and a polyester B composed of a polybasic acid and a polyhydric alcohol. The present invention relates to a porous film characterized in that

Hereinafter, the present invention will be described in more detail.

The polyolefin resin used in the present invention refers to those containing ethylene, propylene, butene and other monoolefin polymers and copolymers as main components, for example, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, Examples include polypropylene, ethylene-propylene block copolymers, polybutene, ethylene-vinyl acetate copolymers, and mixtures thereof. Of these, linear low-density polyethylene is preferable because it is flexible and tough.

In the present invention, as the filler, inorganic and organic fillers are used, and as the inorganic filler, calcium carbonate,
Gypsum, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium phosphate, aluminum hydroxide, zinc oxide, titanium oxide, alumina, mica, zeolite,
Carbon black or the like is used, and as the organic filler,
Wood flour, pulp flour, etc. are used. You may use these individually or in mixture.

The average particle size of the filler is preferably 30 μm or less, more preferably 10 μm or less, and most preferably 0.5 to 5.0 μm.

Surface treatment of the filler is important for uniform dispersion in the resin,
The surface treatment agent is preferably one that can make the surface hydrophobic, such as fatty acid or a metal salt thereof.

The monoester A used in the present invention has 10 carbon atoms.
Any ester obtained by dehydration condensation of the above monobasic acid such as monocarboxylic acid and monohydric alcohol such as monoalcohol having 10 or more carbon atoms may be used, but preferably the molecular weight is
It is a monoester having 240 or more, more preferably a monoester having a branched hydrocarbon chain and having 20 or more carbon atoms.

Polyester B used in the present invention includes polybasic acids such as dicarboxylic acid, tricarboxylic acid or tetracarboxylic acid, and polyhydric alcohols such as diols, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol and sucrose. Therefore, the polyester obtained by dehydration condensation may have a total carbon number of 50 or more. The terminal group may remain in the form of carboxylic acid or alcohol. When the terminal is a carboxylic acid, most of it is esterified with a monoalcohol of a long-chain hydrocarbon such as stearyl alcohol, oleyl alcohol, and Guerbet alcohol, and when the terminal is an alcohol, most of it is stearic acid, hydroxystearic acid, End-capped polyesters esterified with a long-chain hydrocarbon monocarboxylic acid such as oleic acid are preferred, but in these cases as well, it is not necessary that all the ends be capped. or,
An ester containing a branched acid or alcohol as an ester constituent is more preferable.

The monoester A as the third component contributes to the improvement of the moisture permeability and the vertical tear strength of the obtained porous film, and the polyester B contributes to the improvement of the moisture permeability and the appearance.

A porous film within the scope of the present invention tends to have a reduced appearance when trying to improve moisture permeability and vertical tear strength, and a lower vertical tear strength when trying to improve moisture permeability and appearance. Therefore, in order to improve all of these physical properties at the same time, there is a limit only by the single third component, and the third component needs to be a composite composition composed of components having different functions.

The blending weight ratio A / B of the monoester A and the polyester B as the third component is preferably 3/7 to 7/3, but it is 1/9 to 10 depending on the desired level of moisture permeability, vertical tear strength, and appearance according to the application. You can choose freely within the range of 9/1.

The preferred blending ratio of the polyolefin resin, the filler and the third component in the present invention is 50 to 250 parts by weight of the filler and 5 to 50 parts by weight of the third component to 100 parts by weight of the polyolefin resin.

The polyolefin resin, the filler and the third component can be mixed by a usual method. For example, after premixing with a Henschel mixer or the like, kneading with a twin-screw extruder can be performed.

The film may be formed by a usual method, that is, an inflation method or a T-die method. The stretching may be uniaxial roll stretching, biaxial sequential or simultaneous stretching, but uniaxial stretching with a stretching ratio of 1.5 to 3.0 is particularly preferable.

〔Example〕

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

The composition and characteristic values of the ester used in the examples are shown in Table 1.
Shown in. These esters were produced by a conventional dehydration esterification reaction.

Example 1 Linear low density polyethylene resin (Ultzex 3010F,
Mitsui Petrochemical Co., Ltd.) 100 parts by weight, surface-treated calcium carbonate (average particle size 1 μ) 150 parts by weight, ester A1 21 parts by weight and ester B1 9 parts by weight as a third component are premixed with a super mixer, The resulting mixture is a twin-screw kneader
The mixture was kneaded and granulated with PCM-45 (manufactured by Ikegai Tekko KK).
This was film-formed by a T-die with an extruder having a screw diameter of 50 mm to obtain a film having a thickness of 70 μm. The film thus obtained was uniaxially stretched by a roll uniaxial stretching machine. The stretching conditions were as follows.

Film width = 400 mm Preheating temperature = 80 ° C. Stretching temperature = 50 ° C. Stretching ratio = 2.2 times Pulling speed = 22 m / min The performance of the obtained porous film is shown in Table 2. The test method for each performance item is as follows.

Water vapor transmission rate: According to JIS Z-0208.

Vertical tear strength: According to JIS P-8116.

Appearance: O ... Almost no stretching unevenness is observed.

 Δ: There is uneven stretching.

 X: Stretching unevenness is noticeable.

Comparative Examples 1 to 5 Porous films were obtained in exactly the same manner as in Example 1 except that the hydrocarbon shown in Table 2 was used without using ester as the third component.

Table 2 shows the respective performance evaluation results.

[Advantages of the Invention] A moisture permeable leak-proof sheet used for sanitary materials such as diapers and the like has a moisture permeability of 1.0 g / 10 according to JIS Z-0208.
If it is 0 cm ² Hr or more, the effect of preventing stuffiness during use is recognized. In Table 2, Comparative Examples 1 and 2 have the moisture vapor transmission rate and the appearance in the first good range, but the vertical tear strength is extremely weak and cannot be used in the field where the fastening function should be shared with the fastening tape. In Comparative Examples 3 to 4, although the vertical tear strength is moderate, not only stretching unevenness is conspicuous in the appearance but also moisture permeability is extremely small, and stuffiness prevention during use can hardly be expected.

In Comparative Example 5, which is a blend of Comparative Example 1 and Comparative Example 4, the balance of appearance, moisture permeability and vertical tear strength is considerably improved, but not at a satisfactory level.

On the other hand, in Example 1 according to the present invention, it was confirmed that the moisture permeability as well as the appearance and the vertical tear strength were significantly improved. That is,
It was confirmed that the water vapor transmission rate was improved by about 50% as compared with Comparative Example 5, which was a combination of known third components.

Claims (6)

[Claims] 1. A porous film obtained by melt-molding a composition containing a polyolefin resin, a filler and a third component to form a film, and then subjecting the film to a stretching treatment, wherein the third component is A porous film, which is a mixture of a monoester A composed of a monobasic acid and a monohydric alcohol and a polyester B composed of a polybasic acid and a polyhydric alcohol. 2. The porous film according to claim 1, wherein at least one of the acid and alcohol constituting the ester is branched. 3. The compounding ratio of the polyolefin resin, the filler and the third component is 50 to 250 parts by weight of the filler and 5 to 50 parts by weight of the third component to 100 parts by weight of the polyolefin resin. The porous film according to item 1 or 2. 4. The polyolefin resin is polyethylene and / or
Or polypropylene, claims 1 to 3.
The porous film according to any one of items. 5. The porous film according to claim 4, wherein the polyolefin resin is linear low density polyethylene. 6. The porous film according to any one of claims 1 to 5, wherein the stretching treatment is uniaxial stretching of 1.5 to 3.0 times.