JPH0159105B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a porous resin laminated film having excellent surface strength and air permeability, useful for disposable diapers, sanitary napkins, electrolytic diaphragms, etc. [Prior art] In sanitary napkins and disposable diapers,
Polyolefin porous resin film, which has breathability and waterproof properties, is used as a leak-proof material. Such porous resin film uses high-density polyethylene, linear polyethylene, or a mixture of both as a resin material, and contains calcium carbonate, titanium oxide,
Extrusion of a composition containing inorganic fine powder such as fired clay or diatomaceous earth, and if necessary, a flexibility improver such as polyethylene wax, liquid butadiene rubber, liquid isobutylene rubber, liquid polyethylene wax, liquid hydrogenated castor oil, etc. It is manufactured by melt-forming into a film using a machine, and then stretching and forming using a mandrel, a stretching device that utilizes the peripheral speed difference between a group of rolls, or a tenter.
No. 47334, No. 57-203520, No. 58-15538, No. 58
−149925, No. 58-149303, No. 59-62117,
59-140235, 60-6442). [Problems with the prior art] This porous resin film has a large number of fine continuous pores with a core of inorganic fine powder, and a highly air permeable single layer uniaxially stretched film with voids communicating with the atmosphere on the surface. This biaxially stretched film is useful as a waterproof cover sheet for disposable diapers. When this porous resin film is used as a waterproof cover sheet for disposable diapers, a double-sided adhesive tape with release paper on the surface is used as a fastener, and after the diaper is attached to the baby's crotch,
Peel off the release paper on the surface of the double-sided adhesive tape and use the exposed adhesive to fix the disposable diaper. When this adhesive tape is attached to the wrong position of the porous resin film or when you want to slightly shift the attached position, you can use it to reapply the adhesive tape and peel it off from the diaper. The stretched film has fine inorganic powder protruding from the surface.
The pores are either free or attached to the resin film base material and exposed, and the pores are circular or elliptical, making it easy for the inorganic fine powder to fall off, so this inorganic fine powder moves to the adhesive surface of the adhesive tape. However, since the surface strength of the porous resin film is low, the surface of the film may peel off like paper flakes. On the other hand, in a uniaxially stretched film, the pores are long and the stretching area ratio is smaller than that of a biaxially stretched film, so the amount of inorganic fine powder falling off is less than that of a biaxially stretched film, and the surface strength is also lower than that of a biaxially stretched film. Although it has stronger advantages than film, it has directionality and poor creep resistance, and the diaper cover stretches and loosens during use, making it impossible to satisfy leak-proof properties. Especially the tensile elongation at break
Anything over 500% is not desirable. [Specific means for solving the problem] In the present invention, the porous resin film has a multilayer structure of a biaxially stretched film and a uniaxially stretched film,
The base layer is a biaxially stretched film that provides creep resistance, and the surface layer to which the adhesive tape is attached is a porous resin uniaxially stretched film containing inorganic fine powder to improve surface strength and transfer to the adhesive tape. This problem is solved by reducing the amount of inorganic fine powder. That is, the present invention uses 50 to 75% by weight of inorganic fine powder.
The base layer includes a biaxially stretched porous film (A) of polyolefin containing a proportion of
A porous resin laminated film comprising a surface layer (B) consisting of a uniaxially stretched porous film containing polyolefin in a proportion of 55 to 75% by weight, the porous resin laminated film having an air permeability of 40 at 20°C. ~7000
seconds, and the moisture permeability at 20℃ is 100 to 10,000 g/
The ^present invention provides a porous resin laminated film characterized by a pressure of 1 atm for 24 hours. (Resin) In the practice of the present invention, polyolefins such as high-density polyethylene, linear polyethylene, low-density polyethylene, polypropylene, ethylene-propylene copolymer, polybutene, etc. are used as the resin material for each (A) layer and (B) layer. Examples include polyolefin or a mixture of two or more of these, and in particular, when considering waterproof cover sheets for disposable diapers, polyolefins have a specific gravity of 0.92 to 0.97 and a melt index (MI) of 0.06.
~1g/10min (190℃) high density polyethylene 65
~30% by weight, specific gravity 0.91-0.94, MI 0.1-10
When a mixture with 35 to 70% by weight of linear polyethylene of 35 to 70 g/10 min is used, the resulting porous resin film has good texture and touch. (Inorganic fine powder) As the inorganic fine powder, those having an average particle size of 20 microns or less, preferably 3 microns or less are used, and include calcium carbonate, diatomaceous earth, calcined clay,
Examples include aluminum silicate and talc. (Optional ingredients) In addition to polyolefin and inorganic fine powder, stabilizers, pigments, dispersants, plasticizers, antistatic agents,
Liquid butadiene rubber, polyethylene wax, liquid isobutylene rubber, attack polypropylene,
Dibutyl phthalate, liquid hydrogenated castor oil, etc. may be blended. (Laminated film) Porous laminated film is produced by melt-kneading polyolefin (A) containing 50 to 75% by weight of inorganic fine powder in an extruder, extruding it into a sheet from a die, and cooling the sheet to a temperature lower than the melting point of the polyolefin. , heated to a temperature that allows stretching (usually 3 to 35 degrees Celsius lower than the melting point), and then stretched in the longitudinal direction using the difference in circumferential speed of the roll group.
After stretching 1.3 to 7 times, preferably 1.8 times, a molten film of polyolefin (B) containing 55 to 75% by weight of inorganic fine powder is melt-laminated on one or both sides of this longitudinally stretched film, and this laminated film is After cooling to a temperature lower than the melting point of the polyolefin, it is stretched 1.2 to 10 times, preferably 1.2 to 3.5 times in the transverse direction using a tenter, and then heat treated if necessary.
Manufactured by cooling and slitting the ears. As another manufacturing example, the base layer film and/or the surface layer film may be manufactured as a laminated film of a composition in which the type and blending amount of resin or inorganic fine powder are changed. This porous resin laminated film has a moisture permeability of 100 to 10,000 g/m ² when measured at 20°C according to JIS Z-0208.
24 hours/1 atm, preferably 200-5000g/ ^m2 .
24 hours, 1 atm, 20℃ measured by the following method
The air permeability is 40~7000 seconds, preferably 100~
It is 4000 seconds. Air permeability measurement method Oken type air permeability made in accordance with JIS P-8117 (measured using a smoothness tester (manufactured by Asahi Seiko)) If the air permeability and moisture permeability are out of the previous range When this porous laminated film is used as a waterproof cover for diapers or as a leak-proof material for disposable sanitary napkins, it tends to get stuffy or lacks liquid-proof properties. (Effects) Since the porous laminated film of the present invention includes the biaxially stretched film base layer (A), it has excellent strength balance and has little creep elongation or tearing. In addition, the inorganic fine powder of the uniaxially stretched film (B) in the surface layer protrudes and has a matte-like (rough surface), so the embossing process of this porous resin laminated film has an appearance similar to that of cloth, and Good to the touch. In addition, since the surface layer (B) is a uniaxially stretched film, the inorganic fine powder of the protruding layer (B) is less likely to fall off from the film surface, and the degree of fibrillation on the surface is low, so it is difficult to fall off from the surface of the film. It has a stronger surface strength than a stretched film, the surface does not peel off like paper flakes, and paper dust problems (poor adhesive tape re-adhesion) are less likely to occur. Example 1 (1) Density 0.92g/cm ³ , Melt index 1.0
g/10 min linear polyethylene 20 parts by weight, density
20 parts by weight of high-density polyethylene of 0.95 g/cm ³ , melt index 0.08 g/10 min and average particle size
A resin composition (A) consisting of 60 parts by weight of 1.8 micron calcium carbonate is melt-kneaded using an extruder,
It was extruded into a sheet through a die at 220°C, cooled to 70°C, heated to 110°C, and stretched 2.5 times in the longitudinal direction using the difference in circumferential speed between the roll groups to obtain a longitudinally stretched film. (2) Density 0.92g/cm ³ , Melt index 1.0
g/10 min linear polyethylene 20 parts by weight, density
20 parts by weight of high-density polyethylene of 0.95 g/cm ³ , melt index 0.08 g/10 min and average particle size
A resin composition (B) consisting of 60 parts by weight of 1.8 micron calcium carbonate is melt-kneaded using an extruder,
This was extruded into a sheet form through a die, laminated on both sides of the longitudinally stretched film obtained in (1) above, cooled to 60°C, then introduced into a heating oven,
After heating to ℃, crosswise using a tenter.
After stretching 2.5 times and heat treating it at about 118℃,
Cool to 50℃ and slit the ears (B)／(A)／
A three-layer laminated film (B) having thicknesses of 10μ, 40μ, and 10μ was obtained. This laminated film has air permeability (20℃), moisture permeability (20℃), paper powder trouble level, and creep degree (JIS
Tensile elongation at break measured with P-8132. ) are shown in Table 1. The degree of paper dust trouble was measured by the following method. Adhesive tape "Cellophane Tape" (trade name, LP-18 manufactured by Nichiban) was applied to the film surface, rubbed 5 times with the pad of the thumb, and then rubbed at a speed of 200 mm/min with Tensilon (manufactured by Toyo Paul de Bowin). Peel off the adhesive tape. The amount of light transmitted through this adhesive tape was measured using a color meter (manufactured by Suga Test Instruments). The amount of light transmitted through the adhesive tape before adhesion was measured as a blank value, and the value divided by this value was defined as the light transmittance (the larger the value, the less paper dust trouble occurs). Items with a light transmittance of 80% or more were noted as having some problems in addition to the light transmittance, and items with a light transmittance of 70% or less were noted as defective. In addition, when the surface layer of the porous resin film was broken during peeling and the light transmittance could not be measured, it was described as a paper smudge defect. Examples 2 to 7, Comparative Examples 1 to 3 The procedure was the same as in Example 1, except that the ratio of each composition or the stretching ratio was changed as shown in Table 1, or the thickness of each layer was changed as shown in Table 1. A two-layer or three-layer laminated film was obtained. The air permeability, moisture permeability, paper dust trouble level, and creep degree of these laminated films are shown in the same table. Comparative example 4 Density 0.92g/cm ³ , Melt index 1.0g/
20 parts by weight of 10-minute linear polyethylene, density 0.95 g/
Resin composition ( ^A ) consisting of 20 parts by weight of high-density polyethylene with a melt index of 0.08 g/10 min and 60 parts by weight of calcium carbonate with an average particle size of 1.8 microns.
were melt-kneaded using an extruder, extruded into a sheet from a die at 220°C, and this sheet was cooled to 70°C. This sheet was heated to 110° C. and stretched 2.5 times in the longitudinal direction using the difference in peripheral speed between the roll groups to obtain a longitudinally stretched film. Table 1 shows the physical properties of this uniaxially stretched film. Comparative Example 5 The longitudinally stretched film of Comparative Example 4 above was further guided into a heating oven, heated to about 114°C, then stretched twice in the transverse direction using a tenter, heat-treated at 118°C, and then heated to 50°C. The film was cooled to a temperature of 50 μm, and the edges were slit to obtain a 50 μm biaxially stretched film. Table 1 shows the physical properties of this film.

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Claims (1)

[Claims] 1. A biaxially stretched porous film (A) of polyolefin containing 50 to 75% by weight of inorganic fine powder as a base layer; A porous resin laminated film comprising a surface layer (B) made of a uniaxially stretched porous film containing polyolefin, the porous resin laminated film has an air permeability of 40 to 7000 seconds at 20°C, and
A porous resin laminated film having a moisture permeability of 100 to 10,000 g/m ² and a pressure of 1 atm for 24 hours. 2. The porous resin laminated film according to claim 1, characterized in that the tensile elongation at break measured at 20°C in accordance with JIS-P-8132 is 500% or less in both the longitudinal and transverse directions. . 3 The material resin of the base layer (A) or surface layer (B) has a specific gravity
0.92-0.97, melt index 0.06-1g/10
Min high density polyethylene 65-30% by weight, specific gravity
The porous resin laminated film according to claim 1, which is a mixture of 35 to 70% by weight of linear polyethylene with a melt index of 0.91 to 0.94 and a melt index of 0.1 to 10 g/10 min. 4. The porous resin laminated film according to claim 1, wherein the film (B) is a uniaxially stretched film with a stretching ratio of 1.2 to 3.5 times.