JPH0564096B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The porous resin film obtained by carrying out the present invention can be used as a leak-proof material for disposable diapers, sanitary napkins, etc., as an external material for electrolytic diaphragms, and structures. It is useful as a moisture-proof membrane interposed between interior materials. [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,
Extract 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). It has also been proposed that this porous resin film can be used as an electrolytic diaphragm. [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. Furthermore, when this porous resin film is used as an electrolytic diaphragm, depending on the type of electrolyte, the electrolyte may be denatured by the inorganic fine powder that protrudes from the porous resin film, or the inorganic fine powder may be eluted and the electrolyte may deteriorate. Function deteriorates. In addition, various perforated films and their manufacturing methods have been proposed, but although some of these films exhibit waterproofness at atmospheric pressure, they do not work well when used as leak-proof films for diaper covers or disposable diapers. , leakage occurs in areas where weight is applied. [Specific Means for Solving the Problems] In the present invention, a perforated resin having air permeability and water leakage resistance is used by heat-shrinking a perforated heat-shrinkable resin film. That is, the present invention provides a heat-shrinkable resin film with 10 to 250 holes/cm ² with a diameter of 50 to 600 microns.
This heat-shrinkable resin film is then heat-treated to shrink by 10 to 70% in terms of area.
A method for producing a perforated resin film characterized by obtaining a resin film having an air permeability of 30 to 10,000 seconds at 20°C and a moisture permeability of 50 to 10,000 g/ ^m2 /24 hours/1 atm at 20°C. This is what we provide. (Heat-shrinkable resin film) Heat-shrinkable resin film is made by heating a thermoplastic resin film at a temperature lower than the melting point of the resin, and increasing the area by 1.3 to 70 times the area in one or two axis directions of the film.
It is preferably obtained by stretching 1.3 to 50 times. Thermoplastic resins include linear polyethylene (MP approx. 121℃, stretching temperature 115-119℃), high-density polyethylene (MP approx. 133℃, stretching temperature 129-131℃),
℃), homopolypropylene (MP approx. 164℃, stretching temperature 150-162℃), propylene-ethylene random copolymer (MP approx. 134℃, stretching temperature 125-132℃),
Polyethylene terephthalate (MP approx. 247℃, stretching temperature 102-120℃), polystyrene or polyvinyl chloride (softening point approx. 163-168℃, stretching temperature 145℃)
~158℃), polyamide (melting point approx. 248℃, stretching temperature
120 to 180°C), etc. Note that the melting point (MP) and stretching temperature in parentheses are examples, and the melting point (softening point in the case of amorphous resins such as polystyrene and polyvinyl chloride) of the same resin with different melting points is also The stretching temperature is selected based on a temperature difference of approximately the same width as a reference. Stretching is carried out using the difference in circumferential speed between the mandrel, tenter, and roll group. The stretching ratio is 1.3 to 10 times for a uniaxially stretched film, and 1.6 to 70 times for a biaxially stretched film. Films are generally formed by an inflation method or a T-die method. The thickness of the heat-shrinkable resin film before perforation is usually 10 to 100 microns and is easily available on the market. For example, a heat-shrinkable resin film made of linear polyethylene is manufactured by Kojin Co., Ltd. under the trade name Kojin Polyset-U, and a heat-shrinkable resin film made of polyvinyl chloride is manufactured by Mitsubishi Plastics Co., Ltd. under the trade name Himilex-MBS. A heat-shrinkable resin film made of polypropylene is sold by Kojin Co., Ltd. under the trade name Kojin Polyset. (Perforation) Heat-shrinkable resin film has 10 to 250 holes/
Perforated at the rate of cm ² . A needle or a laser beam can be used as the perforation means. Of course, you can also use a hot needle. The diameter of the pores is preferably between 50 and 600 microns.
It is mechanically difficult to drill holes smaller than 50 microns with current drilling means. With pores larger than 600 microns, it is difficult to provide water leakage properties to the resin film due to shrinkage. (Heat Shrinkage) Heat shrinkage involves heat shrinking a perforated heat-shrinkable resin film in a heating furnace. The temperature for heat shrinking is a temperature slightly higher than these temperatures (1 to
Shrinkage of the heat-shrinkable resin film occurs when the temperature of the resin film becomes lower than the temperature (3°C higher). Therefore, the temperature in the heating furnace and the residence time of the film in the heating furnace should be determined from the viewpoints of molding cycle, quality, and economy so that the resin film can absorb this amount of heat. For example, when there is one heating furnace and the temperature inside the furnace is uniform, it is 2 to 10 degrees lower than the drawing temperature or heat set temperature.
Set the furnace temperature to ℃ higher. Change the temperature in the heating furnace in three stages. For example, when drawing a linear polyethylene heat shrink film with a stretching temperature of 119°C, the first temperature is 135°C, the next temperature is 115°C, and the final temperature is 122°C.
℃, the heat treatment temperature can be shortened.
In addition, using three hot air stoves, the temperature was set to the above,
The heat-shrinkable film may be introduced into these hot air ovens for heat treatment. This heat shrinking process results in a film with an area of 10 to 70
% shrinkage. While the perforated holes shrink due to this shrinkage, the perforated dregs do not shrink sufficiently, and it is therefore presumed that the heat-treated film is imparted with water leakproof properties. The heat shrinkage rate (surface area of the film after heat treatment/percentage of the surface area of the film before heat treatment) depends on the stretching ratio when manufacturing the heat-shrinkable resin film, but it is approximately the same as this stretching ratio. This is preferable because the perforated film has no uneven shrinkage and has an excellent appearance. (Porous resin film) The porous resin film obtained by heat treatment is
Moisture permeability measured at 20℃ in accordance with JIS Z-0208
50-10000g/m ² , 24 hours, 1 atm, preferably
1000-6000g/ ^m2 , 24 hours, 1 atm, and the air permeability at 20℃ measured by the following method is 30-10000
seconds, preferably 100 to 3000 seconds. Measuring method of air permeability: If the measured air permeability and moisture permeability are out of the range, When this perforated resin 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. Example 1 A transparent heat-shrinkable film made of linear polyethylene "Kojin Polyset U" (trade name) manufactured by Kojin Co., Ltd. with a wall thickness of 20 microns, a length of 200 mm, and a width of 200 mm was made to have a diameter of 200 microns using a syringe needle. holes were drilled at a rate of 25 holes per cm ² . This perforated film was introduced into a hot air drying oven with an internal temperature of 120°C, and left in the oven for 1 minute to cause heat shrinkage (approx.
40% shrinkage) and then led out of the furnace to obtain a perforated resin film. The moisture permeability of this perforated resin film is 1700g/
m ² / 24 hours / 1 atm, the air permeability was 2300 seconds. In addition, when the water leak resistance was tested using the following method, there was no water leak. Water leak resistance test: A perforated resin film of the present invention measuring 100 mm in length and 100 mm in width was placed on a filter paper with a diameter of 80 mm, and 0.3 cc of distilled water was dropped into the center of the perforated resin film. On this perforated resin film, the width 120mm, height 120mm, weight
A 200 g acrylic resin plate was placed so as to cover the perforated resin film. At this time, if the water droplets spread toward the periphery of the perforated resin film without being sucked into the filter paper, the water leakage properties of the perforated resin film are good, and if the water is absorbed by the lower filter paper through the holes, then there is The water leakage properties of the porous resin film are poor. Examples 2 to 3 A perforated resin film was obtained in the same manner as in Example 1, except that the holding time of the shrinkable resin film in the hot air stove was changed and the amount of shrinkage was changed to 20% or 60% instead of 40%. . Examples 4-5 A perforated resin film was obtained in the same manner as in Example 1, except that the perforation diameter was changed from 200μ to 80μ or 500μ. Comparative Example 1 The heat-shrinkable resin film "Kojin Polyset U" used in Example 1 was shrunk by 40% to obtain a non-porous film. Comparative Examples 2 to 4 In Example 1, the amount of shrinkage was 0%, 5% or
A perforated film was obtained in the same manner as in Example 1 except that the ratio was changed to 80%. Table 1 shows the physical properties of these resin films. 【table】

Claims (1)

[Claims] 1. A heat-shrinkable resin film is perforated with holes of 50-600 microns in diameter at a rate of 10-250 holes/ ^cm2 , and the heat-shrinkable resin film is heat-treated to 10-70% in area. Air permeability at 20℃ after shrinking
30~10000 seconds, moisture permeability at 20℃ is 50~
A method for producing a perforated resin film, characterized by obtaining a resin film having a pressure of 10,000 g/m ² for 24 hours and 1 atm.