JPWO2019130990A1 - Stretched porous film and its manufacturing method - Google Patents

Abstract

Achieves a stretched porous film that has breathability, water resistance, and flexibility. The stretched porous film according to the embodiment of the present invention contains a resin composition containing a specific polyolefin resin and liquid paraffin in a specific mass ratio, and the stretched porous film has a moisture permeability of 1400 g / m 2.24 h or more. Is.

Description

The present invention relates to a stretched porous film and a method for producing the same.

Conventionally, personal care products such as diapers have been required to allow air, steam and the like to pass through and not to allow liquids to pass through in order to prevent stuffiness and the like. Therefore, personal care products such as diapers are required to have breathability and water resistance. In order to meet this demand, a porous film in which a water-repellent resin such as a polyolefin resin is formed into a film to form fine pores is used. Such a porous film has a structure that allows air or the like to pass through but does not allow liquid to pass through.

Patent Document 1 discloses a breathable film obtained by melt-molding a resin composition containing a polyethylene-based resin, liquid paraffin, and an inorganic filler.

Japanese Patent Publication "Japanese Patent Laid-Open No. 62-250038"

However, the above-mentioned breathable film has room for improvement in terms of flexibility.

One aspect of the present invention has been made in view of the above problems, and an object of the present invention is to realize a stretched porous film having breathability, water resistance and flexibility suitable for personal care products such as diapers. That is.

As a result of diligent research conducted by the present inventor in order to solve the above-mentioned problems, a polyolefin-based resin having a specific melt mass flow rate is used, and liquid paraffin is added to a specific mass ratio to the polyolefin-based resin. It has been found that a stretched porous film having both breathability, water resistance and flexibility can be realized by using the resin composition containing the resin composition and adjusting the moisture permeability to a specific range, and by combining these. That is, the present invention includes the following configurations.

Density 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin resin 100 mass parts, 5.0 parts by mass or more, and the liquid paraffin 20 parts by mass or less The melt mass flow rate of the resin composition, which is composed of a resin composition containing an inorganic filler and measured at 190 ° C. according to JIS K 7210, is 2.0 g / 10 min. Greater than or equal and, 40 ° C. according to ASTM E96, stretched porous film moisture permeability measured at 60% relative humidity conditions, characterized in that at 1400g ^/ m 2 · 24h or more.

Density 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin resin 100 mass parts, 5.0 parts by mass or more, and the liquid paraffin 20 parts by mass or less , An inorganic filler, and a mixing step to obtain a resin composition, a molding step of molding the resin composition into a film, and stretching the film obtained by the molding step at least in the mechanical direction. The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210, which comprises a porosification step of making the resin composition, is 2.0 g / 10 min. A method for producing a stretched porous film, which is characterized by the above.

According to one aspect of the present invention, there is an effect that a stretched porous film having both breathability, moisture permeability and flexibility can be obtained.

An embodiment of the present invention will be described below, but the present invention is not limited thereto.

As a result of diligent studies by the present inventor, it was found that the above-mentioned prior art has the following problems. For example, the film shown in Patent Document 1 is considered to have poor flexibility because it uses a polyethylene resin having a low melt index.

Therefore, the stretched porous film according to the embodiment of the present invention solves the above-mentioned problems of the prior art, and has breathability, moisture permeability, and flexibility. The details will be described below.

[1. Stretched porous film]
Stretched porous film according to an embodiment of the present invention has a density of 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin-based resin 100 parts by weight, 5. The melt mass flow rate of the resin composition is composed of a resin composition containing 0 parts by mass or more and 20 parts by mass or less of liquid paraffin and an inorganic filler, and is measured at 190 ° C. according to JIS K 7210. 2.0 g / 10 min. Greater than or equal and, 40 ° C. according to ASTM E96, is moisture permeability measured at 60% relative humidity conditions 1400g ^/ m 2 · 24h or more. By combining liquid paraffin at a specific mass ratio with the polyolefin resin having specific physical properties as described above, desired flexibility can be obtained in addition to water resistance. Further, by setting the moisture permeability within a specific range, desired air permeability can be obtained. Therefore, it is possible to realize a stretched porous film having both breathability, water resistance and flexibility.

The stretched porous film may be made of a resin composition containing a polyolefin-based resin, liquid paraffin, and an inorganic filler. For example, a sheet of another material is laminated in addition to the resin composition. It may be the one that has been used.

<1-1. Polyolefin resin>
The polyolefin resin has a density of 0.900 g / cm ³ or more and 0.940 g / cm ³ or less, more preferably 0.905 g / cm ³ or more and 0.935 g / cm ³ or less. When the density is within the above range, a stretched porous film having desired flexibility can be obtained by combining with liquid paraffin described later. Also, the density and melting point correlate to some extent. When the density is within the above range, the heat-fixing temperature is separated from the melting point to some extent, so that it is possible to prevent the polyolefin-based resin from melting at the same time as heat-fixing and closing the pores of the stretched porous film. Therefore, it is possible to prevent a decrease in air permeability.

Examples of the polyolefin resin include linear low density polyethylene (LLDPE) and branched low density polyethylene (LDPE). It is preferable to use a plurality of types of polyolefin resins because the melt mass flow rate can be easily adjusted. As the polyolefin-based resin, linear low-density polyethylene and branched low-density polyethylene may be combined. From the viewpoint of improving heat resistance, a polyolefin resin having a density of 0.930 g / cm ³ or more and 0.970 g / cm ³ or less may be contained with respect to 100 parts by mass of the polyolefin resin. In that case, the density of the entire polyolefin resin used (density of a mixture of a plurality of types of polyolefin resins) may be 0.940 g / cm ³ or less. The density of the polyolefin resin is more preferable to use all 0.900 g / cm ³ or more and 0.940 g / cm ³ or less.

<1-2. Liquid paraffin>
Liquid paraffin is a mixture of hydrocarbons obtained from crude oil that is liquid at room temperature and has a wide range of carbon atoms of about 15 to 35, and has a density of 0.790 g / cm ³ or more and 0.920 g / cm ³ or less. Say something.

Liquid paraffin is added for the purpose of improving flexibility. The content ratio of the liquid paraffin is preferably 5.0 parts by mass or more and 20 parts by mass or less, and more preferably 7.0 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polyolefin resin. preferable. When the content ratio of the liquid paraffin is 5.0 parts by mass or more, more flexibility can be imparted to the stretched porous film. Further, when the content ratio of the liquid paraffin is 20 parts by mass or less, the strength of the stretched porous film can be increased. Moreover, since the occurrence of the draw resonance phenomenon can be suppressed, the productivity can be improved.

<1-3. Inorganic filler>
Inorganic filler is added to make the film porous. Known inorganic fillers can be used endlessly, for example, inorganic salts such as calcium carbonate, barium sulfate, calcium sulfate, barium carbonate, magnesium hydroxide and aluminum hydroxide, and inorganic oxides such as zinc oxide, magnesium oxide and silica. , Mica, silicates such as vermiculite and talc, and organic metal salts. Of the inorganic fillers, calcium carbonate is preferable from the viewpoint of cost performance and dissociation with the polyolefin resin.

In the resin composition, the blending ratio of the inorganic filler is preferably 80 parts by mass or more and 200 parts by mass or less, and 85 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the total of the polyolefin resin and the liquid paraffin. Is more preferable. When the blending ratio of the inorganic filler is 80 parts by mass or more, the frequency of void generation per unit area, which is formed by the dissociation between the polyolefin resin and the inorganic filler, can be increased. Therefore, adjacent voids can easily communicate with each other, and the air permeability becomes good. When the compounding ratio of the inorganic filler is 200 parts by mass or less, the film has good elongation at the time of stretching and is easy to stretch.

<1-4. Other ingredients>
The resin composition may further contain additives used in ordinary resin compositions. Examples of such additives include antioxidants, heat stabilizers, light stabilizers, UV absorbers, neutralizers, lubricants, antifogging agents, antiblocking agents, antistatic agents, slip agents, colorants, plasticizers and the like. Can be mentioned. The resin composition may contain a small amount of resin components other than the polyolefin-based resin and the liquid paraffin as long as the effects of the present invention are not impaired. Specifically, if it is within 5.0 parts by mass, more preferably within 2.5 parts by mass with respect to 100 parts by mass of the total of the polyolefin resin and liquid paraffin, it is permissible to add other resin components. To. The stretched porous film and the resin composition according to the embodiment of the present invention may not contain a thermoplastic elastomer.

<1-5. Physical properties of stretched porous film>
Moisture permeability of the stretched porous film is preferably at 1400g ^/ m 2 · 24h or more, more preferably 1600g ^/ m 2 · 24h or more. When the moisture permeability is within the above range, the air permeability and moisture permeability are excellent. For example, when a stretched porous film is used as a back sheet for a disposable diaper, it is possible to prevent stuffiness during wearing. The upper limit of moisture permeability, mechanical properties, from the viewpoints of water resistance and liquid leakage resistance is preferably not more than 10000g ^/ m 2 · 24h, more preferably at most 4000g ^/ m 2 · 24h. By the upper limit of moisture permeability than 4000g / m 2 · ^24h, diapers with the stretched porous film is liquid leakage may become lower that generated during wear. Furthermore, presumably because it exceeds the permeability any humidity 4000g / m 2 · ^24h of disclosed in Patent Document 1 film, liquid leakage when worn and used like the diaper may occur.

The water permeation is measured according to ASTM E96 under the conditions of 40 ° C., relative humidity 60%, measurement time 24 hours, and pure water method. In the present specification, the moisture permeability is an average value of 10 10 cm × 10 cm samples collected from a stretched porous film.

The 5% elongation strength of the stretched porous film is preferably 0.3 N / 25 mm or more and less than 2.5 N / 25 mm, and more preferably 0.5 N / 25 mm or more and 2.3 N / 25 mm or less. The smaller the 5% elongation strength, the more flexible it is. If the 5% elongation strength is less than 2.5 N / 25 mm, more flexibility can be imparted. When the 5% elongation strength is 0.3 N / 25 mm or more, the elongation of the film with respect to the line tension applied in the machine direction during the secondary processing can be suppressed.

For 5% elongation strength, the sample was subjected to a chuck distance of 50 mm and a tensile speed of 200 mm / min according to JIS K 7127. It is pulled in the mechanical direction and measured as the strength in the mechanical direction when the sample is stretched by 5%. That is, the 5% elongation strength is measured as the stress in the mechanical direction when the distance between chucks is extended by 2.5 mm. Further, in the present specification, the 5% elongation strength is a value measured for a sample having a width of 25 mm and a length of 150 mm in the mechanical direction collected from a stretched porous film.

The melt mass flow rate of the resin composition is 2.0 g / 10 min. The above is preferable, and 2.0 g / 10 min. As mentioned above, 6.0 g / 10 min. It is more preferably 2.0 g / 10 min. As mentioned above, 5.0 g / 10 min. The following is more preferable. If the melt mass flow rate is within the above range, more stable film formation can be performed. Melt mass flow rate is 2.0 g / 10 min. With the above, the resin pressure of the extruder during film formation can be suppressed, and adverse effects on film formation can be prevented. In addition, the melt mass flow rate was 6.0 g / 10 min. If the following, neck-in when forming a film with a T-die can be further suppressed. Therefore, the required product width can be easily obtained. Also, melt mass flow rate and 5% elongation strength tend to correlate. Decreasing the melt mass flow rate increases the 5% elongation strength, and therefore tends to result in a stretched porous film having poor flexibility. The melt mass flow rate of the resin composition is measured by the A method at 190 ° C. according to JIS K 7210.

The air permeability of the stretched porous film is preferably 300 seconds / 100 mL or more and 2000 seconds / 100 mL or less, more preferably 400 seconds / 100 mL or more and 1600 seconds / 100 mL or less, and 400 seconds / 100 mL or more. It is more preferably 1100 seconds / 100 mL or less. The smaller the air permeability, the easier it is for gas to pass through. When the air permeability is within the above range, it is possible to prevent stuffiness during wearing when the stretched porous film is used as a back sheet for a disposable diaper. The air permeability is measured by the Oken test machine method according to JIS P 8117.

The heat shrinkage rate of the stretched porous film in the mechanical direction is preferably 5.0% or less, and more preferably 3.5% or less. If the 5% elongation strength is high and the heat shrinkage rate in the machine direction is 5.0% or less, the elongation of the film with respect to the line tension applied in the machine direction during secondary processing can be further suppressed. The heat shrinkage in the mechanical direction is preferably closer to 0%, but practically 0.5% or more.

The heat shrinkage in the mechanical direction is measured by the following method. A 15 cm x 15 cm sample is taken from the stretched porous film. Mark lines are placed in this sample so that the distance between the marked lines is 10 cm in the machine direction. After allowing this sample to stand at 50 ° C. for 24 hours, it is cooled to room temperature and the length between marked lines is measured. The heat shrinkage rate in the mechanical direction is obtained from the following formula I.
Formula I: Thermal shrinkage in the mechanical direction (%) = {(10 cm-length between marked lines after cooling (cm)) / 10 cm} × 100.

The basis weight is preferably 10 g / m ² or more and 35 g / m ² or less, more preferably 11 g / m ² or more and 32 g / m ² or less, and 12 g / m ² or more and 30 g / m ² or less. It is more preferable to have. When the basis weight is in the above range, a stretched porous film having excellent breathability, moisture permeability and mechanical strength can be obtained. When the basis weight is 10 g / m ² or more, the mechanical strength of the film can be increased. Further, when the basis weight is 35 g / m ² or less, sufficient moisture permeability can be obtained.

[2. Method for producing stretched porous film]
Method for producing a stretched porous film according to an embodiment of the present invention has a density of 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin-based resin 100 parts by weight , 5.0 parts by mass or more and 20 parts by mass or less of liquid paraffin and an inorganic filler to obtain a resin composition, and a molding step of molding the resin composition into a film. The film includes a porosity step of stretching the film obtained by the molding step at least in the mechanical direction to make the film porous. By combining liquid paraffin with a polyolefin resin having specific physical properties at a specific mass ratio in this way, a stretched porous film having desired flexibility in addition to water resistance can be obtained. The resin composition provided with the melt mass flow rate in a specific range has good fluidity of the resin composition, and a stretched porous film having flexibility can be obtained. Further, by stretching and making a film containing a resin composition having a specific composition into a porous film, a stretched porous film having a desired air permeability can be obtained. Therefore, it is possible to realize a stretched porous film having both breathability, water resistance and flexibility. In addition, [1. With respect to the matters already described in [Stretched porous film], the description thereof will be omitted below, and the above description will be incorporated as appropriate.

<2-1. Mixing process>
Mixing step has a density of 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin resin 100 mass parts, 5.0 parts by mass or more, below 20 parts by weight This is a step of mixing a certain liquid paraffin and an inorganic filler to obtain a resin composition. First, a polyolefin resin, liquid paraffin, an inorganic filler, and if necessary, an additive to be blended are mixed. The mixing method is not particularly limited, and a known method can be adopted. For example, it is preferable to mix for about 5 minutes to 1 hour using a mixer such as a Henschel mixer, a super mixer, or a tumbler mixer.

The obtained mixture can be kneaded and pelletized by a method such as strand cut, hot cut, or underwater cut, generally using a kneader such as a high kneading type twin-screw extruder or a tandem type kneader. Pre-mixing, kneading and pelletizing are preferable because they can promote uniform dispersion of the resin composition. Further, depending on the composition of the resin composition, it can be directly put into a kneader without mixing and pelletized.

<2-2. Molding process>
The molding step is a step of molding the resin composition into a film. It is preferable that the pellets obtained as described above are formed into a film by a circular die or a T die mounted on the tip of the extruder. At this time, the cooling method when the T-die method is used is not particularly limited, and a known method such as a nipple roll method, an air knife method, or an air chamber method can be adopted. Depending on the composition of the resin composition, the resin composition may be directly put into the extruder without mixing and kneading to form a film.

<2-3. Porousization process>
The porosity step is a step of pouring the film obtained by the molding step by stretching it at least in the mechanical direction. By stretching the film obtained by the molding step, the interface between the resin component (the polyolefin-based resin and the liquid paraffin) and the inorganic filler is peeled off. Then, minute voids are formed at the peeled interface, and the voids form communication holes penetrating in the thickness direction of the film to form a stretched porous film. Stretching can be performed by a known method such as a roll stretching method or a tenter stretching method. Further, the stretching may be uniaxial stretching or biaxial stretching.

It is preferable that the draw ratio in the mechanical direction in the porosity step is represented by the following formula II:
1.4 ≤ Y ≤ 0.075X + 1.8 ... (Equation II)
(In the formula, X indicates the mixing ratio (parts by mass) of liquid paraffin to 100 parts by mass of the polyolefin resin, and Y indicates the draw ratio (times)).

By carrying out stretching under the condition that the above formula II is established, the obtained film is sufficiently stretched while maintaining flexibility, is less likely to cause uneven thickness, and has good tear strength, which is sufficient. Holes of number and size are formed. Therefore, with such a stretch ratio, a stretched porous film having both breathability, moisture permeability and flexibility can be obtained more easily. The stretching may be one-step stretching or multi-step stretching.

The stretching temperature is preferably in a temperature range of room temperature or higher and lower than the softening point of the resin composition. When the stretching temperature is at room temperature or higher, uneven stretching is unlikely to occur, so that the thickness tends to be uniform. Further, when the stretching temperature is lower than the softening point, it is possible to prevent the stretched porous film from melting. Therefore, it is possible to prevent the pores of the stretched porous film from being crushed and the air permeability and moisture permeability from being lowered. The stretching temperature can be appropriately adjusted by combining the physical properties of the resin composition used and the stretching ratio.

<2-4. Heat fixing process>
The manufacturing method may include a heat fixing step. The heat fixing step is a step of heat fixing the stretched porous film after stretching in order to suppress heat shrinkage in the stretching direction. Heat fixation is a heat treatment performed in an environment in which the dimensions of the stretched film are not changed while the stretched film is maintained in a tense state due to stretching. As a result, heat fixation can suppress elastic recovery during storage, shrinkage and squeezing due to heat, and the like.

As a heat fixing method when the roll stretching method is adopted as the stretching method, a method of heating the stretched film with a heated roll (annealing roll) can be mentioned. Further, as a heat fixing method when the tenter stretching method is adopted as the stretching method, a method of heating the stretched film in the vicinity of the tenter outlet can be mentioned.

The heat fixing temperature is preferably 70 ° C. or higher and 95 ° C. or lower, and preferably 80 ° C. or higher and 95 ° C. or lower. When the heat fixing temperature is 70 ° C. or higher, heat shrinkage can be suppressed by sufficient heat fixing. Further, when the heat fixing temperature is 95 ° C. or lower, it is possible to further prevent the pores of the stretched porous film from being crushed by heat.

The heat fixing time is preferably 0.2 seconds or longer, more preferably 0.5 seconds or longer, and even more preferably 1.0 second or longer. If the heat fixing time is 0.2 seconds or more, heat shrinkage can be suppressed by sufficient heat fixing. The heat fixing time is preferably 20 seconds or less, more preferably 15 seconds or less. Although it cannot be said unconditionally because it depends on the combination with the heat fixing temperature, if the heat fixing time is 20 seconds or less, it is possible to further prevent the pores from being crushed by melting the stretched porous film. Therefore, it is possible to prevent a decrease in air permeability and moisture permeability.

The heat-fixing time is the time during which the stretched porous film is held at the heat-fixing temperature. For example, when the roll stretching method is adopted, it means the time during which the film is in contact with the annealing roll. The number of annealing rolls is not particularly limited, but when there are two or more, the heat fixing time is the sum of the times during which the stretched porous film is in contact with each annealing roll. Further, when the tenter stretching method is adopted, the heat fixing time indicates the time for being heated and maintained at the heat fixing temperature at the tenter outlet. When the heat fixation is divided into a plurality of times and heated, it is the sum of the heating times for each.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples.

〔Evaluation method〕
The physical property values of the stretched porous films of Examples and Comparative Examples described later were measured by the methods shown below.

(1) Melt mass flow rate The melt mass flow rate of the resin composition was measured by the method A at which 190 ° C. was selected as the measurement temperature according to JIS K 7210. In the following, the melt mass flow rate will also be referred to as MI (melt index).

(2) Metsuke A 10 cm × 10 cm sample was cut from the stretched porous film, and the mass was measured with a balance. The basis weight was determined from the area and mass of this sample.

(3) Moisture Permeability Ten 10 cm × 10 cm samples were collected from the stretched porous film. For these, the permeation rate was measured under the conditions of 40 ° C., 60% relative humidity, 24 hours measurement time, and pure water method according to ASTM E96, and the average value was calculated.

(4) Air permeability The air permeability was measured by the Oken type testing machine method according to JIS P 8117.

(5) 5% Stretch Strength According to JIS K 7127, a sample having a width of 25 mm and a length of 150 mm in the mechanical direction was taken from the stretched porous film. This sample was subjected to a chuck distance of 50 mm and a tensile speed of 200 mm / min. The strength in the mechanical direction when the sample was stretched by 5% was measured as the 5% stretch strength. That is, the stress in the mechanical direction when the distance between the chucks was extended by 2.5 mm was measured.

(6) Heat Shrinkage Rate in the Mechanical Direction A sample of 15 cm × 15 cm was taken from the stretched porous film. Marked lines were placed in this sample so that the distance between the marked lines in the machine direction was 10 cm. After allowing this sample to stand at 50 ° C. for 24 hours, it was cooled to room temperature and the length between the marked lines was measured. The heat shrinkage in the machine direction was calculated from the following mathematical formula (Formula I).
Formula I: Thermal shrinkage in the mechanical direction (%) = {(10 cm-length between marked lines after cooling (cm)) / 10 cm} × 100.

[Ingredients used]
A: Linear low-density polyethylene [manufactured by Dow Chemical Co., Ltd., trade name: Dowlex 2047, density: 0.917 g / cm ³ , MI: 2.3 g / 10 min. ]
B: Linear low-density polyethylene [manufactured by Dow Chemical Co., Ltd., trade name: Dowlex 2035G, density: 0.919 g / cm ³ , MI: 6.0 g / 10 min. ]
C: Linear low-density polyethylene [manufactured by Dow Chemical Co., Ltd., trade name: Dowlex 2036P, density: 0.935 g / cm ³ , MI: 2.5 g / 10 min. ]
D: Linear low-density polyethylene [manufactured by Dow Chemical Co., Ltd., trade name: Dowlex 2045G, density: 0.920 g / cm ³ , MI: 1.0 g / 10 min. ]
E: Branched low-density polyethylene [Mitsui / DuPont Polychemical Co., Ltd., trade name: Mirason 16P, density: 0.917 g / cm ³ , MI: 3.7 g / 10 min. ]
F: Ultra-low density polyethylene [manufactured by Dow Chemical Co., Ltd., trade name: Athein 4607GC, density 0.904 g / cm ³ , MI: 4.0 g / 10 min. ]
G: High-density polyethylene [manufactured by Tosoh Corporation, trade name: Niporon Hard 4200, density: 0.961 g / cm ³ , MI: 2.3 g / 10 min. ]
H: Liquid paraffin [manufactured by Wako Pure Chemical Industries, Ltd., trade name: liquid paraffin, density: 0.860 to 0.890 g / cm ³ ]
I: Liquid paraffin [manufactured by Wako Pure Chemical Industries, Ltd., trade name: liquid paraffin, density: 0.825 to 0.850 g / cm ³ ]
J: Liquid paraffin [manufactured by Wako Pure Chemical Industries, Ltd., trade name: liquid paraffin, density: 0.800 to 0.835 g / cm ³ ]
K: Paraffin [manufactured by Wako Pure Chemical Industries, Ltd., trade name: paraffin, melting point: 42 to 44 ° C, density: 0.900 g / cm ³ ]
L: Hydrogenated polybutadiene [manufactured by Nippon Soda Co., Ltd., trade name: Nisso-PB BI-2000, density: 0.860 g / cm ³ ]
M: Polybutene [manufactured by NOF CORPORATION, trade name: Polybutene 3N, density: 0.880 g / cm ³ ]
N: Hydrogenated polybutene [manufactured by NOF CORPORATION, trade name: Pearl Dream 4, density: 0.793 g / cm ³ ]
O: Calcium carbonate [manufactured by Imerys Minerals Co., Ltd., trade name: FL-520]
P: Additive [titanium oxide (manufactured by Huntsman Co., Ltd., trade name: TR28) 50% by mass, hindered phenol-based heat stabilizer (manufactured by Ciba Japan Co., Ltd., trade name: IRGANOX3114) 20% by mass, Phosphorus-based heat stabilizer (manufactured by Ciba Japan Co., Ltd., trade name: IRGAFOS168), a mixture with 30% by mass].

[Example 1]
A resin composition obtained by mixing the polyolefin-based resin, hydrocarbon, inorganic filler and additive shown in Table 1 was prepared. It was granulated and then filmed.

Granulation (preparation of pellets) was carried out as follows. Using a φ30 mm twin-screw extruder with a vent, the resin composition was extruded into a strand shape at a cylinder temperature of 160 ° C. and cooled in a water tank. Then, the extruded resin composition was cut to about 5 mm and dried to prepare pellets.

Next, a film was formed from the pellets using a φ400 mm T-die film forming machine. Here, lip clearance: 1.5 mm, die temperature: 200 ° C., air gap: 105 mm, take-up speed: 10 m / min. , Cast roll temperature: 20 ° C. The obtained film was further uniaxially stretched (stretching ratio: 1.8 times) only in the mechanical direction with a roll stretching machine set at 40 ° C., and then in-line annealing was performed with a heat set roll set at 90 ° C. (heat fixing time 4). Seconds). The heat shrinkage rate in the mechanical direction at the time of heat fixing was 8%.

In Examples 2 to 13 and Comparative Examples 1 to 8, the compounding ratio of each component or the stretching condition (stretching ratio or heat fixing temperature) was changed as shown in Tables 1 and 2, except that the blending ratio or the stretching condition (stretching ratio or heat fixing temperature) was changed as described in Table 1 and Table 2. A film was formed in the same manner.

なお、「ポリオレフィン系樹脂：配合割合（質量％）」は樹脂組成物に含まれるポリオレフィン系樹脂１００質量％に対する各ポリエチレン系樹脂の配合割合を表す。「炭化水素：配合割合（質量部）」は、ポリオレフィン系樹脂１００質量部に対する炭化水素の配合割合を表す。炭酸カルシウムおよび添加剤の配合割合は、ポリオレフィン系樹脂と炭化水素との合計１００質量部に対する配合割合として記載されている。

The "polyolefin-based resin: blending ratio (mass%)" represents the blending ratio of each polyethylene-based resin to 100% by mass of the polyolefin-based resin contained in the resin composition. "Hydrogen: blending ratio (parts by mass)" represents the blending ratio of hydrocarbon to 100 parts by mass of the polyolefin resin. The blending ratio of calcium carbonate and the additive is described as a blending ratio with respect to a total of 100 parts by mass of the polyolefin resin and the hydrocarbon.

Further, the stretching condition * 1 represents a stretching ratio of 1.8 times and a heat fixing temperature of 90 ° C. The stretching conditions * 2 represent a stretching ratio of 3.2 times and a heat fixing temperature of 90 ° C. Stretching conditions * 3 indicate a stretching ratio of 2.5 times and a heat fixing temperature of 90 ° C. The stretching condition * 4 indicates a stretching condition 1.3 times and a heat fixing temperature of 90 ° C.

〔result〕
The basis weight, moisture permeability, air permeability, 5% elongation strength and heat shrinkage of the stretched porous films obtained in Examples 1 to 13 and Comparative Examples 1 to 8 were measured and shown in Table 3.

実施例１〜１３の延伸多孔性フィルムは、いずれも１４００ｇ／ｍ^２・２４ｈ以上の良好な透湿度を示すとともに、良好な風合いを有していた。また、実施例１〜８、および１０〜１２の延伸多孔性フィルムは、５％伸張強度および熱収縮率について低い値を保持していた。さらに、本実施例１〜８、および１０〜１２の延伸多孔性フィルムは、いずれの延伸倍率も式ＩＩを満たす。

Expanded porous films of Examples 1 to 13 are all together show a more favorable moisture permeability 1400g ^/ m 2 · 24h, and had a good hand. In addition, the stretched porous films of Examples 1 to 8 and 10 to 12 maintained low values for 5% elongation strength and heat shrinkage. Further, the stretched porous films of Examples 1 to 8 and 10 to 12 satisfy the formula II at any stretching ratio.

In Examples 3 and 4, polyolefin resins having different densities were used. In Example 4, polyethylene having a density of 0.961 g / cm ³ was used. In Example 4 in which high-density polyethylene is added, the moisture permeability is higher and the air permeability is lower than in Example 3. In addition, Example 4 had a high 5% elongation strength, but was better than that of Comparative Example.

Comparing Examples 6 to 8, it can be seen that as the density of the liquid paraffin decreases, the air permeability decreases, and the moisture permeability and the 5% elongation strength increase.

In addition, Examples 9 and 13 in which the stretching ratio does not satisfy the formula II have higher 5% elongation strength than Examples 1 to 8 and 10 to 12 satisfying the formula II, but the moisture permeability is higher than that of the comparative example. The balance between air permeability, 5% elongation strength and heat shrinkage was good.

Moreover, in Examples 2, 9, and 12, the draw ratio of the stretched porous film having the same composition was changed. From these, it can be seen that by increasing the draw ratio, the moisture permeability is increased and the air permeability and heat shrinkage are decreased.

In Comparative Example 1, hydrocarbons were not used. As a result, the obtained stretched porous film had a high stretch strength of 5%, and a stretched porous film having poor flexibility was obtained.

In Comparative Examples 2 to 5, hydrocarbons other than liquid paraffin were used as the hydrocarbon. As a result, in Comparative Example 2 in which paraffin was used as the hydrocarbon and Comparative Example 5 in which hydrogenated polybutene was used as the hydrocarbon, a stretched porous film having high 5% elongation strength and poor flexibility was obtained. In Comparative Example 3 in which hydrogenated polybutadiene was used as the hydrocarbon and Comparative Example 4 in which polybutene was used as the hydrocarbon, a stretched porous film having low humidity permeability and easy to get stuffy was obtained.

In Comparative Example 6, 75% by mass of polyethylene having a density of 0.961 g / cm ³ was used with respect to 100 parts by mass of the polyolefin resin. As a result, a stretched porous film having low air permeability, high moisture permeability and 5% elongation strength, and poor flexibility was obtained.

In Comparative Example 7, a polyolefin resin having a low melt mass flow rate was used. As a result, the obtained stretched porous film had a low humidity permeability, and a stretched porous film that was easily stuffy was obtained.

In Comparative Example 8, since the moisture permeability was low, the stretched porous film was inferior in air permeability.

[Summary]
[1] density 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin resin 100 mass parts, 5.0 parts by mass or more, is 20 parts by mass or less The melt mass flow rate of the resin composition, which is composed of a resin composition containing liquid paraffin and an inorganic filler and is measured at 190 ° C. according to JIS K 7210, is 2.0 g / 10 min. Greater than or equal and, 40 ° C. according to ASTM E96, stretched porous film moisture permeability measured at 60% relative humidity conditions, characterized in that at 1400g ^/ m 2 · 24h or more.

[2] According to JIS K 7127, the distance between chucks is 50 mm and the tensile speed is 200 mm / min. The stretched porosity according to [1], wherein the strength in the machine direction is 0.3 N / 25 mm or more and less than 2.5 N / 25 mm when the distance between chucks is increased by 5% when pulled in the machine direction. the film.

[3] The description according to [1] or [2], wherein the air permeability measured by the Oken test machine method according to JIS P 8117 is 300 seconds / 100 mL or more and 2000 seconds / 100 mL or less. Stretched porous film.

[4] density 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin resin 100 mass parts, 5.0 parts by mass or more, is 20 parts by mass or less A mixing step of mixing liquid paraffin and an inorganic filler to obtain a resin composition, a molding step of molding the resin composition into a film, and stretching the film obtained by the molding step at least in the mechanical direction. The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210, which comprises a porosity step of making the resin composition porous, is 2.0 g / 10 min. A method for producing a stretched porous film, which is characterized by the above.

[5] The method for producing a stretched porous film according to [4], wherein the stretching ratio in the mechanical direction in the porosity step is represented by the following formula II:
1.4 ≤ Y ≤ 0.075X + 1.8 ... (Equation II)
(In the formula, X indicates the mixing ratio (parts by mass) of liquid paraffin to 100 parts by mass of the polyolefin resin, and Y indicates the draw ratio (times)).

The present invention can be suitably used for personal care products such as diapers.

Claims (5)

Density 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less,
Liquid paraffin which is 5.0 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the polyolefin resin.
Consists of a resin composition containing an inorganic filler and
The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210 is 2.0 g / 10 min. That's all
According to ASTM E96 and 40 ° C., stretched porous film moisture permeability measured at 60% relative humidity conditions, characterized in that at 1400g ^/ m 2 · 24h or more. According to JIS K 7127, the distance between chucks is 50 mm and the tensile speed is 200 mm / min. The stretched porosity according to claim 1, wherein the strength in the machine direction is 0.3 N / 25 mm or more and 2.5 N / 25 mm or less when the distance between chucks is increased by 5% when pulled in the machine direction. the film. The stretched porous film according to claim 1 or 2, wherein the air permeability measured by the Oken type testing machine method according to JIS P 8117 is 300 seconds / 100 mL or more and 2000 seconds / 100 mL or less. Density 0.900 g / cm ³ or more, and a polyolefin resin is 0.940 g / cm ³ or less, relative to the polyolefin resin 100 mass parts, 5.0 parts by mass or more, and the liquid paraffin 20 parts by mass or less , Inorganic filler, and a mixing step to obtain a resin composition.
A molding step of molding the resin composition into a film, and
The film includes a porosity step of stretching the film obtained by the molding step at least in the mechanical direction to make the film porous.
The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210 is 2.0 g / 10 min. A method for producing a stretched porous film, which is characterized by the above. The method for producing a stretched porous film according to claim 4, wherein the stretching ratio in the mechanical direction in the porosity step is represented by the following formula II:
1.4 ≤ Y ≤ 0.075X + 1.8 ... (Equation II)
(In the formula, X indicates the mixing ratio (parts by mass) of liquid paraffin to 100 parts by mass of the polyolefin resin, and Y indicates the draw ratio (times)).