WO2019130990A1

WO2019130990A1 - Stretched porous film and method for producing same

Info

Publication number: WO2019130990A1
Application number: PCT/JP2018/044257
Authority: WO
Inventors: 邦男鎌田; 田中　伸幸
Original assignee: 株式会社トクヤマ
Priority date: 2017-12-26
Filing date: 2018-11-30
Publication date: 2019-07-04
Also published as: JP7112430B2; JPWO2019130990A1

Abstract

The present invention enables the achievement of a stretched porous film which has air permeability, water resistance and flexibility at the same time. A stretched porous film according to one embodiment of the present invention contains a resin composition that contains a specific polyolefin resin and a liquid paraffin at a specific mass ratio; and the water vapor permeability of this stretched porous film is 1,400 g/m2·24 h or more.

Description

Stretched porous film and method for producing the same

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

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

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 Application Publication "Japanese Patent Application 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 is made in view of the above-mentioned problems, and the object thereof is to realize a stretched porous film having both breathability, water resistance and flexibility suitable for personal care products such as diapers. It is.

As a result of intensive studies conducted by the present inventor in order to solve the above-mentioned problems, it is possible to use a polyolefin resin having a specific melt mass flow rate, to make a specific mass ratio of liquid paraffin to the polyolefin resin. It has been found that a stretched porous film having both air permeability, water resistance, and flexibility can be realized by using a resin composition containing N, and adjusting the moisture permeability to a specific range, and a combination thereof. 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 And 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. This is a stretched porous film characterized by having the moisture permeability of 1400 g / m ² · 24 h or more measured under the conditions of 40 ° C. and 60% relative humidity according to ASTM E96.

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 Mixing the inorganic filler to obtain a resin composition, forming the resin composition into a film, and stretching the film obtained by the forming at least in the machine direction. The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210, including a porosifying step of porosifying, at 2.0 g / 10 min. It is the above, The manufacturing method of the extending | stretching porous film characterized by the above-mentioned.

According to one aspect of the present invention, it is possible to obtain a stretched porous film having both air permeability, moisture permeability and flexibility.

Although one embodiment of the present invention is described below, the present invention is not limited to this.

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

Therefore, the stretched porous film according to one embodiment of the present invention solves the problems of the prior art described above, and has both air permeability, 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 measured at 190 ° C. according to JIS K 7210. 2.0 g / 10 min. This is the above, and the moisture permeability measured under the conditions of 40 ° C. and 60% relative humidity in accordance with ASTM E96 is 1400 g / m ² · 24 h or more. Thus, by combining liquid paraffin with a specific weight ratio to a polyolefin resin having specific physical properties, desired flexibility can be obtained in addition to water resistance. Further, by setting the moisture permeability in a specific range, desired air permeability can be obtained. Therefore, a stretched porous film having both air permeability, water resistance and flexibility can be realized.

The stretched porous film may be made of a resin composition containing a polyolefin resin, liquid paraffin and an inorganic filler, and, for example, a sheet of another material or the like may be laminated in addition to the resin composition. It may also be

<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. If the density is in the above-mentioned range, a stretched porous film having desired flexibility can be obtained by combining with liquid paraffin described later. Also, the density and the melting point are correlated to some extent. If the density is in the above range, the heat setting temperature is somewhat different from the melting point, so that it is possible to prevent the polyolefin resin from melting and blocking the pores of the stretched porous film simultaneously with the heat setting. Therefore, the decrease in air permeability can be prevented.

As said polyolefin resin, linear low density polyethylene (LLDPE) and branched low density polyethylene (LDPE) are mentioned. The use of a plurality of types of polyolefin resins is preferable because the melt mass flow rate can be easily adjusted. As the polyolefin 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 (the density of the mixture of plural 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 having a wide range of about 15 to 35 carbon atoms that is liquid at normal temperature and obtained from crude oil, and has a density of 0.790 g / cm ³ or more and 0.920 g / cm ³ or less I say something.

Liquid paraffin is added to improve 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. If the content ratio of liquid paraffin is 5.0 parts by mass or more, flexibility can be further imparted to the stretched porous film. Moreover, if the content rate of liquid paraffin is 20 mass parts or less, the intensity | strength of an extending | stretching porous film can be raised. In addition, since the occurrence of the draw resonance phenomenon can be suppressed, the productivity can be improved.

<1-3. Inorganic filler>
Inorganic fillers are added to make the film porous. Known inorganic fillers can be used without limitation. For example, inorganic salts such as calcium carbonate, barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, and aluminum hydroxide, inorganic oxides such as zinc oxide, magnesium oxide and silica And silicates such as mica, vermiculite and talc, and organic metal salts. Among the above-mentioned inorganic fillers, calcium carbonate is preferable from the viewpoint of cost performance and dissociativeness with a 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 based on 100 parts by mass of the polyolefin resin and liquid paraffin in total. It is more preferable that If the blending ratio of the inorganic filler is 80 parts by mass or more, it is possible to increase the frequency of void generation per unit area, which is caused by the separation of the polyolefin resin and the inorganic filler. Therefore, the adjacent voids are likely to communicate with each other, and the air permeability becomes good. When the proportion of the inorganic filler is 200 parts by mass or less, the elongation at the time of film stretching is good, and the stretching is easy.

<1-4. Other ingredients>
The resin composition may further contain an additive used in a normal resin composition. Such additives include antioxidants, heat stabilizers, light stabilizers, ultraviolet light absorbers, neutralizing agents, lubricants, antifogging agents, antiblocking agents, antistatic agents, slip agents, coloring agents, plasticizers, etc. It can be mentioned. In addition, in the resin composition, a small amount of a resin component other than that constituting the polyolefin resin and the liquid paraffin may be blended within a range not impairing the effects of the present invention. Specifically, if it is within 5.0 parts by mass, more preferably within 2.5 parts by mass with respect to a total of 100 parts by mass of the polyolefin resin and the liquid paraffin, it is acceptable even if other resin components are blended. Ru. In addition, the stretched porous film and the resin composition according to an embodiment of the present invention may not contain a thermoplastic elastomer.

<1-5. Physical Properties of Stretched Porous Film>
The moisture permeability of the stretched porous film is preferably 1400 g / m ² · 24 h or more, and more preferably 1600 g / m ² · 24 h or more. When the moisture permeability is in the above range, the air permeability and the moisture permeability are excellent. For example, when the stretched porous film is used as a back sheet of a paper diaper, it is possible to prevent the stuffiness at the time of 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 setting the upper limit of the moisture permeability to 4000 g / m ² · 24 h or less, the diaper using the stretched porous film has a lower possibility of liquid leakage when worn. Moreover, since the moisture permeability of the film shown by patent document 1 is over 4000 g / m ² · 24 h in all cases, it is considered that there is a possibility that liquid leakage may occur at the time of wearing when used for a diaper or the like.

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

The 5% tensile 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% tensile strength, the more flexible it is. If the 5% tensile strength is less than 2.5 N / 25 mm, more flexibility can be imparted. If the 5% tensile strength is 0.3 N / 25 mm or more, it is possible to suppress the film elongation to the line tension applied in the machine direction at the time of secondary processing.

According to JIS K 7127, the 5% tensile strength of the sample at a chuck distance of 50 mm and a tensile speed of 200 mm / min. The tensile strength in the machine direction is measured as the strength in the machine direction when the sample is stretched 5%. That is, 5% tensile strength is measured as stress in the machine direction when the distance between chucks is expanded by 2.5 mm. Further, in the present specification, 5% tensile strength is a value measured for a sample having a width of 25 mm and a length in the machine direction of 150 mm collected from a stretched porous film.

The melt mass flow rate of the resin composition is 2.0 g / 10 min. It is preferable that it is more than 2.0 g / 10 min. Above, 6.0 g / 10 min. Or less, more preferably 2.0 g / 10 min. Above, 5.0 g / 10 min. It is more preferable that it is the following. If the melt mass flow rate is in the above range, more stable film formation can be performed. The melt mass flow rate is 2.0 g / 10 min. If it is the above, the resin pressure of the film forming extruder can be suppressed, and an adverse effect on film forming can be prevented. Moreover, the melt mass flow rate is 6.0 g / 10 min. If it is the following, the neck-in at the time of forming into a film with T-die can be suppressed more. Therefore, the required product width can be easily obtained. Also, melt mass flow rate and 5% tensile strength tend to be correlated. Decreasing the melt mass flow rate increases the 5% tensile strength and therefore tends to result in a stretched porous film with poor flexibility. The melt mass flow rate of the resin composition is measured by Method A 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. More preferably, it is 1100 seconds / 100 mL or less. The lower the permeability, the easier it is for gas to pass. When the air permeability is in the above-mentioned range, when the stretched porous film is used as a back sheet of a paper diaper, it is possible to prevent stuffiness when worn. The air permeability is measured by the Oken type tester according to JIS P 8117.

The heat shrinkage rate in the machine direction of the stretched porous film is preferably 5.0% or less, and more preferably 3.5% or less. If the 5% tensile strength is high and the heat shrinkage rate in the machine direction is 5.0% or less, the film elongation to the line tension applied in the machine direction at the time of secondary processing can be further suppressed. The heat shrinkage rate in the machine direction is preferably as close to 0% as possible, but is practically 0.5% or more.

The heat shrinkage rate in the machine direction is measured by the following method. A sample of 15 cm × 15 cm is taken from the stretched porous film. Make a mark on this sample so that there is 10 cm between marks in the machine direction. The sample is left at 50 ° C. for 24 hours, then cooled to room temperature and the length between marks is measured. The heat shrinkage rate in the machine direction can be obtained from the following formula I.
Formula I: Thermal contraction rate in machine 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 further preferred that When the weight per unit area is in the above range, a stretched porous film excellent in air permeability, 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. Moreover, if the fabric 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 A mixing step of mixing a liquid paraffin of 5.0 parts by mass or more and 20 parts by mass or less and an inorganic filler to obtain a resin composition, and a forming step of forming the resin composition into a film shape; And V. a porosification step in which the film obtained by the molding step is made porous by drawing at least in the machine direction. Thus, by combining liquid paraffin with a specific weight ratio to a polyolefin resin having specific physical properties, a stretched porous film having desired flexibility in addition to water resistance can be obtained. A resin composition having a melt mass flow rate in a specific range improves the flowability of the resin composition, and a flexible stretched porous film is obtained. Further, by stretching and porosifying a film containing a resin composition of a specific composition, a stretched porous film having desired air permeability can be obtained. Therefore, a stretched porous film having both air permeability, water resistance and flexibility can be realized. [1. About the matter already demonstrated by stretched porous film], below, description is abbreviate | omitted and the above-mentioned description is suitably used.

<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 In this step, a liquid paraffin and an inorganic filler are mixed to obtain a resin composition. First, a polyolefin resin, liquid paraffin, an inorganic filler, and, if necessary, additives to be blended are mixed. The mixing method is not particularly limited, and known methods 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 generally kneaded and pelletized by a method such as strand cut, hot cut or underwater cut using a kneader such as a high kneader type twin screw extruder or a tandem type kneader. It is preferable because mixing and kneading in advance and pelletization 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. The pellets obtained as described above are preferably formed into a film by a circular die or a T-die attached to the tip of an extruder. At this time, the cooling method in the case of using the T-die method 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 film may be formed by directly charging the resin composition into an extruder without mixing and kneading.

<2-3. Porous process>
The porosifying step is a step in which the film obtained by the forming step is rendered porous by drawing at least in the machine direction. By stretching the film obtained by the forming step, the interface between the resin component (the polyolefin resin and the liquid paraffin) and the inorganic filler is peeled off. Then, a minute void is formed at the peeled interface, and the void forms a communicating hole penetrating in the thickness direction of the film, whereby a stretched porous film is formed. Stretching can be performed by a known method such as roll stretching or tenter stretching. The stretching may be uniaxial stretching or biaxial stretching.

In addition, it is preferable that the draw ratio of the machine direction in the said porosification process is shown by the following formula II:
1.4 ≦ Y ≦ 0.075X + 1.8 (Formula II)
(In the formula, X represents a blending ratio (parts by mass) of liquid paraffin to 100 parts by mass of a polyolefin resin, and Y represents a stretching ratio (fold)).

By carrying out the stretching under the condition that the above-mentioned formula II is established, the obtained film is sufficiently stretched while having flexibility, so that the thickness unevenness is unlikely to occur, and the tear strength is good and sufficient. Holes of number and size are formed. Therefore, with such a stretching ratio, a stretched porous film having both air permeability, moisture permeability and flexibility can be obtained more easily. The stretching may be single-stage stretching or multi-stage stretching.

It is preferable that extending | stretching temperature is a temperature range above normal temperature and less than the softening point of a resin composition. If the stretching temperature is equal to or higher than normal temperature, stretching unevenness is unlikely to occur, so the thickness tends to be uniform. In addition, when the stretching temperature is less 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 the moisture permeability being lowered. The stretching temperature can be appropriately adjusted by the combination of the physical properties of the resin composition used and the stretching ratio.

<2-4. Heat setting process>
The manufacturing method may include a heat setting step. The heat setting step is a step of heat setting the stretched porous film after stretching in order to suppress heat shrinkage in the stretching direction. The heat setting is a heat treatment performed in an environment in which the dimensions are not changed while maintaining a stretched state of the stretched film. As a result, it is possible to suppress elastic recovery during storage, contraction due to heat, squeezing, etc. by heat setting.

As a heat setting method in the case of adopting a roll drawing method as a drawing method, a method of heating a film after drawing with a heated roll (annealing roll) can be mentioned. In addition, as a heat setting method in the case where the tenter stretching method is adopted as the stretching method, a method of heating the film after stretching in the vicinity of the tenter outlet may be mentioned.

The heat setting temperature is preferably 70 ° C. or more and 95 ° C. or less, and more preferably 80 ° C. or more and 95 ° C. or less. If the heat setting temperature is 70 ° C. or more, heat shrinkage can be suppressed by sufficient heat setting. In addition, when the heat setting temperature is 95 ° C. or less, the pores of the stretched porous film can be further prevented from being crushed by heat.

The heat setting time is preferably 0.2 seconds or more, more preferably 0.5 seconds or more, and still more preferably 1.0 seconds or more. If the heat setting time is 0.2 seconds or more, the heat shrinkage can be suppressed by sufficient heat setting. The heat setting time is preferably 20 seconds or less, more preferably 15 seconds or less. Although it depends on the combination with the heat setting temperature, it can not be said in general, but if the heat setting time is 20 seconds or less, it is possible to prevent the pores from being crushed by melting of the stretched porous film. Therefore, the air permeability and the moisture permeability can be prevented from being lowered.

The heat setting time is the time for which the stretched porous film is kept at the heat setting temperature. For example, when the roll stretching method is adopted, it refers to the time during which the film is in contact with the annealing roll. The number of annealing rolls is not particularly limited, but in the case of two or more, the heat setting time is the sum of the time when the stretched porous film is in contact with each annealing roll. Also, when the tenter stretching method is adopted, the time of heat setting indicates the time of heating and maintaining at the heat setting temperature at the tenter outlet. When heat setting is divided into multiple times and heated, it is the sum of each heating time.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and 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 value of the extending | stretching porous film of the below-mentioned Example and a comparative example is measured by the method shown below.

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

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

(3) Moisture Permeability Ten sheets of 10 cm × 10 cm were collected from the stretched porous film. With respect to these, according to ASTM E96, the moisture permeability was measured under the conditions of a pure water method at 40 ° C., a relative humidity of 60%, and a measurement time of 24 hours, and the average value was determined.

(4) Permeability Permeability was measured by the Oken type tester according to JIS P 8117.

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

(6) Thermal contraction rate in the machine direction A 15 cm × 15 cm sample was taken from the stretched porous film. The samples were marked so that there was 10 cm between them in the machine direction. The sample was left at 50 ° C. for 24 hours, cooled to room temperature, and the length between the marked lines was measured. The heat shrinkage rate in the machine direction was determined by the following formula (Formula I).
Formula I: Thermal contraction rate in machine direction (%) = {(10 cm−length between marked lines after cooling (cm)) / 10 cm} × 100.

[Component used]
A: Linear low density polyethylene [Dow Chemical Co., Ltd., trade name: Dowrex 2047, density: 0.917 g / cm ³ , MI: 2.3 g / 10 min. ]
B: Linear low density polyethylene [Dow Chemical Co., Ltd., trade name: Dowrex 2035 G, density: 0.919 g / cm ³ , MI: 6.0 g / 10 min. ]
C: Linear low density polyethylene [Dow Chemical Co., Ltd., trade name: Dowrex 2036P, density: 0.935 g / cm ³ , MI: 2.5 g / 10 min. ]
D: Linear low density polyethylene [Dow Chemical Co., Ltd., trade name: Dowrex 2045 G, density: 0.920 g / cm ³ , MI: 1.0 g / 10 min. ]
E: Branched low density polyethylene [Mitsui-Dupont Polychemicals Co., Ltd., trade name: Mirason 16P, density: 0.917 g / cm ³ , MI: 3.7 g / 10 min. ]
F: Ultra-low density polyethylene [Dow Chemical Co., Ltd., trade name: Atein 4607 GC, density 0.904 g / cm ³ , MI: 4.0 g / 10 min. ]
G: High density polyethylene [manufactured by Tosoh Corp., trade name: Nipolon 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 Reme 4, density: 0.793 g / cm ³ )
O: Calcium carbonate [manufactured by Imerys Minerals, trade name: FL-520]
P: Additive [Titanium oxide (Huntsman Co., Ltd., trade name: TR28) 50% by mass, and hindered phenol heat stabilizer (Ciba Japan Co., Ltd., trade name: IRGANOX 3114) 20% by mass, Mixture with a phosphorus-based heat stabilizer (Ciba Japan Ltd., trade name: IRGAFOS 168) and 30% by mass].

Example 1
It was set as the resin composition which mixed the polyolefin resin of Table 1, hydrocarbon, an inorganic filler, and an additive. It was granulated and then film formation was performed.

Granulation (preparation of pellets) was performed as follows. The resin composition was extruded into strands at a cylinder temperature of 160 ° C. using a vented φ30 mm twin-screw extruder, and cooled in a water bath. Thereafter, 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 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 machine direction by a roll stretcher set at 40 ° C., and then inline annealing was performed by a heat set roll set at 90 ° C. (heat setting time 4) Seconds). The heat shrinkage rate in the machine direction at the time of heat setting was 8%.

In Examples 2 to 13 and Comparative Examples 1 to 8, Example 1 is used except that the blending ratio of each component or the stretching condition (stretching ratio or heat setting temperature) is changed as described in Table 1 and Table 2. A film was formed as well.

In addition, "polyolefin resin: compounding ratio (mass%)" represents the compounding ratio of each polyethylene resin with respect to 100 mass% of polyolefin resin contained in a resin composition. "Hydrocarbon: blending ratio (parts by mass)" represents the blending ratio of hydrocarbons to 100 parts by mass of the polyolefin resin. The blending ratio of calcium carbonate and additives is described as a blending ratio with respect to a total of 100 parts by mass of the polyolefin resin and the hydrocarbon.

The stretching condition * 1 represents a stretching ratio of 1.8 times and a heat setting temperature of 90 ° C. The stretching condition * 2 represents a stretching ratio of 3.2 times and a heat setting temperature of 90 ° C. The stretching condition * 3 indicates a stretching ratio of 2.5 times and a heat setting temperature of 90 ° C. The stretching condition * 4 indicates that the stretching condition is 1.3 times and the heat setting temperature is 90 ° C.

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

The stretched porous films of Examples 1 to 13 all exhibited good moisture permeability of at least 1400 g / m ² · 24 h, and also had good texture. Also, the stretched porous films of Examples 1-8 and 10-12 maintained low values for 5% tensile strength and thermal shrinkage. Furthermore, in the stretched porous films of Examples 1 to 8 and 10 to 12, any stretching ratio satisfies Formula II.

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 to which high density polyethylene is added, the moisture permeability is higher and the air permeability is lower than Example 3. Moreover, although the result of 5% elongation strength was high in Example 4, it was better than the comparative example.

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

In Examples 9 and 13 in which the draw ratio does not satisfy Formula II, the 5% tensile strength is higher than Examples 1 to 8 and 10 to 12 which satisfy Formula II, but the moisture permeability is higher than that of Comparative Example. The balance of air permeability, 5% tensile strength and heat shrinkage was good.

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

In Comparative Example 1, no hydrocarbon was used. As a result, the obtained stretched porous film had a high 5% tensile strength, and a stretched porous film poor in flexibility was obtained.

In Comparative Examples 2 to 5, hydrocarbons other than liquid paraffin were used as the hydrocarbons. As a result, in Comparative Example 2 in which paraffin was used as a hydrocarbon and Comparative Example 5 in which hydrogenated polybutene was used as a 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, the moisture permeability was low in any case, and a stretchable porous film which is easily steamed 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 less flexible stretched porous film with low air permeability, high moisture permeability and 5% tensile strength 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 has a low moisture permeability, and a stretched porous film which is easy to steam is obtained.

Comparative Example 8 was a stretched porous film inferior in air permeability because of low moisture 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 resin composition is composed of a liquid paraffin and 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. This is a stretched porous film characterized by having the moisture permeability of 1400 g / m ² · 24 h or more measured under the conditions of 40 ° C. and 60% relative humidity according to ASTM E96.

[2] According to JIS K 7127, the distance between chucks is 50 mm, the tensile speed is 200 mm / min. Tensile strength in the machine direction when the distance between chucks is extended by 5% in the machine direction, and the tensile strength in the machine direction is 0.3 N / 25 mm or more and 2.5 N / 25 mm or less. the film.

[3] The air permeability measured by the Oken type tester according to JIS P 8117 is 300 seconds / 100 mL or more and 2000 seconds / 100 mL or less, according to [1] or [2]. 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 forming step of forming the resin composition into a film shape, and stretching the film obtained by the forming step at least in the machine direction The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210 is 2.0 g / 10 min. It is the above, The manufacturing method of the extending | stretching porous film characterized by the above-mentioned.

[5] The method for producing a stretched porous film according to [4], wherein the stretching ratio in the machine direction in the above-mentioned porosifying step is represented by the following formula II:
1.4 ≦ Y ≦ 0.075X + 1.8 (Formula II)
(In the formula, X represents a blending ratio (parts by mass) of liquid paraffin to 100 parts by mass of a polyolefin resin, and Y represents a stretching ratio (fold)).

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

Claims

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,
A resin composition containing an inorganic filler;
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 it,
A stretched porous film characterized by having a moisture permeability of 1400 g / m 2 · 24 h or more measured under the conditions of 40 ° C and a relative humidity of 60% according to ASTM E96.
According to JIS K 7127, the distance between chucks 50 mm, the tension speed 200 mm / min. The tensile porosity according to claim 1, characterized in that the strength in the machine direction when the distance between chucks is stretched by 5% by pulling in the machine direction is 0.3 N / 25 mm or more and 2.5 N / 25 mm or less. the film.
The stretched porous film according to claim 1 or 2, wherein the air permeability measured by the Oken type tester 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 Mixing an inorganic filler to obtain a resin composition;
A forming step of forming the resin composition into a film shape;
And V. a porosifying step of porosifying the film obtained by the forming step by at least stretching in the machine direction,
The melt mass flow rate of the resin composition measured at 190 ° C. according to JIS K 7210 is 2.0 g / 10 min. It is the above, The manufacturing method of the extending | stretching porous film characterized by the above-mentioned.
The method for producing a stretched porous film according to claim 4, wherein the stretching ratio in the machine direction in the porosifying step is represented by the following formula II:
1.4 ≦ Y ≦ 0.075X + 1.8 (Formula II)
(In the formula, X represents a blending ratio (parts by mass) of liquid paraffin to 100 parts by mass of a polyolefin resin, and Y represents a stretching ratio (fold)).