JP7404739B2 - Heat sealing film - Google Patents

Description

The present invention relates to a heat-sealing film, and more particularly to a heat-sealing film suitable for producing a pouch with excellent impact resistance in a low temperature range.

CPP film (also called unstretched polypropylene film or cast PP film), which is made of polypropylene and has heat sealability, has excellent heat resistance and is used for making pouches for storing various foods and the like. By the way, in recent years, impact polypropylene (hereinafter sometimes referred to as impact PP) has been used for the production of CPP films as more heat resistance and impact resistance are required for retort sterilization (heated steam sterilization), etc. It has started to be done.

Impact PP is also called block PP, impact copolymer, or high impact polypropylene, and contains rubber components such as ethylene-propylene copolymer (EPR) or styrene-butadiene copolymer (SBR) in a matrix of homopolypropylene or random polypropylene. are dispersed therein, and the impact resistance strength is significantly improved due to the dispersion of such rubber components.

By the way, in addition to properties such as heat seal strength and impact resistance, CPP films used for producing pouches supplied for retort sterilization and the like are also required to have blocking resistance and yuzu skin resistance. In other words, it goes without saying that films need to have anti-blocking properties that prevent blocking when they are stacked on top of each other, but when subjected to heated steam sterilization such as retort sterilization, the oil content of the contents is absorbed into the film. This can cause the pouch to become deformed and look like yuzu skin, so it is also required to prevent such yuzu skin deformation. The film formed from the above-mentioned impact PP has poor blocking resistance and yuzu skin resistance, and therefore needs to be modified.

Various means for improving the above properties have been proposed. For example, Patent Documents 1 and 2 disclose a method in which linear low density polyethylene (LLDPE) is added to a propylene-based impact copolymer (corresponding to impact PP). A blended propylene-based resin composition has been proposed, and it has been disclosed that a heat-sealing film with excellent various properties can be obtained using such a resin composition.

Patent Documents 1 and 2 aim to improve the physical properties of a heat-sealing film made of impact PP by blending linear low-density polyethylene with impact PP, but in terms of impact resistance at low temperatures, Further improvements are needed. In other words, pouches filled with various foods usually require impact resistance at low temperatures, but this property is still insufficient. The reality is that if a bag is stored at a temperature of 5°C filled with something and then subjected to a drop test from a height of 120 cm, there is a high probability that the bag will break. In Patent Document 2, the impact resistance is evaluated by a drop test at 0° C., but the drop height is as low as 55 cm, and the impact resistance at low temperatures cannot be said to be sufficient.

Patent No. 4844091 WO2017/038349

Therefore, an object of the present invention is to provide a heat sealing film with improved impact resistance at low temperatures.

The present inventors prepared a propylene-based resin composition by combining various commercially available impact PP (block polypropylene) and linear low-density polyethylene, and prepared a heat-sealable film from this composition at low temperature. When the impact resistance of this film was tested, the tan δ (loss tangent) of this film at 5°C and 10 Hz was a constant value, and the impact resistance of ethylene in PP (block polypropylene) calculated from the dynamic viscoelasticity test of this film was found to be a constant value. By adjusting the type and amount ratio of impact PP (block polypropylene) and linear low density polyethylene so that the glass transition temperature derived from the copolymer is within a certain range, impact resistance at low temperatures can be greatly improved. The present invention was completed based on the findings that the present invention can be improved.

That is, according to the present invention, there is provided a heat-sealable film formed from a polypropylene resin composition containing block polypropylene made of homopolypropylene and an ethylene-propylene copolymer, and linear low-density polyethylene, The tan δ (5° C., 10 Hz) measured in a dynamic viscoelasticity test for the film is in the range of 0.070 or more , and the xylene soluble fraction contained in the film is 7.5% by mass or more, 10 % by mass, containing the linear low-density polyethylene in an amount of 10 to 20% by mass, and derived from the ethylene-propylene copolymer calculated from the tan δ temperature curve obtained in the dynamic viscoelasticity test. Provided is a heat-sealable film having a glass transition temperature higher than -35°C.

In the heat-sealing film of the present invention, the following embodiments are preferably employed.
(1) The glass transition temperature derived from the ethylene-propylene copolymer is in the range of -35 to -15°C.
(2) The linear low density polyethylene contains hexene-1 or 4-methylpentene-1 as a comonomer.
(3) The comonomer is 4-methylpentene-1.
(4) A plurality of types of block polypropylene (impact polypropylene) are used that differ in at least either the ethylene/propylene copolymer content or the ethylene/propylene ratio of the ethylene/propylene copolymer.

The above heat-sealing film is laminated with other resins or metal foils as a heat-sealing layer to be used as a multilayer film, particularly a multilayer film for pouches.

In the present invention, the xylene soluble fraction derived from the ethylene-propylene copolymer in the block polypropylene (Impact PP) component is determined by dissolving the film in boiling xylene, as shown in the examples below. It is measured by cooling and separating solid and liquid, reprecipitating the soluble content with methanol, filtering and drying the precipitate, and weighing the dry matter. That is, this xylene soluble content corresponds to the amount of ethylene-propylene copolymer in the block polypropylene , and the xylene insoluble content corresponds to the amount of the remaining components (polypropylene and linear low density polyethylene used as a modifying component). corresponds to the amount.
In this case, the amount of ethylene-propylene copolymer can also be measured by dissolving the block polypropylene as it is in boiling xylene.
In addition, the glass transition temperature derived from the ethylene-propylene copolymer in the block polypropylene component is determined by creating a tan δ change curve (tan δ temperature curve) with respect to temperature at 10 Hz in dynamic viscoelasticity measurement (DMA). It is determined as the maximum point on the low temperature side of the change curve.

The above-mentioned heat-sealing film of the present invention has significantly improved impact resistance at low temperatures despite the small amount of ethylene-propylene copolymer, and pouches made using this heat-sealing film has extremely high drop impact resistance at low temperatures, and effectively prevents the pouch from breaking when the pouch is filled with contents and kept at 5°C and dropped from a height of 120 cm. I can do it.

Furthermore, the heat-sealing film of the present invention is obtained by melt-extruding a blend of block polypropylene (block PP) and linear low-density polyethylene (LLDPE), and is measured by a dynamic viscoelasticity test of the film. Provided that the tan δ (loss tangent) at 5°C and 10 Hz is 0.070 or more, the amount of ethylene-propylene copolymer contained in the block PP is within a certain range (i.e. , the xylene soluble fraction of the film is less than 10% by mass), the amount ratio of block PP and LLDPE is adjusted, and the ethylene/ By selecting the type of block PP or LLDPE to be used so that the glass transition temperature of the propylene copolymer is higher than -35°C, the low-temperature impact resistance of the heat-sealing film can be greatly improved. That is, the great advantage of the present invention is that it does not require the trouble of producing a block PP having specific physical properties or measuring the ethylene/propylene ratio of the ethylene/propylene copolymer in the block PP . The point is that the impact resistance of the film at low temperatures can be greatly improved by adjusting the physical properties by combining linear low density polyethylene (LLDPE) with the combination of block PP (impact PP) . In other words, the present invention can be easily implemented even by non-polymer manufacturers, and is extremely useful industrially.

FIG. 3 is a diagram showing a tan δ temperature curve obtained by dynamic viscoelasticity measurement of the heat-sealing film of the present invention obtained in Example 1.

The heat-sealing film of the present invention (hereinafter sometimes referred to as CPP film) is produced using a blend of a block polypropylene component (A) and a modifying component (B) (i.e., linear low-density polyethylene). Although obtained by melt extrusion, this film must have the following physical properties.
Note that hereinafter, block polypropylene may be referred to as block PP, impact polypropylene, or even impact PP.
(i) tan δ (5° C., 10 Hz) measured by a dynamic viscoelasticity test is 0.070 or more, particularly 0.074 or more.
(ii) The xylene soluble fraction is less than 10% by mass and is in the range of 7.5% by mass or more .
(iii) The glass transition temperature derived from the ethylene-propylene copolymer in the impact PP calculated from the tan δ temperature curve obtained in the dynamic viscoelasticity test is higher than -35°C, particularly -30°C or higher. .

First, to explain the characteristic (i) above, tan δ (loss tangent) is a temperature-dependent parameter expressed by the ratio of loss modulus/storage modulus, and the larger this value, the better the characteristics as a viscous body. The larger or smaller the value, the greater the properties as an elastic body. In the present invention, using a dynamic viscoelasticity measuring device, viscoelasticity is measured under conditions where stress is applied to the film at 10 Hz, and a temperature change curve of tan δ is created. A value of 0.070 or more, particularly 0.074 or more is necessary in order to obtain good low-temperature impact resistance. Since the CPP film of the present invention exhibits a relatively large value of tan δ at 5°C, a large force is required to deform this film at low temperatures, which makes it difficult to improve impact resistance at low temperatures. It becomes possible.

The value of tan δ at 5°C mainly depends on the ratio of the amounts of impact PP and LLDPE, and the higher the amount of LLDPE in the CPP film, the higher the value of tan δ. It varies depending on the type of impact PP used.

In addition, as mentioned above, the xylene soluble fraction in (ii) above is measured by dissolving the CPP film in boiling xylene, and the ethylene-propylene copolymer ( (hereinafter sometimes referred to as EPR). That is, this EPR is contained in the impact PP used to form the film. Such a xylene soluble fraction greatly contributes to improving impact resistance, but in the present invention, if this amount exceeds the above range, the blocking resistance and yuzu skin resistance of the film are impaired. Put it away. Moreover, there is also a possibility that the heat sealing strength will be reduced. On the other hand, if this amount is too small, the desired impact resistance will decrease. Therefore, in the CPP of the present invention, the xylene soluble content is less than 10% by mass, and particularly needs to be in the range of 7.5% by mass or more.

Further, the glass transition temperature (iii) above is derived from EPR in impact PP, and is calculated from the tan δ temperature curve measured in the above dynamic viscoelasticity test.
FIG. 1 is a tan δ temperature curve of a CPP film of the present invention produced in Example 1, which will be described later. If this is explained as a model diagram, the glass transition temperature is the temperature indicating the maximum point of this curve. As can be understood from FIG. 1, the CPP film of the present invention has two maximum points, and the maximum point at temperatures above 0°C originates from the polypropylene in the impact PP. The position of is almost constant regardless of the type of impact PP used. On the other hand, the maximum point occurring on the negative temperature side originates from the EPR in the impact PP. That is, in the present invention, in order to improve the impact resistance at low temperatures, in addition to the above-mentioned characteristics (i) and (ii), the glass transition temperature derived from this EPR must be lower than -50°C. By setting the temperature to be high, preferably higher than -35°C, particularly preferably -30°C or higher, the impact resistance at low temperatures is greatly improved.

In the present invention, the fact that the glass transition temperature of EPR in impact PP exhibits a high value as described above means that the glass transition temperature of EPR exhibits a high value as shown in FIG. This means that the temperature is close to that of Although the principle has not been precisely elucidated, the fact that the glass transition temperature of EPR approaches that of polypropylene suggests that the compatibilizing effect of LLDPE used as the modifier (B) is effective. However, EPR becomes more finely dispersed in polypropylene. The present inventors estimate that as a result of this, the impact resistance at low temperatures will be greatly improved.

In the present invention, the glass transition temperature derived from EPR as described above largely depends on the ethylene/propylene ratio of this EPR, and the present inventors have found that the larger the ethylene/propylene ratio, the higher the glass transition temperature. It has been confirmed that the lower the ethylene/propylene ratio, the higher the glass transition temperature.

As described above, the CPP film of the present invention can achieve the above (i) to (iii) by selecting the types and quantitative ratios of impact PP and LLDPE to be used, preparing a blend, and forming the blend by melt extrusion. A CPP film that satisfies the characteristics and has excellent impact resistance at low temperatures can be obtained.

The CPP film of the present invention is produced by dry-blending each component, putting it into an extruder, melt-kneading it, melt-extruding the blend into a film from a T-die, and transferring the extruded film-like melt to a cooling roll. Although it is produced by contacting it to solidify it and winding it up, depending on the cooling conditions and winding speed at this time, various values measured by dynamic viscoelasticity tests may become unstable. That is, in the present invention, since the type and amount ratio of impact PP and LLDPE to be used are determined in advance through a laboratory test, instability of the measured values should be avoided. Therefore, in the present invention, the temperature of the cooling roll is set to 60° C. or lower.

Further, the thickness of the CPP film of the present invention is not particularly limited, but in consideration of rigidity, unsealability, etc., it is usually preferably in the range of 20 to 100 μm, particularly 50 to 80 μm.

Each component used in forming the CPP film of the present invention will be explained below.

<Impact PP component (A)>
The impact PP component (A) is made of impact polypropylene (impact PP), and the impact PP used in the present invention is particularly composed of homo or random polypropylene in which ethylene-propylene copolymer (EPR) is dispersed. It has a structure. That is, by dispersing EPR in polypropylene, impact resistance is imparted to polypropylene. In addition to EPR, other known rubber components dispersed in polypropylene include styrene-butadiene copolymer (SBR) and ethylene-propylene-butene copolymer (EPBR). Impact resistance at low temperatures, which is the object of the invention, can be improved.

In the present invention, the impact PP as described above has an MFR (melt flow rate, 230° C.) in a range of about 0.5 to 10 g/10 min from the viewpoint of film moldability (extrusion moldability) and the like.

By the way, in the CPP film of the present invention, as mentioned above, the xylene soluble fraction derived from EPR in the CPP film is less than 10% by mass, particularly in the range of 7.5% by mass or more, and most preferably 7.5% by mass or more. It is within the range of .5 to 9.9% by mass. That is, the EPR content in the CPP film can be adjusted within the above range by mixing impact PP containing an excessively high EPR content with impact PP containing a small amount of EPR.
Note that the EPR content in this impact PP can be measured by dissolving the impact PP in boiling xylene, similarly to the film.

Furthermore, the EPR in the above CPP film requires that the glass transition temperature (Tg) measured in a dynamic viscoelasticity test of the film be higher than -35°C, particularly -30°C or higher. As mentioned earlier, the glass transition temperature of EPR in impact PP largely depends on the composition of ethylene and propylene, and the higher the ethylene content (lower the propylene content) in EPR, the lower the glass transition temperature. , the lower the ethylene content (the higher the propylene content), the higher the glass transition temperature. For example, when the ethylene/propylene molar ratio of this EPR is 45/55 or less, the glass transition temperature tends to be -35°C or less. Therefore, in the present invention, it is necessary to use impact PP containing EPR with a small ethylene/propylene molar ratio, but such a glass transition temperature is determined by the change in tan δ with respect to temperature at 10 Hz in dynamic rheological measurements (DMA). It corresponds to the maximum point of the curve and can be easily measured. Therefore, the formulation can be adjusted based on the glass transition temperature and xylene soluble content calculated by simple measurements without measuring the composition such as the ethylene/propylene ratio of EPR contained in the impact PP used. This is a great advantage of the invention.

That is, in the present invention, if there is impact PP that satisfies the EPR content (xylene soluble content) and glass transition temperature as described above, it can be used as an impact PP component as is, but impact PP that does not satisfy these requirements can be used as is. Even with PP, the EPR content and glass transition temperature can be satisfied by blending multiple types of impact PP. For example, even if impact PP has a glass transition temperature derived from the EPR of -35°C or lower, by blending impact PP with a glass transition temperature higher than -35°C, the glass transition temperature can be within the above-mentioned range. It can be adjusted so that

<Modifying component (B)>
In the present invention, linear low density polyethylene (LLDPE) is used as the modifying component (B). That is, when this LLDPE is mixed with the above-mentioned impact PP, it functions as a compatibilizer between polypropylene (PP) and ethylene-propylene copolymer (EPR), and greatly improves the dispersibility of EPR in PP. This makes it possible to fully exhibit the impact improving effect of EPR, thereby improving impact resistance at low temperatures.

Such LLDPE is a linear low-density polyethylene with a density in the range of 0.910 to 0.925 g/cm ³ , for example, α-1, hexene-1, 4-methylpentene-1, etc. It is made by copolymerizing a small amount (about a few percent) of olefin with ethylene, and it has a low density by introducing short α-olein chains into long ethylene chains as branches, and the linearity of the molecule Extremely sensitive.

In the present invention, the LLDPE used as the modifying component (B) is preferably one with an MFR (190°C) of 1.0 to 15 g/10 min from the viewpoint of film formability, and as a comonomer component, , hexene-1 and 4-methylpentene-1 are preferred, and 4-methylpentene-1 is particularly preferred in terms of low-temperature impact resistance.

Further, in the present invention, it is preferable that LLDPE has a comonomer α-olefin content of 10 mol % or less, and a number average molecular weight measured by GPC in terms of polystyrene of 10,000 or more. That is, when the content of α-olefin as a comonomer is high, or when the number average molecular weight is small and a large amount of low molecular weight components are contained, the oil resistance and the flavor imparted to the contents will be poor. Moreover, a part of LLDPE may be dissolved in xylene, and the xylene soluble fraction in the formed film no longer corresponds to the EPR originating in the impact PP.

The above-mentioned LLDPE is used in an amount that satisfies the above-mentioned film properties (i) to (iii), but generally the amount of LLDPE in the film is 20% by mass or less, particularly 10% by mass or less. It is preferable that the composition of the film is designed so that That is, if LLDPE is contained excessively, the blocking resistance and heat resistance of the film may be impaired.

Incidentally, as long as it does not affect the measurement of the film properties (i) to (iii) described above, additives known per se, such as antioxidants, may be added to the impact PP component (A) and the modifying component (B). ), it is also possible to form films.

<Usage form of heat sealing film>
The heat-sealing film of the present invention described above is usually laminated with other films and used as a multilayer film for manufacturing packaging bags.
In such a multilayer film, this heat sealing film is provided on one surface side of the multilayer film as a heat sealing layer. Examples of other films to be laminated include a stretched polypropylene film, a stretched nylon film, a stretched polyester film, and a metal foil such as aluminum foil. When laminating, a dry laminating adhesive such as a urethane adhesive or an epoxy adhesive can be used as appropriate, or a printed layer can be interposed between them. Furthermore, surface treatments such as corona treatment, flame treatment, and plasma treatment can be performed to improve the adhesion of the film.
The multilayer film obtained in this way not only has excellent heat resistance, yuzu skin resistance, and blocking resistance, but also has excellent impact resistance at low temperatures, so it cannot be sterilized by sterilization such as retort sterilization. Moreover, it is suitably applied to the production of packaging bags (pouches) for foods that are stored at low temperatures in cold regions.

The excellent effects of the present invention will be explained in the following examples.
In addition, the following materials were used in the following experiment.

<Impact PP component (a)>
Block PP (a1);
Sun Allomer PC480A
MFR (230℃): 2.0g/10min
EPR content: 17.5mass%
EPR intrinsic viscosity: 2.19 dl/g
Block PP (a2);
Lotte Chemical FC330R
MFR (230℃): 3.0g/10min
EPR content: 7.5mass%
EPR intrinsic viscosity: 1.78 dl/g
homo PP (a3);
FH3011 manufactured by Sumitomo Chemical Co., Ltd.
MFR (230℃): 2.3g/10min
EPR content: 6.4mass%
EPR intrinsic viscosity: 0.56 dl/g

<Modifying component (b)>
LLDPE (b1);
Manufactured by Sumitomo Chemical Co., Ltd. (Sumikasen) FV205
MFR (190℃): 2.2g/10min
Density: 921kg/ ^m3
α-olefin species: hexene-1
LLDPE (b2);
Urto Zex 2022L manufactured by Prime Polymer Co., Ltd.
MFR (190℃): 2.0g/10min
Density: 919kg/ ^m3
α-olefin species: 4-methylpentene-1

Various measurements and CPP film formation were performed by the following methods.

<EPR content (xylene soluble fraction)>
Impact PP or CPP film was dissolved in xylene under reflux, and after cooling, solid-liquid separation was performed.
The xylene soluble content was reprecipitated with methanol, and the precipitate was filtered, dried, and weighed to calculate the EPR content of the soluble content.
<EPR intrinsic viscosity>
Measurement was performed using an Ubbelohde viscometer in a tetralin solvent at 135°C.

<Production of CPP film>
Each composition was dry blended and put into a hopper of a single screw extruder equipped with a T-die. The mixture was melt-kneaded in an extruder, discharged into a film from a T-die, solidified in contact with a cooling roll, and wound up to form a film with a thickness of 70 μm.
The temperature settings for the extruder cylinder are as follows.
C1: 150℃
C2: 200℃
C3: 210℃
C4: 220℃
T-die temperature: 220℃
Further, the temperature of the cooling roll was set to 45° C., and the winding speed was 2.0 to 3.0 m/min.
The obtained CPP film was subjected to corona discharge treatment to make the surface hydrophilic.

<Dynamic viscoelasticity measurement>
A dynamic viscoelasticity measuring device manufactured by Seiko Instruments Inc. was used. The test conditions are as follows.
Test piece film: length 20mm, width 10mm
Distance between chucks: 5mm
Temperature range: -60℃~60℃
Temperature increase rate: 3℃/min
Frequency: 10Hz
tan δ (loss tangent): Calculated as loss modulus/storage modulus at 5°C.
<Glass transition temperature of EPR>
Dynamic viscoelasticity was measured for the produced CPP film, and the value was determined at the maximum point of tan δ in the observed negative region.
<Laminate>
A layered structure of stretched PET (thickness 12 μm)/stretched nylon (thickness 15 μm)/aluminum foil (thickness 7 μm)/CPP (thickness 70 μm) was laminated by a dry lamination method using a urethane adhesive.

<Pouch bag making>
Two sheets of 140 mm x 180 mm were cut out of the laminated CPP film and filled with 200 g of water to form a bag. For bag making, an impulse sealer manufactured by Fuji Impulse Co., Ltd. was used.
Sealing conditions: 220℃, 1.4 (s), cooling 3.0 (s)
Seal width: 5mm
<Retort conditions>
121℃, 30 minutes shower type <Pouch drop test>
The pouches, which had been cooled overnight at 5° C., were dropped from a height of 120 cm horizontally in two stacks for measurement. The lower pouch was the test pouch. The test was conducted three times, each time the bag was dropped 20 times, and the average number of times the bag remained unbroken in the three tests was measured.
<Yuzu skin resistance>
The laminated pouch prepared in the above procedure was filled with 130g of Ajinomoto Co.'s Cook Do Chinese seasoning for dried roasted shrimp as the contents, and the surface of the pouch after retort sterilization was visually observed to determine the yuzu skin resistance as follows. It was evaluated based on the criteria.
○: No change in appearance is observed on the pouch surface.
×: The surface of the pouch had changed significantly like the skin of a yuzu.

<Example 1>
A CPP film was formed at a weight ratio of block PP (a2)/block PP (a1)/LLDPE (b1) = 65/15/20.
Regarding this CPP film, the xylene soluble content (EPR content) was measured, and the dynamic viscoelasticity was measured to determine the tan δ at 5°C. The glass transition temperature of EPR was calculated. Incidentally, the temperature curve of tan δ obtained by this measurement is shown in FIG.
After laminating the above CPP film, it was made into a pouch. The pouch was subjected to retort treatment and a drop bag test was conducted.
The results of each measurement are shown in Table 1.
Moreover, the evaluation of the yuzu skin resistance of this pouch was 0.

<Example 2>
A CPP film was produced in the same manner as in Example 1, except that the modifying component (b) was changed to LLDPE (b2), and various measurements and drop bag tests were conducted in the same manner as in Example 1. It is shown in Table 1.

<Example 3>
A CPP film was formed at a weight ratio of block PP (a2)/block PP (a1)/LLDPE (b1) = 70/20/10.
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 1>
A CPP film was formed using only block PP (a2).
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 2>
A CPP film was formed at a weight ratio of block PP (a2)/LLDPE (b1) = 80/20.
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 3>
A CPP film was formed at a weight ratio of block PP (a2)/block PP (a1)/LLDPE (b1) = 70/10/20.
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 4>
A CPP film was formed in the same manner as in Example 1 except that the weight ratio of homoPP (a3)/LLDPE (b1) was 80/20 and the film forming temperature was changed to 45°C.
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 5>
A CPP film was formed at a weight ratio of block PP (a2)/block PP (a1)/LLDPE (b1) = 75/20/5.
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 6>
A CPP film was formed at a weight ratio of block PP (a1)/block PP (a2) = 80/20.
Various measurements and drop bag tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1.

<Comparative example 7>
A CPP film was formed using block PP (a1). The cooling roll was formed into a film at 60°C.
Various measurements and bag drop tests were conducted in the same manner as in Example 1, except that the above CPP film was used, and the results are shown in Table 1. The evaluation of the yuzu skin resistance of this pouch was ×.

Claims (6)

A heat-sealing film formed from a polypropylene resin composition containing block polypropylene made of homopolypropylene and an ethylene-propylene copolymer, and linear low-density polyethylene, and a dynamic viscoelasticity test on the film. The tan δ ( 5 ° C, 10 Hz) measured at It contains density polyethylene in an amount of 10 to 20% by mass, and the glass transition temperature derived from the ethylene-propylene copolymer calculated from the tan δ temperature curve obtained in the dynamic viscoelasticity test is lower than -35 ° C. A heat-sealing film that is characterized by its high price. The heat sealing film according to claim 1, wherein the glass transition temperature derived from the ethylene-propylene copolymer is in the range of -35 to -15°C. The heat sealing film according to claim 1 or 2 , wherein the linear low density polyethylene contains hexene-1 or 4-methylpentene-1 as a comonomer. The heat sealing film according to claim 3, wherein the comonomer is 4-methylpentene-1. The heat seal according to any one of claims 1 to 4, wherein a plurality of types of block polypropylenes having different at least one of the ethylene/propylene copolymer content and the ethylene/propylene ratio of the ethylene/propylene copolymer are used. Film for. A multilayer film comprising the heat sealing film according to any one of claims 1 to 5 as a heat sealing layer.