JP7589472B2 - Packaging laminates - Google Patents

Description

The present invention relates to a packaging laminate, and more specifically to a packaging laminate with high recyclability that is suitable for producing pouches by attaching with heat sealing.

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 to make pouches for storing various foods, etc. In recent years, however, greater heat resistance and impact resistance are required for retort sterilization (heated steam sterilization), etc., so impact polypropylene (hereinafter sometimes referred to as impact PP) has come to be used to make CPP film.

Impact PP, also known as block PP, impact copolymer, or high impact polypropylene, is made by dispersing rubber components such as ethylene-propylene copolymer (EPR) or styrene-butadiene copolymer (SBR) in a matrix of homopolypropylene or random polypropylene. The dispersion of these rubber components significantly improves impact resistance.

CPP films used to make pouches to be supplied for retort sterilization, etc., are required to have properties such as heat seal strength and impact resistance, as well as blocking resistance and resistance to yuzu peel. In other words, it goes without saying that blocking resistance is necessary to prevent blocking when films are stacked together, but when the film is subjected to heated steam sterilization such as retort sterilization, the oils in the contents may seep into the film, causing the pouch to deform in appearance like yuzu peel, so it is also necessary to prevent such yuzu peel-like deformation. Films formed from the above-mentioned impact PP have poor blocking resistance and yuzu peel resistance, so they need to be modified.

Various means have been proposed to improve the above-mentioned characteristics. For example, Patent Documents 1 and 2 propose a propylene-based resin composition in which linear low-density polyethylene (LLDPE) is blended with a propylene-based impact copolymer (corresponding to impact PP), and disclose that such a resin composition can produce a heat-sealable film with a variety of excellent characteristics.

In Patent Documents 1 and 2, the physical properties of a heat-sealable film made of impact PP are improved by blending linear low-density polyethylene with impact PP. For example, a pouch is made using this film, and when the pouch is filled with the contents and stored at a temperature of 5°C, and then a bag drop test is performed from any height, the pouch shows good low-temperature impact resistance.

Nowadays, retort pouches are often heated in a microwave oven for convenience. Furthermore, these pouches are provided with a mechanism for releasing steam generated from the contents by heating from inside the pouch. This steam release mechanism suppresses excessive pressure buildup inside the pouch and prevents the pouch from breaking. However, when a CPP film containing a large amount of a rubber dispersion or linear low-density polyethylene, which has lower heat resistance than polypropylene, is used as in Patent Documents 1 and 2, the seal around the pouch may peel off regardless of the presence or absence of a steam release mechanism, which may lead to the pouch breaking.

Furthermore, with the recent growing awareness of environmental conservation and the efficient use of resources, there is a demand to reconsider the film material used for retort pouches. In other words, from the perspective of recyclability, pouches made from a single material are more desirable than pouches made from different materials, such as the current combination of PET film, Ny film, aluminum foil, CPP film, etc. As for the material, it is desirable to make the pouch out of polypropylene-based resin, due to its properties such as heat sealability and heat resistance. Therefore, in order to improve recyclability, it is necessary to use polypropylene-based resin to achieve the impact resistance that has been achieved with different materials so far.

When constructing the film material for retort pouches from polypropylene-based resins, the CPP film is required to have even higher low-temperature impact resistance than ever before. However, it is difficult to achieve both low-temperature impact resistance and heat resistance. For these reasons, the current situation is that conventional CPP films and film configurations for retort pouches lack either low-temperature impact resistance, heat resistance to withstand microwave heating, or recyclability.

Patent No. 4844091 WO2017/038349

SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a packaging laminate which has excellent impact resistance at low temperatures, suitability for microwave heating, and excellent recyclability.
Another object of the present invention is to provide a retort pouch obtained from the above-mentioned packaging laminate.

According to the present invention, in a packaging laminate having a structure in which a base film and a heat seal film are laminated with an adhesive layer sandwiched therebetween,
A stretched polypropylene film is used as the base film,
A propylene-based film is used as the heat seal film,
The propylene-based film used as the heat seal film has a loss tangent (tan δ) of more than 0.0594 at 5°C and a storage modulus (E') of more than 1 MPa at 110°C in a dynamic viscoelasticity test measurement.

The following aspects are preferably applied to the packaging laminate of the present invention.
(1) The propylene-based film is formed from a cast film containing an impact polypropylene component.
(2) The cast film contains an impact polypropylene component (A) in which an ethylene-propylene copolymer is dispersed in polypropylene, and a linear low-density polyethylene (B).
(3) The cast film contains 8% by mass or more of a xylene soluble fraction derived from an ethylene-propylene copolymer.
(4) The cast film contains the linear low-density polyethylene (B) in an amount of 20 mass% or less.
(5) The adhesive layer is formed from a dry lamination adhesive.
(6) A stretched film containing at least one selected from an olefin resin, a polyamide resin, and an ethylene-vinyl alcohol copolymer is laminated separately from the base film.
(7) The olefin-based resin is polypropylene.

The present invention also provides a pouch made of the above-mentioned packaging laminate.

The packaging laminate of the present invention has a basic structure in which a base film and a heat seal film are laminated via an adhesive layer, but in addition to this basic structure, the propylene-based film used as the heat seal film has dynamic viscoelastic properties, specifically, an important feature in that the loss tangent (tan δ) at 5° C. exceeds 0.0594 and the storage modulus (E′) at 110° C. exceeds 1 MPa in dynamic viscoelasticity test measurements. That is, since the propylene-based film has the above-mentioned viscoelastic properties, the packaging laminate of the present invention not only exhibits excellent impact resistance even when subjected to heat treatment such as retort sterilization, but also has excellent impact resistance even in a low temperature range of about 5° C., and can ensure a seal strength that can withstand microwave heating.
For example, as shown in the examples described later, in a pouch made from a laminate having a loss tangent (tan δ) and a storage modulus (E') of a propylene-based film (heat seal film) within the above range, the number of times that the pouch was horizontally broken in an environment of 5°C was at least 19 times (Example 2), and the seal strength at 110°C was at least 15N (Example 1), despite the fact that the pouch was subjected to retort treatment. On the other hand, in Comparative Example 3, in which the loss tangent (tan δ) is 0.059, which is smaller than 0.0594, the number of times that the pouch was horizontally broken in an environment of 5°C was 7 times, which is smaller than Examples 1 and 2, and the impact resistance at low temperatures is poor. In Comparative Example 2, in which the storage modulus E' is less than 1 MPa, the seal strength at 110°C was 4N, which is extremely small compared to Examples 1 and 2, and the seal strength at high temperatures was small, and it cannot be applied to microwave oven heating, for example.

Another important feature of the present invention is that an oriented polypropylene (OPP) film is used as the base film. In other words, by using an OPP film as the base film, most of the main materials used in this packaging laminate are propylene-based materials, and as a result, this packaging laminate has excellent recyclability.

FIG. 1 is a diagram showing a schematic cross-sectional structure of a packaging laminate of the present invention. FIG. 2 is a diagram showing the loss tangent (tan δ) temperature curve (10 Hz) obtained by dynamic viscoelasticity measurement of the propylene-based films used in the examples and comparative examples. FIG. 2 is a diagram showing the storage modulus curve (E′) temperature curve (10 Hz) obtained by dynamic viscoelasticity measurement of the propylene-based films used in the examples and comparative examples.

Referring to FIG. 1, the packaging laminate 10 of the present invention, generally designated 10, has a laminate structure including a base film 1, an adhesive layer 3, and a heat seal film 5. In simple terms, it has a structure in which the base film 1 and the heat seal film 5 are laminated together with an adhesive.

<Base film 1>
A stretched polypropylene film (hereinafter sometimes referred to as OPP film) is used as the base film 1. This OPP film is a film obtained by stretching a propylene-based resin film produced by a known means such as extrusion molding in a uniaxial or biaxial direction. This ensures the drop strength, puncture strength, and rigidity of the pouch. The stretching ratio may be such that the film does not break due to overstretching, and is usually 2 times or more.

The propylene-based resin used to form the OPP film is typically polypropylene (a homopolymer of propylene), but as long as the properties of polypropylene are not compromised, it may be a random or block copolymer in which an α-olefin such as ethylene, 1-butene, or 4-methyl-1-pentene or a cyclic olefin is copolymerized.

The thickness of the base film 1 formed from the above-mentioned OPP film is appropriate depending on the capacity of the pouch to be finally manufactured, but generally, it is sufficient if the thickness is 10 μm or more.

In addition, the above-mentioned base film 1 may be laminated with a gas barrier resin such as an ethylene-vinyl alcohol copolymer in order to improve the gas barrier property, or an inorganic coating may be formed on the surface of the base film 1, or an organic material such as polyvinyl alcohol may be formed. The inorganic coating may be formed by coating, or may be a vapor deposition film. Such a gas barrier resin layer is formed by attaching a gas barrier resin film using an adhesive such as dry lamination. The vapor deposition film is an inorganic vapor deposition film formed by physical vapor deposition such as sputtering, vacuum deposition, and ion plating, or chemical vapor deposition such as plasma CVD, and is formed from various metals or metal oxides such as silicon oxide and aluminum oxide. Such a vapor deposition film is formed from an inorganic material, and therefore exhibits higher oxygen barrier properties than gas barrier resins such as ethylene-vinyl alcohol copolymer.

When the gas barrier resin layer or inorganic coating as described above is formed on a base film 1 made of a propylene-based resin, the heat seal film 5 described later may be attached to the gas barrier resin layer or inorganic coating via the adhesive layer 3, or may be attached to the base film 1 side.

In addition, the oriented polypropylene film (OPP film) used as the base film 1 may experience relaxation of the oriented structure due to the effects of heat such as heat sealing, which may lead to a decrease in the drop strength. Therefore, in order to prevent a decrease in strength, it is preferable to provide a stretched film layer containing at least one selected from olefin resins, polyamide resins, and ethylene-vinyl alcohol copolymers as a strength reinforcing layer. Such a strength reinforcing layer is intended to mitigate the loss of orientation due to heat treatment such as heat sealing, and to effectively suppress a decrease in strength.

Such a strength reinforcing layer is a stretched molded product of a blend or laminate of an olefin resin and a reinforcing resin with a higher melting point than the olefin resin. In particular, a stretched film of a blend of an olefin resin and a polyamide resin or an ethylene-vinyl alcohol copolymer is preferred, and the mass ratio of olefin resin to reinforcing resin is usually in the range of about 50:50 to 90:10. In other words, if the amount of reinforcing resin is too large, the strength reinforcing effect is excellent but recyclability is low, and if the amount of reinforcing resin is too small, the strength reinforcing effect of this layer is impaired.

In addition, as the olefin-based resin used to form the above-mentioned strength reinforcing layer, the same type of resin as the propylene-based resin used to form the stretched polyolefin film used as the above-mentioned base film 1, particularly polypropylene, is optimal for (improving) recyclability.
The polyamide resin to be blended with the olefin resin is not particularly limited and various types can be exemplified. In general, nylon 6, nylon 6, 6, nylon 11, nylon 12, nylon 13, nylon 6/nylon 6,6 copolymer, aromatic nylon (e.g., polymetaxylylene adipamide), amorphous nylon (e.g., nylon 6I/nylon 6T), etc. are preferably used.

The strength reinforcing layer may have a laminated structure in which a layer of olefin-based resin and a layer of reinforcing resin are laminated. In such a laminated structure, the thickness ratio of the olefin-based resin layer to the reinforcing resin layer is usually in the range of about 1/1 to 3/1. In other words, if the thickness of the reinforcing resin is too large, the recyclability of the packaging bag is greatly lost, and if the amount of reinforcing resin is small, the amount of oriented crystals present in the seal portion will be small, and there is a risk that the improvement of the drop strength of the bag will be insufficient.

The strength reinforcing layer may be formed by co-extrusion of the blend and stretching, or by multi-layer extrusion stretching. The layer is formed by stretching in a uniaxial or biaxial direction. In addition, the blend or multi-layer may be co-extruded at the same time as the base film 1 is formed, and the co-extruded film may be stretched in a uniaxial or biaxial direction.

The thickness of the strength reinforcing layer is not particularly limited, and may be set appropriately to the thickness of the base film 1, which is set according to the volume of the desired pouch. In general, a thickness of 5 μm or more is preferable, and a thickness in the range of about 5 to 30 μm is particularly preferable.

The above-mentioned strength reinforcing layer may be provided between the base film 1 and the heat seal film 5, or may be provided on the outside of the base film 1.

The adhesive used to laminate the above-mentioned strength reinforcing layer to the base film 1, etc., is the same type of adhesive as that used for the adhesive layer 3 described below.

<Adhesive layer 3>
The adhesive layer 3 is a layer formed using an adhesive, and the heat seal film 5 is laminated onto the base film 1 using this adhesive.

As such adhesives, known dry laminate adhesives such as urethane-based adhesives and epoxy-based adhesives can be used.

For example, a urethane-based dry lamination adhesive may be one that is made from a reaction product of an isocyanate with a (meth)acrylic compound or a polyester polyol. This adhesive usually contains a known curing catalyst such as an amine catalyst, a metal catalyst, or a phosphoric acid-modified compound. The amount of curing catalyst is set according to the type of curing catalyst so that a dense cured film (adhesive layer) can be formed at a temperature and for a time that does not cause thermal deformation of the underlying resin.

The epoxy adhesive contains a liquid resin having an epoxy group in its molecule and an epoxy curing agent.
Liquid resins having epoxy groups in the molecule are typically those obtained by reacting epichlorohydrin with a phenol compound, an amine compound, a carboxylic acid, etc., or those obtained by oxidizing an unsaturated compound such as butadiene with an organic peroxide, etc., and any type of resin can be used. Specific examples include bisphenol A or bisphenol F type epoxy resins, novolac type epoxy resins, cyclic aliphatic type epoxy resins, long-chain aliphatic type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, etc.
As the epoxy curing agent, known agents such as amines, acid anhydrides, polyamides, etc. can be used, but aromatic polyamines such as metaphenylenediamine are particularly preferred.

The ratio of epoxy resin to curing agent should be set according to the epoxy equivalent of the epoxy resin so that a sufficient cured film is formed.

The above-mentioned urethane-based or epoxy-based dry lamination adhesive is applied to the surface of the above-mentioned propylene resin-based substrate film 1 in the form of a coating liquid in which it is dissolved or dispersed in a volatile organic solvent such as a hydrocarbon, alcohol, ketone, ester, or ether solvent. The adhesive is then dried to volatilize the organic solvent, after which a heat-sealing film (described later) is attached, and the heat-sealing film can be adhered and fixed by heating and curing.
The thickness of the adhesive layer 3 thus formed is usually about 0.1 to 10 μm.

In the above-mentioned dry laminate adhesive, when a vapor deposition film is formed on the surface of the base film 1 (OPP film), when a heat seal film 5 or the like is attached onto it, an epoxy-based dry laminate adhesive is advantageous in terms of avoiding a decrease in gas barrier properties due to retort treatment.
The dry lamination adhesive is also used for forming the multi-layer strength reinforcement described above, that is, for laminating an olefin resin-based stretched film and a polyamide resin-based stretched film.

<Heat seal film 5>
The heat seal film 5 is laminated onto the above-mentioned base film 1 by placing the film 5 on the coating layer of the adhesive and pressing it, and then heating and curing the adhesive in this state. The heat seal film 5 melts easily when heated and immediately solidifies when cooled, and by utilizing this property, the laminate 10 (heat seal film 5) can be thermally bonded (heat sealed) to each other to produce a pouch.

In the present invention, the heat seal film 5 is a propylene-based film having dynamic viscoelastic properties, and the loss tangent (tan δ) at 5°C in dynamic viscoelasticity measurement at 10 Hz exceeds 0.0594. That is, by having such viscoelasticity at 5°C, the heat seal film 5 in the packaging laminate 10 exhibits good low-temperature impact resistance in the low-temperature range (around 5°C) and is very difficult to break. In addition, this heat seal film 5 must have a storage modulus (E') at 110°C in dynamic viscoelasticity measurement at 10 Hz of more than 1 MPa. That is, by having such a large value of storage modulus E' at 110°C, this heat seal film 5 exhibits appropriate elasticity in the high-temperature range (around 110°C) and maintains sufficient seal strength to seal a pouch even at high temperatures. Therefore, the pouch obtained from this laminate 10 has high seal strength at high temperatures, effectively prevents seal destruction due to microwave heating, and enables effective microwave heating.

In the present invention, the heat seal film 5 (propylene-based film) having the above-mentioned viscoelasticity is obtained by using a cast film (hereinafter simply referred to as CPP film) containing impact polypropylene (impact PP) and adjusting the composition of the impact PP and the type and amount of the modified resin component used in combination.

That is, the CPP film having the above-mentioned viscoelasticity is obtained by melt extrusion of a resin composition containing an impact PP component (A) and a modified resin component (B).

Impact PP component (A);
The impact PP component (A) is made of impact polypropylene (impact PP), and this impact PP has a structure in which ethylene-propylene copolymer (EPR) is dispersed in homo- or random polypropylene. That is, the dispersion of EPR in polypropylene imparts impact resistance to the polypropylene. As rubber components dispersed in polypropylene, styrene-butadiene copolymer (SBR), ethylene-propylene-butene copolymer (EPBR), etc. are known in addition to EPR, and although those other than EPR can also improve the low-temperature impact resistance (tan δ at 5°C is greater than 0.0594) that is the object of the present invention, EPR is optimal.

From the viewpoint of film formability (extrusion formability), the MFR (melt flow rate, 230°C) of the above-mentioned impact PP is in the range of approximately 0.5 to 10 g/10 min.

The EPR content in the impact PP can be expressed as the xylene-soluble fraction of the CPP film used to form the heat seal film 5. The xylene-soluble fraction is the proportion of components that do not precipitate when the impact PP resin is completely dissolved in boiling xylene and the xylene solution is cooled to room temperature. It is desirable that this xylene-soluble fraction is 8% by mass or more, and particularly in the range of 8 to 20% by mass. In other words, if the xylene-soluble fraction is smaller than the above range, the amount of EPR is small, and the impact resistance of the pouch decreases. Also, if the soluble fraction is excessively high, the heat resistance of the pouch decreases, and further, the pouch may have a poor appearance.

Furthermore, it is preferable that the intrinsic viscosity (measured using tetralin at 135°C as a solvent) of the above-mentioned xylene soluble fraction (EPR) is in the range of 1.0 to 2.9 dl/g. This intrinsic viscosity is a parameter corresponding to the molecular weight of the EPR in the impact PP. When this value is outside the above range, the impact resistance tends to be unsatisfactory. This is probably because the size of the EPR molecule is either larger or smaller than necessary, which prevents the properties of the modifying resin component (B) described below from being fully exhibited.

Modified resin component (B);
This modifying resin component (B) is a component that enhances the compatibility between the polypropylene (PP) and the ethylene-propylene copolymer (EPR) in the above-mentioned impact PP and greatly improves the dispersibility of the EPR in the PP, thereby enabling the EPR to fully exert its impact property improving effect.

In the present invention, linear low density polyethylene (LLDPE) is preferably used as the modifying resin component (B). This LLDPE is a linear low density polyethylene having a density in the range of 0.860 to 0.925 g/ ^cm3 , and is obtained by copolymerizing a small amount (about a few percent) of an α-olefin such as butene-1, hexene-1, or 4-methylpentene-1 with ethylene to reduce the density, and has an extremely high molecular linearity.

In addition, since this LLDPE is used in combination with impact PP, it is preferable to use one with an MFR (190°C) of 1.0 to 15 g/10 min in order to avoid impairing film formability.

Furthermore, it is preferable that the LLDPE contains 12 mol% or less of α-olefin comonomer and has a number average molecular weight of 10,000 or more in terms of polystyrene as measured by GPC. In other words, if the content of α-olefin comonomer is high or if the number average molecular weight is low and a large amount of low molecular weight components are included, the oil resistance and flavor of the contents will be poor when used as a pouch. Also, some of the LLDPE may dissolve in xylene, and the xylene-soluble content in the molded film may not correspond to the EPR derived from the impact PP.

It is preferable that the composition of the film is designed so that the amount of LLDPE in the CPP film (corresponding to the amount of LLDPE in the heat-sealable resin layer 5) is 20% by mass or less. In other words, if an excessive amount of LLDPE is contained, the blocking resistance and heat resistance of the film may be impaired.

In addition, additives that are known per se can also be blended into the resin composition used to form the CPP film.

The CPP film containing the above-mentioned impact PP components is produced by dry blending the components, feeding them into an extruder to melt-knead them, melt-extruding the blend into a film from a T-die, bringing the extruded molten film into contact with a cooling roll to solidify it, and winding it up.
There are no particular limitations on the thickness of such a CPP film, but taking into consideration the rigidity, ease of opening, etc., it is usually suitable that the thickness is in the range of 20 to 100 μm, particularly 50 to 80 μm.

The packaging laminate 10 of the present invention obtained by laminating the above-mentioned layers or films can also have, for example, a printed layer or a transparent protective layer (PET film) laminated on the outer surface side of the base film 1.

<Use of the packaging laminate>
The packaging laminate 10 of the present invention described above is made into a bag by attaching it by heat sealing with the heat seal film 5, and used as a pouch (bag-like container).
The bag is made by a known method, for example, by making an empty pouch by sealing three sides of two laminates, filling the pouch with contents through the opening, and finally closing the opening by heat sealing.
Alternatively, an empty pouch can be made by folding back one laminate and heat sealing both side edges. In this case, it is not necessary to heat seal the bottom. Furthermore, an empty pouch can be made by using a laminate dedicated to the side or bottom. Such a method is advantageous in increasing the volume of the pouch or imparting standing properties.

In this way, pouches made from the packaging laminate 10 of the present invention and filled with contents are effectively prevented from losing performance due to retort treatment (sterilization treatment with heated steam at 100-130°C), and even after retort treatment, they not only have excellent impact resistance at low temperatures, but also exhibit high seal strength at high temperatures, so they can withstand microwave heating. Therefore, such pouches are particularly suitable for storing food products.

The advantageous effects of the present invention are illustrated in the following examples.
The materials and measuring methods used in the following experiments are shown below.

<Propylene-based film (CPP film) material>
Impact PP (A): SunAllomer PC480A
MFR (230℃): 2.0g/10min
EPR content (xylene soluble content): 17.5% by mass
Modified resin component (B)
LLDPE (B1);
Urutozex 2022L manufactured by Prime Polymer Co., Ltd.
MFR (190℃): 2.0g/10min
Density: 919kg/ ^m3
Alpha-olefin species: 4-methylpentene-1
LLDPE (B2);
Mitsui Chemicals, Inc. Toughmer A1085S
MFR (190℃): 1.2g/10min
Density: 885kg/ ^m3
Alpha-olefin species: butene-1

<Commercially available CPP film>
As commercially available CPP films, ZK500 and ZK401 (both 70 μm thick, surface hydrophilized) manufactured by Toray Advanced Film Co., Ltd. were used.
ZK500;
EPR content: 16.9% by mass
ZK401;
EPR content: 16.6% by mass

<EPR content (xylene soluble content)>
The impact PP or CPP film was dissolved in xylene under reflux, allowed to cool, and then subjected to solid-liquid separation.
The xylene soluble matter was reprecipitated with methanol, and the precipitate was filtered, dried, and weighed to calculate the EPR content.

<Dynamic viscoelasticity measurement method>
A dynamic viscoelasticity measuring device manufactured by Seiko Instruments Inc. was used. The test conditions were as follows.
Test piece film: length 20 mm, width 10 mm
Chuck distance: 5mm
Temperature range: -70℃ to 150℃
Heating rate: 3°C/min
Frequency: 10Hz
tan δ (loss tangent): Calculated by loss modulus at 5° C./storage modulus.
E' (storage modulus): Measured at 110°C.

<Pouch for horizontal drop bag test>
The pouches used for the horizontal bag drop test were made by using an oriented polypropylene film (OPP, thickness 20 μm) as a base layer, and laminating a layer structure of OPP film/CPP film (thickness 70 μm) by a dry lamination method using a urethane adhesive to obtain a packaging bag.

<Pouch for seal strength measurement test>
The pouch for the seal strength measurement test had a layer structure of stretched PET film (OPET, thickness 12 μm)/stretched Ny film (ONy, thickness 15 μm)/aluminum foil (Al, thickness 7 μm)/CPP film (thickness 70 μm) as the base layer, and was laminated by a dry lamination method using a urethane-based adhesive.

<Pouch manufacturing>
The laminated film with the CPP film was cut into two pieces measuring 140 mm (MD) x 180 mm (TD), and filled with 200 g of water to form a bag. The bag was formed using an impulse sealer manufactured by Fuji Impulse Co., Ltd.
Pouch for horizontal drop bag test;
Sealing conditions: 200°C, 1.4 (s), cooling 3.0 (s)
Seal width: 5mm
Pouches for seal strength measurement tests;
Sealing conditions: 220°C, 1.4 (s), cooling 3.0 (s)
Seal width: 5mm

<Horizontal drop bag test method>
The pouches were retorted at 121°C for 30 minutes using a shower and cooled overnight in a 5°C environment. Two pouches were dropped horizontally from a height of 120 cm to measure the strength of the pouches. The lower pouch was the test pouch. The test was carried out on three samples, which were dropped 20 times, and the average number of unbroken bags was measured.

<Seal strength measurement test method>
An autograph (AG-I/30N-10KN) manufactured by Shimadzu Corporation was used. The test conditions were as follows.
Test specimen film:
The heat-sealed portion of the pouch was cut at a right angle from the short side (140 mm) to prepare a strip of 15 mm width. Six test pieces were prepared.
Ambient temperature: 110°C
Tensile speed: 300 mm/min

Example 1
A CPP film was produced with a weight ratio of impact PP (A)/LLDPE (B1)=86/14.
The CPP film was formed by the following method.
The impact PP (A) and LLDPE (B1) were dry-blended in the above composition and fed into a hopper of a single-screw extruder equipped with a T-die. The mixture was melt-kneaded in the extruder set at 230°C and extruded into a film from the T-die. The mixture was solidified by contacting with a cooling roll at 60°C and wound up to produce a film having a thickness of 70 μm.
The obtained film was subjected to a corona discharge treatment to make the surface hydrophilic.

Dynamic viscoelasticity measurements were performed on this CPP film to determine tan δ at 5° C. and E′ at 110° C. The temperature curves of tan δ and E′ obtained by this measurement are shown in FIGS.
Pouches for horizontal bag drop tests and pouches for seal strength measurements were prepared by laminating the above-mentioned CPP film, and the horizontal bag drop tests and seal strength measurements were carried out. The results are shown in Table 1.

Example 2
A CPP film was prepared in the same manner as in Example 1, except that the ratio of the impact PP (A) and the LLDPE (B2) was changed to 95/5. The dynamic viscoelasticity measurement, the bag drop test, and the seal strength measurement were also performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
A sealant film was prepared in the same manner as in Example 1, except that the CPP film was prepared using only impact PP (A). Dynamic viscoelasticity measurement, bag drop test, and seal strength measurement were also performed in the same manner as in Example 1, and the results are shown in Table 1.

<Comparative Example 2>
The dynamic viscoelasticity measurement, bag drop test, and seal strength measurement were carried out in the same manner as in Example 1, except that the CPP film was changed to ZK500 manufactured by Toray Advanced Film Co., Ltd. The results are shown in Table 1.

<Comparative Example 3>
The dynamic viscoelasticity measurement, bag drop test, and seal strength measurement were carried out in the same manner as in Example 1, except that the CPP film was changed to ZK401 manufactured by Toray Advanced Film Co., Ltd. The results are shown in Table 1.

1: Base film 3: Adhesive layer 5: Heat seal film 10: Packaging laminate

Claims (6)

In a packaging laminate having a structure in which a base film and a heat seal film are laminated with an adhesive layer sandwiched therebetween,
A stretched polypropylene film is used as the base film,
A propylene-based film is used as the heat seal film,
The propylene-based film used as the heat seal film has a loss tangent (tan δ) of more than 0.0594 at 5° C. and a storage modulus (E′) of more than 1 MPa at 110° C. in a dynamic viscoelasticity test measurement ,
The propylene-based film is formed from a cast film that includes an impact polypropylene component;
The cast film contains an impact polypropylene component (A) in which an ethylene-propylene copolymer is dispersed in polypropylene, and a linear low-density polyethylene (B),
The cast film contains 8 to 20% by mass of a xylene soluble fraction derived from an ethylene-propylene copolymer,
The cast film comprises the linear low-density polyethylene (B) in an amount of 14% by mass or less . 2. The packaging laminate according to claim 1 , wherein the adhesive layer is formed from a dry lamination adhesive. 3. The packaging laminate according to claim 1 or 2, further comprising a stretched film comprising at least one selected from an olefin-based resin, a polyamide-based resin, and an ethylene-vinyl alcohol copolymer, laminated separately from the base film. 4. The packaging laminate according to claim 3 , wherein the olefin resin is polypropylene. A pouch comprising the packaging laminate according to any one of claims 1 to 4 . The pouch according to claim 5 , wherein the pouch has an olefin-based resin content of 80% by mass or more.